root/coders/dds.c

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DEFINITIONS

This source file includes following definitions.
  1. DDSDecoder
  2. Min
  3. ReadDDSImage
  4. ReadDDSInfo
  5. CalculateColors
  6. ReadDXT1
  7. ReadDXT3
  8. ReadDXT5
  9. ReadUncompressedRGB
  10. ReadUncompressedRGBA
  11. SkipDXTMipmaps
  12. SkipRGBMipmaps
  13. IsDDS
  14. RegisterDDSImage
  15. UnregisterDDSImage

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%                            DDDD   DDDD   SSSSS                              %
%                            D   D  D   D  SS                                 %
%                            D   D  D   D   SSS                               %
%                            D   D  D   D     SS                              %
%                            DDDD   DDDD   SSSSS                              %
%                                                                             %
%                                                                             %
%              Read Microsoft Direct Draw Surface Image Format                %
%                                                                             %
%                              Software Design                                %
%                             Bianca van Schaik                               %
%                                March 2008                                   %
%                                                                             %
%                                                                             %
%  Copyright 1999-2013 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/colorspace.h"
#include "magick/exception.h"
#include "magick/exception-private.h"
#include "magick/image.h"
#include "magick/image-private.h"
#include "magick/list.h"
#include "magick/log.h"
#include "magick/magick.h"
#include "magick/memory_.h"
#include "magick/monitor.h"
#include "magick/monitor-private.h"
#include "magick/pixel-accessor.h"
#include "magick/profile.h"
#include "magick/quantum-private.h"
#include "magick/static.h"
#include "magick/string_.h"
#include "magick/module.h"
#include "magick/transform.h"
#include "magick/studio.h"
#include "magick/blob.h"
#include "magick/blob-private.h"
#include "magick/colorspace.h"
#include "magick/exception.h"
#include "magick/exception-private.h"
#include "magick/compress.h"
#include "magick/image.h"
#include "magick/image-private.h"
#include "magick/list.h"
#include "magick/magick.h"
#include "magick/memory_.h"
#include "magick/monitor.h"
#include "magick/monitor-private.h"
#include "magick/pixel-accessor.h"
#include "magick/quantum.h"
#include "magick/static.h"
#include "magick/string_.h"

/*
  Definitions
*/
#define DDSD_CAPS         0x00000001
#define DDSD_HEIGHT       0x00000002
#define DDSD_WIDTH        0x00000004
#define DDSD_PITCH        0x00000008
#define DDSD_PIXELFORMAT  0x00001000
#define DDSD_MIPMAPCOUNT  0x00020000
#define DDSD_LINEARSIZE   0x00080000
#define DDSD_DEPTH        0x00800000

#define DDPF_ALPHAPIXELS  0x00000001
#define DDPF_FOURCC       0x00000004
#define DDPF_RGB          0x00000040

#define FOURCC_DXT1       0x31545844
#define FOURCC_DXT3       0x33545844
#define FOURCC_DXT5       0x35545844

#define DDSCAPS_COMPLEX   0x00000008
#define DDSCAPS_TEXTURE   0x00001000
#define DDSCAPS_MIPMAP    0x00400000

#define DDSCAPS2_CUBEMAP  0x00000200
#define DDSCAPS2_CUBEMAP_POSITIVEX  0x00000400
#define DDSCAPS2_CUBEMAP_NEGATIVEX  0x00000800
#define DDSCAPS2_CUBEMAP_POSITIVEY  0x00001000
#define DDSCAPS2_CUBEMAP_NEGATIVEY  0x00002000
#define DDSCAPS2_CUBEMAP_POSITIVEZ  0x00004000
#define DDSCAPS2_CUBEMAP_NEGATIVEZ  0x00008000
#define DDSCAPS2_VOLUME   0x00200000

/*
  Structure declarations.
*/
typedef struct _DDSPixelFormat
{
  size_t
    flags,
    fourcc,
    rgb_bitcount,
    r_bitmask,
    g_bitmask,
    b_bitmask,
    alpha_bitmask;
} DDSPixelFormat;

typedef struct _DDSInfo
{
  size_t
    flags,
    height,
    width,
    pitchOrLinearSize,
    depth,
    mipmapcount,
    ddscaps1,
    ddscaps2;

  DDSPixelFormat
    pixelformat;
} DDSInfo;

typedef struct _DDSColors
{
  unsigned char
    r[4],
    g[4],
    b[4],
    a[4];
} DDSColors;

typedef MagickBooleanType
  DDSDecoder(Image *,DDSInfo *);

/*
  Macros
*/
#define C565_r(x) (((x) & 0xF800) >> 11)
#define C565_g(x) (((x) & 0x07E0) >> 5)
#define C565_b(x)  ((x) & 0x001F)

