root/magick/threshold.c

DEFINITIONS

1. AdaptiveThresholdImage
2. BilevelImage
3. BilevelImageChannel
4. BlackThresholdImage
5. BlackThresholdImageChannel
6. ClampImage
7. ClampImageChannel
8. DestroyThresholdMap
9. GetThresholdMapFile
10. GetThresholdMap
11. ListThresholdMapFile
12. ListThresholdMaps
13. OrderedDitherImage
14. OrderedDitherImageChannel
15. OrderedPosterizeImage
16. OrderedPosterizeImageChannel
17. PerceptibleThreshold
18. PerceptibleImage
19. PerceptibleImageChannel
20. RandomThresholdImage
21. RandomThresholdImageChannel
22. WhiteThresholdImage
23. WhiteThresholdImageChannel

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%       TTTTT  H   H  RRRR   EEEEE  SSSSS  H   H   OOO   L      DDDD          %
%         T    H   H  R   R  E      SS     H   H  O   O  L      D   D         %
%         T    HHHHH  RRRR   EEE     SSS   HHHHH  O   O  L      D   D         %
%         T    H   H  R R    E         SS  H   H  O   O  L      D   D         %
%         T    H   H  R  R   EEEEE  SSSSS  H   H   OOO   LLLLL  DDDD          %
%                                                                             %
%                                                                             %
%                      MagickCore Image Threshold Methods                     %
%                                                                             %
%                               Software Design                               %
%                                    Cristy                                   %
%                                 October 1996                                %
%                                                                             %
%                                                                             %
%  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/property.h"
#include "magick/blob.h"
#include "magick/cache-view.h"
#include "magick/color.h"
#include "magick/color-private.h"
#include "magick/colormap.h"
#include "magick/colorspace.h"
#include "magick/colorspace-private.h"
#include "magick/configure.h"
#include "magick/constitute.h"
#include "magick/decorate.h"
#include "magick/draw.h"
#include "magick/enhance.h"
#include "magick/exception.h"
#include "magick/exception-private.h"
#include "magick/effect.h"
#include "magick/fx.h"
#include "magick/gem.h"
#include "magick/geometry.h"
#include "magick/image-private.h"
#include "magick/list.h"
#include "magick/log.h"
#include "magick/memory_.h"
#include "magick/monitor.h"
#include "magick/monitor-private.h"
#include "magick/montage.h"
#include "magick/option.h"
#include "magick/pixel-private.h"
#include "magick/quantize.h"
#include "magick/quantum.h"
#include "magick/random_.h"
#include "magick/random-private.h"
#include "magick/resize.h"
#include "magick/resource_.h"
#include "magick/segment.h"
#include "magick/shear.h"
#include "magick/signature-private.h"
#include "magick/string_.h"
#include "magick/string-private.h"
#include "magick/thread-private.h"
#include "magick/threshold.h"
#include "magick/transform.h"
#include "magick/xml-tree.h"

/*
  Define declarations.
*/
#define ThresholdsFilename  "thresholds.xml"

/*
  Typedef declarations.
*/
struct _ThresholdMap
{
  char
    *map_id,
    *description;

  size_t
    width,
    height;

  ssize_t
    divisor,
    *levels;
};

/*
  Static declarations.
*/
static const char
  *MinimalThresholdMap =
    "<?xml version=\"1.0\"?>"
    "<thresholds>"
    "  <threshold map=\"threshold\" alias=\"1x1\">"
    "    <description>Threshold 1x1 (non-dither)</description>"
    "    <levels width=\"1\" height=\"1\" divisor=\"2\">"
    "        1"
    "    </levels>"
    "  </threshold>"
    "  <threshold map=\"checks\" alias=\"2x1\">"
    "    <description>Checkerboard 2x1 (dither)</description>"
    "    <levels width=\"2\" height=\"2\" divisor=\"3\">"
    "       1 2"
    "       2 1"
    "    </levels>"
    "  </threshold>"
    "</thresholds>";

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%     A d a p t i v e T h r e s h o l d I m a g e                             %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  AdaptiveThresholdImage() selects an individual threshold for each pixel
%  based on the range of intensity values in its local neighborhood.  This
%  allows for thresholding of an image whose global intensity histogram
%  doesn't contain distinctive peaks.
%
%  The format of the AdaptiveThresholdImage method is:
%
%      Image *AdaptiveThresholdImage(const Image *image,
%        const size_t width,const size_t height,
%        const ssize_t offset,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o width: the width of the local neighborhood.
%
%    o height: the height of the local neighborhood.
%
%    o offset: the mean offset.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport Image *AdaptiveThresholdImage(const Image *image,
  const size_t width,const size_t height,const ssize_t offset,
  ExceptionInfo *exception)
{
#define ThresholdImageTag  "Threshold/Image"

  CacheView
    *image_view,
    *threshold_view;

  Image
    *threshold_image;

  MagickBooleanType
    status;

  MagickOffsetType
    progress;

  MagickPixelPacket
    zero;

  MagickRealType
    number_pixels;

  ssize_t
    y;

  assert(image != (const Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  assert(exception != (ExceptionInfo *) NULL);
  assert(exception->signature == MagickSignature);
  threshold_image=CloneImage(image,0,0,MagickTrue,exception);
  if (threshold_image == (Image *) NULL)
    return((Image *) NULL);
  if (SetImageStorageClass(threshold_image,DirectClass) == MagickFalse)
    {
      InheritException(exception,&threshold_image->exception);
      threshold_image=DestroyImage(threshold_image);
      return((Image *) NULL);
    }
  /*
    Local adaptive threshold.
  */
  status=MagickTrue;
  progress=0;
  GetMagickPixelPacket(image,&zero);
  number_pixels=(MagickRealType) (width*height);
  image_view=AcquireVirtualCacheView(image,exception);
  threshold_view=AcquireAuthenticCacheView(threshold_image,exception);
#if defined(MAGICKCORE_OPENMP_SUPPORT)
  #pragma omp parallel for schedule(static,4) shared(progress,status) \
    magick_threads(image,threshold_image,image->rows,1)
#endif
  for (y=0; y < (ssize_t) image->rows; y++)
  {
    MagickBooleanType
      sync;

    MagickPixelPacket
      channel_bias,
      channel_sum;

    register const IndexPacket
      *magick_restrict indexes;

    register const PixelPacket
      *magick_restrict p,
      *magick_restrict r;

    register IndexPacket
      *magick_restrict threshold_indexes;

    register PixelPacket
      *magick_restrict q;

    register ssize_t
      x;

    ssize_t
      u,
      v;

    if (status == MagickFalse)
      continue;
    p=GetCacheViewVirtualPixels(image_view,-((ssize_t) width/2L),y-(ssize_t)
      height/2L,image->columns+width,height,exception);
    q=GetCacheViewAuthenticPixels(threshold_view,0,y,threshold_image->columns,1,
      exception);
    if ((p == (const PixelPacket *) NULL) || (q == (PixelPacket *) NULL))
      {
        status=MagickFalse;
        continue;
      }
    indexes=GetCacheViewVirtualIndexQueue(image_view);
    threshold_indexes=GetCacheViewAuthenticIndexQueue(threshold_view);
    channel_bias=zero;
    channel_sum=zero;
    r=p;
    for (v=0; v < (ssize_t) height; v++)
    {
      for (u=0; u < (ssize_t) width; u++)
      {
        if (u == (ssize_t) (width-1))
          {
            channel_bias.red+=r[u].red;
            channel_bias.green+=r[u].green;
            channel_bias.blue+=r[u].blue;
            channel_bias.opacity+=r[u].opacity;
            if (image->colorspace == CMYKColorspace)
              channel_bias.index=(MagickRealType)
                GetPixelIndex(indexes+(r-p)+u);
          }
        channel_sum.red+=r[u].red;
        channel_sum.green+=r[u].green;
        channel_sum.blue+=r[u].blue;
        channel_sum.opacity+=r[u].opacity;
        if (image->colorspace == CMYKColorspace)
          channel_sum.index=(MagickRealType) GetPixelIndex(indexes+(r-p)+u);
      }
      r+=image->columns+width;
    }
    for (x=0; x < (ssize_t) image->columns; x++)
    {
      MagickPixelPacket
        mean;

