root/magick/cache.c

DEFINITIONS

1. AcquirePixelCache
2. AcquirePixelCacheNexus
3. AcquirePixelCachePixels
4. CacheComponentGenesis
5. CacheComponentTerminus
6. ClipPixelCacheNexus
7. ClonePixelCache
8. ClonePixelCacheMethods
9. ClonePixelCacheOnDisk
10. ClonePixelCacheRepository
11. DestroyImagePixelCache
12. DestroyImagePixels
13. ClosePixelCacheOnDisk
14. RelinquishPixelCachePixels
15. DestroyPixelCache
16. RelinquishCacheNexusPixels
17. DestroyPixelCacheNexus
18. GetAuthenticIndexesFromCache
19. GetAuthenticIndexQueue
20. GetAuthenticPixelCacheNexus
21. GetAuthenticPixelsFromCache
22. GetAuthenticPixelQueue
23. GetAuthenticPixels
24. GetAuthenticPixelsCache
25. GetImageExtent
26. ValidatePixelCacheMorphology
27. GetImagePixelCache
28. GetPixelCacheType
29. GetImagePixelCacheType
30. GetOneAuthenticPixel
31. GetOneAuthenticPixelFromCache
32. GetOneVirtualMagickPixel
33. GetOneVirtualMethodPixel
34. GetOneVirtualPixel
35. GetOneVirtualPixelFromCache
36. GetPixelCacheChannels
37. GetPixelCacheColorspace
38. GetPixelCacheMethods
39. GetPixelCacheNexusExtent
40. GetPixelCachePixels
41. GetPixelCacheStorageClass
42. GetPixelCacheTileSize
43. GetPixelCacheVirtualMethod
44. GetVirtualIndexesFromCache
45. GetVirtualIndexesFromNexus
46. GetVirtualIndexQueue
47. DitherX
48. DitherY
49. EdgeX
50. EdgeY
51. RandomX
52. RandomY
53. VirtualPixelModulo
54. GetVirtualPixelsFromNexus
55. GetVirtualPixelCache
56. GetVirtualPixelQueue
57. GetVirtualPixels
58. GetVirtualPixelsCache
59. GetVirtualPixelsNexus
60. MagickPixelCompositeMask
61. MaskPixelCacheNexus
62. AllocatePixelCachePixels
63. CacheSignalHandler
64. OpenPixelCacheOnDisk
65. WritePixelCacheRegion
66. SetPixelCacheExtent
67. OpenPixelCache
68. PersistPixelCache
69. QueueAuthenticPixel
70. QueueAuthenticPixelCacheNexus
71. QueueAuthenticPixelsCache
72. QueueAuthenticPixels
73. ReadPixelCacheRegion
74. ReadPixelCacheIndexes
75. ReadPixelCachePixels
76. ReferencePixelCache
77. SetPixelCacheMethods
78. AcquireCacheNexusPixels
79. IsAuthenticPixelCache
80. PrefetchPixelCacheNexusPixels
81. SetPixelCacheNexusPixels
82. SetCacheAlphaChannel
83. SetPixelCacheVirtualMethod
84. SyncAuthenticPixelCacheNexus
85. SyncAuthenticPixelsCache
86. SyncAuthenticPixels
87. SyncImagePixelCache
88. WritePixelCacheIndexes
89. WritePixelCachePixels

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%                      CCCC   AAA    CCCC  H   H  EEEEE                       %
%                     C      A   A  C      H   H  E                           %
%                     C      AAAAA  C      HHHHH  EEE                         %
%                     C      A   A  C      H   H  E                           %
%                      CCCC  A   A   CCCC  H   H  EEEEE                       %
%                                                                             %
%                                                                             %
%                       MagickCore Pixel Cache Methods                        %
%                                                                             %
%                              Software Design                                %
%                                   Cristy                                    %
%                                 July 1999                                   %
%                                                                             %
%                                                                             %
%  Copyright 1999-2016 ImageMagick Studio LLC, a non-profit organization      %
%  dedicated to making software imaging solutions freely available.           %
%                                                                             %
%  You may not use this file except in compliance with the License.  You may  %
%  obtain a copy of the License at                                            %
%                                                                             %
%    http://www.imagemagick.org/script/license.php                            %
%                                                                             %
%  Unless required by applicable law or agreed to in writing, software        %
%  distributed under the License is distributed on an "AS IS" BASIS,          %
%  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.   %
%  See the License for the specific language governing permissions and        %
%  limitations under the License.                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%
%
*/

/*
  Include declarations.
*/
#include "magick/studio.h"
#include "magick/blob.h"
#include "magick/blob-private.h"
#include "magick/cache.h"
#include "magick/cache-private.h"
#include "magick/color-private.h"
#include "magick/colorspace.h"
#include "magick/colorspace-private.h"
#include "magick/composite-private.h"
#include "magick/distribute-cache-private.h"
#include "magick/exception.h"
#include "magick/exception-private.h"
#include "magick/geometry.h"
#include "magick/list.h"
#include "magick/log.h"
#include "magick/magick.h"
#include "magick/memory_.h"
#include "magick/memory-private.h"
#include "magick/nt-base-private.h"
#include "magick/option.h"
#include "magick/pixel.h"
#include "magick/pixel-accessor.h"
#include "magick/pixel-private.h"
#include "magick/policy.h"
#include "magick/quantum.h"
#include "magick/random_.h"
#include "magick/registry.h"
#include "magick/resource_.h"
#include "magick/semaphore.h"
#include "magick/splay-tree.h"
#include "magick/string_.h"
#include "magick/string-private.h"
#include "magick/thread-private.h"
#include "magick/utility.h"
#include "magick/utility-private.h"
#if defined(MAGICKCORE_ZLIB_DELEGATE)
#include "zlib.h"
#endif

/*
  Define declarations.
*/
#define CacheTick(offset,extent)  QuantumTick((MagickOffsetType) offset,extent)
#define IsFileDescriptorLimitExceeded() (GetMagickResource(FileResource) > \
  GetMagickResourceLimit(FileResource) ? MagickTrue : MagickFalse)

/*
  Typedef declarations.
*/
typedef struct _MagickModulo
{
  ssize_t
    quotient,
    remainder;
} MagickModulo;

/*
  Forward declarations.
*/
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif

static Cache
  GetImagePixelCache(Image *,const MagickBooleanType,ExceptionInfo *)
    magick_hot_spot;

static const IndexPacket
  *GetVirtualIndexesFromCache(const Image *);

static const PixelPacket
  *GetVirtualPixelCache(const Image *,const VirtualPixelMethod,const ssize_t,
    const ssize_t,const size_t,const size_t,ExceptionInfo *),
  *GetVirtualPixelsCache(const Image *);

static MagickBooleanType
  GetOneAuthenticPixelFromCache(Image *,const ssize_t,const ssize_t,
    PixelPacket *,ExceptionInfo *),
  GetOneVirtualPixelFromCache(const Image *,const VirtualPixelMethod,
    const ssize_t,const ssize_t,PixelPacket *,ExceptionInfo *),
  OpenPixelCache(Image *,const MapMode,ExceptionInfo *),
  OpenPixelCacheOnDisk(CacheInfo *,const MapMode),
  ReadPixelCacheIndexes(CacheInfo *magick_restrict,NexusInfo *magick_restrict,
    ExceptionInfo *),
  ReadPixelCachePixels(CacheInfo *magick_restrict,NexusInfo *magick_restrict,
    ExceptionInfo *),
  SyncAuthenticPixelsCache(Image *,ExceptionInfo *),
  WritePixelCacheIndexes(CacheInfo *,NexusInfo *magick_restrict,
    ExceptionInfo *),
  WritePixelCachePixels(CacheInfo *,NexusInfo *magick_restrict,
    ExceptionInfo *);

static PixelPacket
  *GetAuthenticPixelsCache(Image *,const ssize_t,const ssize_t,const size_t,
    const size_t,ExceptionInfo *),
  *QueueAuthenticPixelsCache(Image *,const ssize_t,const ssize_t,const size_t,
    const size_t,ExceptionInfo *),
  *SetPixelCacheNexusPixels(const CacheInfo *,const MapMode,
    const RectangleInfo *,const MagickBooleanType,NexusInfo *,ExceptionInfo *)
    magick_hot_spot;

#if defined(__cplusplus) || defined(c_plusplus)
}
#endif

/*
  Global declarations.
*/
static volatile MagickBooleanType
  instantiate_cache = MagickFalse;

static SemaphoreInfo
  *cache_semaphore = (SemaphoreInfo *) NULL;

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   A c q u i r e P i x e l C a c h e                                         %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  AcquirePixelCache() acquires a pixel cache.
%
%  The format of the AcquirePixelCache() method is:
%
%      Cache AcquirePixelCache(const size_t number_threads)
%
%  A description of each parameter follows:
%
%    o number_threads: the number of nexus threads.
%
*/
MagickExport Cache AcquirePixelCache(const size_t number_threads)
{
  CacheInfo
    *magick_restrict cache_info;

  char
    *synchronize;

  cache_info=(CacheInfo *) AcquireQuantumMemory(1,sizeof(*cache_info));
  if (cache_info == (CacheInfo *) NULL)
    ThrowFatalException(ResourceLimitFatalError,"MemoryAllocationFailed");
  (void) ResetMagickMemory(cache_info,0,sizeof(*cache_info));
  cache_info->type=UndefinedCache;
  cache_info->mode=IOMode;
  cache_info->colorspace=sRGBColorspace;
  cache_info->channels=4;
  cache_info->file=(-1);
  cache_info->id=GetMagickThreadId();
  cache_info->number_threads=number_threads;
  if (GetOpenMPMaximumThreads() > cache_info->number_threads)
    cache_info->number_threads=GetOpenMPMaximumThreads();
  if (GetMagickResourceLimit(ThreadResource) > cache_info->number_threads)
    cache_info->number_threads=(size_t) GetMagickResourceLimit(ThreadResource);
  if (cache_info->number_threads == 0)
    cache_info->number_threads=1;
  cache_info->nexus_info=AcquirePixelCacheNexus(cache_info->number_threads);
  if (cache_info->nexus_info == (NexusInfo **) NULL)
    ThrowFatalException(ResourceLimitFatalError,"MemoryAllocationFailed");
  synchronize=GetEnvironmentValue("MAGICK_SYNCHRONIZE");
  if (synchronize != (const char *) NULL)
    {
      cache_info->synchronize=IsStringTrue(synchronize);
      synchronize=DestroyString(synchronize);
    }
  cache_info->semaphore=AllocateSemaphoreInfo();
  cache_info->reference_count=1;
  cache_info->file_semaphore=AllocateSemaphoreInfo();
  cache_info->debug=IsEventLogging();
  cache_info->signature=MagickSignature;
  return((Cache ) cache_info);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   A c q u i r e P i x e l C a c h e N e x u s                               %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  AcquirePixelCacheNexus() allocates the NexusInfo structure.
%
%  The format of the AcquirePixelCacheNexus method is:
%
%      NexusInfo **AcquirePixelCacheNexus(const size_t number_threads)
%
%  A description of each parameter follows:
%
%    o number_threads: the number of nexus threads.
%
*/
MagickExport NexusInfo **AcquirePixelCacheNexus(const size_t number_threads)
{
  NexusInfo
    **magick_restrict nexus_info;

  register ssize_t
    i;

  nexus_info=(NexusInfo **) MagickAssumeAligned(AcquireAlignedMemory(
    number_threads,sizeof(*nexus_info)));
  if (nexus_info == (NexusInfo **) NULL)
    ThrowFatalException(ResourceLimitFatalError,"MemoryAllocationFailed");
  nexus_info[0]=(NexusInfo *) AcquireQuantumMemory(number_threads,
    sizeof(**nexus_info));
  if (nexus_info[0] == (NexusInfo *) NULL)
    ThrowFatalException(ResourceLimitFatalError,"MemoryAllocationFailed");
  (void) ResetMagickMemory(nexus_info[0],0,number_threads*sizeof(**nexus_info));
  for (i=0; i < (ssize_t) number_threads; i++)
  {
    nexus_info[i]=(&nexus_info[0][i]);
    nexus_info[i]->signature=MagickSignature;
  }
  return(nexus_info);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   A c q u i r e P i x e l C a c h e P i x e l s                             %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  AcquirePixelCachePixels() returns the pixels associated with the specified
%  image.
%
%  The format of the AcquirePixelCachePixels() method is:
%
%      const void *AcquirePixelCachePixels(const Image *image,
%        MagickSizeType *length,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o length: the pixel cache length.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport const void *AcquirePixelCachePixels(const Image *image,
  MagickSizeType *length,ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(exception != (ExceptionInfo *) NULL);
  assert(exception->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  (void) exception;
  *length=0;
  if ((cache_info->type != MemoryCache) && (cache_info->type != MapCache))
    return((const void *) NULL);
  *length=cache_info->length;
  return((const void *) cache_info->pixels);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   C a c h e C o m p o n e n t G e n e s i s                                 %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  CacheComponentGenesis() instantiates the cache component.
%
%  The format of the CacheComponentGenesis method is:
%
%      MagickBooleanType CacheComponentGenesis(void)
%
*/
MagickExport MagickBooleanType CacheComponentGenesis(void)
{
  if (cache_semaphore == (SemaphoreInfo *) NULL)
    cache_semaphore=AllocateSemaphoreInfo();
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   C a c h e C o m p o n e n t T e r m i n u s                               %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  CacheComponentTerminus() destroys the cache component.
%
%  The format of the CacheComponentTerminus() method is:
%
%      CacheComponentTerminus(void)
%
*/
MagickExport void CacheComponentTerminus(void)
{
  if (cache_semaphore == (SemaphoreInfo *) NULL)
    ActivateSemaphoreInfo(&cache_semaphore);
  LockSemaphoreInfo(cache_semaphore);
  instantiate_cache=MagickFalse;
  UnlockSemaphoreInfo(cache_semaphore);
  DestroySemaphoreInfo(&cache_semaphore);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   C l i p P i x e l C a c h e N e x u s                                     %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  ClipPixelCacheNexus() clips the cache nexus as defined by the image clip
%  mask.  The method returns MagickTrue if the pixel region is clipped,
%  otherwise MagickFalse.
%
%  The format of the ClipPixelCacheNexus() method is:
%
%      MagickBooleanType ClipPixelCacheNexus(Image *image,NexusInfo *nexus_info,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o nexus_info: the cache nexus to clip.
%
%    o exception: return any errors or warnings in this structure.
%
*/
static MagickBooleanType ClipPixelCacheNexus(Image *image,
  NexusInfo *nexus_info,ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  MagickSizeType
    number_pixels;

  NexusInfo
    **magick_restrict clip_nexus,
    **magick_restrict image_nexus;

  register const PixelPacket
    *magick_restrict r;

  register IndexPacket
    *magick_restrict nexus_indexes,
    *magick_restrict indexes;

  register PixelPacket
    *magick_restrict p,
    *magick_restrict q;

  register ssize_t
    i;

  /*
    Apply clip mask.
  */
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  if ((image->clip_mask == (Image *) NULL) ||
      (image->storage_class == PseudoClass))
    return(MagickTrue);
  cache_info=(CacheInfo *) image->cache;
  if (cache_info == (Cache) NULL)
    return(MagickFalse);
  image_nexus=AcquirePixelCacheNexus(1);
  clip_nexus=AcquirePixelCacheNexus(1);
  if ((image_nexus == (NexusInfo **) NULL) ||
      (clip_nexus == (NexusInfo **) NULL))
    ThrowBinaryException(CacheError,"UnableToGetCacheNexus",image->filename);
  p=GetAuthenticPixelCacheNexus(image,nexus_info->region.x,nexus_info->region.y,
    nexus_info->region.width,nexus_info->region.height,image_nexus[0],
    exception);
  indexes=image_nexus[0]->indexes;
  q=nexus_info->pixels;
  nexus_indexes=nexus_info->indexes;
  r=GetVirtualPixelsFromNexus(image->clip_mask,MaskVirtualPixelMethod,
    nexus_info->region.x,nexus_info->region.y,nexus_info->region.width,
    nexus_info->region.height,clip_nexus[0],exception);
  number_pixels=(MagickSizeType) nexus_info->region.width*
    nexus_info->region.height;
  for (i=0; i < (ssize_t) number_pixels; i++)
  {
    if ((p == (PixelPacket *) NULL) || (r == (const PixelPacket *) NULL))
      break;
    if (GetPixelIntensity(image,r) > (QuantumRange/2.0))
      {
        SetPixelRed(q,GetPixelRed(p));
        SetPixelGreen(q,GetPixelGreen(p));
        SetPixelBlue(q,GetPixelBlue(p));
        SetPixelOpacity(q,GetPixelOpacity(p));
        if (cache_info->active_index_channel != MagickFalse)
          SetPixelIndex(nexus_indexes+i,GetPixelIndex(indexes+i));
      }
    p++;
    q++;
    r++;
  }
  clip_nexus=DestroyPixelCacheNexus(clip_nexus,1);
  image_nexus=DestroyPixelCacheNexus(image_nexus,1);
  if (i < (ssize_t) number_pixels)
    return(MagickFalse);
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   C l o n e P i x e l C a c h e                                             %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  ClonePixelCache() clones a pixel cache.
%
%  The format of the ClonePixelCache() method is:
%
%      Cache ClonePixelCache(const Cache cache)
%
%  A description of each parameter follows:
%
%    o cache: the pixel cache.
%
*/
MagickExport Cache ClonePixelCache(const Cache cache)
{
  CacheInfo
    *magick_restrict clone_info;

  const CacheInfo
    *magick_restrict cache_info;

  assert(cache != NULL);
  cache_info=(const CacheInfo *) cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
      cache_info->filename);
  clone_info=(CacheInfo *) AcquirePixelCache(cache_info->number_threads);
  if (clone_info == (Cache) NULL)
    return((Cache) NULL);
  clone_info->virtual_pixel_method=cache_info->virtual_pixel_method;
  return((Cache ) clone_info);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   C l o n e P i x e l C a c h e M e t h o d s                               %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  ClonePixelCacheMethods() clones the pixel cache methods from one cache to
%  another.
%
%  The format of the ClonePixelCacheMethods() method is:
%
%      void ClonePixelCacheMethods(Cache clone,const Cache cache)
%
%  A description of each parameter follows:
%
%    o clone: Specifies a pointer to a Cache structure.
%
%    o cache: the pixel cache.
%
*/
MagickExport void ClonePixelCacheMethods(Cache clone,const Cache cache)
{
  CacheInfo
    *magick_restrict cache_info,
    *magick_restrict source_info;

  assert(clone != (Cache) NULL);
  source_info=(CacheInfo *) clone;
  assert(source_info->signature == MagickSignature);
  if (source_info->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
      source_info->filename);
  assert(cache != (Cache) NULL);
  cache_info=(CacheInfo *) cache;
  assert(cache_info->signature == MagickSignature);
  source_info->methods=cache_info->methods;
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   C l o n e P i x e l C a c h e R e p o s i t o r y                         %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %
%  ClonePixelCacheRepository() clones the source pixel cache to the destination
%  cache.
%
%  The format of the ClonePixelCacheRepository() method is:
%
%      MagickBooleanType ClonePixelCacheRepository(CacheInfo *cache_info,
%        CacheInfo *source_info,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o cache_info: the pixel cache.
%
%    o source_info: the source pixel cache.
%
%    o exception: return any errors or warnings in this structure.
%
*/

static MagickBooleanType ClonePixelCacheOnDisk(
  CacheInfo *magick_restrict cache_info,CacheInfo *magick_restrict clone_info,
  ExceptionInfo *exception)
{
  MagickSizeType
    extent;

  size_t
    quantum;

  ssize_t
    count;

  struct stat
    file_stats;

  unsigned char
    *buffer;