#define C565_red(x)   ( (C565_r(x) << 3 | C565_r(x) >> 2))
#define C565_green(x) ( (C565_g(x) << 2 | C565_g(x) >> 4))
#define C565_blue(x)  ( (C565_b(x) << 3 | C565_b(x) >> 2))

#define DIV2(x)  ((x) > 1 ? ((x) >> 1) : 1)

/*
  Forward declarations
*/
static MagickBooleanType
  ReadDDSInfo(Image *image, DDSInfo *dds_info);

static void
  CalculateColors(unsigned short c0, unsigned short c1,
    DDSColors *c, MagickBooleanType ignoreAlpha);

static MagickBooleanType
  ReadDXT1(Image *image, DDSInfo *dds_info);

static MagickBooleanType
  ReadDXT3(Image *image, DDSInfo *dds_info);

static MagickBooleanType
  ReadDXT5(Image *image, DDSInfo *dds_info);

static MagickBooleanType
  ReadUncompressedRGB(Image *image, DDSInfo *dds_info);

static MagickBooleanType
  ReadUncompressedRGBA(Image *image, DDSInfo *dds_info);

static void
  SkipDXTMipmaps(Image *image, DDSInfo *dds_info, int texel_size);

static void
  SkipRGBMipmaps(Image *image, DDSInfo *dds_info, int pixel_size);

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   R e a d D D S I m a g e                                                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  ReadDDSImage() reads a DirectDraw Surface image file and returns it.  It
%  allocates the memory necessary for the new Image structure and returns a
%  pointer to the new image.
%
%  The format of the ReadDDSImage method is:
%
%      Image *ReadDDSImage(const ImageInfo *image_info,ExceptionInfo *exception)
%
%  A description of each parameter follows:
%
%    o image_info: The image info.
%
%    o exception: return any errors or warnings in this structure.
%
*/

static inline size_t Min(size_t one, size_t two)
{
  if (one < two)
    return one;
  return two;
}

static Image *ReadDDSImage(const ImageInfo *image_info,ExceptionInfo *exception)
{
  Image
    *image;

  MagickBooleanType
    status,
    cubemap = MagickFalse,
    volume = MagickFalse,
    matte;

  CompressionType
    compression;

  DDSInfo
    dds_info;

  DDSDecoder
    *decoder;

  size_t
    n, num_images;

  /*
    Open image file.
  */
  assert(image_info != (const ImageInfo *) NULL);
  assert(image_info->signature == MagickSignature);
  if (image_info->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
      image_info->filename);
  assert(exception != (ExceptionInfo *) NULL);
  assert(exception->signature == MagickSignature);
  image=AcquireImage(image_info);
  status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
  if (status == MagickFalse)
    {
      image=DestroyImageList(image);
      return((Image *) NULL);
    }

  /*
    Initialize image structure.
  */
  if (ReadDDSInfo(image, &dds_info) != MagickTrue) {
    ThrowReaderException(CorruptImageError,"ImproperImageHeader");
  }

  if (dds_info.ddscaps2 & DDSCAPS2_CUBEMAP)
    cubemap = MagickTrue;

  if (dds_info.ddscaps2 & DDSCAPS2_VOLUME && dds_info.depth > 0)
    volume = MagickTrue;

  (void) SeekBlob(image, 128, SEEK_SET);

  /*
    Determine pixel format
  */
  if (dds_info.pixelformat.flags & DDPF_RGB)
    {
      compression = NoCompression;
      if (dds_info.pixelformat.flags & DDPF_ALPHAPIXELS)
        {
          matte = MagickTrue;
          decoder = ReadUncompressedRGBA;
        }
      else
        {
          matte = MagickTrue;
          decoder = ReadUncompressedRGB;
        }
    }
  else if (dds_info.pixelformat.flags & DDPF_FOURCC)
    {
      switch (dds_info.pixelformat.fourcc)
      {
        case FOURCC_DXT1:
        {
          matte = MagickFalse;
          compression = DXT1Compression;
          decoder = ReadDXT1;
          break;
        }

        case FOURCC_DXT3:
        {
          matte = MagickTrue;
          compression = DXT3Compression;
          decoder = ReadDXT3;
          break;
        }

        case FOURCC_DXT5:
        {
          matte = MagickTrue;
          compression = DXT5Compression;
          decoder = ReadDXT5;
          break;
        }

        default:
        {
          /* Unknown FOURCC */
          ThrowReaderException(CorruptImageError, "ImageTypeNotSupported");
        }
      }
    }
  else
    {
      /* Neither compressed nor uncompressed... thus unsupported */
      ThrowReaderException(CorruptImageError, "ImageTypeNotSupported");
    }