      mean=zero;
      r=p;
      channel_sum.red-=channel_bias.red;
      channel_sum.green-=channel_bias.green;
      channel_sum.blue-=channel_bias.blue;
      channel_sum.opacity-=channel_bias.opacity;
      channel_sum.index-=channel_bias.index;
      channel_bias=zero;
      for (v=0; v < (ssize_t) height; v++)
      {
        channel_bias.red+=r[0].red;
        channel_bias.green+=r[0].green;
        channel_bias.blue+=r[0].blue;
        channel_bias.opacity+=r[0].opacity;
        if (image->colorspace == CMYKColorspace)
          channel_bias.index=(MagickRealType) GetPixelIndex(indexes+x+(r-p)+0);
        channel_sum.red+=r[width-1].red;
        channel_sum.green+=r[width-1].green;
        channel_sum.blue+=r[width-1].blue;
        channel_sum.opacity+=r[width-1].opacity;
        if (image->colorspace == CMYKColorspace)
          channel_sum.index=(MagickRealType) GetPixelIndex(indexes+x+(r-p)+
            width-1);
        r+=image->columns+width;
      }
      mean.red=(MagickRealType) (channel_sum.red/number_pixels+offset);
      mean.green=(MagickRealType) (channel_sum.green/number_pixels+offset);
      mean.blue=(MagickRealType) (channel_sum.blue/number_pixels+offset);
      mean.opacity=(MagickRealType) (channel_sum.opacity/number_pixels+offset);
      if (image->colorspace == CMYKColorspace)
        mean.index=(MagickRealType) (channel_sum.index/number_pixels+offset);
      SetPixelRed(q,((MagickRealType) GetPixelRed(q) <= mean.red) ?
        0 : QuantumRange);
      SetPixelGreen(q,((MagickRealType) GetPixelGreen(q) <= mean.green) ?
        0 : QuantumRange);
      SetPixelBlue(q,((MagickRealType) GetPixelBlue(q) <= mean.blue) ?
        0 : QuantumRange);
      SetPixelOpacity(q,((MagickRealType) GetPixelOpacity(q) <= mean.opacity) ?
        0 : QuantumRange);
      if (image->colorspace == CMYKColorspace)
        SetPixelIndex(threshold_indexes+x,(((MagickRealType) GetPixelIndex(
          threshold_indexes+x) <= mean.index) ? 0 : QuantumRange));
      p++;
      q++;
    }
    sync=SyncCacheViewAuthenticPixels(threshold_view,exception);
    if (sync == MagickFalse)
      status=MagickFalse;
    if (image->progress_monitor != (MagickProgressMonitor) NULL)
      {
        MagickBooleanType
          proceed;

#if defined(MAGICKCORE_OPENMP_SUPPORT)
        #pragma omp critical (MagickCore_AdaptiveThresholdImage)
#endif
        proceed=SetImageProgress(image,ThresholdImageTag,progress++,
          image->rows);
        if (proceed == MagickFalse)
          status=MagickFalse;
      }
  }
  threshold_view=DestroyCacheView(threshold_view);
  image_view=DestroyCacheView(image_view);
  if (status == MagickFalse)
    threshold_image=DestroyImage(threshold_image);
  return(threshold_image);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%     B i l e v e l I m a g e                                                 %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  BilevelImage() changes the value of individual pixels based on the
%  intensity of each pixel channel.  The result is a high-contrast image.
%
%  More precisely each channel value of the image is 'thresholded' so that if
%  it is equal to or less than the given value it is set to zero, while any
%  value greater than that give is set to it maximum or QuantumRange.
%
%  This function is what is used to implement the "-threshold" operator for
%  the command line API.
%
%  If the default channel setting is given the image is thresholded using just
%  the gray 'intensity' of the image, rather than the individual channels.
%
%  The format of the BilevelImageChannel method is:
%
%      MagickBooleanType BilevelImage(Image *image,const double threshold)
%      MagickBooleanType BilevelImageChannel(Image *image,
%        const ChannelType channel,const double threshold)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o channel: the channel type.
%
%    o threshold: define the threshold values.
%
%  Aside: You can get the same results as operator using LevelImageChannels()
%  with the 'threshold' value for both the black_point and the white_point.
%
*/

MagickExport MagickBooleanType BilevelImage(Image *image,const double threshold)
{
  MagickBooleanType
    status;

  status=BilevelImageChannel(image,DefaultChannels,threshold);
  return(status);
}

MagickExport MagickBooleanType BilevelImageChannel(Image *image,
  const ChannelType channel,const double threshold)
{
#define ThresholdImageTag  "Threshold/Image"

  CacheView
    *image_view;

  ExceptionInfo
    *exception;

  MagickBooleanType
    status;

  MagickOffsetType
    progress;

  ssize_t
    y;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  if (SetImageStorageClass(image,DirectClass) == MagickFalse)
    return(MagickFalse);
  if (IsGrayColorspace(image->colorspace) != MagickFalse)
    (void) SetImageColorspace(image,sRGBColorspace);
  /*
    Bilevel threshold image.
  */
  status=MagickTrue;
  progress=0;
  exception=(&image->exception);
  image_view=AcquireAuthenticCacheView(image,exception);
#if defined(MAGICKCORE_OPENMP_SUPPORT)
  #pragma omp parallel for schedule(static,4) shared(progress,status) \
    magick_threads(image,image,image->rows,1)
#endif
  for (y=0; y < (ssize_t) image->rows; y++)
  {
    register IndexPacket
      *magick_restrict indexes;

    register ssize_t
      x;

    register PixelPacket
      *magick_restrict q;

    if (status == MagickFalse)
      continue;
    q=GetCacheViewAuthenticPixels(image_view,0,y,image->columns,1,exception);
    if (q == (PixelPacket *) NULL)
      {
        status=MagickFalse;
        continue;
      }
    indexes=GetCacheViewAuthenticIndexQueue(image_view);
    if ((channel & SyncChannels) != 0)
      {
        for (x=0; x < (ssize_t) image->columns; x++)
        {
          SetPixelRed(q,GetPixelIntensity(image,q) <= threshold ? 0 :
            QuantumRange);
          SetPixelGreen(q,GetPixelRed(q));
          SetPixelBlue(q,GetPixelRed(q));
          q++;
        }
      }
    else
      for (x=0; x < (ssize_t) image->columns; x++)
      {
        if ((channel & RedChannel) != 0)
          SetPixelRed(q,(MagickRealType) GetPixelRed(q) <= threshold ? 0 :
            QuantumRange);
        if ((channel & GreenChannel) != 0)
          SetPixelGreen(q,(MagickRealType) GetPixelGreen(q) <= threshold ? 0 :
            QuantumRange);
        if ((channel & BlueChannel) != 0)
          SetPixelBlue(q,(MagickRealType) GetPixelBlue(q) <= threshold ? 0 :
            QuantumRange);
        if ((channel & OpacityChannel) != 0)
          {
            if (image->matte == MagickFalse)
              SetPixelOpacity(q,(MagickRealType) GetPixelOpacity(q) <=
                threshold ? 0 : QuantumRange);
            else
              SetPixelOpacity(q,(MagickRealType) GetPixelOpacity(q) <=
                threshold ? OpaqueOpacity : TransparentOpacity);
          }
        if (((channel & IndexChannel) != 0) &&
            (image->colorspace == CMYKColorspace))
          SetPixelIndex(indexes+x,(MagickRealType) GetPixelIndex(indexes+x) <=
            threshold ? 0 : QuantumRange);
        q++;
      }
    if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
      status=MagickFalse;
    if (image->progress_monitor != (MagickProgressMonitor) NULL)
      {
        MagickBooleanType
          proceed;

#if defined(MAGICKCORE_OPENMP_SUPPORT)
        #pragma omp critical (MagickCore_BilevelImageChannel)
#endif
        proceed=SetImageProgress(image,ThresholdImageTag,progress++,
          image->rows);
        if (proceed == MagickFalse)
          status=MagickFalse;
      }
  }
  image_view=DestroyCacheView(image_view);
  return(status);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%     B l a c k T h r e s h o l d I m a g e                                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  BlackThresholdImage() is like ThresholdImage() but forces all pixels below
%  the threshold into black while leaving all pixels at or above the threshold
%  unchanged.
%
%  The format of the BlackThresholdImage method is:
%
%      MagickBooleanType BlackThresholdImage(Image *image,const char *threshold)
%      MagickBooleanType BlackThresholdImageChannel(Image *image,
%        const ChannelType channel,const char *threshold,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o channel: the channel or channels to be thresholded.
%
%    o threshold: Define the threshold value.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport MagickBooleanType BlackThresholdImage(Image *image,
  const char *threshold)
{
  MagickBooleanType
    status;

  status=BlackThresholdImageChannel(image,DefaultChannels,threshold,
    &image->exception);
  return(status);
}

MagickExport MagickBooleanType BlackThresholdImageChannel(Image *image,
  const ChannelType channel,const char *thresholds,ExceptionInfo *exception)
{
#define ThresholdImageTag  "Threshold/Image"

  CacheView
    *image_view;

  GeometryInfo
    geometry_info;

  MagickBooleanType
    status;

  MagickOffsetType
    progress;

  MagickPixelPacket
    threshold;