  /*
    Clone pixel cache on disk with identical morphology.
  */
  if ((OpenPixelCacheOnDisk(cache_info,ReadMode) == MagickFalse) ||
      (OpenPixelCacheOnDisk(clone_info,IOMode) == MagickFalse))
    return(MagickFalse);
  quantum=(size_t) MagickMaxBufferExtent;
  if ((fstat(cache_info->file,&file_stats) == 0) && (file_stats.st_size > 0))
    quantum=(size_t) MagickMin(file_stats.st_size,MagickMaxBufferExtent);
  buffer=(unsigned char *) AcquireQuantumMemory(quantum,sizeof(*buffer));
  if (buffer == (unsigned char *) NULL)
    ThrowFatalException(ResourceLimitFatalError,"MemoryAllocationFailed");
  extent=0;
  while ((count=read(cache_info->file,buffer,quantum)) > 0)
  {
    ssize_t
      number_bytes;

    number_bytes=write(clone_info->file,buffer,(size_t) count);
    if (number_bytes != count)
      break;
    extent+=number_bytes;
  }
  buffer=(unsigned char *) RelinquishMagickMemory(buffer);
  if (extent != cache_info->length)
    return(MagickFalse);
  return(MagickTrue);
}

static MagickBooleanType ClonePixelCacheRepository(
  CacheInfo *magick_restrict clone_info,CacheInfo *magick_restrict cache_info,
  ExceptionInfo *exception)
{
#define MaxCacheThreads  2
#define cache_threads(source,destination) \
  num_threads(((source)->type == DiskCache) || \
    ((destination)->type == DiskCache) || (((source)->rows) < \
    (16*GetMagickResourceLimit(ThreadResource))) ? 1 : \
    GetMagickResourceLimit(ThreadResource) < MaxCacheThreads ? \
    GetMagickResourceLimit(ThreadResource) : MaxCacheThreads)

  MagickBooleanType
    status;

  NexusInfo
    **magick_restrict cache_nexus,
    **magick_restrict clone_nexus;

  size_t
    length;

  ssize_t
    y;

  assert(cache_info != (CacheInfo *) NULL);
  assert(clone_info != (CacheInfo *) NULL);
  assert(exception != (ExceptionInfo *) NULL);
  if (cache_info->type == PingCache)
    return(MagickTrue);
  if ((cache_info->columns == clone_info->columns) &&
      (cache_info->rows == clone_info->rows) &&
      (cache_info->active_index_channel == clone_info->active_index_channel))
    {
      /*
        Identical pixel cache morphology.
      */
      if (((cache_info->type == MemoryCache) ||
           (cache_info->type == MapCache)) &&
          ((clone_info->type == MemoryCache) ||
           (clone_info->type == MapCache)))
        {
          (void) memcpy(clone_info->pixels,cache_info->pixels,
            cache_info->columns*cache_info->rows*sizeof(*cache_info->pixels));
          if ((cache_info->active_index_channel != MagickFalse) &&
              (clone_info->active_index_channel != MagickFalse))
            (void) memcpy(clone_info->indexes,cache_info->indexes,
              cache_info->columns*cache_info->rows*
              sizeof(*cache_info->indexes));
          return(MagickTrue);
        }
      if ((cache_info->type == DiskCache) && (clone_info->type == DiskCache))
        return(ClonePixelCacheOnDisk(cache_info,clone_info,exception));
    }
  /*
    Mismatched pixel cache morphology.
  */
  cache_nexus=AcquirePixelCacheNexus(MaxCacheThreads);
  clone_nexus=AcquirePixelCacheNexus(MaxCacheThreads);
  if ((cache_nexus == (NexusInfo **) NULL) ||
      (clone_nexus == (NexusInfo **) NULL))
    ThrowFatalException(ResourceLimitFatalError,"MemoryAllocationFailed");
  length=(size_t) MagickMin(cache_info->columns,clone_info->columns)*
    sizeof(*cache_info->pixels);
  status=MagickTrue;
#if defined(MAGICKCORE_OPENMP_SUPPORT)
  #pragma omp parallel for schedule(static,4) shared(status) \
    cache_threads(cache_info,clone_info)
#endif
  for (y=0; y < (ssize_t) cache_info->rows; y++)
  {
    const int
      id = GetOpenMPThreadId();

    PixelPacket
      *pixels;

    RectangleInfo
      region;

    if (status == MagickFalse)
      continue;
    if (y == (ssize_t) clone_info->rows)
      continue;
    region.width=cache_info->columns;
    region.height=1;
    region.x=0;
    region.y=y;
    pixels=SetPixelCacheNexusPixels(cache_info,ReadMode,&region,MagickTrue,
      cache_nexus[id],exception);
    if (pixels == (PixelPacket *) NULL)
      continue;
    status=ReadPixelCachePixels(cache_info,cache_nexus[id],exception);
    if (status == MagickFalse)
      continue;
    region.width=clone_info->columns;
    pixels=SetPixelCacheNexusPixels(clone_info,WriteMode,&region,MagickTrue,
      clone_nexus[id],exception);
    if (pixels == (PixelPacket *) NULL)
      continue;
    (void) ResetMagickMemory(clone_nexus[id]->pixels,0,(size_t)
      clone_nexus[id]->length);
    (void) memcpy(clone_nexus[id]->pixels,cache_nexus[id]->pixels,length);
    status=WritePixelCachePixels(clone_info,clone_nexus[id],exception);
  }
  if ((cache_info->active_index_channel != MagickFalse) &&
      (clone_info->active_index_channel != MagickFalse))
    {
      /*
        Clone indexes.
      */
      length=(size_t) MagickMin(cache_info->columns,clone_info->columns)*
        sizeof(*cache_info->indexes);
#if defined(MAGICKCORE_OPENMP_SUPPORT)
      #pragma omp parallel for schedule(static,4) shared(status) \
        cache_threads(cache_info,clone_info)
#endif
      for (y=0; y < (ssize_t) cache_info->rows; y++)
      {
        const int
          id = GetOpenMPThreadId();

        PixelPacket
          *pixels;

        RectangleInfo
          region;

        if (status == MagickFalse)
          continue;
        if (y == (ssize_t) clone_info->rows)
          continue;
        region.width=cache_info->columns;
        region.height=1;
        region.x=0;
        region.y=y;
        pixels=SetPixelCacheNexusPixels(cache_info,ReadMode,&region,MagickTrue,
          cache_nexus[id],exception);
        if (pixels == (PixelPacket *) NULL)
          continue;
        status=ReadPixelCacheIndexes(cache_info,cache_nexus[id],exception);
        if (status == MagickFalse)
          continue;
        region.width=clone_info->columns;
        pixels=SetPixelCacheNexusPixels(clone_info,WriteMode,&region,MagickTrue,
          clone_nexus[id],exception);
        if (pixels == (PixelPacket *) NULL)
          continue;
        (void) memcpy(clone_nexus[id]->indexes,cache_nexus[id]->indexes,length);
        status=WritePixelCacheIndexes(clone_info,clone_nexus[id],exception);
      }
    }
  cache_nexus=DestroyPixelCacheNexus(cache_nexus,MaxCacheThreads);
  clone_nexus=DestroyPixelCacheNexus(clone_nexus,MaxCacheThreads);
  if (cache_info->debug != MagickFalse)
    {
      char
        message[MaxTextExtent];

      (void) FormatLocaleString(message,MaxTextExtent,"%s => %s",
        CommandOptionToMnemonic(MagickCacheOptions,(ssize_t) cache_info->type),
        CommandOptionToMnemonic(MagickCacheOptions,(ssize_t) clone_info->type));
      (void) LogMagickEvent(CacheEvent,GetMagickModule(),"%s",message);
    }
  return(status);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   D e s t r o y I m a g e P i x e l C a c h e                               %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  DestroyImagePixelCache() deallocates memory associated with the pixel cache.
%
%  The format of the DestroyImagePixelCache() method is:
%
%      void DestroyImagePixelCache(Image *image)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
*/
static void DestroyImagePixelCache(Image *image)
{
  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  if (image->cache == (void *) NULL)
    return;
  image->cache=DestroyPixelCache(image->cache);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   D e s t r o y I m a g e P i x e l s                                       %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  DestroyImagePixels() deallocates memory associated with the pixel cache.
%
%  The format of the DestroyImagePixels() method is:
%
%      void DestroyImagePixels(Image *image)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
*/
MagickExport void DestroyImagePixels(Image *image)
{
  CacheInfo
    *magick_restrict cache_info;

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->methods.destroy_pixel_handler != (DestroyPixelHandler) NULL)
    {
      cache_info->methods.destroy_pixel_handler(image);
      return;
    }
  image->cache=DestroyPixelCache(image->cache);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   D e s t r o y P i x e l C a c h e                                         %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  DestroyPixelCache() deallocates memory associated with the pixel cache.
%
%  The format of the DestroyPixelCache() method is:
%
%      Cache DestroyPixelCache(Cache cache)
%
%  A description of each parameter follows:
%
%    o cache: the pixel cache.
%
*/

static MagickBooleanType ClosePixelCacheOnDisk(CacheInfo *cache_info)
{
  int
    status;

  status=(-1);
  if (cache_info->file != -1)
    {
      status=close(cache_info->file);
      cache_info->file=(-1);
      RelinquishMagickResource(FileResource,1);
    }
  return(status == -1 ? MagickFalse : MagickTrue);
}

static inline void RelinquishPixelCachePixels(CacheInfo *cache_info)
{
  switch (cache_info->type)
  {
    case MemoryCache:
    {
      if (cache_info->mapped == MagickFalse)
        cache_info->pixels=(PixelPacket *) RelinquishAlignedMemory(
          cache_info->pixels);
      else
        {
          (void) UnmapBlob(cache_info->pixels,(size_t) cache_info->length);
          cache_info->pixels=(PixelPacket *) NULL;
        }
      RelinquishMagickResource(MemoryResource,cache_info->length);
      break;
    }
    case MapCache:
    {
      (void) UnmapBlob(cache_info->pixels,(size_t) cache_info->length);
      cache_info->pixels=(PixelPacket *) NULL;
      if (cache_info->mode != ReadMode)
        (void) RelinquishUniqueFileResource(cache_info->cache_filename);
      *cache_info->cache_filename='\0';
      RelinquishMagickResource(MapResource,cache_info->length);
    }
    case DiskCache:
    {
      if (cache_info->file != -1)
        (void) ClosePixelCacheOnDisk(cache_info);
      if (cache_info->mode != ReadMode)
        (void) RelinquishUniqueFileResource(cache_info->cache_filename);
      *cache_info->cache_filename='\0';
      RelinquishMagickResource(DiskResource,cache_info->length);
      break;
    }
    case DistributedCache:
    {
      *cache_info->cache_filename='\0';
      (void) RelinquishDistributePixelCache((DistributeCacheInfo *)
        cache_info->server_info);
      break;
    }
    default:
      break;
  }
  cache_info->type=UndefinedCache;
  cache_info->mapped=MagickFalse;
  cache_info->indexes=(IndexPacket *) NULL;
}

MagickExport Cache DestroyPixelCache(Cache cache)
{
  CacheInfo
    *magick_restrict cache_info;

  assert(cache != (Cache) NULL);
  cache_info=(CacheInfo *) cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
      cache_info->filename);
  LockSemaphoreInfo(cache_info->semaphore);
  cache_info->reference_count--;
  if (cache_info->reference_count != 0)
    {
      UnlockSemaphoreInfo(cache_info->semaphore);
      return((Cache) NULL);
    }
  UnlockSemaphoreInfo(cache_info->semaphore);
  if (cache_info->debug != MagickFalse)
    {
      char
        message[MaxTextExtent];

      (void) FormatLocaleString(message,MaxTextExtent,"destroy %s",
        cache_info->filename);
      (void) LogMagickEvent(CacheEvent,GetMagickModule(),"%s",message);
    }
  RelinquishPixelCachePixels(cache_info);
  if (cache_info->server_info != (DistributeCacheInfo *) NULL)
    cache_info->server_info=DestroyDistributeCacheInfo((DistributeCacheInfo *)
      cache_info->server_info);
  if (cache_info->nexus_info != (NexusInfo **) NULL)
    cache_info->nexus_info=DestroyPixelCacheNexus(cache_info->nexus_info,
      cache_info->number_threads);
  if (cache_info->random_info != (RandomInfo *) NULL)
    cache_info->random_info=DestroyRandomInfo(cache_info->random_info);
  if (cache_info->file_semaphore != (SemaphoreInfo *) NULL)
    DestroySemaphoreInfo(&cache_info->file_semaphore);
  if (cache_info->semaphore != (SemaphoreInfo *) NULL)
    DestroySemaphoreInfo(&cache_info->semaphore);
  cache_info->signature=(~MagickSignature);
  cache_info=(CacheInfo *) RelinquishMagickMemory(cache_info);
  cache=(Cache) NULL;
  return(cache);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   D e s t r o y P i x e l C a c h e N e x u s                               %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  DestroyPixelCacheNexus() destroys a pixel cache nexus.
%
%  The format of the DestroyPixelCacheNexus() method is:
%
%      NexusInfo **DestroyPixelCacheNexus(NexusInfo *nexus_info,
%        const size_t number_threads)
%
%  A description of each parameter follows:
%
%    o nexus_info: the nexus to destroy.
%
%    o number_threads: the number of nexus threads.
%
*/

static inline void RelinquishCacheNexusPixels(NexusInfo *nexus_info)
{
  if (nexus_info->mapped == MagickFalse)
    (void) RelinquishAlignedMemory(nexus_info->cache);
  else
    (void) UnmapBlob(nexus_info->cache,(size_t) nexus_info->length);
  nexus_info->cache=(PixelPacket *) NULL;
  nexus_info->pixels=(PixelPacket *) NULL;
  nexus_info->indexes=(IndexPacket *) NULL;
  nexus_info->length=0;
  nexus_info->mapped=MagickFalse;
}

MagickExport NexusInfo **DestroyPixelCacheNexus(NexusInfo **nexus_info,
  const size_t number_threads)
{
  register ssize_t
    i;

  assert(nexus_info != (NexusInfo **) NULL);
  for (i=0; i < (ssize_t) number_threads; i++)
  {
    if (nexus_info[i]->cache != (PixelPacket *) NULL)
      RelinquishCacheNexusPixels(nexus_info[i]);
    nexus_info[i]->signature=(~MagickSignature);
  }
  nexus_info[0]=(NexusInfo *) RelinquishMagickMemory(nexus_info[0]);
  nexus_info=(NexusInfo **) RelinquishAlignedMemory(nexus_info);
  return(nexus_info);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t A u t h e n t i c I n d e x e s F r o m C a c h e                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetAuthenticIndexesFromCache() returns the indexes associated with the last
%  call to QueueAuthenticPixelsCache() or GetAuthenticPixelsCache().
%
%  The format of the GetAuthenticIndexesFromCache() method is:
%
%      IndexPacket *GetAuthenticIndexesFromCache(const Image *image)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
*/
static IndexPacket *GetAuthenticIndexesFromCache(const Image *image)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  assert(id < (int) cache_info->number_threads);
  return(cache_info->nexus_info[id]->indexes);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   G e t A u t h e n t i c I n d e x Q u e u e                               %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetAuthenticIndexQueue() returns the authentic black channel or the colormap
%  indexes associated with the last call to QueueAuthenticPixels() or
%  GetVirtualPixels().  NULL is returned if the black channel or colormap
%  indexes are not available.
%
%  The format of the GetAuthenticIndexQueue() method is:
%
%      IndexPacket *GetAuthenticIndexQueue(const Image *image)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
*/
MagickExport IndexPacket *GetAuthenticIndexQueue(const Image *image)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->methods.get_authentic_indexes_from_handler !=
       (GetAuthenticIndexesFromHandler) NULL)
    return(cache_info->methods.get_authentic_indexes_from_handler(image));
  assert(id < (int) cache_info->number_threads);
  return(cache_info->nexus_info[id]->indexes);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t A u t h e n t i c P i x e l C a c h e N e x u s                     %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetAuthenticPixelCacheNexus() gets authentic pixels from the in-memory or
%  disk pixel cache as defined by the geometry parameters.   A pointer to the
%  pixels is returned if the pixels are transferred, otherwise a NULL is
%  returned.
%
%  The format of the GetAuthenticPixelCacheNexus() method is:
%
%      PixelPacket *GetAuthenticPixelCacheNexus(Image *image,const ssize_t x,
%        const ssize_t y,const size_t columns,const size_t rows,
%        NexusInfo *nexus_info,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o x,y,columns,rows:  These values define the perimeter of a region of
%      pixels.
%
%    o nexus_info: the cache nexus to return.
%
%    o exception: return any errors or warnings in this structure.
%
*/

MagickExport PixelPacket *GetAuthenticPixelCacheNexus(Image *image,
  const ssize_t x,const ssize_t y,const size_t columns,const size_t rows,
  NexusInfo *nexus_info,ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  PixelPacket
    *magick_restrict pixels;