  num_images = 1;
  if (cubemap)
    {
      /*
        Determine number of faces defined in the cubemap
      */
      num_images = 0;
      if (dds_info.ddscaps2 & DDSCAPS2_CUBEMAP_POSITIVEX) num_images++;
      if (dds_info.ddscaps2 & DDSCAPS2_CUBEMAP_NEGATIVEX) num_images++;
      if (dds_info.ddscaps2 & DDSCAPS2_CUBEMAP_POSITIVEY) num_images++;
      if (dds_info.ddscaps2 & DDSCAPS2_CUBEMAP_NEGATIVEY) num_images++;
      if (dds_info.ddscaps2 & DDSCAPS2_CUBEMAP_POSITIVEZ) num_images++;
      if (dds_info.ddscaps2 & DDSCAPS2_CUBEMAP_NEGATIVEZ) num_images++;
    }

  if (volume)
    num_images = dds_info.depth;

  for (n = 0; n < num_images; n++)
  {
    if (n != 0)
      {
        /* Start a new image */
        AcquireNextImage(image_info,image);
        if (GetNextImageInList(image) == (Image *) NULL)
          {
            image = DestroyImageList(image);
            return((Image *) NULL);
          }
        image=SyncNextImageInList(image);
      }
 
    image->matte = matte;
    image->compression = compression;
    image->columns = dds_info.width;
    image->rows = dds_info.height;
    image->storage_class = DirectClass;
    image->endian = LSBEndian;
    image->depth = 8;
    if (image_info->ping != MagickFalse)
      {
        (void) CloseBlob(image);
        return(GetFirstImageInList(image));
      }

    if ((decoder)(image, &dds_info) != MagickTrue)
      {
        (void) CloseBlob(image);
        return(GetFirstImageInList(image));
      }
  }

  if (EOFBlob(image) != MagickFalse)
    ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",
      image->filename);

  (void) CloseBlob(image);
  return(GetFirstImageInList(image));
}

static MagickBooleanType ReadDDSInfo(Image *image, DDSInfo *dds_info)
{
  size_t
    hdr_size,
    required;

  /* Seek to start of header */
  (void) SeekBlob(image, 4, SEEK_SET);

  /* Check header field */
  hdr_size = ReadBlobLSBLong(image);
  if (hdr_size != 124)
    return MagickFalse;

  /* Fill in DDS info struct */
  dds_info->flags = ReadBlobLSBLong(image);

  /* Check required flags */
  required=(size_t) (DDSD_WIDTH | DDSD_HEIGHT | DDSD_PIXELFORMAT);
  if ((dds_info->flags & required) != required)
    return MagickFalse;

  dds_info->height = ReadBlobLSBLong(image);
  dds_info->width = ReadBlobLSBLong(image);
  dds_info->pitchOrLinearSize = ReadBlobLSBLong(image);
  dds_info->depth = ReadBlobLSBLong(image);
  dds_info->mipmapcount = ReadBlobLSBLong(image);

  (void) SeekBlob(image, 44, SEEK_CUR);   /* reserved region of 11 DWORDs */

  /* Read pixel format structure */
  hdr_size = ReadBlobLSBLong(image);
  if (hdr_size != 32)
    return MagickFalse;

  dds_info->pixelformat.flags = ReadBlobLSBLong(image);
  dds_info->pixelformat.fourcc = ReadBlobLSBLong(image);
  dds_info->pixelformat.rgb_bitcount = ReadBlobLSBLong(image);
  dds_info->pixelformat.r_bitmask = ReadBlobLSBLong(image);
  dds_info->pixelformat.g_bitmask = ReadBlobLSBLong(image);
  dds_info->pixelformat.b_bitmask = ReadBlobLSBLong(image);
  dds_info->pixelformat.alpha_bitmask = ReadBlobLSBLong(image);

  dds_info->ddscaps1 = ReadBlobLSBLong(image);
  dds_info->ddscaps2 = ReadBlobLSBLong(image);
  (void) SeekBlob(image, 12, SEEK_CUR); /* 3 reserved DWORDs */

  return MagickTrue;
}

static void CalculateColors(unsigned short c0, unsigned short c1,
  DDSColors *c, MagickBooleanType ignoreAlpha)
{
  c->a[0] = c->a[1] = c->a[2] = c->a[3] = 0;

  c->r[0] = (unsigned char) C565_red(c0);
  c->g[0] = (unsigned char) C565_green(c0);
  c->b[0] = (unsigned char) C565_blue(c0);