  MagickStatusType
    flags;

  ssize_t
    y;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  if (thresholds == (const char *) NULL)
    return(MagickTrue);
  if (SetImageStorageClass(image,DirectClass) == MagickFalse)
    return(MagickFalse);
  GetMagickPixelPacket(image,&threshold);
  flags=ParseGeometry(thresholds,&geometry_info);
  threshold.red=geometry_info.rho;
  threshold.green=geometry_info.sigma;
  if ((flags & SigmaValue) == 0)
    threshold.green=threshold.red;
  threshold.blue=geometry_info.xi;
  if ((flags & XiValue) == 0)
    threshold.blue=threshold.red;
  threshold.opacity=geometry_info.psi;
  if ((flags & PsiValue) == 0)
    threshold.opacity=threshold.red;
  threshold.index=geometry_info.chi;
  if ((flags & ChiValue) == 0)
    threshold.index=threshold.red;
  if ((flags & PercentValue) != 0)
    {
      threshold.red*=(MagickRealType) (QuantumRange/100.0);
      threshold.green*=(MagickRealType) (QuantumRange/100.0);
      threshold.blue*=(MagickRealType) (QuantumRange/100.0);
      threshold.opacity*=(MagickRealType) (QuantumRange/100.0);
      threshold.index*=(MagickRealType) (QuantumRange/100.0);
    }
  if ((IsMagickGray(&threshold) == MagickFalse) &&
      (IsGrayColorspace(image->colorspace) != MagickFalse))
    (void) SetImageColorspace(image,sRGBColorspace);
  /*
    Black threshold image.
  */
  status=MagickTrue;
  progress=0;
  image_view=AcquireAuthenticCacheView(image,exception);
#if defined(MAGICKCORE_OPENMP_SUPPORT)
  #pragma omp parallel for schedule(static,4) shared(progress,status) \
    magick_threads(image,image,image->rows,1)
#endif
  for (y=0; y < (ssize_t) image->rows; y++)
  {
    register IndexPacket
      *magick_restrict indexes;

    register ssize_t
      x;

    register PixelPacket
      *magick_restrict q;

    if (status == MagickFalse)
      continue;
    q=GetCacheViewAuthenticPixels(image_view,0,y,image->columns,1,exception);
    if (q == (PixelPacket *) NULL)
      {
        status=MagickFalse;
        continue;
      }
    indexes=GetCacheViewAuthenticIndexQueue(image_view);
    for (x=0; x < (ssize_t) image->columns; x++)
    {
      if (((channel & RedChannel) != 0) &&
          ((MagickRealType) GetPixelRed(q) < threshold.red))
        SetPixelRed(q,0);
      if (((channel & GreenChannel) != 0) &&
          ((MagickRealType) GetPixelGreen(q) < threshold.green))
        SetPixelGreen(q,0);
      if (((channel & BlueChannel) != 0) &&
          ((MagickRealType) GetPixelBlue(q) < threshold.blue))
        SetPixelBlue(q,0);
      if (((channel & OpacityChannel) != 0) &&
          ((MagickRealType) GetPixelOpacity(q) < threshold.opacity))
        SetPixelOpacity(q,0);
      if (((channel & IndexChannel) != 0) &&
          (image->colorspace == CMYKColorspace) &&
          ((MagickRealType) GetPixelIndex(indexes+x) < threshold.index))
        SetPixelIndex(indexes+x,0);
      q++;
    }
    if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
      status=MagickFalse;
    if (image->progress_monitor != (MagickProgressMonitor) NULL)
      {
        MagickBooleanType
          proceed;

#if defined(MAGICKCORE_OPENMP_SUPPORT)
        #pragma omp critical (MagickCore_BlackThresholdImageChannel)
#endif
        proceed=SetImageProgress(image,ThresholdImageTag,progress++,
          image->rows);
        if (proceed == MagickFalse)
          status=MagickFalse;
      }
  }
  image_view=DestroyCacheView(image_view);
  return(status);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%     C l a m p I m a g e                                                     %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  ClampImage() set each pixel whose value is below zero to zero and any the
%  pixel whose value is above the quantum range to the quantum range (e.g.
%  65535) otherwise the pixel value remains unchanged.
%
%  The format of the ClampImageChannel method is:
%
%      MagickBooleanType ClampImage(Image *image)
%      MagickBooleanType ClampImageChannel(Image *image,
%        const ChannelType channel)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o channel: the channel type.
%
*/

MagickExport MagickBooleanType ClampImage(Image *image)
{
  MagickBooleanType
    status;

  status=ClampImageChannel(image,DefaultChannels);
  return(status);
}

MagickExport MagickBooleanType ClampImageChannel(Image *image,
  const ChannelType channel)
{
#define ClampImageTag  "Clamp/Image"

  CacheView
    *image_view;

  ExceptionInfo
    *exception;

  MagickBooleanType
    status;

  MagickOffsetType
    progress;

  ssize_t
    y;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  if (image->storage_class == PseudoClass)
    {
      register ssize_t
        i;

      register PixelPacket
        *magick_restrict q;

      q=image->colormap;
      for (i=0; i < (ssize_t) image->colors; i++)
      {
        SetPixelRed(q,ClampPixel(GetPixelRed(q)));
        SetPixelGreen(q,ClampPixel(GetPixelGreen(q)));
        SetPixelBlue(q,ClampPixel(GetPixelBlue(q)));
        SetPixelOpacity(q,ClampPixel(GetPixelOpacity(q)));
        q++;
      }
      return(SyncImage(image));
    }
  /*
    Clamp image.
  */
  status=MagickTrue;
  progress=0;
  exception=(&image->exception);
  image_view=AcquireAuthenticCacheView(image,exception);
#if defined(MAGICKCORE_OPENMP_SUPPORT)
  #pragma omp parallel for schedule(static,4) shared(progress,status) \
    magick_threads(image,image,image->rows,1)
#endif
  for (y=0; y < (ssize_t) image->rows; y++)
  {
    register IndexPacket
      *magick_restrict indexes;

    register ssize_t
      x;

    register PixelPacket
      *magick_restrict q;

    if (status == MagickFalse)
      continue;
    q=GetCacheViewAuthenticPixels(image_view,0,y,image->columns,1,exception);
    if (q == (PixelPacket *) NULL)
      {
        status=MagickFalse;
        continue;
      }
    indexes=GetCacheViewAuthenticIndexQueue(image_view);
    for (x=0; x < (ssize_t) image->columns; x++)
    {
      if ((channel & RedChannel) != 0)
        SetPixelRed(q,ClampPixel(GetPixelRed(q)));
      if ((channel & GreenChannel) != 0)
        SetPixelGreen(q,ClampPixel(GetPixelGreen(q)));
      if ((channel & BlueChannel) != 0)
        SetPixelBlue(q,ClampPixel(GetPixelBlue(q)));
      if ((channel & OpacityChannel) != 0)
        SetPixelOpacity(q,ClampPixel(GetPixelOpacity(q)));
      if (((channel & IndexChannel) != 0) &&
          (image->colorspace == CMYKColorspace))
        SetPixelIndex(indexes+x,ClampPixel(GetPixelIndex(indexes+x)));
      q++;
    }
    if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
      status=MagickFalse;
    if (image->progress_monitor != (MagickProgressMonitor) NULL)
      {
        MagickBooleanType
          proceed;

#if defined(MAGICKCORE_OPENMP_SUPPORT)
        #pragma omp critical (MagickCore_ClampImageChannel)
#endif
        proceed=SetImageProgress(image,ClampImageTag,progress++,image->rows);
        if (proceed == MagickFalse)
          status=MagickFalse;
      }
  }
  image_view=DestroyCacheView(image_view);
  return(status);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%  D e s t r o y T h r e s h o l d M a p                                      %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  DestroyThresholdMap() de-allocate the given ThresholdMap
%
%  The format of the ListThresholdMaps method is:
%
%      ThresholdMap *DestroyThresholdMap(Threshold *map)
%
%  A description of each parameter follows.
%
%    o map:    Pointer to the Threshold map to destroy
%
*/
MagickExport ThresholdMap *DestroyThresholdMap(ThresholdMap *map)
{
  assert(map != (ThresholdMap *) NULL);
  if (map->map_id != (char *) NULL)
    map->map_id=DestroyString(map->map_id);
  if (map->description != (char *) NULL)
    map->description=DestroyString(map->description);
  if (map->levels != (ssize_t *) NULL)
    map->levels=(ssize_t *) RelinquishMagickMemory(map->levels);
  map=(ThresholdMap *) RelinquishMagickMemory(map);
  return(map);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+  G e t T h r e s h o l d M a p F i l e                                      %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetThresholdMapFile() look for a given threshold map name or alias in the
%  given XML file data, and return the allocated the map when found.
%
%  The format of the ListThresholdMaps method is:
%
%      ThresholdMap *GetThresholdMap(const char *xml,const char *filename,
%         const char *map_id,ExceptionInfo *exception)
%
%  A description of each parameter follows.
%
%    o xml:  The threshold map list in XML format.
%
%    o filename:  The threshold map XML filename.
%
%    o map_id:  ID of the map to look for in XML list.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport ThresholdMap *GetThresholdMapFile(const char *xml,
  const char *filename,const char *map_id,ExceptionInfo *exception)
{
  const char
    *attribute,
    *content;

  double
    value;