  /*
    Transfer pixels from the cache.
  */
  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  pixels=QueueAuthenticPixelCacheNexus(image,x,y,columns,rows,MagickTrue,
    nexus_info,exception);
  if (pixels == (PixelPacket *) NULL)
    return((PixelPacket *) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  if (nexus_info->authentic_pixel_cache != MagickFalse)
    return(pixels);
  if (ReadPixelCachePixels(cache_info,nexus_info,exception) == MagickFalse)
    return((PixelPacket *) NULL);
  if (cache_info->active_index_channel != MagickFalse)
    if (ReadPixelCacheIndexes(cache_info,nexus_info,exception) == MagickFalse)
      return((PixelPacket *) NULL);
  return(pixels);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t A u t h e n t i c P i x e l s F r o m C a c h e                     %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetAuthenticPixelsFromCache() returns the pixels associated with the last
%  call to the QueueAuthenticPixelsCache() or GetAuthenticPixelsCache() methods.
%
%  The format of the GetAuthenticPixelsFromCache() method is:
%
%      PixelPacket *GetAuthenticPixelsFromCache(const Image image)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
*/
static PixelPacket *GetAuthenticPixelsFromCache(const Image *image)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  assert(id < (int) cache_info->number_threads);
  return(cache_info->nexus_info[id]->pixels);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   G e t A u t h e n t i c P i x e l Q u e u e                               %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetAuthenticPixelQueue() returns the authentic pixels associated with the
%  last call to QueueAuthenticPixels() or GetAuthenticPixels().
%
%  The format of the GetAuthenticPixelQueue() method is:
%
%      PixelPacket *GetAuthenticPixelQueue(const Image image)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
*/
MagickExport PixelPacket *GetAuthenticPixelQueue(const Image *image)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->methods.get_authentic_pixels_from_handler !=
       (GetAuthenticPixelsFromHandler) NULL)
    return(cache_info->methods.get_authentic_pixels_from_handler(image));
  assert(id < (int) cache_info->number_threads);
  return(cache_info->nexus_info[id]->pixels);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   G e t A u t h e n t i c P i x e l s                                       %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetAuthenticPixels() obtains a pixel region for read/write access. If the
%  region is successfully accessed, a pointer to a PixelPacket array
%  representing the region is returned, otherwise NULL is returned.
%
%  The returned pointer may point to a temporary working copy of the pixels
%  or it may point to the original pixels in memory. Performance is maximized
%  if the selected region is part of one row, or one or more full rows, since
%  then there is opportunity to access the pixels in-place (without a copy)
%  if the image is in memory, or in a memory-mapped file. The returned pointer
%  must *never* be deallocated by the user.
%
%  Pixels accessed via the returned pointer represent a simple array of type
%  PixelPacket. If the image type is CMYK or if the storage class is
%  PseduoClass, call GetAuthenticIndexQueue() after invoking
%  GetAuthenticPixels() to obtain the black color component or colormap indexes
%  (of type IndexPacket) corresponding to the region.  Once the PixelPacket
%  (and/or IndexPacket) array has been updated, the changes must be saved back
%  to the underlying image using SyncAuthenticPixels() or they may be lost.
%
%  The format of the GetAuthenticPixels() method is:
%
%      PixelPacket *GetAuthenticPixels(Image *image,const ssize_t x,
%        const ssize_t y,const size_t columns,const size_t rows,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o x,y,columns,rows:  These values define the perimeter of a region of
%      pixels.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport PixelPacket *GetAuthenticPixels(Image *image,const ssize_t x,
  const ssize_t y,const size_t columns,const size_t rows,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->methods.get_authentic_pixels_handler !=
       (GetAuthenticPixelsHandler) NULL)
    return(cache_info->methods.get_authentic_pixels_handler(image,x,y,columns,
      rows,exception));
  assert(id < (int) cache_info->number_threads);
  return(GetAuthenticPixelCacheNexus(image,x,y,columns,rows,
    cache_info->nexus_info[id],exception));
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t A u t h e n t i c P i x e l s C a c h e                             %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetAuthenticPixelsCache() gets pixels from the in-memory or disk pixel cache
%  as defined by the geometry parameters.   A pointer to the pixels is returned
%  if the pixels are transferred, otherwise a NULL is returned.
%
%  The format of the GetAuthenticPixelsCache() method is:
%
%      PixelPacket *GetAuthenticPixelsCache(Image *image,const ssize_t x,
%        const ssize_t y,const size_t columns,const size_t rows,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o x,y,columns,rows:  These values define the perimeter of a region of
%      pixels.
%
%    o exception: return any errors or warnings in this structure.
%
*/
static PixelPacket *GetAuthenticPixelsCache(Image *image,const ssize_t x,
  const ssize_t y,const size_t columns,const size_t rows,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  if (cache_info == (Cache) NULL)
    return((PixelPacket *) NULL);
  assert(cache_info->signature == MagickSignature);
  assert(id < (int) cache_info->number_threads);
  return(GetAuthenticPixelCacheNexus(image,x,y,columns,rows,
    cache_info->nexus_info[id],exception));
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t I m a g e E x t e n t                                               %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetImageExtent() returns the extent of the pixels associated with the
%  last call to QueueAuthenticPixels() or GetAuthenticPixels().
%
%  The format of the GetImageExtent() method is:
%
%      MagickSizeType GetImageExtent(const Image *image)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
*/
MagickExport MagickSizeType GetImageExtent(const Image *image)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  assert(id < (int) cache_info->number_threads);
  return(GetPixelCacheNexusExtent(cache_info,cache_info->nexus_info[id]));
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t I m a g e P i x e l C a c h e                                       %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetImagePixelCache() ensures that there is only a single reference to the
%  pixel cache to be modified, updating the provided cache pointer to point to
%  a clone of the original pixel cache if necessary.
%
%  The format of the GetImagePixelCache method is:
%
%      Cache GetImagePixelCache(Image *image,const MagickBooleanType clone,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o clone: any value other than MagickFalse clones the cache pixels.
%
%    o exception: return any errors or warnings in this structure.
%
*/

static inline MagickBooleanType ValidatePixelCacheMorphology(
  const Image *magick_restrict image)
{
  CacheInfo
    *magick_restrict cache_info;

  /*
    Does the image match the pixel cache morphology?
  */
  cache_info=(CacheInfo *) image->cache;
  if ((image->storage_class != cache_info->storage_class) ||
      (image->colorspace != cache_info->colorspace) ||
      (image->channels != cache_info->channels) ||
      (image->columns != cache_info->columns) ||
      (image->rows != cache_info->rows) ||
      (cache_info->nexus_info == (NexusInfo **) NULL))
    return(MagickFalse);
  return(MagickTrue);
}

static Cache GetImagePixelCache(Image *image,const MagickBooleanType clone,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  MagickBooleanType
    destroy,
    status;

  static MagickSizeType
    cpu_throttle = MagickResourceInfinity,
    cycles = 0,
    time_limit = 0;

  static time_t
    cache_timestamp = 0;

  status=MagickTrue;
  if (cpu_throttle == MagickResourceInfinity)
    cpu_throttle=GetMagickResourceLimit(ThrottleResource);
  if ((cpu_throttle != 0) && ((cycles++ % 32) == 0))
    MagickDelay(cpu_throttle);
  if (time_limit == 0)
    {
      /*
        Set the expire time in seconds.
      */
      time_limit=GetMagickResourceLimit(TimeResource);
      cache_timestamp=time((time_t *) NULL);
    }
  if ((time_limit != MagickResourceInfinity) &&
      ((MagickSizeType) (time((time_t *) NULL)-cache_timestamp) >= time_limit))
     {
#if defined(ECANCELED)
       errno=ECANCELED;
#endif
       ThrowFatalException(ResourceLimitFatalError,"TimeLimitExceeded");
     }
  LockSemaphoreInfo(image->semaphore);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  destroy=MagickFalse;
  if ((cache_info->reference_count > 1) || (cache_info->mode == ReadMode))
    {
      LockSemaphoreInfo(cache_info->semaphore);
      if ((cache_info->reference_count > 1) || (cache_info->mode == ReadMode))
        {
          CacheInfo
            *clone_info;

          Image
            clone_image;

          /*
            Clone pixel cache.
          */
          clone_image=(*image);
          clone_image.semaphore=AllocateSemaphoreInfo();
          clone_image.reference_count=1;
          clone_image.cache=ClonePixelCache(cache_info);
          clone_info=(CacheInfo *) clone_image.cache;
          status=OpenPixelCache(&clone_image,IOMode,exception);
          if (status != MagickFalse)
            {
              if (clone != MagickFalse)
                status=ClonePixelCacheRepository(clone_info,cache_info,
                  exception);
              if (status != MagickFalse)
                {
                  if (cache_info->reference_count == 1)
                    cache_info->nexus_info=(NexusInfo **) NULL;
                  destroy=MagickTrue;
                  image->cache=clone_image.cache;
                }
            }
          DestroySemaphoreInfo(&clone_image.semaphore);
        }
      UnlockSemaphoreInfo(cache_info->semaphore);
    }
  if (destroy != MagickFalse)
    cache_info=(CacheInfo *) DestroyPixelCache(cache_info);
  if (status != MagickFalse)
    {
      /*
        Ensure the image matches the pixel cache morphology.
      */
      image->type=UndefinedType;
      if (ValidatePixelCacheMorphology(image) == MagickFalse)
        {
          status=OpenPixelCache(image,IOMode,exception);
          cache_info=(CacheInfo *) image->cache;
          if (cache_info->type == DiskCache)
            (void) ClosePixelCacheOnDisk(cache_info);
        }
    }
  UnlockSemaphoreInfo(image->semaphore);
  if (status == MagickFalse)
    return((Cache) NULL);
  return(image->cache);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t I m a g e P i x e l C a c h e T y p e                               %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetImagePixelCacheType() returns the pixel cache type: UndefinedCache,
%  DiskCache, MapCache, MemoryCache, or PingCache.
%
%  The format of the GetImagePixelCacheType() method is:
%
%      CacheType GetImagePixelCacheType(const Image *image)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
*/

MagickExport CacheType GetPixelCacheType(const Image *image)
{
  return(GetImagePixelCacheType(image));
}

MagickExport CacheType GetImagePixelCacheType(const Image *image)
{
  CacheInfo
    *magick_restrict cache_info;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  return(cache_info->type);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   G e t O n e A u t h e n t i c P i x e l                                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetOneAuthenticPixel() returns a single pixel at the specified (x,y)
%  location.  The image background color is returned if an error occurs.
%
%  The format of the GetOneAuthenticPixel() method is:
%
%      MagickBooleanType GetOneAuthenticPixel(const Image image,const ssize_t x,
%        const ssize_t y,PixelPacket *pixel,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o x,y:  These values define the location of the pixel to return.
%
%    o pixel: return a pixel at the specified (x,y) location.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport MagickBooleanType GetOneAuthenticPixel(Image *image,
  const ssize_t x,const ssize_t y,PixelPacket *pixel,ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  PixelPacket
    *magick_restrict pixels;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  *pixel=image->background_color;
  if (cache_info->methods.get_one_authentic_pixel_from_handler !=
       (GetOneAuthenticPixelFromHandler) NULL)
    return(cache_info->methods.get_one_authentic_pixel_from_handler(image,x,y,
      pixel,exception));
  pixels=GetAuthenticPixelsCache(image,x,y,1UL,1UL,exception);
  if (pixels == (PixelPacket *) NULL)
    return(MagickFalse);
  *pixel=(*pixels);
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t O n e A u t h e n t i c P i x e l F r o m C a c h e                 %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetOneAuthenticPixelFromCache() returns a single pixel at the specified (x,y)
%  location.  The image background color is returned if an error occurs.
%
%  The format of the GetOneAuthenticPixelFromCache() method is:
%
%      MagickBooleanType GetOneAuthenticPixelFromCache(const Image image,
%        const ssize_t x,const ssize_t y,PixelPacket *pixel,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o x,y:  These values define the location of the pixel to return.
%
%    o pixel: return a pixel at the specified (x,y) location.
%
%    o exception: return any errors or warnings in this structure.
%
*/
static MagickBooleanType GetOneAuthenticPixelFromCache(Image *image,
  const ssize_t x,const ssize_t y,PixelPacket *pixel,ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  PixelPacket
    *magick_restrict pixels;

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  *pixel=image->background_color;
  assert(id < (int) cache_info->number_threads);
  pixels=GetAuthenticPixelCacheNexus(image,x,y,1UL,1UL,
    cache_info->nexus_info[id],exception);
  if (pixels == (PixelPacket *) NULL)
    return(MagickFalse);
  *pixel=(*pixels);
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   G e t O n e V i r t u a l M a g i c k P i x e l                           %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetOneVirtualMagickPixel() returns a single pixel at the specified (x,y)
%  location.  The image background color is returned if an error occurs.  If
%  you plan to modify the pixel, use GetOneAuthenticPixel() instead.
%
%  The format of the GetOneVirtualMagickPixel() method is:
%
%      MagickBooleanType GetOneVirtualMagickPixel(const Image image,
%        const ssize_t x,const ssize_t y,MagickPixelPacket *pixel,
%        ExceptionInfo exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o x,y:  these values define the location of the pixel to return.
%
%    o pixel: return a pixel at the specified (x,y) location.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport MagickBooleanType GetOneVirtualMagickPixel(const Image *image,
  const ssize_t x,const ssize_t y,MagickPixelPacket *pixel,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  register const IndexPacket
    *magick_restrict indexes;

  register const PixelPacket
    *magick_restrict pixels;

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  assert(id < (int) cache_info->number_threads);
  pixels=GetVirtualPixelsFromNexus(image,GetPixelCacheVirtualMethod(image),x,y,
    1UL,1UL,cache_info->nexus_info[id],exception);
  GetMagickPixelPacket(image,pixel);
  if (pixels == (const PixelPacket *) NULL)
    return(MagickFalse);
  indexes=GetVirtualIndexesFromNexus(cache_info,cache_info->nexus_info[id]);
  SetMagickPixelPacket(image,pixels,indexes,pixel);
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   G e t O n e V i r t u a l M e t h o d P i x e l                           %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetOneVirtualMethodPixel() returns a single pixel at the specified (x,y)
%  location as defined by specified pixel method.  The image background color
%  is returned if an error occurs.  If you plan to modify the pixel, use
%  GetOneAuthenticPixel() instead.
%
%  The format of the GetOneVirtualMethodPixel() method is:
%
%      MagickBooleanType GetOneVirtualMethodPixel(const Image image,
%        const VirtualPixelMethod virtual_pixel_method,const ssize_t x,
%        const ssize_t y,Pixelpacket *pixel,ExceptionInfo exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o virtual_pixel_method: the virtual pixel method.
%
%    o x,y:  These values define the location of the pixel to return.
%
%    o pixel: return a pixel at the specified (x,y) location.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport MagickBooleanType GetOneVirtualMethodPixel(const Image *image,
  const VirtualPixelMethod virtual_pixel_method,const ssize_t x,const ssize_t y,
  PixelPacket *pixel,ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  const PixelPacket
    *magick_restrict pixels;

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  *pixel=image->background_color;
  if (cache_info->methods.get_one_virtual_pixel_from_handler !=
       (GetOneVirtualPixelFromHandler) NULL)
    return(cache_info->methods.get_one_virtual_pixel_from_handler(image,
      virtual_pixel_method,x,y,pixel,exception));
  assert(id < (int) cache_info->number_threads);
  pixels=GetVirtualPixelsFromNexus(image,virtual_pixel_method,x,y,1UL,1UL,
    cache_info->nexus_info[id],exception);
  if (pixels == (const PixelPacket *) NULL)
    return(MagickFalse);
  *pixel=(*pixels);
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   G e t O n e V i r t u a l P i x e l                                       %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetOneVirtualPixel() returns a single virtual pixel at the specified
%  (x,y) location.  The image background color is returned if an error occurs.
%  If you plan to modify the pixel, use GetOneAuthenticPixel() instead.
%
%  The format of the GetOneVirtualPixel() method is:
%
%      MagickBooleanType GetOneVirtualPixel(const Image image,const ssize_t x,
%        const ssize_t y,PixelPacket *pixel,ExceptionInfo exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o x,y:  These values define the location of the pixel to return.
%
%    o pixel: return a pixel at the specified (x,y) location.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport MagickBooleanType GetOneVirtualPixel(const Image *image,
  const ssize_t x,const ssize_t y,PixelPacket *pixel,ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  const PixelPacket
    *magick_restrict pixels;

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  *pixel=image->background_color;
  if (cache_info->methods.get_one_virtual_pixel_from_handler !=
       (GetOneVirtualPixelFromHandler) NULL)
    return(cache_info->methods.get_one_virtual_pixel_from_handler(image,
      GetPixelCacheVirtualMethod(image),x,y,pixel,exception));
  assert(id < (int) cache_info->number_threads);
  pixels=GetVirtualPixelsFromNexus(image,GetPixelCacheVirtualMethod(image),x,y,
    1UL,1UL,cache_info->nexus_info[id],exception);
  if (pixels == (const PixelPacket *) NULL)
    return(MagickFalse);
  *pixel=(*pixels);
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t O n e V i r t u a l P i x e l F r o m C a c h e                     %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetOneVirtualPixelFromCache() returns a single virtual pixel at the
%  specified (x,y) location.  The image background color is returned if an
%  error occurs.
%
%  The format of the GetOneVirtualPixelFromCache() method is:
%
%      MagickBooleanType GetOneVirtualPixelFromCache(const Image image,
%        const VirtualPixelPacket method,const ssize_t x,const ssize_t y,
%        PixelPacket *pixel,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o virtual_pixel_method: the virtual pixel method.
%
%    o x,y:  These values define the location of the pixel to return.
%
%    o pixel: return a pixel at the specified (x,y) location.
%
%    o exception: return any errors or warnings in this structure.
%
*/
static MagickBooleanType GetOneVirtualPixelFromCache(const Image *image,
  const VirtualPixelMethod virtual_pixel_method,const ssize_t x,const ssize_t y,
  PixelPacket *pixel,ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  const PixelPacket
    *magick_restrict pixels;

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  assert(id < (int) cache_info->number_threads);
  *pixel=image->background_color;
  pixels=GetVirtualPixelsFromNexus(image,virtual_pixel_method,x,y,1UL,1UL,
    cache_info->nexus_info[id],exception);
  if (pixels == (const PixelPacket *) NULL)
    return(MagickFalse);
  *pixel=(*pixels);
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t P i x e l C a c h e C h a n n e l s                                 %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetPixelCacheChannels() returns the number of pixel channels associated
%  with this instance of the pixel cache.
%
%  The format of the GetPixelCacheChannels() method is:
%
%      size_t GetPixelCacheChannels(Cache cache)
%
%  A description of each parameter follows:
%
%    o type: GetPixelCacheChannels returns DirectClass or PseudoClass.
%
%    o cache: the pixel cache.
%
*/
MagickExport size_t GetPixelCacheChannels(const Cache cache)
{
  CacheInfo
    *magick_restrict cache_info;

  assert(cache != (Cache) NULL);
  cache_info=(CacheInfo *) cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
      cache_info->filename);
  return(cache_info->channels);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t P i x e l C a c h e C o l o r s p a c e                             %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetPixelCacheColorspace() returns the class type of the pixel cache.
%
%  The format of the GetPixelCacheColorspace() method is:
%
%      Colorspace GetPixelCacheColorspace(Cache cache)
%
%  A description of each parameter follows:
%
%    o cache: the pixel cache.
%
*/
MagickExport ColorspaceType GetPixelCacheColorspace(const Cache cache)
{
  CacheInfo
    *magick_restrict cache_info;

  assert(cache != (Cache) NULL);
  cache_info=(CacheInfo *) cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
      cache_info->filename);
  return(cache_info->colorspace);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t P i x e l C a c h e M e t h o d s                                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetPixelCacheMethods() initializes the CacheMethods structure.
%
%  The format of the GetPixelCacheMethods() method is:
%
%      void GetPixelCacheMethods(CacheMethods *cache_methods)
%
%  A description of each parameter follows:
%
%    o cache_methods: Specifies a pointer to a CacheMethods structure.
%
*/
MagickExport void GetPixelCacheMethods(CacheMethods *cache_methods)
{
  assert(cache_methods != (CacheMethods *) NULL);
  (void) ResetMagickMemory(cache_methods,0,sizeof(*cache_methods));
  cache_methods->get_virtual_pixel_handler=GetVirtualPixelCache;
  cache_methods->get_virtual_pixels_handler=GetVirtualPixelsCache;
  cache_methods->get_virtual_indexes_from_handler=GetVirtualIndexesFromCache;
  cache_methods->get_one_virtual_pixel_from_handler=GetOneVirtualPixelFromCache;
  cache_methods->get_authentic_pixels_handler=GetAuthenticPixelsCache;
  cache_methods->get_authentic_indexes_from_handler=
    GetAuthenticIndexesFromCache;
  cache_methods->get_authentic_pixels_from_handler=GetAuthenticPixelsFromCache;
  cache_methods->get_one_authentic_pixel_from_handler=
    GetOneAuthenticPixelFromCache;
  cache_methods->queue_authentic_pixels_handler=QueueAuthenticPixelsCache;
  cache_methods->sync_authentic_pixels_handler=SyncAuthenticPixelsCache;
  cache_methods->destroy_pixel_handler=DestroyImagePixelCache;
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t P i x e l C a c h e N e x u s E x t e n t                           %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetPixelCacheNexusExtent() returns the extent of the pixels associated with
%  the last call to SetPixelCacheNexusPixels() or GetPixelCacheNexusPixels().
%
%  The format of the GetPixelCacheNexusExtent() method is:
%
%      MagickSizeType GetPixelCacheNexusExtent(const Cache cache,
%        NexusInfo *nexus_info)
%
%  A description of each parameter follows:
%
%    o nexus_info: the nexus info.
%
*/
MagickExport MagickSizeType GetPixelCacheNexusExtent(const Cache cache,
  NexusInfo *nexus_info)
{
  CacheInfo
    *magick_restrict cache_info;

  MagickSizeType
    extent;

  assert(cache != NULL);
  cache_info=(CacheInfo *) cache;
  assert(cache_info->signature == MagickSignature);
  extent=(MagickSizeType) nexus_info->region.width*nexus_info->region.height;
  if (extent == 0)
    return((MagickSizeType) cache_info->columns*cache_info->rows);
  return(extent);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t P i x e l C a c h e P i x e l s                                     %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetPixelCachePixels() returns the pixels associated with the specified image.
%
%  The format of the GetPixelCachePixels() method is:
%
%      void *GetPixelCachePixels(Image *image,MagickSizeType *length,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o length: the pixel cache length.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport void *GetPixelCachePixels(Image *image,MagickSizeType *length,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  assert(length != (MagickSizeType *) NULL);
  assert(exception != (ExceptionInfo *) NULL);
  assert(exception->signature == MagickSignature);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  (void) exception;
  *length=0;
  if ((cache_info->type != MemoryCache) && (cache_info->type != MapCache))
    return((void *) NULL);
  *length=cache_info->length;
  return((void *) cache_info->pixels);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t P i x e l C a c h e S t o r a g e C l a s s                         %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetPixelCacheStorageClass() returns the class type of the pixel cache.
%
%  The format of the GetPixelCacheStorageClass() method is:
%
%      ClassType GetPixelCacheStorageClass(Cache cache)
%
%  A description of each parameter follows:
%
%    o type: GetPixelCacheStorageClass returns DirectClass or PseudoClass.
%
%    o cache: the pixel cache.
%
*/
MagickExport ClassType GetPixelCacheStorageClass(const Cache cache)
{
  CacheInfo
    *magick_restrict cache_info;

  assert(cache != (Cache) NULL);
  cache_info=(CacheInfo *) cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
      cache_info->filename);
  return(cache_info->storage_class);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t P i x e l C a c h e T i l e S i z e                                 %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetPixelCacheTileSize() returns the pixel cache tile size.
%
%  The format of the GetPixelCacheTileSize() method is:
%
%      void GetPixelCacheTileSize(const Image *image,size_t *width,
%        size_t *height)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o width: the optimize cache tile width in pixels.
%
%    o height: the optimize cache tile height in pixels.
%
*/
MagickExport void GetPixelCacheTileSize(const Image *image,size_t *width,
  size_t *height)
{
  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  *width=2048UL/sizeof(PixelPacket);
  if (GetImagePixelCacheType(image) == DiskCache)
    *width=8192UL/sizeof(PixelPacket);
  *height=(*width);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t P i x e l C a c h e V i r t u a l M e t h o d                       %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetPixelCacheVirtualMethod() gets the "virtual pixels" method for the
%  pixel cache.  A virtual pixel is any pixel access that is outside the
%  boundaries of the image cache.
%
%  The format of the GetPixelCacheVirtualMethod() method is:
%
%      VirtualPixelMethod GetPixelCacheVirtualMethod(const Image *image)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
*/
MagickExport VirtualPixelMethod GetPixelCacheVirtualMethod(const Image *image)
{
  CacheInfo
    *magick_restrict cache_info;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  return(cache_info->virtual_pixel_method);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t V i r t u a l I n d e x e s F r o m C a c h e                       %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetVirtualIndexesFromCache() returns the indexes associated with the last
%  call to QueueAuthenticPixelsCache() or GetVirtualPixelCache().
%
%  The format of the GetVirtualIndexesFromCache() method is:
%
%      IndexPacket *GetVirtualIndexesFromCache(const Image *image)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
*/
static const IndexPacket *GetVirtualIndexesFromCache(const Image *image)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  assert(id < (int) cache_info->number_threads);
  return(GetVirtualIndexesFromNexus(cache_info,cache_info->nexus_info[id]));
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t V i r t u a l I n d e x e s F r o m N e x u s                       %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetVirtualIndexesFromNexus() returns the indexes associated with the
%  specified cache nexus.
%
%  The format of the GetVirtualIndexesFromNexus() method is:
%
%      const IndexPacket *GetVirtualIndexesFromNexus(const Cache cache,
%        NexusInfo *nexus_info)
%
%  A description of each parameter follows:
%
%    o cache: the pixel cache.
%
%    o nexus_info: the cache nexus to return the colormap indexes.
%
*/
MagickExport const IndexPacket *GetVirtualIndexesFromNexus(const Cache cache,
  NexusInfo *nexus_info)
{
  CacheInfo
    *magick_restrict cache_info;

  assert(cache != (Cache) NULL);
  cache_info=(CacheInfo *) cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->storage_class == UndefinedClass)
    return((IndexPacket *) NULL);
  return(nexus_info->indexes);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   G e t V i r t u a l I n d e x Q u e u e                                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetVirtualIndexQueue() returns the virtual black channel or the
%  colormap indexes associated with the last call to QueueAuthenticPixels() or
%  GetVirtualPixels().  NULL is returned if the black channel or colormap
%  indexes are not available.
%
%  The format of the GetVirtualIndexQueue() method is:
%
%      const IndexPacket *GetVirtualIndexQueue(const Image *image)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
*/
MagickExport const IndexPacket *GetVirtualIndexQueue(const Image *image)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->methods.get_virtual_indexes_from_handler !=
       (GetVirtualIndexesFromHandler) NULL)
    return(cache_info->methods.get_virtual_indexes_from_handler(image));
  assert(id < (int) cache_info->number_threads);
  return(GetVirtualIndexesFromNexus(cache_info,cache_info->nexus_info[id]));
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t V i r t u a l P i x e l s F r o m N e x u s                         %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetVirtualPixelsFromNexus() gets virtual pixels from the in-memory or disk
%  pixel cache as defined by the geometry parameters.   A pointer to the pixels
%  is returned if the pixels are transferred, otherwise a NULL is returned.
%
%  The format of the GetVirtualPixelsFromNexus() method is:
%
%      PixelPacket *GetVirtualPixelsFromNexus(const Image *image,
%        const VirtualPixelMethod method,const ssize_t x,const ssize_t y,
%        const size_t columns,const size_t rows,NexusInfo *nexus_info,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o virtual_pixel_method: the virtual pixel method.
%
%    o x,y,columns,rows:  These values define the perimeter of a region of
%      pixels.
%
%    o nexus_info: the cache nexus to acquire.
%
%    o exception: return any errors or warnings in this structure.
%
*/

static ssize_t
  DitherMatrix[64] =
  {
     0,  48,  12,  60,   3,  51,  15,  63,
    32,  16,  44,  28,  35,  19,  47,  31,
     8,  56,   4,  52,  11,  59,   7,  55,
    40,  24,  36,  20,  43,  27,  39,  23,
     2,  50,  14,  62,   1,  49,  13,  61,
    34,  18,  46,  30,  33,  17,  45,  29,
    10,  58,   6,  54,   9,  57,   5,  53,
    42,  26,  38,  22,  41,  25,  37,  21
  };

static inline ssize_t DitherX(const ssize_t x,const size_t columns)
{
  ssize_t
    index;

  index=x+DitherMatrix[x & 0x07]-32L;
  if (index < 0L)
    return(0L);
  if (index >= (ssize_t) columns)
    return((ssize_t) columns-1L);
  return(index);
}

static inline ssize_t DitherY(const ssize_t y,const size_t rows)
{
  ssize_t
    index;

  index=y+DitherMatrix[y & 0x07]-32L;
  if (index < 0L)
    return(0L);
  if (index >= (ssize_t) rows)
    return((ssize_t) rows-1L);
  return(index);
}

static inline ssize_t EdgeX(const ssize_t x,const size_t columns)
{
  if (x < 0L)
    return(0L);
  if (x >= (ssize_t) columns)
    return((ssize_t) (columns-1));
  return(x);
}

static inline ssize_t EdgeY(const ssize_t y,const size_t rows)
{
  if (y < 0L)
    return(0L);
  if (y >= (ssize_t) rows)
    return((ssize_t) (rows-1));
  return(y);
}

static inline ssize_t RandomX(RandomInfo *random_info,const size_t columns)
{
  return((ssize_t) (columns*GetPseudoRandomValue(random_info)));
}

static inline ssize_t RandomY(RandomInfo *random_info,const size_t rows)
{
  return((ssize_t) (rows*GetPseudoRandomValue(random_info)));
}

/*
  VirtualPixelModulo() computes the remainder of dividing offset by extent.  It
  returns not only the quotient (tile the offset falls in) but also the positive
  remainer within that tile such that 0 <= remainder < extent.  This method is
  essentially a ldiv() using a floored modulo division rather than the normal
  default truncated modulo division.
*/
static inline MagickModulo VirtualPixelModulo(const ssize_t offset,
  const size_t extent)
{
  MagickModulo
    modulo;

  modulo.quotient=offset/(ssize_t) extent;
  if (offset < 0L)
    modulo.quotient--;
  modulo.remainder=offset-modulo.quotient*(ssize_t) extent;
  return(modulo);
}

MagickExport const PixelPacket *GetVirtualPixelsFromNexus(const Image *image,
  const VirtualPixelMethod virtual_pixel_method,const ssize_t x,const ssize_t y,
  const size_t columns,const size_t rows,NexusInfo *nexus_info,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  IndexPacket
    virtual_index;

  MagickOffsetType
    offset;

  MagickSizeType
    length,
    number_pixels;

  NexusInfo
    **magick_restrict virtual_nexus;

  PixelPacket
    *magick_restrict pixels,
    virtual_pixel;

  RectangleInfo
    region;

  register const IndexPacket
    *magick_restrict virtual_indexes;

  register const PixelPacket
    *magick_restrict p;

  register IndexPacket
    *magick_restrict indexes;

  register PixelPacket
    *magick_restrict q;

  register ssize_t
    u,
    v;

  /*
    Acquire pixels.
  */
  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->type == UndefinedCache)
    return((const PixelPacket *) NULL);
  region.x=x;
  region.y=y;
  region.width=columns;
  region.height=rows;
  pixels=SetPixelCacheNexusPixels(cache_info,ReadMode,&region,
    (image->clip_mask != (Image *) NULL) || (image->mask != (Image *) NULL) ?
    MagickTrue : MagickFalse,nexus_info,exception);
  if (pixels == (PixelPacket *) NULL)
    return((const PixelPacket *) NULL);
  offset=(MagickOffsetType) nexus_info->region.y*cache_info->columns+
    nexus_info->region.x;
  length=(MagickSizeType) (nexus_info->region.height-1L)*cache_info->columns+
    nexus_info->region.width-1L;
  number_pixels=(MagickSizeType) cache_info->columns*cache_info->rows;
  if ((offset >= 0) && (((MagickSizeType) offset+length) < number_pixels))
    if ((x >= 0) && ((ssize_t) (x+columns) <= (ssize_t) cache_info->columns) &&
        (y >= 0) && ((ssize_t) (y+rows) <= (ssize_t) cache_info->rows))
      {
        MagickBooleanType
          status;

        /*
          Pixel request is inside cache extents.
        */
        if (nexus_info->authentic_pixel_cache != MagickFalse)
          return(pixels);
        status=ReadPixelCachePixels(cache_info,nexus_info,exception);
        if (status == MagickFalse)
          return((const PixelPacket *) NULL);
        if ((cache_info->storage_class == PseudoClass) ||
            (cache_info->colorspace == CMYKColorspace))
          {
            status=ReadPixelCacheIndexes(cache_info,nexus_info,exception);
            if (status == MagickFalse)
              return((const PixelPacket *) NULL);
          }
        return(pixels);
      }
  /*
    Pixel request is outside cache extents.
  */
  q=pixels;
  indexes=nexus_info->indexes;
  virtual_nexus=AcquirePixelCacheNexus(1);
  if (virtual_nexus == (NexusInfo **) NULL)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),CacheError,
        "UnableToGetCacheNexus","`%s'",image->filename);
      return((const PixelPacket *) NULL);
    }
  switch (virtual_pixel_method)
  {
    case BlackVirtualPixelMethod:
    {
      SetPixelRed(&virtual_pixel,0);
      SetPixelGreen(&virtual_pixel,0);
      SetPixelBlue(&virtual_pixel,0);
      SetPixelOpacity(&virtual_pixel,OpaqueOpacity);
      break;
    }
    case GrayVirtualPixelMethod:
    {
      SetPixelRed(&virtual_pixel,QuantumRange/2);
      SetPixelGreen(&virtual_pixel,QuantumRange/2);
      SetPixelBlue(&virtual_pixel,QuantumRange/2);
      SetPixelOpacity(&virtual_pixel,OpaqueOpacity);
      break;
    }
    case TransparentVirtualPixelMethod:
    {
      SetPixelRed(&virtual_pixel,0);
      SetPixelGreen(&virtual_pixel,0);
      SetPixelBlue(&virtual_pixel,0);
      SetPixelOpacity(&virtual_pixel,TransparentOpacity);
      break;
    }
    case MaskVirtualPixelMethod:
    case WhiteVirtualPixelMethod:
    {
      SetPixelRed(&virtual_pixel,QuantumRange);
      SetPixelGreen(&virtual_pixel,QuantumRange);
      SetPixelBlue(&virtual_pixel,QuantumRange);
      SetPixelOpacity(&virtual_pixel,OpaqueOpacity);
      break;
    }
    default:
    {
      virtual_pixel=image->background_color;
      break;
    }
  }
  virtual_index=0;
  for (v=0; v < (ssize_t) rows; v++)
  {
    ssize_t
      y_offset;

    y_offset=y+v;
    if ((virtual_pixel_method == EdgeVirtualPixelMethod) ||
        (virtual_pixel_method == UndefinedVirtualPixelMethod))
      y_offset=EdgeY(y_offset,cache_info->rows);
    for (u=0; u < (ssize_t) columns; u+=length)
    {
      ssize_t
        x_offset;

      x_offset=x+u;
      length=(MagickSizeType) MagickMin(cache_info->columns-x_offset,columns-u);
      if (((x_offset < 0) || (x_offset >= (ssize_t) cache_info->columns)) ||
          ((y_offset < 0) || (y_offset >= (ssize_t) cache_info->rows)) ||
          (length == 0))
        {
          MagickModulo
            x_modulo,
            y_modulo;