  ThresholdMap
     *map;

  XMLTreeInfo
     *description,
     *levels,
     *threshold,
     *thresholds;

  map = (ThresholdMap *) NULL;
  (void) LogMagickEvent(ConfigureEvent,GetMagickModule(),
    "Loading threshold map file \"%s\" ...",filename);
  thresholds=NewXMLTree(xml,exception);
  if ( thresholds == (XMLTreeInfo *) NULL )
    return(map);
  for (threshold = GetXMLTreeChild(thresholds,"threshold");
       threshold != (XMLTreeInfo *) NULL;
       threshold = GetNextXMLTreeTag(threshold) )
  {
    attribute=GetXMLTreeAttribute(threshold, "map");
    if ((attribute != (char *) NULL) && (LocaleCompare(map_id,attribute) == 0))
      break;
    attribute=GetXMLTreeAttribute(threshold, "alias");
    if ((attribute != (char *) NULL) && (LocaleCompare(map_id,attribute) == 0))
      break;
  }
  if (threshold == (XMLTreeInfo *) NULL)
    {
      thresholds=DestroyXMLTree(thresholds);
      return(map);
    }
  description=GetXMLTreeChild(threshold,"description");
  if (description == (XMLTreeInfo *) NULL)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingElement", "<description>, map \"%s\"", map_id);
      thresholds=DestroyXMLTree(thresholds);
      return(map);
    }
  levels=GetXMLTreeChild(threshold,"levels");
  if (levels == (XMLTreeInfo *) NULL)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingElement", "<levels>, map \"%s\"", map_id);
      thresholds=DestroyXMLTree(thresholds);
      return(map);
    }
  /*
    The map has been found -- allocate a Threshold Map to return
  */
  map=(ThresholdMap *) AcquireMagickMemory(sizeof(ThresholdMap));
  if (map == (ThresholdMap *) NULL)
    ThrowFatalException(ResourceLimitFatalError,"UnableToAcquireThresholdMap");
  map->map_id=(char *) NULL;
  map->description=(char *) NULL;
  map->levels=(ssize_t *) NULL;
  /*
    Assign basic attributeibutes.
  */
  attribute=GetXMLTreeAttribute(threshold,"map");
  if (attribute != (char *) NULL)
    map->map_id=ConstantString(attribute);
  content=GetXMLTreeContent(description);
  if (content != (char *) NULL)
    map->description=ConstantString(content);
  attribute=GetXMLTreeAttribute(levels,"width");
  if (attribute == (char *) NULL)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingAttribute", "<levels width>, map \"%s\"",map_id);
      thresholds=DestroyXMLTree(thresholds);
      map=DestroyThresholdMap(map);
      return(map);
    }
  map->width=StringToUnsignedLong(attribute);
  if (map->width == 0)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
       "XmlInvalidAttribute", "<levels width>, map \"%s\"", map_id);
      thresholds=DestroyXMLTree(thresholds);
      map=DestroyThresholdMap(map);
      return(map);
    }
  attribute=GetXMLTreeAttribute(levels,"height");
  if (attribute == (char *) NULL)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingAttribute", "<levels height>, map \"%s\"", map_id);
      thresholds=DestroyXMLTree(thresholds);
      map=DestroyThresholdMap(map);
      return(map);
    }
  map->height=StringToUnsignedLong(attribute);
  if (map->height == 0)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlInvalidAttribute", "<levels height>, map \"%s\"", map_id);
      thresholds=DestroyXMLTree(thresholds);
      map=DestroyThresholdMap(map);
      return(map);
    }
  attribute=GetXMLTreeAttribute(levels, "divisor");
  if (attribute == (char *) NULL)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingAttribute", "<levels divisor>, map \"%s\"", map_id);
      thresholds=DestroyXMLTree(thresholds);
      map=DestroyThresholdMap(map);
      return(map);
    }
  map->divisor=(ssize_t) StringToLong(attribute);
  if (map->divisor < 2)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlInvalidAttribute", "<levels divisor>, map \"%s\"", map_id);
      thresholds=DestroyXMLTree(thresholds);
      map=DestroyThresholdMap(map);
      return(map);
    }
  /*
    Allocate theshold levels array.
  */
  content=GetXMLTreeContent(levels);
  if (content == (char *) NULL)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingContent", "<levels>, map \"%s\"", map_id);
      thresholds=DestroyXMLTree(thresholds);
      map=DestroyThresholdMap(map);
      return(map);
    }
  map->levels=(ssize_t *) AcquireQuantumMemory((size_t) map->width,map->height*
    sizeof(*map->levels));
  if (map->levels == (ssize_t *) NULL)
    ThrowFatalException(ResourceLimitFatalError,"UnableToAcquireThresholdMap");
  {
    char
      *p;

    register ssize_t
      i;

    /*
      Parse levels into integer array.
    */
    for (i=0; i< (ssize_t) (map->width*map->height); i++)
    {
      map->levels[i]=(ssize_t) strtol(content,&p,10);
      if (p == content)
        {
          (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
            "XmlInvalidContent", "<level> too few values, map \"%s\"", map_id);
          thresholds=DestroyXMLTree(thresholds);
          map=DestroyThresholdMap(map);
          return(map);
        }
      if ((map->levels[i] < 0) || (map->levels[i] > map->divisor))
        {
          (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
            "XmlInvalidContent", "<level> %.20g out of range, map \"%s\"",
            (double) map->levels[i],map_id);
          thresholds=DestroyXMLTree(thresholds);
          map=DestroyThresholdMap(map);
          return(map);
        }
      content=p;
    }
    value=(double) strtol(content,&p,10);
    (void) value;
    if (p != content)
      {
        (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
          "XmlInvalidContent", "<level> too many values, map \"%s\"", map_id);
       thresholds=DestroyXMLTree(thresholds);
       map=DestroyThresholdMap(map);
       return(map);
     }
  }
  thresholds=DestroyXMLTree(thresholds);
  return(map);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%  G e t T h r e s h o l d M a p                                              %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  GetThresholdMap() load and search one or more threshold map files for the
%  a map matching the given name or aliase.
%
%  The format of the GetThresholdMap method is:
%
%      ThresholdMap *GetThresholdMap(const char *map_id,
%         ExceptionInfo *exception)
%
%  A description of each parameter follows.
%
%    o map_id:  ID of the map to look for.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport ThresholdMap *GetThresholdMap(const char *map_id,
  ExceptionInfo *exception)
{
  const StringInfo
    *option;

  LinkedListInfo
    *options;

  ThresholdMap
    *map;

  map=GetThresholdMapFile(MinimalThresholdMap,"built-in",map_id,exception);
  if (map != (ThresholdMap *) NULL)
    return(map);
  options=GetConfigureOptions(ThresholdsFilename,exception);
  option=(const StringInfo *) GetNextValueInLinkedList(options);
  while (option != (const StringInfo *) NULL)
  {
    map=GetThresholdMapFile((const char *) GetStringInfoDatum(option),
      GetStringInfoPath(option),map_id,exception);
    if (map != (ThresholdMap *) NULL)
      break;
    option=(const StringInfo *) GetNextValueInLinkedList(options);
  }
  options=DestroyConfigureOptions(options);
  return(map);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
+  L i s t T h r e s h o l d M a p F i l e                                    %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  ListThresholdMapFile() lists the threshold maps and their descriptions
%  in the given XML file data.
%
%  The format of the ListThresholdMaps method is:
%
%      MagickBooleanType ListThresholdMaps(FILE *file,const char*xml,
%         const char *filename,ExceptionInfo *exception)
%
%  A description of each parameter follows.
%
%    o file:  An pointer to the output FILE.
%
%    o xml:  The threshold map list in XML format.
%
%    o filename:  The threshold map XML filename.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickBooleanType ListThresholdMapFile(FILE *file,const char *xml,
  const char *filename,ExceptionInfo *exception)
{
  XMLTreeInfo *thresholds,*threshold,*description;
  const char *map,*alias,*content;

  assert( xml != (char *) NULL );
  assert( file != (FILE *) NULL );

  (void) LogMagickEvent(ConfigureEvent,GetMagickModule(),
    "Loading threshold map file \"%s\" ...",filename);
  thresholds=NewXMLTree(xml,exception);
  if ( thresholds == (XMLTreeInfo *) NULL )
    return(MagickFalse);

  (void) FormatLocaleFile(file,"%-16s %-12s %s\n","Map","Alias","Description");
  (void) FormatLocaleFile(file,
    "----------------------------------------------------\n");

  for( threshold = GetXMLTreeChild(thresholds,"threshold");
       threshold != (XMLTreeInfo *) NULL;
       threshold = GetNextXMLTreeTag(threshold) )
  {
    map = GetXMLTreeAttribute(threshold, "map");
    if (map == (char *) NULL) {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingAttribute", "<map>");
      thresholds=DestroyXMLTree(thresholds);
      return(MagickFalse);
    }
    alias = GetXMLTreeAttribute(threshold, "alias");
    /* alias is optional, no if test needed */
    description=GetXMLTreeChild(threshold,"description");
    if ( description == (XMLTreeInfo *) NULL ) {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingElement", "<description>, map \"%s\"", map);
      thresholds=DestroyXMLTree(thresholds);
      return(MagickFalse);
    }
    content=GetXMLTreeContent(description);
    if ( content == (char *) NULL ) {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingContent", "<description>, map \"%s\"", map);
      thresholds=DestroyXMLTree(thresholds);
      return(MagickFalse);
    }
    (void) FormatLocaleFile(file,"%-16s %-12s %s\n",map,alias ? alias : "",
      content);
  }
  thresholds=DestroyXMLTree(thresholds);
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%  L i s t T h r e s h o l d M a p s                                          %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  ListThresholdMaps() lists the threshold maps and their descriptions
%  as defined by "threshold.xml" to a file.
%
%  The format of the ListThresholdMaps method is:
%
%      MagickBooleanType ListThresholdMaps(FILE *file,ExceptionInfo *exception)
%
%  A description of each parameter follows.
%
%    o file:  An pointer to the output FILE.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport MagickBooleanType ListThresholdMaps(FILE *file,
  ExceptionInfo *exception)
{
  const StringInfo
    *option;

  LinkedListInfo
    *options;

  MagickStatusType
    status;

  status=MagickTrue;
  if (file == (FILE *) NULL)
    file=stdout;
  options=GetConfigureOptions(ThresholdsFilename,exception);
  (void) FormatLocaleFile(file,
    "\n   Threshold Maps for Ordered Dither Operations\n");
  option=(const StringInfo *) GetNextValueInLinkedList(options);
  while (option != (const StringInfo *) NULL)
  {
    (void) FormatLocaleFile(file,"\nPath: %s\n\n",GetStringInfoPath(option));
    status&=ListThresholdMapFile(file,(const char *) GetStringInfoDatum(option),
      GetStringInfoPath(option),exception);
    option=(const StringInfo *) GetNextValueInLinkedList(options);
  }
  options=DestroyConfigureOptions(options);
  return(status != 0 ? MagickTrue : MagickFalse);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   O r d e r e d D i t h e r I m a g e                                       %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  OrderedDitherImage() uses the ordered dithering technique of reducing color
%  images to monochrome using positional information to retain as much
%  information as possible.
%
%  WARNING: This function is deprecated, and is now just a call to
%  the more more powerful OrderedPosterizeImage(); function.
%
%  The format of the OrderedDitherImage method is:
%
%      MagickBooleanType OrderedDitherImage(Image *image)
%      MagickBooleanType OrderedDitherImageChannel(Image *image,
%        const ChannelType channel,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o channel: the channel or channels to be thresholded.
%
%    o exception: return any errors or warnings in this structure.
%
*/

MagickExport MagickBooleanType OrderedDitherImage(Image *image)
{
  MagickBooleanType
    status;

  status=OrderedDitherImageChannel(image,DefaultChannels,&image->exception);
  return(status);
}

MagickExport MagickBooleanType OrderedDitherImageChannel(Image *image,
 const ChannelType channel,ExceptionInfo *exception)
{
  MagickBooleanType
    status;

  /*
    Call the augumented function OrderedPosterizeImage()
  */
  status=OrderedPosterizeImageChannel(image,channel,"o8x8",exception);
  return(status);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%     O r d e r e d P o s t e r i z e I m a g e                               %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  OrderedPosterizeImage() will perform a ordered dither based on a number
%  of pre-defined dithering threshold maps, but over multiple intensity
%  levels, which can be different for different channels, according to the
%  input argument.
%
%  The format of the OrderedPosterizeImage method is:
%
%      MagickBooleanType OrderedPosterizeImage(Image *image,
%        const char *threshold_map,ExceptionInfo *exception)
%      MagickBooleanType OrderedPosterizeImageChannel(Image *image,
%        const ChannelType channel,const char *threshold_map,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o channel: the channel or channels to be thresholded.
%
%    o threshold_map: A string containing the name of the threshold dither
%      map to use, followed by zero or more numbers representing the number
%      of color levels tho dither between.
%
%      Any level number less than 2 will be equivalent to 2, and means only
%      binary dithering will be applied to each color channel.
%
%      No numbers also means a 2 level (bitmap) dither will be applied to all
%      channels, while a single number is the number of levels applied to each
%      channel in sequence.  More numbers will be applied in turn to each of
%      the color channels.
%
%      For example: "o3x3,6" will generate a 6 level posterization of the
%      image with a ordered 3x3 diffused pixel dither being applied between
%      each level. While checker,8,8,4 will produce a 332 colormaped image
%      with only a single checkerboard hash pattern (50% grey) between each
%      color level, to basically double the number of color levels with
%      a bare minimim of dithering.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport MagickBooleanType OrderedPosterizeImage(Image *image,
  const char *threshold_map,ExceptionInfo *exception)
{
  MagickBooleanType
    status;

  status=OrderedPosterizeImageChannel(image,DefaultChannels,threshold_map,
    exception);
  return(status);
}

MagickExport MagickBooleanType OrderedPosterizeImageChannel(Image *image,
  const ChannelType channel,const char *threshold_map,ExceptionInfo *exception)
{
#define DitherImageTag  "Dither/Image"

  CacheView
    *image_view;

  LongPixelPacket
    levels;

  MagickBooleanType
    status;

  MagickOffsetType
    progress;

  ssize_t
    y;

  ThresholdMap
    *map;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  assert(exception != (ExceptionInfo *) NULL);
  assert(exception->signature == MagickSignature);
  if (threshold_map == (const char *) NULL)
    return(MagickTrue);
  {
    char
      token[MaxTextExtent];

    register const char
      *p;

    p=(char *)threshold_map;
    while (((isspace((int) ((unsigned char) *p)) != 0) || (*p == ',')) &&
                    (*p != '\0'))
      p++;
    threshold_map=p;
    while (((isspace((int) ((unsigned char) *p)) == 0) && (*p != ',')) &&
                    (*p != '\0')) {
      if ((p-threshold_map) >= (MaxTextExtent-1))
        break;
      token[p-threshold_map] = *p;
      p++;
    }
    token[p-threshold_map] = '\0';
    map = GetThresholdMap(token, exception);
    if ( map == (ThresholdMap *) NULL ) {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "InvalidArgument","%s : '%s'","ordered-dither",threshold_map);
      return(MagickFalse);
    }
  }
  /* Set channel levels from extra comma separated arguments
     Default to 2, the single value given, or individual channel values
  */
#if 1
  { /* parse directly as a comma separated list of integers */
    char *p;

    p = strchr((char *) threshold_map,',');
    if ( p != (char *) NULL && isdigit((int) ((unsigned char) *(++p))) )
      levels.index = (unsigned int) strtoul(p, &p, 10);
    else
      levels.index = 2;

    levels.red     = ((channel & RedChannel  )   != 0) ? levels.index : 0;
    levels.green   = ((channel & GreenChannel)   != 0) ? levels.index : 0;
    levels.blue    = ((channel & BlueChannel)    != 0) ? levels.index : 0;
    levels.opacity = ((channel & OpacityChannel) != 0) ? levels.index : 0;
    levels.index   = ((channel & IndexChannel)   != 0
            && (image->colorspace == CMYKColorspace)) ? levels.index : 0;