          /*
            Transfer a single pixel.
          */
          length=(MagickSizeType) 1;
          switch (virtual_pixel_method)
          {
            case BackgroundVirtualPixelMethod:
            case ConstantVirtualPixelMethod:
            case BlackVirtualPixelMethod:
            case GrayVirtualPixelMethod:
            case TransparentVirtualPixelMethod:
            case MaskVirtualPixelMethod:
            case WhiteVirtualPixelMethod:
            {
              p=(&virtual_pixel);
              virtual_indexes=(&virtual_index);
              break;
            }
            case EdgeVirtualPixelMethod:
            default:
            {
              p=GetVirtualPixelsFromNexus(image,virtual_pixel_method,
                EdgeX(x_offset,cache_info->columns),
                EdgeY(y_offset,cache_info->rows),1UL,1UL,*virtual_nexus,
                exception);
              virtual_indexes=GetVirtualIndexesFromNexus(cache_info,
                *virtual_nexus);
              break;
            }
            case RandomVirtualPixelMethod:
            {
              if (cache_info->random_info == (RandomInfo *) NULL)
                cache_info->random_info=AcquireRandomInfo();
              p=GetVirtualPixelsFromNexus(image,virtual_pixel_method,
                RandomX(cache_info->random_info,cache_info->columns),
                RandomY(cache_info->random_info,cache_info->rows),1UL,1UL,
                *virtual_nexus,exception);
              virtual_indexes=GetVirtualIndexesFromNexus(cache_info,
                *virtual_nexus);
              break;
            }
            case DitherVirtualPixelMethod:
            {
              p=GetVirtualPixelsFromNexus(image,virtual_pixel_method,
                DitherX(x_offset,cache_info->columns),
                DitherY(y_offset,cache_info->rows),1UL,1UL,*virtual_nexus,
                exception);
              virtual_indexes=GetVirtualIndexesFromNexus(cache_info,
                *virtual_nexus);
              break;
            }
            case TileVirtualPixelMethod:
            {
              x_modulo=VirtualPixelModulo(x_offset,cache_info->columns);
              y_modulo=VirtualPixelModulo(y_offset,cache_info->rows);
              p=GetVirtualPixelsFromNexus(image,virtual_pixel_method,
                x_modulo.remainder,y_modulo.remainder,1UL,1UL,*virtual_nexus,
                exception);
              virtual_indexes=GetVirtualIndexesFromNexus(cache_info,
                *virtual_nexus);
              break;
            }
            case MirrorVirtualPixelMethod:
            {
              x_modulo=VirtualPixelModulo(x_offset,cache_info->columns);
              if ((x_modulo.quotient & 0x01) == 1L)
                x_modulo.remainder=(ssize_t) cache_info->columns-
                  x_modulo.remainder-1L;
              y_modulo=VirtualPixelModulo(y_offset,cache_info->rows);
              if ((y_modulo.quotient & 0x01) == 1L)
                y_modulo.remainder=(ssize_t) cache_info->rows-
                  y_modulo.remainder-1L;
              p=GetVirtualPixelsFromNexus(image,virtual_pixel_method,
                x_modulo.remainder,y_modulo.remainder,1UL,1UL,*virtual_nexus,
                exception);
              virtual_indexes=GetVirtualIndexesFromNexus(cache_info,
                *virtual_nexus);
              break;
            }
            case CheckerTileVirtualPixelMethod:
            {
              x_modulo=VirtualPixelModulo(x_offset,cache_info->columns);
              y_modulo=VirtualPixelModulo(y_offset,cache_info->rows);
              if (((x_modulo.quotient ^ y_modulo.quotient) & 0x01) != 0L)
                {
                  p=(&virtual_pixel);
                  virtual_indexes=(&virtual_index);
                  break;
                }
              p=GetVirtualPixelsFromNexus(image,virtual_pixel_method,
                x_modulo.remainder,y_modulo.remainder,1UL,1UL,*virtual_nexus,
                exception);
              virtual_indexes=GetVirtualIndexesFromNexus(cache_info,
                *virtual_nexus);
              break;
            }
            case HorizontalTileVirtualPixelMethod:
            {
              if ((y_offset < 0) || (y_offset >= (ssize_t) cache_info->rows))
                {
                  p=(&virtual_pixel);
                  virtual_indexes=(&virtual_index);
                  break;
                }
              x_modulo=VirtualPixelModulo(x_offset,cache_info->columns);
              y_modulo=VirtualPixelModulo(y_offset,cache_info->rows);
              p=GetVirtualPixelsFromNexus(image,virtual_pixel_method,
                x_modulo.remainder,y_modulo.remainder,1UL,1UL,*virtual_nexus,
                exception);
              virtual_indexes=GetVirtualIndexesFromNexus(cache_info,
                *virtual_nexus);
              break;
            }
            case VerticalTileVirtualPixelMethod:
            {
              if ((x_offset < 0) || (x_offset >= (ssize_t) cache_info->columns))
                {
                  p=(&virtual_pixel);
                  virtual_indexes=(&virtual_index);
                  break;
                }
              x_modulo=VirtualPixelModulo(x_offset,cache_info->columns);
              y_modulo=VirtualPixelModulo(y_offset,cache_info->rows);
              p=GetVirtualPixelsFromNexus(image,virtual_pixel_method,
                x_modulo.remainder,y_modulo.remainder,1UL,1UL,*virtual_nexus,
                exception);
              virtual_indexes=GetVirtualIndexesFromNexus(cache_info,
                *virtual_nexus);
              break;
            }
            case HorizontalTileEdgeVirtualPixelMethod:
            {
              x_modulo=VirtualPixelModulo(x_offset,cache_info->columns);
              p=GetVirtualPixelsFromNexus(image,virtual_pixel_method,
                x_modulo.remainder,EdgeY(y_offset,cache_info->rows),1UL,1UL,
                *virtual_nexus,exception);
              virtual_indexes=GetVirtualIndexesFromNexus(cache_info,
                *virtual_nexus);
              break;
            }
            case VerticalTileEdgeVirtualPixelMethod:
            {
              y_modulo=VirtualPixelModulo(y_offset,cache_info->rows);
              p=GetVirtualPixelsFromNexus(image,virtual_pixel_method,
                EdgeX(x_offset,cache_info->columns),y_modulo.remainder,1UL,1UL,
                *virtual_nexus,exception);
              virtual_indexes=GetVirtualIndexesFromNexus(cache_info,
                *virtual_nexus);
              break;
            }
          }
          if (p == (const PixelPacket *) NULL)
            break;
          *q++=(*p);
          if ((indexes != (IndexPacket *) NULL) &&
              (virtual_indexes != (const IndexPacket *) NULL))
            *indexes++=(*virtual_indexes);
          continue;
        }
      /*
        Transfer a run of pixels.
      */
      p=GetVirtualPixelsFromNexus(image,virtual_pixel_method,x_offset,y_offset,
        (size_t) length,1UL,*virtual_nexus,exception);
      if (p == (const PixelPacket *) NULL)
        break;
      virtual_indexes=GetVirtualIndexesFromNexus(cache_info,*virtual_nexus);
      (void) memcpy(q,p,(size_t) length*sizeof(*p));
      q+=length;
      if ((indexes != (IndexPacket *) NULL) &&
          (virtual_indexes != (const IndexPacket *) NULL))
        {
          (void) memcpy(indexes,virtual_indexes,(size_t) length*
            sizeof(*virtual_indexes));
          indexes+=length;
        }
    }
  }
  virtual_nexus=DestroyPixelCacheNexus(virtual_nexus,1);
  return(pixels);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t V i r t u a l P i x e l C a c h e                                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetVirtualPixelCache() get virtual pixels from the in-memory or disk pixel
%  cache as defined by the geometry parameters.   A pointer to the pixels
%  is returned if the pixels are transferred, otherwise a NULL is returned.
%
%  The format of the GetVirtualPixelCache() method is:
%
%      const PixelPacket *GetVirtualPixelCache(const Image *image,
%        const VirtualPixelMethod virtual_pixel_method,const ssize_t x,
%        const ssize_t y,const size_t columns,const size_t rows,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o virtual_pixel_method: the virtual pixel method.
%
%    o x,y,columns,rows:  These values define the perimeter of a region of
%      pixels.
%
%    o exception: return any errors or warnings in this structure.
%
*/
static const PixelPacket *GetVirtualPixelCache(const Image *image,
  const VirtualPixelMethod virtual_pixel_method,const ssize_t x,const ssize_t y,
  const size_t columns,const size_t rows,ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  assert(id < (int) cache_info->number_threads);
  return(GetVirtualPixelsFromNexus(image,virtual_pixel_method,x,y,columns,rows,
    cache_info->nexus_info[id],exception));
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   G e t V i r t u a l P i x e l Q u e u e                                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetVirtualPixelQueue() returns the virtual pixels associated with the
%  last call to QueueAuthenticPixels() or GetVirtualPixels().
%
%  The format of the GetVirtualPixelQueue() method is:
%
%      const PixelPacket *GetVirtualPixelQueue(const Image image)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
*/
MagickExport const PixelPacket *GetVirtualPixelQueue(const Image *image)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->methods.get_virtual_pixels_handler !=
       (GetVirtualPixelsHandler) NULL)
    return(cache_info->methods.get_virtual_pixels_handler(image));
  assert(id < (int) cache_info->number_threads);
  return(GetVirtualPixelsNexus(cache_info,cache_info->nexus_info[id]));
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   G e t V i r t u a l P i x e l s                                           %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetVirtualPixels() returns an immutable pixel region. If the
%  region is successfully accessed, a pointer to it is returned, otherwise
%  NULL is returned.  The returned pointer may point to a temporary working
%  copy of the pixels or it may point to the original pixels in memory.
%  Performance is maximized if the selected region is part of one row, or one
%  or more full rows, since there is opportunity to access the pixels in-place
%  (without a copy) if the image is in memory, or in a memory-mapped file.  The
%  returned pointer must *never* be deallocated by the user.
%
%  Pixels accessed via the returned pointer represent a simple array of type
%  PixelPacket.  If the image type is CMYK or the storage class is PseudoClass,
%  call GetAuthenticIndexQueue() after invoking GetAuthenticPixels() to access
%  the black color component or to obtain the colormap indexes (of type
%  IndexPacket) corresponding to the region.
%
%  If you plan to modify the pixels, use GetAuthenticPixels() instead.
%
%  Note, the GetVirtualPixels() and GetAuthenticPixels() methods are not thread-
%  safe.  In a threaded environment, use GetCacheViewVirtualPixels() or
%  GetCacheViewAuthenticPixels() instead.
%
%  The format of the GetVirtualPixels() method is:
%
%      const PixelPacket *GetVirtualPixels(const Image *image,const ssize_t x,
%        const ssize_t y,const size_t columns,const size_t rows,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o x,y,columns,rows:  These values define the perimeter of a region of
%      pixels.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport const PixelPacket *GetVirtualPixels(const Image *image,
  const ssize_t x,const ssize_t y,const size_t columns,const size_t rows,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->methods.get_virtual_pixel_handler !=
       (GetVirtualPixelHandler) NULL)
    return(cache_info->methods.get_virtual_pixel_handler(image,
      GetPixelCacheVirtualMethod(image),x,y,columns,rows,exception));
  assert(id < (int) cache_info->number_threads);
  return(GetVirtualPixelsFromNexus(image,GetPixelCacheVirtualMethod(image),x,y,
    columns,rows,cache_info->nexus_info[id],exception));
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t V i r t u a l P i x e l s F r o m C a c h e                         %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetVirtualPixelsCache() returns the pixels associated with the last call
%  to QueueAuthenticPixelsCache() or GetVirtualPixelCache().
%
%  The format of the GetVirtualPixelsCache() method is:
%
%      PixelPacket *GetVirtualPixelsCache(const Image *image)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
*/
static const PixelPacket *GetVirtualPixelsCache(const Image *image)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  assert(id < (int) cache_info->number_threads);
  return(GetVirtualPixelsNexus(image->cache,cache_info->nexus_info[id]));
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   G e t V i r t u a l P i x e l s N e x u s                                 %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetVirtualPixelsNexus() returns the pixels associated with the specified
%  cache nexus.
%
%  The format of the GetVirtualPixelsNexus() method is:
%
%      const IndexPacket *GetVirtualPixelsNexus(const Cache cache,
%        NexusInfo *nexus_info)
%
%  A description of each parameter follows:
%
%    o cache: the pixel cache.
%
%    o nexus_info: the cache nexus to return the colormap pixels.
%
*/
MagickExport const PixelPacket *GetVirtualPixelsNexus(const Cache cache,
  NexusInfo *nexus_info)
{
  CacheInfo
    *magick_restrict cache_info;

  assert(cache != (Cache) NULL);
  cache_info=(CacheInfo *) cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->storage_class == UndefinedClass)
    return((PixelPacket *) NULL);
  return((const PixelPacket *) nexus_info->pixels);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   M a s k P i x e l C a c h e N e x u s                                     %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  MaskPixelCacheNexus() masks the cache nexus as defined by the image mask.
%  The method returns MagickTrue if the pixel region is masked, otherwise
%  MagickFalse.
%
%  The format of the MaskPixelCacheNexus() method is:
%
%      MagickBooleanType MaskPixelCacheNexus(Image *image,
%        NexusInfo *nexus_info,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o nexus_info: the cache nexus to clip.
%
%    o exception: return any errors or warnings in this structure.
%
*/

static inline void MagickPixelCompositeMask(const MagickPixelPacket *p,
  const MagickRealType alpha,const MagickPixelPacket *q,
  const MagickRealType beta,MagickPixelPacket *composite)
{
  double
    gamma;

  if (alpha == TransparentOpacity)
    {
      *composite=(*q);
      return;
    }
  gamma=1.0-QuantumScale*QuantumScale*alpha*beta;
  gamma=PerceptibleReciprocal(gamma);
  composite->red=gamma*MagickOver_(p->red,alpha,q->red,beta);
  composite->green=gamma*MagickOver_(p->green,alpha,q->green,beta);
  composite->blue=gamma*MagickOver_(p->blue,alpha,q->blue,beta);
  if ((p->colorspace == CMYKColorspace) && (q->colorspace == CMYKColorspace))
    composite->index=gamma*MagickOver_(p->index,alpha,q->index,beta);
}

static MagickBooleanType MaskPixelCacheNexus(Image *image,NexusInfo *nexus_info,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  MagickPixelPacket
    alpha,
    beta;

  MagickSizeType
    number_pixels;

  NexusInfo
    **magick_restrict clip_nexus,
    **magick_restrict image_nexus;

  register const PixelPacket
    *magick_restrict r;

  register IndexPacket
    *magick_restrict nexus_indexes,
    *magick_restrict indexes;

  register PixelPacket
    *magick_restrict p,
    *magick_restrict q;

  register ssize_t
    i;

  /*
    Apply clip mask.
  */
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  if ((image->mask == (Image *) NULL) || (image->storage_class == PseudoClass))
    return(MagickTrue);
  cache_info=(CacheInfo *) image->cache;
  if (cache_info == (Cache) NULL)
    return(MagickFalse);
  image_nexus=AcquirePixelCacheNexus(1);
  clip_nexus=AcquirePixelCacheNexus(1);
  if ((image_nexus == (NexusInfo **) NULL) ||
      (clip_nexus == (NexusInfo **) NULL))
    ThrowBinaryException(CacheError,"UnableToGetCacheNexus",image->filename);
  p=GetAuthenticPixelCacheNexus(image,nexus_info->region.x,
    nexus_info->region.y,nexus_info->region.width,nexus_info->region.height,
    image_nexus[0],exception);
  indexes=image_nexus[0]->indexes;
  q=nexus_info->pixels;
  nexus_indexes=nexus_info->indexes;
  r=GetVirtualPixelsFromNexus(image->mask,MaskVirtualPixelMethod,
    nexus_info->region.x,nexus_info->region.y,nexus_info->region.width,
    nexus_info->region.height,clip_nexus[0],&image->exception);
  GetMagickPixelPacket(image,&alpha);
  GetMagickPixelPacket(image,&beta);
  number_pixels=(MagickSizeType) nexus_info->region.width*
    nexus_info->region.height;
  for (i=0; i < (ssize_t) number_pixels; i++)
  {
    if ((p == (PixelPacket *) NULL) || (r == (const PixelPacket *) NULL))
      break;
    SetMagickPixelPacket(image,p,indexes+i,&alpha);
    SetMagickPixelPacket(image,q,nexus_indexes+i,&beta);
    MagickPixelCompositeMask(&beta,GetPixelIntensity(image,r),&alpha,
      alpha.opacity,&beta);
    SetPixelRed(q,ClampToQuantum(beta.red));
    SetPixelGreen(q,ClampToQuantum(beta.green));
    SetPixelBlue(q,ClampToQuantum(beta.blue));
    SetPixelOpacity(q,ClampToQuantum(beta.opacity));
    if (cache_info->active_index_channel != MagickFalse)
      SetPixelIndex(nexus_indexes+i,GetPixelIndex(indexes+i));
    p++;
    q++;
    r++;
  }
  clip_nexus=DestroyPixelCacheNexus(clip_nexus,1);
  image_nexus=DestroyPixelCacheNexus(image_nexus,1);
  if (i < (ssize_t) number_pixels)
    return(MagickFalse);
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   O p e n P i x e l C a c h e                                               %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  OpenPixelCache() allocates the pixel cache.  This includes defining the cache
%  dimensions, allocating space for the image pixels and optionally the
%  colormap indexes, and memory mapping the cache if it is disk based.  The
%  cache nexus array is initialized as well.
%
%  The format of the OpenPixelCache() method is:
%
%      MagickBooleanType OpenPixelCache(Image *image,const MapMode mode,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o mode: ReadMode, WriteMode, or IOMode.
%
%    o exception: return any errors or warnings in this structure.
%
*/

static inline void AllocatePixelCachePixels(CacheInfo *cache_info)
{
  cache_info->mapped=MagickFalse;
  cache_info->pixels=(PixelPacket *) MagickAssumeAligned(
    AcquireAlignedMemory(1,(size_t) cache_info->length));
  if (cache_info->pixels == (PixelPacket *) NULL)
    {
      cache_info->mapped=MagickTrue;
      cache_info->pixels=(PixelPacket *) MapBlob(-1,IOMode,0,(size_t)
        cache_info->length);
    }
}

#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif

#if defined(SIGBUS)
static void CacheSignalHandler(int status)
{
  ThrowFatalException(CacheFatalError,"UnableToExtendPixelCache");
}
#endif

#if defined(__cplusplus) || defined(c_plusplus)
}
#endif

static MagickBooleanType OpenPixelCacheOnDisk(CacheInfo *cache_info,
  const MapMode mode)
{
  int
    file;

  /*
    Open pixel cache on disk.
  */
  if ((cache_info->file != -1) && (cache_info->mode == mode))
    return(MagickTrue);  /* cache already open and in the proper mode */
  if (*cache_info->cache_filename == '\0')
    file=AcquireUniqueFileResource(cache_info->cache_filename);
  else
    switch (mode)
    {
      case ReadMode:
      {
        file=open_utf8(cache_info->cache_filename,O_RDONLY | O_BINARY,0);
        break;
      }
      case WriteMode:
      {
        file=open_utf8(cache_info->cache_filename,O_WRONLY | O_CREAT |
          O_BINARY | O_EXCL,S_MODE);
        if (file == -1)
          file=open_utf8(cache_info->cache_filename,O_WRONLY | O_BINARY,S_MODE);
        break;
      }
      case IOMode:
      default:
      {
        file=open_utf8(cache_info->cache_filename,O_RDWR | O_CREAT | O_BINARY |
          O_EXCL,S_MODE);
        if (file == -1)
          file=open_utf8(cache_info->cache_filename,O_RDWR | O_BINARY,S_MODE);
        break;
      }
    }
  if (file == -1)
    return(MagickFalse);
  (void) AcquireMagickResource(FileResource,1);
  if (cache_info->file != -1)
    (void) ClosePixelCacheOnDisk(cache_info);
  cache_info->file=file;
  cache_info->mode=mode;
  return(MagickTrue);
}

static inline MagickOffsetType WritePixelCacheRegion(
  const CacheInfo *magick_restrict cache_info,const MagickOffsetType offset,
  const MagickSizeType length,const unsigned char *magick_restrict buffer)
{
  register MagickOffsetType
    i;

  ssize_t
    count;

#if !defined(MAGICKCORE_HAVE_PWRITE)
  if (lseek(cache_info->file,offset,SEEK_SET) < 0)
    return((MagickOffsetType) -1);
#endif
  count=0;
  for (i=0; i < (MagickOffsetType) length; i+=count)
  {
#if !defined(MAGICKCORE_HAVE_PWRITE)
    count=write(cache_info->file,buffer+i,(size_t) MagickMin(length-i,(size_t)
      SSIZE_MAX));
#else
    count=pwrite(cache_info->file,buffer+i,(size_t) MagickMin(length-i,(size_t)
      SSIZE_MAX),(off_t) (offset+i));
#endif
    if (count <= 0)
      {
        count=0;
        if (errno != EINTR)
          break;
      }
  }
  return(i);
}

static MagickBooleanType SetPixelCacheExtent(Image *image,MagickSizeType length)
{
  CacheInfo
    *magick_restrict cache_info;

  MagickOffsetType
    count,
    extent,
    offset;

  cache_info=(CacheInfo *) image->cache;
  if (image->debug != MagickFalse)
    {
      char
        format[MaxTextExtent],
        message[MaxTextExtent];

      (void) FormatMagickSize(length,MagickFalse,format);
      (void) FormatLocaleString(message,MaxTextExtent,
        "extend %s (%s[%d], disk, %s)",cache_info->filename,
        cache_info->cache_filename,cache_info->file,format);
      (void) LogMagickEvent(CacheEvent,GetMagickModule(),"%s",message);
    }
  offset=(MagickOffsetType) lseek(cache_info->file,0,SEEK_END);
  if (offset < 0)
    return(MagickFalse);
  if ((MagickSizeType) offset >= length)
    count=(MagickOffsetType) 1;
  else
    {
      extent=(MagickOffsetType) length-1;
      count=WritePixelCacheRegion(cache_info,extent,1,(const unsigned char *)
        "");
#if defined(MAGICKCORE_HAVE_POSIX_FALLOCATE)
      if (cache_info->synchronize != MagickFalse)
        (void) posix_fallocate(cache_info->file,offset+1,extent-offset);
#endif
#if defined(SIGBUS)
      (void) signal(SIGBUS,CacheSignalHandler);
#endif
    }
  offset=(MagickOffsetType) lseek(cache_info->file,0,SEEK_SET);
  if (offset < 0)
    return(MagickFalse);
  return(count != (MagickOffsetType) 1 ? MagickFalse : MagickTrue);
}

static MagickBooleanType OpenPixelCache(Image *image,const MapMode mode,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info,
    source_info;

  char
    format[MaxTextExtent],
    message[MaxTextExtent];

  const char
    *type;

  MagickSizeType
    length,
    number_pixels;

  MagickStatusType
    status;

  size_t
    columns,
    packet_size;