    /* if more than a single number, each channel has a separate value */
    if ( p != (char *) NULL && *p == ',' ) {
      p=strchr((char *) threshold_map,',');
      p++;
      if ((channel & RedChannel) != 0)
        levels.red = (unsigned int) strtoul(p, &p, 10),   (void)(*p == ',' && p++);
      if ((channel & GreenChannel) != 0)
        levels.green = (unsigned int) strtoul(p, &p, 10), (void)(*p == ',' && p++);
      if ((channel & BlueChannel) != 0)
        levels.blue = (unsigned int) strtoul(p, &p, 10),  (void)(*p == ',' && p++);
      if ((channel & IndexChannel) != 0 && image->colorspace == CMYKColorspace)
        levels.index=(unsigned int) strtoul(p, &p, 10), (void)(*p == ',' && p++);
      if ((channel & OpacityChannel) != 0)
        levels.opacity = (unsigned int) strtoul(p, &p, 10), (void)(*p == ',' && p++);
    }
  }
#else
  /* Parse level values as a geometry */
  /* This difficult!
   * How to map   GeometryInfo structure elements into
   * LongPixelPacket structure elements, but according to channel?
   * Note the channels list may skip elements!!!!
   * EG  -channel BA  -ordered-dither map,2,3
   * will need to map  g.rho -> l.blue, and g.sigma -> l.opacity
   * A simpler way is needed, probably converting geometry to a temporary
   * array, then using channel to advance the index into ssize_t pixel packet.
   */
#endif

#if 0
printf("DEBUG levels  r=%u g=%u b=%u a=%u i=%u\n",
     levels.red, levels.green, levels.blue, levels.opacity, levels.index);
#endif

  { /* Do the posterized ordered dithering of the image */
    ssize_t
      d;

    /* d = number of psuedo-level divisions added between color levels */
    d = map->divisor-1;

    /* reduce levels to levels - 1 */
    levels.red     = levels.red     ? levels.red-1     : 0;
    levels.green   = levels.green   ? levels.green-1   : 0;
    levels.blue    = levels.blue    ? levels.blue-1    : 0;
    levels.opacity = levels.opacity ? levels.opacity-1 : 0;
    levels.index   = levels.index   ? levels.index-1   : 0;

    if (SetImageStorageClass(image,DirectClass) == MagickFalse)
      {
        InheritException(exception,&image->exception);
        return(MagickFalse);
      }
    status=MagickTrue;
    progress=0;
    image_view=AcquireAuthenticCacheView(image,exception);
#if defined(MAGICKCORE_OPENMP_SUPPORT)
    #pragma omp parallel for schedule(static,4) shared(progress,status) \
      magick_threads(image,image,image->rows,1)
#endif
    for (y=0; y < (ssize_t) image->rows; y++)
    {
      register IndexPacket
        *magick_restrict indexes;

      register ssize_t
        x;

      register PixelPacket
        *magick_restrict q;

      if (status == MagickFalse)
        continue;
      q=GetCacheViewAuthenticPixels(image_view,0,y,image->columns,1,exception);
      if (q == (PixelPacket *) NULL)
        {
          status=MagickFalse;
          continue;
        }
      indexes=GetCacheViewAuthenticIndexQueue(image_view);
      for (x=0; x < (ssize_t) image->columns; x++)
      {
        register ssize_t
          threshold,
          t,
          l;

        /*
          Figure out the dither threshold for this pixel
          This must be a integer from 1 to map->divisor-1
        */
        threshold = map->levels[(x%map->width) +map->width*(y%map->height)];

        /* Dither each channel in the image as appropriate
          Notes on the integer Math...
              total number of divisions = (levels-1)*(divisor-1)+1)
              t1 = this colors psuedo_level =
                      q->red * total_divisions / (QuantumRange+1)
              l = posterization level       0..levels
              t = dither threshold level    0..divisor-1  NB: 0 only on last
              Each color_level is of size   QuantumRange / (levels-1)
              NB: All input levels and divisor are already had 1 subtracted
              Opacity is inverted so 'off' represents transparent.
        */
        if (levels.red) {
          t = (ssize_t) (QuantumScale*GetPixelRed(q)*(levels.red*d+1));
          l = t/d;  t = t-l*d;
          SetPixelRed(q,ClampToQuantum((MagickRealType)
            ((l+(t >= threshold))*(MagickRealType) QuantumRange/levels.red)));
        }
        if (levels.green) {
          t = (ssize_t) (QuantumScale*GetPixelGreen(q)*
            (levels.green*d+1));
          l = t/d;  t = t-l*d;
          SetPixelGreen(q,ClampToQuantum((MagickRealType)
            ((l+(t >= threshold))*(MagickRealType) QuantumRange/levels.green)));
        }
        if (levels.blue) {
          t = (ssize_t) (QuantumScale*GetPixelBlue(q)*
            (levels.blue*d+1));
          l = t/d;  t = t-l*d;
          SetPixelBlue(q,ClampToQuantum((MagickRealType)
            ((l+(t >= threshold))*(MagickRealType) QuantumRange/levels.blue)));
        }
        if (levels.opacity) {
          t = (ssize_t) ((1.0-QuantumScale*GetPixelOpacity(q))*
            (levels.opacity*d+1));
          l = t/d;  t = t-l*d;
          SetPixelOpacity(q,ClampToQuantum((MagickRealType)
            ((1.0-l-(t >= threshold))*(MagickRealType) QuantumRange/
            levels.opacity)));
        }
        if (levels.index) {
          t = (ssize_t) (QuantumScale*GetPixelIndex(indexes+x)*
            (levels.index*d+1));
          l = t/d;  t = t-l*d;
          SetPixelIndex(indexes+x,ClampToQuantum((MagickRealType) ((l+
            (t>=threshold))*(MagickRealType) QuantumRange/levels.index)));
        }
        q++;
      }
      if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
        status=MagickFalse;
      if (image->progress_monitor != (MagickProgressMonitor) NULL)
        {
          MagickBooleanType
            proceed;

#if defined(MAGICKCORE_OPENMP_SUPPORT)
          #pragma omp critical (MagickCore_OrderedPosterizeImageChannel)
#endif
          proceed=SetImageProgress(image,DitherImageTag,progress++,image->rows);
          if (proceed == MagickFalse)
            status=MagickFalse;
        }
    }
    image_view=DestroyCacheView(image_view);
  }
  map=DestroyThresholdMap(map);
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%     P e r c e p t i b l e I m a g e                                         %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  PerceptibleImage() set each pixel whose value is less than |epsilon| to
%  epsilon or -epsilon (whichever is closer) otherwise the pixel value remains
%  unchanged.
%
%  The format of the PerceptibleImageChannel method is:
%
%      MagickBooleanType PerceptibleImage(Image *image,const double epsilon)
%      MagickBooleanType PerceptibleImageChannel(Image *image,
%        const ChannelType channel,const double epsilon)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o channel: the channel type.
%
%    o epsilon: the epsilon threshold (e.g. 1.0e-9).
%
*/

static inline Quantum PerceptibleThreshold(const Quantum quantum,
  const double epsilon)
{
  double
    sign;

  sign=(double) quantum < 0.0 ? -1.0 : 1.0;
  if ((sign*quantum) >= epsilon)
    return(quantum);
  return((Quantum) (sign*epsilon));
}

MagickExport MagickBooleanType PerceptibleImage(Image *image,
  const double epsilon)
{
  MagickBooleanType
    status;

  status=PerceptibleImageChannel(image,DefaultChannels,epsilon);
  return(status);
}

MagickExport MagickBooleanType PerceptibleImageChannel(Image *image,
  const ChannelType channel,const double epsilon)
{
#define PerceptibleImageTag  "Perceptible/Image"

  CacheView
    *image_view;

  ExceptionInfo
    *exception;

  MagickBooleanType
    status;

  MagickOffsetType
    progress;

  ssize_t
    y;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  if (image->storage_class == PseudoClass)
    {
      register ssize_t
        i;

      register PixelPacket
        *magick_restrict q;

      q=image->colormap;
      for (i=0; i < (ssize_t) image->colors; i++)
      {
        SetPixelRed(q,PerceptibleThreshold(GetPixelRed(q),epsilon));
        SetPixelGreen(q,PerceptibleThreshold(GetPixelGreen(q),epsilon));
        SetPixelBlue(q,PerceptibleThreshold(GetPixelBlue(q),epsilon));
        SetPixelOpacity(q,PerceptibleThreshold(GetPixelOpacity(q),epsilon));
        q++;
      }
      return(SyncImage(image));
    }
  /*
    Perceptible image.
  */
  status=MagickTrue;
  progress=0;
  exception=(&image->exception);
  image_view=AcquireAuthenticCacheView(image,exception);
#if defined(MAGICKCORE_OPENMP_SUPPORT)
  #pragma omp parallel for schedule(static,4) shared(progress,status) \
    magick_threads(image,image,image->rows,1)
#endif
  for (y=0; y < (ssize_t) image->rows; y++)
  {
    register IndexPacket
      *magick_restrict indexes;

    register ssize_t
      x;

    register PixelPacket
      *magick_restrict q;

    if (status == MagickFalse)
      continue;
    q=GetCacheViewAuthenticPixels(image_view,0,y,image->columns,1,exception);
    if (q == (PixelPacket *) NULL)
      {
        status=MagickFalse;
        continue;
      }
    indexes=GetCacheViewAuthenticIndexQueue(image_view);
    for (x=0; x < (ssize_t) image->columns; x++)
    {
      if ((channel & RedChannel) != 0)
        SetPixelRed(q,PerceptibleThreshold(GetPixelRed(q),epsilon));
      if ((channel & GreenChannel) != 0)
        SetPixelGreen(q,PerceptibleThreshold(GetPixelGreen(q),epsilon));
      if ((channel & BlueChannel) != 0)
        SetPixelBlue(q,PerceptibleThreshold(GetPixelBlue(q),epsilon));
      if ((channel & OpacityChannel) != 0)
        SetPixelOpacity(q,PerceptibleThreshold(GetPixelOpacity(q),epsilon));
      if (((channel & IndexChannel) != 0) &&
          (image->colorspace == CMYKColorspace))
        SetPixelIndex(indexes+x,PerceptibleThreshold(GetPixelIndex(indexes+x),
          epsilon));
      q++;
    }
    if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
      status=MagickFalse;
    if (image->progress_monitor != (MagickProgressMonitor) NULL)
      {
        MagickBooleanType
          proceed;