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  if ((image->columns == 0) || (image->rows == 0))
    ThrowBinaryException(CacheError,"NoPixelsDefinedInCache",image->filename);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  if ((AcquireMagickResource(WidthResource,image->columns) == MagickFalse) ||
      (AcquireMagickResource(HeightResource,image->rows) == MagickFalse))
    ThrowBinaryException(ResourceLimitError,"PixelCacheAllocationFailed",
      image->filename);
  source_info=(*cache_info);
  source_info.file=(-1);
  (void) FormatLocaleString(cache_info->filename,MaxTextExtent,"%s[%.20g]",
    image->filename,(double) GetImageIndexInList(image));
  cache_info->mode=mode;
  cache_info->rows=image->rows;
  cache_info->columns=image->columns;
  cache_info->channels=image->channels;
  cache_info->active_index_channel=((image->storage_class == PseudoClass) ||
    (image->colorspace == CMYKColorspace)) ? MagickTrue : MagickFalse;
  number_pixels=(MagickSizeType) cache_info->columns*cache_info->rows;
  packet_size=sizeof(PixelPacket);
  if (cache_info->active_index_channel != MagickFalse)
    packet_size+=sizeof(IndexPacket);
  length=number_pixels*packet_size;
  columns=(size_t) (length/cache_info->rows/packet_size);
  if ((cache_info->columns != columns) || ((ssize_t) cache_info->columns < 0) ||
      ((ssize_t) cache_info->rows < 0))
    ThrowBinaryException(ResourceLimitError,"PixelCacheAllocationFailed",
      image->filename);
  cache_info->length=length;
  if (image->ping != MagickFalse)
    {
      cache_info->storage_class=image->storage_class;
      cache_info->colorspace=image->colorspace;
      cache_info->type=PingCache;
      return(MagickTrue);
    }
  status=AcquireMagickResource(AreaResource,cache_info->length);
  length=number_pixels*(sizeof(PixelPacket)+sizeof(IndexPacket));
  if ((status != MagickFalse) && (length == (MagickSizeType) ((size_t) length)))
    {
      status=AcquireMagickResource(MemoryResource,cache_info->length);
      if (((cache_info->type == UndefinedCache) && (status != MagickFalse)) ||
          (cache_info->type == MemoryCache))
        {
          AllocatePixelCachePixels(cache_info);
          if (cache_info->pixels == (PixelPacket *) NULL)
            cache_info->pixels=source_info.pixels;
          else
            {
              /*
                Create memory pixel cache.
              */
              cache_info->colorspace=image->colorspace;
              cache_info->type=MemoryCache;
              cache_info->indexes=(IndexPacket *) NULL;
              if (cache_info->active_index_channel != MagickFalse)
                cache_info->indexes=(IndexPacket *) (cache_info->pixels+
                  number_pixels);
              if ((source_info.storage_class != UndefinedClass) &&
                  (mode != ReadMode))
                {
                  status&=ClonePixelCacheRepository(cache_info,&source_info,
                    exception);
                  RelinquishPixelCachePixels(&source_info);
                }
              if (image->debug != MagickFalse)
                {
                  (void) FormatMagickSize(cache_info->length,MagickTrue,format);
                  type=CommandOptionToMnemonic(MagickCacheOptions,(ssize_t)
                    cache_info->type);
                  (void) FormatLocaleString(message,MaxTextExtent,
                    "open %s (%s %s, %.20gx%.20g %s)",cache_info->filename,
                    cache_info->mapped != MagickFalse ? "Anonymous" : "Heap",
                    type,(double) cache_info->columns,(double) cache_info->rows,
                    format);
                  (void) LogMagickEvent(CacheEvent,GetMagickModule(),"%s",
                    message);
                }
              cache_info->storage_class=image->storage_class;
              return(MagickTrue);
            }
        }
      RelinquishMagickResource(MemoryResource,cache_info->length);
    }
  /*
    Create pixel cache on disk.
  */
  status=AcquireMagickResource(DiskResource,cache_info->length);
  if ((status == MagickFalse) || (cache_info->type == DistributedCache))
    {
      DistributeCacheInfo
        *server_info;

      if (cache_info->type == DistributedCache)
        RelinquishMagickResource(DiskResource,cache_info->length);
      server_info=AcquireDistributeCacheInfo(exception);
      if (server_info != (DistributeCacheInfo *) NULL)
        {
          status=OpenDistributePixelCache(server_info,image);
          if (status == MagickFalse)
            {
              ThrowFileException(exception,CacheError,"UnableToOpenPixelCache",
                GetDistributeCacheHostname(server_info));
              server_info=DestroyDistributeCacheInfo(server_info);
            }
          else
            {
              /*
                Create a distributed pixel cache.
              */
              cache_info->type=DistributedCache;
              cache_info->storage_class=image->storage_class;
              cache_info->colorspace=image->colorspace;
              cache_info->server_info=server_info;
              (void) FormatLocaleString(cache_info->cache_filename,
                MaxTextExtent,"%s:%d",GetDistributeCacheHostname(
                (DistributeCacheInfo *) cache_info->server_info),
                GetDistributeCachePort((DistributeCacheInfo *)
                cache_info->server_info));
              if ((source_info.storage_class != UndefinedClass) &&
                  (mode != ReadMode))
                {
                  status=ClonePixelCacheRepository(cache_info,&source_info,
                    exception);
                  RelinquishPixelCachePixels(&source_info);
                }
              if (image->debug != MagickFalse)
                {
                  (void) FormatMagickSize(cache_info->length,MagickFalse,
                    format);
                  type=CommandOptionToMnemonic(MagickCacheOptions,(ssize_t)
                    cache_info->type);
                  (void) FormatLocaleString(message,MaxTextExtent,
                    "open %s (%s[%d], %s, %.20gx%.20g %s)",cache_info->filename,
                    cache_info->cache_filename,GetDistributeCacheFile(
                    (DistributeCacheInfo *) cache_info->server_info),type,
                    (double) cache_info->columns,(double) cache_info->rows,
                    format);
                  (void) LogMagickEvent(CacheEvent,GetMagickModule(),"%s",
                    message);
                }
              return(MagickTrue);
            }
        }
      RelinquishMagickResource(DiskResource,cache_info->length);
      (void) ThrowMagickException(exception,GetMagickModule(),CacheError,
        "CacheResourcesExhausted","`%s'",image->filename);
      return(MagickFalse);
    }
  if ((source_info.storage_class != UndefinedClass) && (mode != ReadMode))
    {
      (void) ClosePixelCacheOnDisk(cache_info);
      *cache_info->cache_filename='\0';
    }
  if (OpenPixelCacheOnDisk(cache_info,mode) == MagickFalse)
    {
      RelinquishMagickResource(DiskResource,cache_info->length);
      ThrowFileException(exception,CacheError,"UnableToOpenPixelCache",
        image->filename);
      return(MagickFalse);
    }
  status=SetPixelCacheExtent(image,(MagickSizeType) cache_info->offset+
    cache_info->length);
  if (status == MagickFalse)
    {
      ThrowFileException(exception,CacheError,"UnableToExtendCache",
        image->filename);
      return(MagickFalse);
    }
  cache_info->storage_class=image->storage_class;
  cache_info->colorspace=image->colorspace;
  length=number_pixels*(sizeof(PixelPacket)+sizeof(IndexPacket));
  if (length != (MagickSizeType) ((size_t) length))
    cache_info->type=DiskCache;
  else
    {
      status=AcquireMagickResource(MapResource,cache_info->length);
      if ((status == MagickFalse) && (cache_info->type != MapCache) &&
          (cache_info->type != MemoryCache))
        cache_info->type=DiskCache;
      else
        {
          cache_info->pixels=(PixelPacket *) MapBlob(cache_info->file,mode,
            cache_info->offset,(size_t) cache_info->length);
          if (cache_info->pixels == (PixelPacket *) NULL)
            {
              cache_info->pixels=source_info.pixels;
              cache_info->type=DiskCache;
            }
          else
            {
              /*
                Create file-backed memory-mapped pixel cache.
              */
              (void) ClosePixelCacheOnDisk(cache_info);
              cache_info->type=MapCache;
              cache_info->mapped=MagickTrue;
              cache_info->indexes=(IndexPacket *) NULL;
              if (cache_info->active_index_channel != MagickFalse)
                cache_info->indexes=(IndexPacket *) (cache_info->pixels+
                  number_pixels);
              if ((source_info.storage_class != UndefinedClass) &&
                  (mode != ReadMode))
                {
                  status=ClonePixelCacheRepository(cache_info,&source_info,
                    exception);
                  RelinquishPixelCachePixels(&source_info);
                }
              if (image->debug != MagickFalse)
                {
                  (void) FormatMagickSize(cache_info->length,MagickTrue,format);
                  type=CommandOptionToMnemonic(MagickCacheOptions,(ssize_t)
                    cache_info->type);
                  (void) FormatLocaleString(message,MaxTextExtent,
                    "open %s (%s[%d], %s, %.20gx%.20g %s)",
                    cache_info->filename,cache_info->cache_filename,
                    cache_info->file,type,(double) cache_info->columns,(double)
                    cache_info->rows,format);
                  (void) LogMagickEvent(CacheEvent,GetMagickModule(),"%s",
                    message);
                }
              return(MagickTrue);
            }
        }
      RelinquishMagickResource(MapResource,cache_info->length);
    }
  if ((source_info.storage_class != UndefinedClass) && (mode != ReadMode))
    {
      status=ClonePixelCacheRepository(cache_info,&source_info,exception);
      RelinquishPixelCachePixels(&source_info);
    }
  if (image->debug != MagickFalse)
    {
      (void) FormatMagickSize(cache_info->length,MagickFalse,format);
      type=CommandOptionToMnemonic(MagickCacheOptions,(ssize_t)
        cache_info->type);
      (void) FormatLocaleString(message,MaxTextExtent,
        "open %s (%s[%d], %s, %.20gx%.20g %s)",cache_info->filename,
        cache_info->cache_filename,cache_info->file,type,(double)
        cache_info->columns,(double) cache_info->rows,format);
      (void) LogMagickEvent(CacheEvent,GetMagickModule(),"%s",message);
    }
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   P e r s i s t P i x e l C a c h e                                         %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  PersistPixelCache() attaches to or initializes a persistent pixel cache.  A
%  persistent pixel cache is one that resides on disk and is not destroyed
%  when the program exits.
%
%  The format of the PersistPixelCache() method is:
%
%      MagickBooleanType PersistPixelCache(Image *image,const char *filename,
%        const MagickBooleanType attach,MagickOffsetType *offset,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o filename: the persistent pixel cache filename.
%
%    o attach: A value other than zero initializes the persistent pixel cache.
%
%    o initialize: A value other than zero initializes the persistent pixel
%      cache.
%
%    o offset: the offset in the persistent cache to store pixels.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport MagickBooleanType PersistPixelCache(Image *image,
  const char *filename,const MagickBooleanType attach,MagickOffsetType *offset,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info,
    *magick_restrict clone_info;

  Image
    clone_image;

  MagickBooleanType
    status;

  ssize_t
    page_size;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  assert(image->cache != (void *) NULL);
  assert(filename != (const char *) NULL);
  assert(offset != (MagickOffsetType *) NULL);
  page_size=GetMagickPageSize();
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  if (attach != MagickFalse)
    {
      /*
        Attach existing persistent pixel cache.
      */
      if (image->debug != MagickFalse)
        (void) LogMagickEvent(CacheEvent,GetMagickModule(),
          "attach persistent cache");
      (void) CopyMagickString(cache_info->cache_filename,filename,
        MaxTextExtent);
      cache_info->type=DiskCache;
      cache_info->offset=(*offset);
      if (OpenPixelCache(image,ReadMode,exception) == MagickFalse)
        return(MagickFalse);
      *offset+=cache_info->length+page_size-(cache_info->length % page_size);
      return(MagickTrue);
    }
  if ((cache_info->mode != ReadMode) && (cache_info->type != MemoryCache) &&
      (cache_info->reference_count == 1))
    {
      LockSemaphoreInfo(cache_info->semaphore);
      if ((cache_info->mode != ReadMode) && (cache_info->type != MemoryCache) &&
          (cache_info->reference_count == 1))
        {
          int
            status;

          /*
            Usurp existing persistent pixel cache.
          */
          status=rename_utf8(cache_info->cache_filename,filename);
          if (status == 0)
            {
              (void) CopyMagickString(cache_info->cache_filename,filename,
                MaxTextExtent);
              *offset+=cache_info->length+page_size-(cache_info->length %
                page_size);
              UnlockSemaphoreInfo(cache_info->semaphore);
              cache_info=(CacheInfo *) ReferencePixelCache(cache_info);
              if (image->debug != MagickFalse)
                (void) LogMagickEvent(CacheEvent,GetMagickModule(),
                  "Usurp resident persistent cache");
              return(MagickTrue);
            }
        }
      UnlockSemaphoreInfo(cache_info->semaphore);
    }
  /*
    Clone persistent pixel cache.
  */
  clone_image=(*image);
  clone_info=(CacheInfo *) clone_image.cache;
  image->cache=ClonePixelCache(cache_info);
  cache_info=(CacheInfo *) ReferencePixelCache(image->cache);
  (void) CopyMagickString(cache_info->cache_filename,filename,MaxTextExtent);
  cache_info->type=DiskCache;
  cache_info->offset=(*offset);
  cache_info=(CacheInfo *) image->cache;
  status=OpenPixelCache(image,IOMode,exception);
  if (status != MagickFalse)
    status=ClonePixelCacheRepository(cache_info,clone_info,&image->exception);
  *offset+=cache_info->length+page_size-(cache_info->length % page_size);
  clone_info=(CacheInfo *) DestroyPixelCache(clone_info);
  return(status);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   Q u e u e A u t h e n t i c P i x e l C a c h e N e x u s                 %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  QueueAuthenticPixelCacheNexus() allocates an region to store image pixels as
%  defined by the region rectangle and returns a pointer to the region.  This
%  region is subsequently transferred from the pixel cache with
%  SyncAuthenticPixelsCache().  A pointer to the pixels is returned if the
%  pixels are transferred, otherwise a NULL is returned.
%
%  The format of the QueueAuthenticPixelCacheNexus() method is:
%
%      PixelPacket *QueueAuthenticPixelCacheNexus(Image *image,const ssize_t x,
%        const ssize_t y,const size_t columns,const size_t rows,
%        const MagickBooleanType clone,NexusInfo *nexus_info,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o x,y,columns,rows:  These values define the perimeter of a region of
%      pixels.
%
%    o nexus_info: the cache nexus to set.
%
%    o clone: clone the pixel cache.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport PixelPacket *QueueAuthenticPixel(Image *image,const ssize_t x,
  const ssize_t y,const size_t columns,const size_t rows,
  const MagickBooleanType clone,NexusInfo *nexus_info,
  ExceptionInfo *exception)
{
  return(QueueAuthenticPixelCacheNexus(image,x,y,columns,rows,clone,nexus_info,
    exception));
}

MagickExport PixelPacket *QueueAuthenticPixelCacheNexus(Image *image,
  const ssize_t x,const ssize_t y,const size_t columns,const size_t rows,
  const MagickBooleanType clone,NexusInfo *nexus_info,ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  MagickOffsetType
    offset;

  MagickSizeType
    number_pixels;

  PixelPacket
    *magick_restrict pixels;

  RectangleInfo
    region;

  /*
    Validate pixel cache geometry.
  */
  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) GetImagePixelCache(image,clone,exception);
  if (cache_info == (Cache) NULL)
    return((PixelPacket *) NULL);
  assert(cache_info->signature == MagickSignature);
  if ((cache_info->columns == 0) || (cache_info->rows == 0) || (x < 0) ||
      (y < 0) || (x >= (ssize_t) cache_info->columns) ||
      (y >= (ssize_t) cache_info->rows))
    {
      (void) ThrowMagickException(exception,GetMagickModule(),CacheError,
        "PixelsAreNotAuthentic","`%s'",image->filename);
      return((PixelPacket *) NULL);
    }
  offset=(MagickOffsetType) y*cache_info->columns+x;
  if (offset < 0)
    return((PixelPacket *) NULL);
  number_pixels=(MagickSizeType) cache_info->columns*cache_info->rows;
  offset+=(MagickOffsetType) (rows-1)*cache_info->columns+columns-1;
  if ((MagickSizeType) offset >= number_pixels)
    return((PixelPacket *) NULL);
  /*
    Return pixel cache.
  */
  region.x=x;
  region.y=y;
  region.width=columns;
  region.height=rows;
  pixels=SetPixelCacheNexusPixels(cache_info,WriteMode,&region,
    (image->clip_mask != (Image *) NULL) || (image->mask != (Image *) NULL) ?
    MagickTrue : MagickFalse,nexus_info,exception);
  return(pixels);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   Q u e u e A u t h e n t i c P i x e l s C a c h e                         %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  QueueAuthenticPixelsCache() allocates an region to store image pixels as
%  defined by the region rectangle and returns a pointer to the region.  This
%  region is subsequently transferred from the pixel cache with
%  SyncAuthenticPixelsCache().  A pointer to the pixels is returned if the
%  pixels are transferred, otherwise a NULL is returned.
%
%  The format of the QueueAuthenticPixelsCache() method is:
%
%      PixelPacket *QueueAuthenticPixelsCache(Image *image,const ssize_t x,
%        const ssize_t y,const size_t columns,const size_t rows,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o x,y,columns,rows:  These values define the perimeter of a region of
%      pixels.
%
%    o exception: return any errors or warnings in this structure.
%
*/
static PixelPacket *QueueAuthenticPixelsCache(Image *image,const ssize_t x,
  const ssize_t y,const size_t columns,const size_t rows,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  assert(id < (int) cache_info->number_threads);
  return(QueueAuthenticPixelCacheNexus(image,x,y,columns,rows,MagickFalse,
    cache_info->nexus_info[id],exception));
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   Q u e u e A u t h e n t i c P i x e l s                                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  QueueAuthenticPixels() queues a mutable pixel region.  If the region is
%  successfully initialized a pointer to a PixelPacket array representing the
%  region is returned, otherwise NULL is returned.  The returned pointer may
%  point to a temporary working buffer for the pixels or it may point to the
%  final location of the pixels in memory.
%
%  Write-only access means that any existing pixel values corresponding to
%  the region are ignored.  This is useful if the initial image is being
%  created from scratch, or if the existing pixel values are to be
%  completely replaced without need to refer to their pre-existing values.
%  The application is free to read and write the pixel buffer returned by
%  QueueAuthenticPixels() any way it pleases. QueueAuthenticPixels() does not
%  initialize the pixel array values. Initializing pixel array values is the
%  application's responsibility.
%
%  Performance is maximized if the selected region is part of one row, or
%  one or more full rows, since then there is opportunity to access the
%  pixels in-place (without a copy) if the image is in memory, or in a
%  memory-mapped file. The returned pointer must *never* be deallocated
%  by the user.
%
%  Pixels accessed via the returned pointer represent a simple array of type
%  PixelPacket. If the image type is CMYK or the storage class is PseudoClass,
%  call GetAuthenticIndexQueue() after invoking GetAuthenticPixels() to obtain
%  the black color component or the colormap indexes (of type IndexPacket)
%  corresponding to the region.  Once the PixelPacket (and/or IndexPacket)
%  array has been updated, the changes must be saved back to the underlying
%  image using SyncAuthenticPixels() or they may be lost.
%
%  The format of the QueueAuthenticPixels() method is:
%
%      PixelPacket *QueueAuthenticPixels(Image *image,const ssize_t x,
%        const ssize_t y,const size_t columns,const size_t rows,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o x,y,columns,rows:  These values define the perimeter of a region of
%      pixels.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport PixelPacket *QueueAuthenticPixels(Image *image,const ssize_t x,
  const ssize_t y,const size_t columns,const size_t rows,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->methods.queue_authentic_pixels_handler !=
       (QueueAuthenticPixelsHandler) NULL)
    return(cache_info->methods.queue_authentic_pixels_handler(image,x,y,columns,
      rows,exception));
  assert(id < (int) cache_info->number_threads);
  return(QueueAuthenticPixelCacheNexus(image,x,y,columns,rows,MagickFalse,
    cache_info->nexus_info[id],exception));
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   R e a d P i x e l C a c h e I n d e x e s                                 %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  ReadPixelCacheIndexes() reads colormap indexes from the specified region of
%  the pixel cache.
%
%  The format of the ReadPixelCacheIndexes() method is:
%
%      MagickBooleanType ReadPixelCacheIndexes(CacheInfo *cache_info,
%        NexusInfo *nexus_info,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o cache_info: the pixel cache.
%
%    o nexus_info: the cache nexus to read the colormap indexes.
%
%    o exception: return any errors or warnings in this structure.
%
*/

static inline MagickOffsetType ReadPixelCacheRegion(
  const CacheInfo *magick_restrict cache_info,const MagickOffsetType offset,
  const MagickSizeType length,unsigned char *magick_restrict buffer)
{
  register MagickOffsetType
    i;

  ssize_t
    count;

#if !defined(MAGICKCORE_HAVE_PREAD)
  if (lseek(cache_info->file,offset,SEEK_SET) < 0)
    return((MagickOffsetType) -1);
#endif
  count=0;
  for (i=0; i < (MagickOffsetType) length; i+=count)
  {
#if !defined(MAGICKCORE_HAVE_PREAD)
    count=read(cache_info->file,buffer+i,(size_t) MagickMin(length-i,(size_t)
      SSIZE_MAX));
#else
    count=pread(cache_info->file,buffer+i,(size_t) MagickMin(length-i,(size_t)
      SSIZE_MAX),(off_t) (offset+i));
#endif
    if (count <= 0)
      {
        count=0;
        if (errno != EINTR)
          break;
      }
  }
  return(i);
}

static MagickBooleanType ReadPixelCacheIndexes(
  CacheInfo *magick_restrict cache_info,NexusInfo *magick_restrict nexus_info,
  ExceptionInfo *exception)
{
  MagickOffsetType
    count,
    offset;

  MagickSizeType
    extent,
    length;

  register IndexPacket
    *magick_restrict q;

  register ssize_t
    y;

  size_t
    rows;

  if (cache_info->active_index_channel == MagickFalse)
    return(MagickFalse);
  if (nexus_info->authentic_pixel_cache != MagickFalse)
    return(MagickTrue);
  offset=(MagickOffsetType) nexus_info->region.y*cache_info->columns+
    nexus_info->region.x;
  length=(MagickSizeType) nexus_info->region.width*sizeof(IndexPacket);
  rows=nexus_info->region.height;
  extent=length*rows;
  q=nexus_info->indexes;
  y=0;
  switch (cache_info->type)
  {
    case MemoryCache:
    case MapCache:
    {
      register IndexPacket
        *magick_restrict p;

      /*
        Read indexes from memory.
      */
      if ((cache_info->columns == nexus_info->region.width) &&
          (extent == (MagickSizeType) ((size_t) extent)))
        {
          length=extent;
          rows=1UL;
        }
      p=cache_info->indexes+offset;
      for (y=0; y < (ssize_t) rows; y++)
      {
        (void) memcpy(q,p,(size_t) length);
        p+=cache_info->columns;
        q+=nexus_info->region.width;
      }
      break;
    }
    case DiskCache:
    {
      /*
        Read indexes from disk.
      */
      LockSemaphoreInfo(cache_info->file_semaphore);
      if (OpenPixelCacheOnDisk(cache_info,IOMode) == MagickFalse)
        {
          ThrowFileException(exception,FileOpenError,"UnableToOpenFile",
            cache_info->cache_filename);
          UnlockSemaphoreInfo(cache_info->file_semaphore);
          return(MagickFalse);
        }
      if ((cache_info->columns == nexus_info->region.width) &&
          (extent <= MagickMaxBufferExtent))
        {
          length=extent;
          rows=1UL;
        }
      extent=(MagickSizeType) cache_info->columns*cache_info->rows;
      for (y=0; y < (ssize_t) rows; y++)
      {
        count=ReadPixelCacheRegion(cache_info,cache_info->offset+extent*
          sizeof(PixelPacket)+offset*sizeof(*q),length,(unsigned char *) q);
        if ((MagickSizeType) count < length)
          break;
        offset+=cache_info->columns;
        q+=nexus_info->region.width;
      }
      if (IsFileDescriptorLimitExceeded() != MagickFalse)
        (void) ClosePixelCacheOnDisk(cache_info);
      UnlockSemaphoreInfo(cache_info->file_semaphore);
      break;
    }
    case DistributedCache:
    {
      RectangleInfo
        region;

      /*
        Read indexes from distributed cache.
      */
      LockSemaphoreInfo(cache_info->file_semaphore);
      region=nexus_info->region;
      if ((cache_info->columns != nexus_info->region.width) ||
          (extent > MagickMaxBufferExtent))
        region.height=1UL;
      else
        {
          length=extent;
          rows=1UL;
        }
      for (y=0; y < (ssize_t) rows; y++)
      {
        count=ReadDistributePixelCacheIndexes((DistributeCacheInfo *)
          cache_info->server_info,&region,length,(unsigned char *) q);
        if (count != (MagickOffsetType) length)
          break;
        q+=nexus_info->region.width;
        region.y++;
      }
      UnlockSemaphoreInfo(cache_info->file_semaphore);
      break;
    }
    default:
      break;
  }
  if (y < (ssize_t) rows)
    {
      ThrowFileException(exception,CacheError,"UnableToReadPixelCache",
        cache_info->cache_filename);
      return(MagickFalse);
    }
  if ((cache_info->debug != MagickFalse) &&
      (CacheTick(nexus_info->region.y,cache_info->rows) != MagickFalse))
    (void) LogMagickEvent(CacheEvent,GetMagickModule(),
      "%s[%.20gx%.20g%+.20g%+.20g]",cache_info->filename,(double)
      nexus_info->region.width,(double) nexus_info->region.height,(double)
      nexus_info->region.x,(double) nexus_info->region.y);
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   R e a d P i x e l C a c h e P i x e l s                                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  ReadPixelCachePixels() reads pixels from the specified region of the pixel
%  cache.
%
%  The format of the ReadPixelCachePixels() method is:
%
%      MagickBooleanType ReadPixelCachePixels(CacheInfo *cache_info,
%        NexusInfo *nexus_info,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o cache_info: the pixel cache.
%
%    o nexus_info: the cache nexus to read the pixels.
%
%    o exception: return any errors or warnings in this structure.
%
*/
static MagickBooleanType ReadPixelCachePixels(
  CacheInfo *magick_restrict cache_info,NexusInfo *magick_restrict nexus_info,
  ExceptionInfo *exception)
{
  MagickOffsetType
    count,
    offset;

  MagickSizeType
    extent,
    length;

  register PixelPacket
    *magick_restrict q;

  register ssize_t
    y;

  size_t
    rows;

  if (nexus_info->authentic_pixel_cache != MagickFalse)
    return(MagickTrue);
  offset=(MagickOffsetType) nexus_info->region.y*cache_info->columns;
  if ((ssize_t) (offset/cache_info->columns) != nexus_info->region.y)
    return(MagickFalse);
  offset+=nexus_info->region.x;
  length=(MagickSizeType) nexus_info->region.width*sizeof(PixelPacket);
  if ((length/sizeof(PixelPacket)) != nexus_info->region.width)
    return(MagickFalse);
  rows=nexus_info->region.height;
  extent=length*rows;
  if ((extent == 0) || ((extent/length) != rows))
    return(MagickFalse);
  q=nexus_info->pixels;
  y=0;
  switch (cache_info->type)
  {
    case MemoryCache:
    case MapCache:
    {
      register PixelPacket
        *magick_restrict p;

      /*
        Read pixels from memory.
      */
      if ((cache_info->columns == nexus_info->region.width) &&
          (extent == (MagickSizeType) ((size_t) extent)))
        {
          length=extent;
          rows=1UL;
        }
      p=cache_info->pixels+offset;
      for (y=0; y < (ssize_t) rows; y++)
      {
        (void) memcpy(q,p,(size_t) length);
        p+=cache_info->columns;
        q+=nexus_info->region.width;
      }
      break;
    }
    case DiskCache:
    {
      /*
        Read pixels from disk.
      */
      LockSemaphoreInfo(cache_info->file_semaphore);
      if (OpenPixelCacheOnDisk(cache_info,IOMode) == MagickFalse)
        {
          ThrowFileException(exception,FileOpenError,"UnableToOpenFile",
            cache_info->cache_filename);
          UnlockSemaphoreInfo(cache_info->file_semaphore);
          return(MagickFalse);
        }
      if ((cache_info->columns == nexus_info->region.width) &&
          (extent <= MagickMaxBufferExtent))
        {
          length=extent;
          rows=1UL;
        }
      for (y=0; y < (ssize_t) rows; y++)
      {
        count=ReadPixelCacheRegion(cache_info,cache_info->offset+offset*
          sizeof(*q),length,(unsigned char *) q);
        if ((MagickSizeType) count < length)
          break;
        offset+=cache_info->columns;
        q+=nexus_info->region.width;
      }
      if (IsFileDescriptorLimitExceeded() != MagickFalse)
        (void) ClosePixelCacheOnDisk(cache_info);
      UnlockSemaphoreInfo(cache_info->file_semaphore);
      break;
    }
    case DistributedCache:
    {
      RectangleInfo
        region;

      /*
        Read pixels from distributed cache.
      */
      LockSemaphoreInfo(cache_info->file_semaphore);
      region=nexus_info->region;
      if ((cache_info->columns != nexus_info->region.width) ||
          (extent > MagickMaxBufferExtent))
        region.height=1UL;
      else
        {
          length=extent;
          rows=1UL;
        }
      for (y=0; y < (ssize_t) rows; y++)
      {
        count=ReadDistributePixelCachePixels((DistributeCacheInfo *)
          cache_info->server_info,&region,length,(unsigned char *) q);
        if (count != (MagickOffsetType) length)
          break;
        q+=nexus_info->region.width;
        region.y++;
      }
      UnlockSemaphoreInfo(cache_info->file_semaphore);
      break;
    }
    default:
      break;
  }
  if (y < (ssize_t) rows)
    {
      ThrowFileException(exception,CacheError,"UnableToReadPixelCache",
        cache_info->cache_filename);
      return(MagickFalse);
    }
  if ((cache_info->debug != MagickFalse) &&
      (CacheTick(nexus_info->region.y,cache_info->rows) != MagickFalse))
    (void) LogMagickEvent(CacheEvent,GetMagickModule(),
      "%s[%.20gx%.20g%+.20g%+.20g]",cache_info->filename,(double)
      nexus_info->region.width,(double) nexus_info->region.height,(double)
      nexus_info->region.x,(double) nexus_info->region.y);
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   R e f e r e n c e P i x e l C a c h e                                     %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  ReferencePixelCache() increments the reference count associated with the
%  pixel cache returning a pointer to the cache.
%
%  The format of the ReferencePixelCache method is:
%
%      Cache ReferencePixelCache(Cache cache_info)
%
%  A description of each parameter follows:
%
%    o cache_info: the pixel cache.
%
*/
MagickExport Cache ReferencePixelCache(Cache cache)
{
  CacheInfo
    *magick_restrict cache_info;

  assert(cache != (Cache *) NULL);
  cache_info=(CacheInfo *) cache;
  assert(cache_info->signature == MagickSignature);
  LockSemaphoreInfo(cache_info->semaphore);
  cache_info->reference_count++;
  UnlockSemaphoreInfo(cache_info->semaphore);
  return(cache_info);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   S e t P i x e l C a c h e M e t h o d s                                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  SetPixelCacheMethods() sets the image pixel methods to the specified ones.
%
%  The format of the SetPixelCacheMethods() method is:
%
%      SetPixelCacheMethods(Cache *,CacheMethods *cache_methods)
%
%  A description of each parameter follows:
%
%    o cache: the pixel cache.
%
%    o cache_methods: Specifies a pointer to a CacheMethods structure.
%
*/
MagickExport void SetPixelCacheMethods(Cache cache,CacheMethods *cache_methods)
{
  CacheInfo
    *magick_restrict cache_info;

  GetOneAuthenticPixelFromHandler
    get_one_authentic_pixel_from_handler;

  GetOneVirtualPixelFromHandler
    get_one_virtual_pixel_from_handler;

  /*
    Set cache pixel methods.
  */
  assert(cache != (Cache) NULL);
  assert(cache_methods != (CacheMethods *) NULL);
  cache_info=(CacheInfo *) cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
      cache_info->filename);
  if (cache_methods->get_virtual_pixel_handler != (GetVirtualPixelHandler) NULL)
    cache_info->methods.get_virtual_pixel_handler=
      cache_methods->get_virtual_pixel_handler;
  if (cache_methods->destroy_pixel_handler != (DestroyPixelHandler) NULL)
    cache_info->methods.destroy_pixel_handler=
      cache_methods->destroy_pixel_handler;
  if (cache_methods->get_virtual_indexes_from_handler !=
      (GetVirtualIndexesFromHandler) NULL)
    cache_info->methods.get_virtual_indexes_from_handler=
      cache_methods->get_virtual_indexes_from_handler;
  if (cache_methods->get_authentic_pixels_handler !=
      (GetAuthenticPixelsHandler) NULL)
    cache_info->methods.get_authentic_pixels_handler=
      cache_methods->get_authentic_pixels_handler;
  if (cache_methods->queue_authentic_pixels_handler !=
      (QueueAuthenticPixelsHandler) NULL)
    cache_info->methods.queue_authentic_pixels_handler=
      cache_methods->queue_authentic_pixels_handler;
  if (cache_methods->sync_authentic_pixels_handler !=
      (SyncAuthenticPixelsHandler) NULL)
    cache_info->methods.sync_authentic_pixels_handler=
      cache_methods->sync_authentic_pixels_handler;
  if (cache_methods->get_authentic_pixels_from_handler !=
      (GetAuthenticPixelsFromHandler) NULL)
    cache_info->methods.get_authentic_pixels_from_handler=
      cache_methods->get_authentic_pixels_from_handler;
  if (cache_methods->get_authentic_indexes_from_handler !=
      (GetAuthenticIndexesFromHandler) NULL)
    cache_info->methods.get_authentic_indexes_from_handler=
      cache_methods->get_authentic_indexes_from_handler;
  get_one_virtual_pixel_from_handler=
    cache_info->methods.get_one_virtual_pixel_from_handler;
  if (get_one_virtual_pixel_from_handler !=
      (GetOneVirtualPixelFromHandler) NULL)
    cache_info->methods.get_one_virtual_pixel_from_handler=
      cache_methods->get_one_virtual_pixel_from_handler;
  get_one_authentic_pixel_from_handler=
    cache_methods->get_one_authentic_pixel_from_handler;
  if (get_one_authentic_pixel_from_handler !=
      (GetOneAuthenticPixelFromHandler) NULL)
    cache_info->methods.get_one_authentic_pixel_from_handler=
      cache_methods->get_one_authentic_pixel_from_handler;
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   S e t P i x e l C a c h e N e x u s P i x e l s                           %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  SetPixelCacheNexusPixels() defines the region of the cache for the
%  specified cache nexus.
%
%  The format of the SetPixelCacheNexusPixels() method is:
%
%      PixelPacket SetPixelCacheNexusPixels(const CacheInfo *cache_info,
%        const MapMode mode,const RectangleInfo *region,
%        const MagickBooleanType buffered,NexusInfo *nexus_info,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o cache_info: the pixel cache.
%
%    o mode: ReadMode, WriteMode, or IOMode.
%
%    o region: A pointer to the RectangleInfo structure that defines the
%      region of this particular cache nexus.
%
%    o buffered: pixels are buffered.
%
%    o nexus_info: the cache nexus to set.
%
%    o exception: return any errors or warnings in this structure.
%
*/

static inline MagickBooleanType AcquireCacheNexusPixels(
  const CacheInfo *magick_restrict cache_info,NexusInfo *nexus_info,
  ExceptionInfo *exception)
{
  if (nexus_info->length != (MagickSizeType) ((size_t) nexus_info->length))
    return(MagickFalse);
  nexus_info->mapped=MagickFalse;
  nexus_info->cache=(PixelPacket *) MagickAssumeAligned(AcquireAlignedMemory(1,
    (size_t) nexus_info->length));
  if (nexus_info->cache == (PixelPacket *) NULL)
    {
      nexus_info->mapped=MagickTrue;
      nexus_info->cache=(PixelPacket *) MapBlob(-1,IOMode,0,(size_t)
        nexus_info->length);
    }
  if (nexus_info->cache == (PixelPacket *) NULL)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),
        ResourceLimitError,"MemoryAllocationFailed","`%s'",
        cache_info->filename);
      return(MagickFalse);
    }
  return(MagickTrue);
}

static inline MagickBooleanType IsAuthenticPixelCache(
  const CacheInfo *magick_restrict cache_info,
  const NexusInfo *magick_restrict nexus_info)
{
  MagickBooleanType
    status;

  MagickOffsetType
    offset;

  /*
    Does nexus pixels point directly to in-core cache pixels or is it buffered?
  */
  if (cache_info->type == PingCache)
    return(MagickTrue);
  offset=(MagickOffsetType) nexus_info->region.y*cache_info->columns+
    nexus_info->region.x;
  status=nexus_info->pixels == (cache_info->pixels+offset) ? MagickTrue :
    MagickFalse;
  return(status);
}

static inline void PrefetchPixelCacheNexusPixels(const NexusInfo *nexus_info,
  const MapMode mode)
{
  magick_unreferenced(nexus_info);
  magick_unreferenced(mode);

  if (mode == ReadMode)
    {
      MagickCachePrefetch((unsigned char *) nexus_info->pixels,0,1);
      return;
    }
  MagickCachePrefetch((unsigned char *) nexus_info->pixels,1,1);
}

static PixelPacket *SetPixelCacheNexusPixels(const CacheInfo *cache_info,
  const MapMode mode,const RectangleInfo *region,
  const MagickBooleanType buffered,NexusInfo *nexus_info,
  ExceptionInfo *exception)
{
  MagickBooleanType
    status;