#if defined(MAGICKCORE_OPENMP_SUPPORT)
        #pragma omp critical (MagickCore_PerceptibleImageChannel)
#endif
        proceed=SetImageProgress(image,PerceptibleImageTag,progress++,image->rows);
        if (proceed == MagickFalse)
          status=MagickFalse;
      }
  }
  image_view=DestroyCacheView(image_view);
  return(status);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%     R a n d o m T h r e s h o l d I m a g e                                 %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  RandomThresholdImage() changes the value of individual pixels based on the
%  intensity of each pixel compared to a random threshold.  The result is a
%  low-contrast, two color image.
%
%  The format of the RandomThresholdImage method is:
%
%      MagickBooleanType RandomThresholdImageChannel(Image *image,
%        const char *thresholds,ExceptionInfo *exception)
%      MagickBooleanType RandomThresholdImageChannel(Image *image,
%        const ChannelType channel,const char *thresholds,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o channel: the channel or channels to be thresholded.
%
%    o thresholds: a geometry string containing low,high thresholds.  If the
%      string contains 2x2, 3x3, or 4x4, an ordered dither of order 2, 3, or 4
%      is performed instead.
%
%    o exception: return any errors or warnings in this structure.
%
*/

MagickExport MagickBooleanType RandomThresholdImage(Image *image,
  const char *thresholds,ExceptionInfo *exception)
{
  MagickBooleanType
    status;

  status=RandomThresholdImageChannel(image,DefaultChannels,thresholds,
    exception);
  return(status);
}

MagickExport MagickBooleanType RandomThresholdImageChannel(Image *image,
  const ChannelType channel,const char *thresholds,ExceptionInfo *exception)
{
#define ThresholdImageTag  "Threshold/Image"

  CacheView
    *image_view;

  GeometryInfo
    geometry_info;

  MagickStatusType
    flags;

  MagickBooleanType
    status;

  MagickOffsetType
    progress;

  MagickPixelPacket
    threshold;

  MagickRealType
    min_threshold,
    max_threshold;

  RandomInfo
    **magick_restrict random_info;

  ssize_t
    y;

#if defined(MAGICKCORE_OPENMP_SUPPORT)
  unsigned long
    key;
#endif

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  assert(exception != (ExceptionInfo *) NULL);
  assert(exception->signature == MagickSignature);
  if (thresholds == (const char *) NULL)
    return(MagickTrue);
  GetMagickPixelPacket(image,&threshold);
  min_threshold=0.0;
  max_threshold=(MagickRealType) QuantumRange;
  flags=ParseGeometry(thresholds,&geometry_info);
  min_threshold=geometry_info.rho;
  max_threshold=geometry_info.sigma;
  if ((flags & SigmaValue) == 0)
    max_threshold=min_threshold;
  if (strchr(thresholds,'%') != (char *) NULL)
    {
      max_threshold*=(MagickRealType) (0.01*QuantumRange);
      min_threshold*=(MagickRealType) (0.01*QuantumRange);
    }
  else
    if (((max_threshold == min_threshold) || (max_threshold == 1)) &&
        (min_threshold <= 8))
      {
        /*
          Backward Compatibility -- ordered-dither -- IM v 6.2.9-6.
        */
        status=OrderedPosterizeImageChannel(image,channel,thresholds,exception);
        return(status);
      }
  /*
    Random threshold image.
  */
  status=MagickTrue;
  progress=0;
  if (channel == CompositeChannels)
    {
      if (AcquireImageColormap(image,2) == MagickFalse)
        ThrowBinaryException(ResourceLimitError,"MemoryAllocationFailed",
          image->filename);
      random_info=AcquireRandomInfoThreadSet();
      image_view=AcquireAuthenticCacheView(image,exception);
#if defined(MAGICKCORE_OPENMP_SUPPORT)
      key=GetRandomSecretKey(random_info[0]);
      #pragma omp parallel for schedule(static,4) shared(progress,status) \
        magick_threads(image,image,image->rows,key == ~0UL)
#endif
      for (y=0; y < (ssize_t) image->rows; y++)
      {
        const int
          id = GetOpenMPThreadId();

        MagickBooleanType
          sync;

        register IndexPacket
          *magick_restrict indexes;

        register ssize_t
          x;

        register PixelPacket
          *magick_restrict q;

        if (status == MagickFalse)
          continue;
        q=GetCacheViewAuthenticPixels(image_view,0,y,image->columns,1,
          exception);
        if (q == (PixelPacket *) NULL)
          {
            status=MagickFalse;
            continue;
          }
        indexes=GetCacheViewAuthenticIndexQueue(image_view);
        for (x=0; x < (ssize_t) image->columns; x++)
        {
          IndexPacket
            index;

          MagickRealType
            intensity;

          intensity=GetPixelIntensity(image,q);
          if (intensity < min_threshold)
            threshold.index=min_threshold;
          else if (intensity > max_threshold)
            threshold.index=max_threshold;
          else
            threshold.index=(MagickRealType)(QuantumRange*
              GetPseudoRandomValue(random_info[id]));
          index=(IndexPacket) (intensity <= threshold.index ? 0 : 1);
          SetPixelIndex(indexes+x,index);
          SetPixelRGBO(q,image->colormap+(ssize_t) index);
          q++;
        }
        sync=SyncCacheViewAuthenticPixels(image_view,exception);
        if (sync == MagickFalse)
          status=MagickFalse;
        if (image->progress_monitor != (MagickProgressMonitor) NULL)
          {
            MagickBooleanType
              proceed;

#if defined(MAGICKCORE_OPENMP_SUPPORT)
            #pragma omp critical (MagickCore_RandomThresholdImageChannel)
#endif
            proceed=SetImageProgress(image,ThresholdImageTag,progress++,
              image->rows);
            if (proceed == MagickFalse)
              status=MagickFalse;
          }
      }
      image_view=DestroyCacheView(image_view);
      random_info=DestroyRandomInfoThreadSet(random_info);
      return(status);
    }
  if (SetImageStorageClass(image,DirectClass) == MagickFalse)
    {
      InheritException(exception,&image->exception);
      return(MagickFalse);
    }
  random_info=AcquireRandomInfoThreadSet();
  image_view=AcquireAuthenticCacheView(image,exception);
#if defined(MAGICKCORE_OPENMP_SUPPORT)
  key=GetRandomSecretKey(random_info[0]);
  #pragma omp parallel for schedule(static,4) shared(progress,status) \
    magick_threads(image,image,image->rows,key == ~0UL)
#endif
  for (y=0; y < (ssize_t) image->rows; y++)
  {
    const int
      id = GetOpenMPThreadId();

    register IndexPacket
      *magick_restrict indexes;

    register PixelPacket
      *magick_restrict q;

    register ssize_t
      x;

    if (status == MagickFalse)
      continue;
    q=GetCacheViewAuthenticPixels(image_view,0,y,image->columns,1,exception);
    if (q == (PixelPacket *) NULL)
      {
        status=MagickFalse;
        continue;
      }
    indexes=GetCacheViewAuthenticIndexQueue(image_view);
    for (x=0; x < (ssize_t) image->columns; x++)
    {
      if ((channel & RedChannel) != 0)
        {
          if ((MagickRealType) GetPixelRed(q) < min_threshold)
            threshold.red=min_threshold;
          else
            if ((MagickRealType) GetPixelRed(q) > max_threshold)
              threshold.red=max_threshold;
            else
              threshold.red=(MagickRealType) (QuantumRange*
                GetPseudoRandomValue(random_info[id]));
        }
      if ((channel & GreenChannel) != 0)
        {
          if ((MagickRealType) GetPixelGreen(q) < min_threshold)
            threshold.green=min_threshold;
          else
            if ((MagickRealType) GetPixelGreen(q) > max_threshold)
              threshold.green=max_threshold;
            else
              threshold.green=(MagickRealType) (QuantumRange*
                GetPseudoRandomValue(random_info[id]));
        }
      if ((channel & BlueChannel) != 0)
        {
          if ((MagickRealType) GetPixelBlue(q) < min_threshold)
            threshold.blue=min_threshold;
          else
            if ((MagickRealType) GetPixelBlue(q) > max_threshold)
              threshold.blue=max_threshold;
            else
              threshold.blue=(MagickRealType) (QuantumRange*
                GetPseudoRandomValue(random_info[id]));
        }
      if ((channel & OpacityChannel) != 0)
        {
          if ((MagickRealType) GetPixelOpacity(q) < min_threshold)
            threshold.opacity=min_threshold;
          else
            if ((MagickRealType) GetPixelOpacity(q) > max_threshold)
              threshold.opacity=max_threshold;
            else
              threshold.opacity=(MagickRealType) (QuantumRange*
                GetPseudoRandomValue(random_info[id]));
        }
      if (((channel & IndexChannel) != 0) &&
          (image->colorspace == CMYKColorspace))
        {
          if ((MagickRealType) GetPixelIndex(indexes+x) < min_threshold)
            threshold.index=min_threshold;
          else
            if ((MagickRealType) GetPixelIndex(indexes+x) > max_threshold)
              threshold.index=max_threshold;
            else
              threshold.index=(MagickRealType) (QuantumRange*
                GetPseudoRandomValue(random_info[id]));
        }
      if ((channel & RedChannel) != 0)
        SetPixelRed(q,(MagickRealType) GetPixelRed(q) <= threshold.red ?
          0 : QuantumRange);
      if ((channel & GreenChannel) != 0)
        SetPixelGreen(q,(MagickRealType) GetPixelGreen(q) <= threshold.green ?
          0 : QuantumRange);
      if ((channel & BlueChannel) != 0)
        SetPixelBlue(q,(MagickRealType) GetPixelBlue(q) <= threshold.blue ?
          0 : QuantumRange);
      if ((channel & OpacityChannel) != 0)
        SetPixelOpacity(q,(MagickRealType) GetPixelOpacity(q) <=
          threshold.opacity ? 0 : QuantumRange);
      if (((channel & IndexChannel) != 0) &&
          (image->colorspace == CMYKColorspace))
        SetPixelIndex(indexes+x,(MagickRealType) GetPixelIndex(indexes+x) <=
          threshold.index ? 0 : QuantumRange);
      q++;
    }
    if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
      status=MagickFalse;
    if (image->progress_monitor != (MagickProgressMonitor) NULL)
      {
        MagickBooleanType
          proceed;

#if defined(MAGICKCORE_OPENMP_SUPPORT)
        #pragma omp critical (MagickCore_RandomThresholdImageChannel)
#endif
        proceed=SetImageProgress(image,ThresholdImageTag,progress++,
          image->rows);
        if (proceed == MagickFalse)
          status=MagickFalse;
      }
  }
  image_view=DestroyCacheView(image_view);
  random_info=DestroyRandomInfoThreadSet(random_info);
  return(status);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%     W h i t e T h r e s h o l d I m a g e                                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  WhiteThresholdImage() is like ThresholdImage() but forces all pixels above
%  the threshold into white while leaving all pixels at or below the threshold
%  unchanged.
%
%  The format of the WhiteThresholdImage method is:
%
%      MagickBooleanType WhiteThresholdImage(Image *image,const char *threshold)
%      MagickBooleanType WhiteThresholdImageChannel(Image *image,
%        const ChannelType channel,const char *threshold,
%        ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image: the image.
%
%    o channel: the channel or channels to be thresholded.
%
%    o threshold: Define the threshold value.
%
%    o exception: return any errors or warnings in this structure.
%
*/
MagickExport MagickBooleanType WhiteThresholdImage(Image *image,
  const char *threshold)
{
  MagickBooleanType
    status;

  status=WhiteThresholdImageChannel(image,DefaultChannels,threshold,
    &image->exception);
  return(status);
}

MagickExport MagickBooleanType WhiteThresholdImageChannel(Image *image,
  const ChannelType channel,const char *thresholds,ExceptionInfo *exception)
{
#define ThresholdImageTag  "Threshold/Image"

  CacheView
    *image_view;

  GeometryInfo
    geometry_info;

  MagickBooleanType
    status;

  MagickOffsetType
    progress;

  MagickPixelPacket
    threshold;

  MagickStatusType
    flags;

  ssize_t
    y;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  if (thresholds == (const char *) NULL)
    return(MagickTrue);
  if (SetImageStorageClass(image,DirectClass) == MagickFalse)
    return(MagickFalse);
  flags=ParseGeometry(thresholds,&geometry_info);
  GetMagickPixelPacket(image,&threshold);
  threshold.red=geometry_info.rho;
  threshold.green=geometry_info.sigma;
  if ((flags & SigmaValue) == 0)
    threshold.green=threshold.red;
  threshold.blue=geometry_info.xi;
  if ((flags & XiValue) == 0)
    threshold.blue=threshold.red;
  threshold.opacity=geometry_info.psi;
  if ((flags & PsiValue) == 0)
    threshold.opacity=threshold.red;
  threshold.index=geometry_info.chi;
  if ((flags & ChiValue) == 0)
    threshold.index=threshold.red;
  if ((flags & PercentValue) != 0)
    {
      threshold.red*=(MagickRealType) (QuantumRange/100.0);
      threshold.green*=(MagickRealType) (QuantumRange/100.0);
      threshold.blue*=(MagickRealType) (QuantumRange/100.0);
      threshold.opacity*=(MagickRealType) (QuantumRange/100.0);
      threshold.index*=(MagickRealType) (QuantumRange/100.0);
    }
  if ((IsMagickGray(&threshold) == MagickFalse) &&
      (IsGrayColorspace(image->colorspace) != MagickFalse))
    (void) SetImageColorspace(image,sRGBColorspace);
  /*
    White threshold image.
  */
  status=MagickTrue;
  progress=0;
  image_view=AcquireAuthenticCacheView(image,exception);
#if defined(MAGICKCORE_OPENMP_SUPPORT)
  #pragma omp parallel for schedule(static,4) shared(progress,status) \
    magick_threads(image,image,image->rows,1)
#endif
  for (y=0; y < (ssize_t) image->rows; y++)
  {
    register IndexPacket
      *magick_restrict indexes;

    register ssize_t
      x;

    register PixelPacket
      *magick_restrict q;

    if (status == MagickFalse)
      continue;
    q=GetCacheViewAuthenticPixels(image_view,0,y,image->columns,1,exception);
    if (q == (PixelPacket *) NULL)
      {
        status=MagickFalse;
        continue;
      }
    indexes=GetCacheViewAuthenticIndexQueue(image_view);
    for (x=0; x < (ssize_t) image->columns; x++)
    {
      if (((channel & RedChannel) != 0) &&
          ((MagickRealType) GetPixelRed(q) > threshold.red))
        SetPixelRed(q,QuantumRange);
      if (((channel & GreenChannel) != 0) &&
          ((MagickRealType) GetPixelGreen(q) > threshold.green))
        SetPixelGreen(q,QuantumRange);
      if (((channel & BlueChannel) != 0) &&
          ((MagickRealType) GetPixelBlue(q) > threshold.blue))
        SetPixelBlue(q,QuantumRange);
      if (((channel & OpacityChannel) != 0) &&
          ((MagickRealType) GetPixelOpacity(q) > threshold.opacity))
        SetPixelOpacity(q,QuantumRange);
      if (((channel & IndexChannel) != 0) &&
          (image->colorspace == CMYKColorspace) &&
          ((MagickRealType) GetPixelIndex(indexes+x)) > threshold.index)
        SetPixelIndex(indexes+x,QuantumRange);
      q++;
    }
    if (SyncCacheViewAuthenticPixels(image_view,exception) == MagickFalse)
      status=MagickFalse;
    if (image->progress_monitor != (MagickProgressMonitor) NULL)
      {
        MagickBooleanType
          proceed;

#if defined(MAGICKCORE_OPENMP_SUPPORT)
        #pragma omp critical (MagickCore_WhiteThresholdImageChannel)
#endif
        proceed=SetImageProgress(image,ThresholdImageTag,progress++,
          image->rows);
        if (proceed == MagickFalse)
          status=MagickFalse;
      }
  }
  image_view=DestroyCacheView(image_view);
  return(status);
}