  MagickSizeType
    length,
    number_pixels;

  assert(cache_info != (const CacheInfo *) NULL);
  assert(cache_info->signature == MagickSignature);
  if (cache_info->type == UndefinedCache)
    return((PixelPacket *) NULL);
  nexus_info->region=(*region);
  if (((cache_info->type == MemoryCache) || (cache_info->type == MapCache)) &&
      (buffered == MagickFalse))
    {
      ssize_t
        x,
        y;

      x=nexus_info->region.x+(ssize_t) nexus_info->region.width-1;
      y=nexus_info->region.y+(ssize_t) nexus_info->region.height-1;
      if (((nexus_info->region.x >= 0) && (x < (ssize_t) cache_info->columns) &&
           (nexus_info->region.y >= 0) && (y < (ssize_t) cache_info->rows)) &&
          ((nexus_info->region.height == 1UL) || ((nexus_info->region.x == 0) &&
           ((nexus_info->region.width == cache_info->columns) ||
            ((nexus_info->region.width % cache_info->columns) == 0)))))
        {
          MagickOffsetType
            offset;

          /*
            Pixels are accessed directly from memory.
          */
          offset=(MagickOffsetType) nexus_info->region.y*cache_info->columns+
            nexus_info->region.x;
          nexus_info->pixels=cache_info->pixels+offset;
          nexus_info->indexes=(IndexPacket *) NULL;
          if (cache_info->active_index_channel != MagickFalse)
            nexus_info->indexes=cache_info->indexes+offset;
          PrefetchPixelCacheNexusPixels(nexus_info,mode);
          nexus_info->authentic_pixel_cache=IsAuthenticPixelCache(cache_info,
            nexus_info);
          return(nexus_info->pixels);
        }
    }
  /*
    Pixels are stored in a staging region until they are synced to the cache.
  */
  number_pixels=(MagickSizeType) nexus_info->region.width*
    nexus_info->region.height;
  length=number_pixels*sizeof(PixelPacket);
  if (cache_info->active_index_channel != MagickFalse)
    length+=number_pixels*sizeof(IndexPacket);
  if (nexus_info->cache == (PixelPacket *) NULL)
    {
      nexus_info->length=length;
      status=AcquireCacheNexusPixels(cache_info,nexus_info,exception);
      if (status == MagickFalse)
        {
          nexus_info->length=0;
          return((PixelPacket *) NULL);
        }
    }
  else
    if (nexus_info->length < length)
      {
        RelinquishCacheNexusPixels(nexus_info);
        nexus_info->length=length;
        status=AcquireCacheNexusPixels(cache_info,nexus_info,exception);
        if (status == MagickFalse)
          {
            nexus_info->length=0;
            return((PixelPacket *) NULL);
          }
      }
  nexus_info->pixels=nexus_info->cache;
  nexus_info->indexes=(IndexPacket *) NULL;
  if (cache_info->active_index_channel != MagickFalse)
    nexus_info->indexes=(IndexPacket *) (nexus_info->pixels+number_pixels);
  PrefetchPixelCacheNexusPixels(nexus_info,mode);
  nexus_info->authentic_pixel_cache=IsAuthenticPixelCache(cache_info,
    nexus_info);
  return(nexus_info->pixels);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   S e t P i x e l C a c h e V i r t u a l M e t h o d                       %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  SetPixelCacheVirtualMethod() sets the "virtual pixels" method for the
%  pixel cache and returns the previous setting.  A virtual pixel is any pixel
%  access that is outside the boundaries of the image cache.
%
%  The format of the SetPixelCacheVirtualMethod() method is:
%
%      VirtualPixelMethod SetPixelCacheVirtualMethod(const Image *image,
%        const VirtualPixelMethod virtual_pixel_method)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o virtual_pixel_method: choose the type of virtual pixel.
%
*/

static MagickBooleanType SetCacheAlphaChannel(Image *image,
  const Quantum opacity)
{
  CacheInfo
    *magick_restrict cache_info;

  CacheView
    *magick_restrict image_view;

  MagickBooleanType
    status;

  ssize_t
    y;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  image->matte=MagickTrue;
  status=MagickTrue;
  image_view=AcquireVirtualCacheView(image,&image->exception);  /* must be virtual */
#if defined(MAGICKCORE_OPENMP_SUPPORT)
  #pragma omp parallel for schedule(static,4) shared(status) \
    magick_threads(image,image,1,1)
#endif
  for (y=0; y < (ssize_t) image->rows; y++)
  {
    register PixelPacket
      *magick_restrict q;

    register ssize_t
      x;

    if (status == MagickFalse)
      continue;
    q=GetCacheViewAuthenticPixels(image_view,0,y,image->columns,1,
      &image->exception);
    if (q == (PixelPacket *) NULL)
      {
        status=MagickFalse;
        continue;
      }
    for (x=0; x < (ssize_t) image->columns; x++)
    {
      q->opacity=opacity;
      q++;
    }
    status=SyncCacheViewAuthenticPixels(image_view,&image->exception);
  }
  image_view=DestroyCacheView(image_view);
  return(status);
}

MagickExport VirtualPixelMethod SetPixelCacheVirtualMethod(const Image *image,
  const VirtualPixelMethod virtual_pixel_method)
{
  CacheInfo
    *magick_restrict cache_info;

  VirtualPixelMethod
    method;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  method=cache_info->virtual_pixel_method;
  cache_info->virtual_pixel_method=virtual_pixel_method;
  if ((image->columns != 0) && (image->rows != 0))
    switch (virtual_pixel_method)
    {
      case BackgroundVirtualPixelMethod:
      {
        if ((image->background_color.opacity != OpaqueOpacity) &&
            (image->matte == MagickFalse))
          (void) SetCacheAlphaChannel((Image *) image,OpaqueOpacity);
        if ((IsPixelGray(&image->background_color) == MagickFalse) &&
            (IsGrayColorspace(image->colorspace) != MagickFalse))
          (void) SetImageColorspace((Image *) image,sRGBColorspace);
        break;
      }
      case TransparentVirtualPixelMethod:
      {
        if (image->matte == MagickFalse)
          (void) SetCacheAlphaChannel((Image *) image,OpaqueOpacity);
        break;
      }
      default:
        break;
    }
  return(method);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   S y n c A u t h e n t i c P i x e l C a c h e N e x u s                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  SyncAuthenticPixelCacheNexus() saves the authentic image pixels to the
%  in-memory or disk cache.  The method returns MagickTrue if the pixel region
%  is synced, otherwise MagickFalse.
%
%  The format of the SyncAuthenticPixelCacheNexus() method is:
%
%      MagickBooleanType SyncAuthenticPixelCacheNexus(Image *image,
%        NexusInfo *nexus_info,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o nexus_info: the cache nexus to sync.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport MagickBooleanType SyncAuthenticPixelCacheNexus(Image *image,
  NexusInfo *magick_restrict nexus_info,ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  MagickBooleanType
    status;

  /*
    Transfer pixels to the cache.
  */
  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->cache == (Cache) NULL)
    ThrowBinaryException(CacheError,"PixelCacheIsNotOpen",image->filename);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->type == UndefinedCache)
    return(MagickFalse);
  if ((image->storage_class == DirectClass) &&
      (image->clip_mask != (Image *) NULL) &&
      (ClipPixelCacheNexus(image,nexus_info,exception) == MagickFalse))
    return(MagickFalse);
  if ((image->storage_class == DirectClass) &&
      (image->mask != (Image *) NULL) &&
      (MaskPixelCacheNexus(image,nexus_info,exception) == MagickFalse))
    return(MagickFalse);
  if (nexus_info->authentic_pixel_cache != MagickFalse)
    {
      image->taint=MagickTrue;
      return(MagickTrue);
    }
  assert(cache_info->signature == MagickSignature);
  status=WritePixelCachePixels(cache_info,nexus_info,exception);
  if ((cache_info->active_index_channel != MagickFalse) &&
      (WritePixelCacheIndexes(cache_info,nexus_info,exception) == MagickFalse))
    return(MagickFalse);
  if (status != MagickFalse)
    image->taint=MagickTrue;
  return(status);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   S y n c A u t h e n t i c P i x e l C a c h e                             %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  SyncAuthenticPixelsCache() saves the authentic image pixels to the in-memory
%  or disk cache.  The method returns MagickTrue if the pixel region is synced,
%  otherwise MagickFalse.
%
%  The format of the SyncAuthenticPixelsCache() method is:
%
%      MagickBooleanType SyncAuthenticPixelsCache(Image *image,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o exception: return any errors or warnings in this structure.
%
*/
static MagickBooleanType SyncAuthenticPixelsCache(Image *image,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  MagickBooleanType
    status;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  assert(id < (int) cache_info->number_threads);
  status=SyncAuthenticPixelCacheNexus(image,cache_info->nexus_info[id],
    exception);
  return(status);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   S y n c A u t h e n t i c P i x e l s                                     %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  SyncAuthenticPixels() saves the image pixels to the in-memory or disk cache.
%  The method returns MagickTrue if the pixel region is flushed, otherwise
%  MagickFalse.
%
%  The format of the SyncAuthenticPixels() method is:
%
%      MagickBooleanType SyncAuthenticPixels(Image *image,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport MagickBooleanType SyncAuthenticPixels(Image *image,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  const int
    id = GetOpenMPThreadId();

  MagickBooleanType
    status;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  assert(image->cache != (Cache) NULL);
  cache_info=(CacheInfo *) image->cache;
  assert(cache_info->signature == MagickSignature);
  if (cache_info->methods.sync_authentic_pixels_handler !=
       (SyncAuthenticPixelsHandler) NULL)
    return(cache_info->methods.sync_authentic_pixels_handler(image,exception));
  assert(id < (int) cache_info->number_threads);
  status=SyncAuthenticPixelCacheNexus(image,cache_info->nexus_info[id],
    exception);
  return(status);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   S y n c I m a g e P i x e l C a c h e                                     %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  SyncImagePixelCache() saves the image pixels to the in-memory or disk cache.
%  The method returns MagickTrue if the pixel region is flushed, otherwise
%  MagickFalse.
%
%  The format of the SyncImagePixelCache() method is:
%
%      MagickBooleanType SyncImagePixelCache(Image *image,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickPrivate MagickBooleanType SyncImagePixelCache(Image *image,
  ExceptionInfo *exception)
{
  CacheInfo
    *magick_restrict cache_info;

  assert(image != (Image *) NULL);
  assert(exception != (ExceptionInfo *) NULL);
  cache_info=(CacheInfo *) GetImagePixelCache(image,MagickTrue,exception);
  return(cache_info == (CacheInfo *) NULL ? MagickFalse : MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   W r i t e P i x e l C a c h e I n d e x e s                               %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  WritePixelCacheIndexes() writes the colormap indexes to the specified
%  region of the pixel cache.
%
%  The format of the WritePixelCacheIndexes() method is:
%
%      MagickBooleanType WritePixelCacheIndexes(CacheInfo *cache_info,
%        NexusInfo *nexus_info,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o cache_info: the pixel cache.
%
%    o nexus_info: the cache nexus to write the colormap indexes.
%
%    o exception: return any errors or warnings in this structure.
%
*/
static MagickBooleanType WritePixelCacheIndexes(CacheInfo *cache_info,
  NexusInfo *magick_restrict nexus_info,ExceptionInfo *exception)
{
  MagickOffsetType
    count,
    offset;

  MagickSizeType
    extent,
    length;

  register const IndexPacket
    *magick_restrict p;

  register ssize_t
    y;

  size_t
    rows;

  if (cache_info->active_index_channel == MagickFalse)
    return(MagickFalse);
  if (nexus_info->authentic_pixel_cache != MagickFalse)
    return(MagickTrue);
  offset=(MagickOffsetType) nexus_info->region.y*cache_info->columns+
    nexus_info->region.x;
  length=(MagickSizeType) nexus_info->region.width*sizeof(IndexPacket);
  rows=nexus_info->region.height;
  extent=(MagickSizeType) length*rows;
  p=nexus_info->indexes;
  y=0;
  switch (cache_info->type)
  {
    case MemoryCache:
    case MapCache:
    {
      register IndexPacket
        *magick_restrict q;

      /*
        Write indexes to memory.
      */
      if ((cache_info->columns == nexus_info->region.width) &&
          (extent == (MagickSizeType) ((size_t) extent)))
        {
          length=extent;
          rows=1UL;
        }
      q=cache_info->indexes+offset;
      for (y=0; y < (ssize_t) rows; y++)
      {
        (void) memcpy(q,p,(size_t) length);
        p+=nexus_info->region.width;
        q+=cache_info->columns;
      }
      break;
    }
    case DiskCache:
    {
      /*
        Write indexes to disk.
      */
      LockSemaphoreInfo(cache_info->file_semaphore);
      if (OpenPixelCacheOnDisk(cache_info,IOMode) == MagickFalse)
        {
          ThrowFileException(exception,FileOpenError,"UnableToOpenFile",
            cache_info->cache_filename);
          UnlockSemaphoreInfo(cache_info->file_semaphore);
          return(MagickFalse);
        }
      if ((cache_info->columns == nexus_info->region.width) &&
          (extent <= MagickMaxBufferExtent))
        {
          length=extent;
          rows=1UL;
        }
      extent=(MagickSizeType) cache_info->columns*cache_info->rows;
      for (y=0; y < (ssize_t) rows; y++)
      {
        count=WritePixelCacheRegion(cache_info,cache_info->offset+extent*
          sizeof(PixelPacket)+offset*sizeof(*p),length,(const unsigned char *)
          p);
        if ((MagickSizeType) count < length)
          break;
        p+=nexus_info->region.width;
        offset+=cache_info->columns;
      }
      if (IsFileDescriptorLimitExceeded() != MagickFalse)
        (void) ClosePixelCacheOnDisk(cache_info);
      UnlockSemaphoreInfo(cache_info->file_semaphore);
      break;
    }
    case DistributedCache:
    {
      RectangleInfo
        region;

      /*
        Write indexes to distributed cache.
      */
      LockSemaphoreInfo(cache_info->file_semaphore);
      region=nexus_info->region;
      if ((cache_info->columns != nexus_info->region.width) ||
          (extent > MagickMaxBufferExtent))
        region.height=1UL;
      else
        {
          length=extent;
          rows=1UL;
        }
      for (y=0; y < (ssize_t) rows; y++)
      {
        count=WriteDistributePixelCacheIndexes((DistributeCacheInfo *)
          cache_info->server_info,&region,length,(const unsigned char *) p);
        if (count != (MagickOffsetType) length)
          break;
        p+=nexus_info->region.width;
        region.y++;
      }
      UnlockSemaphoreInfo(cache_info->file_semaphore);
      break;
    }
    default:
      break;
  }
  if (y < (ssize_t) rows)
    {
      ThrowFileException(exception,CacheError,"UnableToWritePixelCache",
        cache_info->cache_filename);
      return(MagickFalse);
    }
  if ((cache_info->debug != MagickFalse) &&
      (CacheTick(nexus_info->region.y,cache_info->rows) != MagickFalse))
    (void) LogMagickEvent(CacheEvent,GetMagickModule(),
      "%s[%.20gx%.20g%+.20g%+.20g]",cache_info->filename,(double)
      nexus_info->region.width,(double) nexus_info->region.height,(double)
      nexus_info->region.x,(double) nexus_info->region.y);
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+   W r i t e P i x e l C a c h e P i x e l s                                 %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  WritePixelCachePixels() writes image pixels to the specified region of the
%  pixel cache.
%
%  The format of the WritePixelCachePixels() method is:
%
%      MagickBooleanType WritePixelCachePixels(CacheInfo *cache_info,
%        NexusInfo *nexus_info,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o cache_info: the pixel cache.
%
%    o nexus_info: the cache nexus to write the pixels.
%
%    o exception: return any errors or warnings in this structure.
%
*/
static MagickBooleanType WritePixelCachePixels(CacheInfo *cache_info,
  NexusInfo *magick_restrict nexus_info,ExceptionInfo *exception)
{
  MagickOffsetType
    count,
    offset;

  MagickSizeType
    extent,
    length;

  register const PixelPacket
    *magick_restrict p;

  register ssize_t
    y;

  size_t
    rows;

  if (nexus_info->authentic_pixel_cache != MagickFalse)
    return(MagickTrue);
  offset=(MagickOffsetType) nexus_info->region.y*cache_info->columns+
    nexus_info->region.x;
  length=(MagickSizeType) nexus_info->region.width*sizeof(PixelPacket);
  rows=nexus_info->region.height;
  extent=length*rows;
  p=nexus_info->pixels;
  y=0;
  switch (cache_info->type)
  {
    case MemoryCache:
    case MapCache:
    {
      register PixelPacket
        *magick_restrict q;

      /*
        Write pixels to memory.
      */
      if ((cache_info->columns == nexus_info->region.width) &&
          (extent == (MagickSizeType) ((size_t) extent)))
        {
          length=extent;
          rows=1UL;
        }
      q=cache_info->pixels+offset;
      for (y=0; y < (ssize_t) rows; y++)
      {
        (void) memcpy(q,p,(size_t) length);
        p+=nexus_info->region.width;
        q+=cache_info->columns;
      }
      break;
    }
    case DiskCache:
    {
      /*
        Write pixels to disk.
      */
      LockSemaphoreInfo(cache_info->file_semaphore);
      if (OpenPixelCacheOnDisk(cache_info,IOMode) == MagickFalse)
        {
          ThrowFileException(exception,FileOpenError,"UnableToOpenFile",
            cache_info->cache_filename);
          UnlockSemaphoreInfo(cache_info->file_semaphore);
          return(MagickFalse);
        }
      if ((cache_info->columns == nexus_info->region.width) &&
          (extent <= MagickMaxBufferExtent))
        {
          length=extent;
          rows=1UL;
        }
      for (y=0; y < (ssize_t) rows; y++)
      {
        count=WritePixelCacheRegion(cache_info,cache_info->offset+offset*
          sizeof(*p),length,(const unsigned char *) p);
        if ((MagickSizeType) count < length)
          break;
        p+=nexus_info->region.width;
        offset+=cache_info->columns;
      }
      if (IsFileDescriptorLimitExceeded() != MagickFalse)
        (void) ClosePixelCacheOnDisk(cache_info);
      UnlockSemaphoreInfo(cache_info->file_semaphore);
      break;
    }
    case DistributedCache:
    {
      RectangleInfo
        region;

      /*
        Write pixels to distributed cache.
      */
      LockSemaphoreInfo(cache_info->file_semaphore);
      region=nexus_info->region;
      if ((cache_info->columns != nexus_info->region.width) ||
          (extent > MagickMaxBufferExtent))
        region.height=1UL;
      else
        {
          length=extent;
          rows=1UL;
        }
      for (y=0; y < (ssize_t) rows; y++)
      {
        count=WriteDistributePixelCachePixels((DistributeCacheInfo *)
          cache_info->server_info,&region,length,(const unsigned char *) p);
        if (count != (MagickOffsetType) length)
          break;
        p+=nexus_info->region.width;
        region.y++;
      }
      UnlockSemaphoreInfo(cache_info->file_semaphore);
      break;
    }
    default:
      break;
  }
  if (y < (ssize_t) rows)
    {
      ThrowFileException(exception,CacheError,"UnableToWritePixelCache",
        cache_info->cache_filename);
      return(MagickFalse);
    }
  if ((cache_info->debug != MagickFalse) &&
      (CacheTick(nexus_info->region.y,cache_info->rows) != MagickFalse))
    (void) LogMagickEvent(CacheEvent,GetMagickModule(),
      "%s[%.20gx%.20g%+.20g%+.20g]",cache_info->filename,(double)
      nexus_info->region.width,(double) nexus_info->region.height,(double)
      nexus_info->region.x,(double) nexus_info->region.y);
  return(MagickTrue);
}