  c->r[1] = (unsigned char) C565_red(c1);
  c->g[1] = (unsigned char) C565_green(c1);
  c->b[1] = (unsigned char) C565_blue(c1);

  if (ignoreAlpha == MagickTrue || c0 > c1)
    {
      c->r[2] = (unsigned char) ((2 * c->r[0] + c->r[1]) / 3);
      c->g[2] = (unsigned char) ((2 * c->g[0] + c->g[1]) / 3);
      c->b[2] = (unsigned char) ((2 * c->b[0] + c->b[1]) / 3);

      c->r[3] = (unsigned char) ((c->r[0] + 2 * c->r[1]) / 3);
      c->g[3] = (unsigned char) ((c->g[0] + 2 * c->g[1]) / 3);
      c->b[3] = (unsigned char) ((c->b[0] + 2 * c->b[1]) / 3);
    }
  else
    {
      c->r[2] = (unsigned char) ((c->r[0] + c->r[1]) / 2);
      c->g[2] = (unsigned char) ((c->g[0] + c->g[1]) / 2);
      c->b[2] = (unsigned char) ((c->b[0] + c->b[1]) / 2);

      c->r[3] = c->g[3] = c->b[3] = 0;
      c->a[3] = 255;
    }
}

static MagickBooleanType ReadDXT1(Image *image, DDSInfo *dds_info)
{
  DDSColors
    colors;

  ExceptionInfo
    *exception;

  PixelPacket
    *q;

  register ssize_t
    i,
    x;

  size_t
    bits;

  ssize_t
    j,
    y;

  unsigned char
    code;

  unsigned short
    c0,
    c1;

  exception=(&image->exception);
  for (y = 0; y < (ssize_t) dds_info->height; y += 4)
  {
    for (x = 0; x < (ssize_t) dds_info->width; x += 4)
    {
      /* Get 4x4 patch of pixels to write on */
      q = QueueAuthenticPixels(image, x, y, Min(4, dds_info->width - x),
        Min(4, dds_info->height - y),exception);

      if (q == (PixelPacket *) NULL)
        return MagickFalse;

      /* Read 8 bytes of data from the image */
      c0 = ReadBlobLSBShort(image);
      c1 = ReadBlobLSBShort(image);
      bits = ReadBlobLSBLong(image);

      CalculateColors(c0, c1, &colors, MagickFalse);

      /* Write the pixels */
      for (j = 0; j < 4; j++)
      {
        for (i = 0; i < 4; i++)
        {
          if ((x + i) < (ssize_t) dds_info->width && (y + j) < (ssize_t) dds_info->height)
            {
              code = (unsigned char) ((bits >> ((j*4+i)*2)) & 0x3);
              SetPixelRed(q,ScaleCharToQuantum(colors.r[code]));
              SetPixelGreen(q,ScaleCharToQuantum(colors.g[code]));
              SetPixelBlue(q,ScaleCharToQuantum(colors.b[code]));
              SetPixelOpacity(q,ScaleCharToQuantum(colors.a[code]));
              if (colors.a[code] && image->matte == MagickFalse)
                /* Correct matte */
                image->matte = MagickTrue;
              q++;
            }
        }
      }

      if (SyncAuthenticPixels(image,exception) == MagickFalse)
        return MagickFalse;
    }
  }

  SkipDXTMipmaps(image, dds_info, 8);

  return MagickTrue;
}

static MagickBooleanType ReadDXT3(Image *image, DDSInfo *dds_info)
{
  DDSColors
    colors;

  ExceptionInfo
    *exception;

  ssize_t
    j,
    y;

  PixelPacket
    *q;

  register ssize_t
    i,
    x;

  unsigned char
    alpha;

  size_t
    a0,
    a1,
    bits,
    code;

  unsigned short
    c0,
    c1;

  exception=(&image->exception);
  for (y = 0; y < (ssize_t) dds_info->height; y += 4)
  {
    for (x = 0; x < (ssize_t) dds_info->width; x += 4)
    {
      /* Get 4x4 patch of pixels to write on */
      q = QueueAuthenticPixels(image, x, y, Min(4, dds_info->width - x),
                         Min(4, dds_info->height - y),exception);

      if (q == (PixelPacket *) NULL)
        return MagickFalse;

      /* Read alpha values (8 bytes) */
      a0 = ReadBlobLSBLong(image);
      a1 = ReadBlobLSBLong(image);

      /* Read 8 bytes of data from the image */
      c0 = ReadBlobLSBShort(image);
      c1 = ReadBlobLSBShort(image);
      bits = ReadBlobLSBLong(image);

      CalculateColors(c0, c1, &colors, MagickTrue);

      /* Write the pixels */
      for (j = 0; j < 4; j++)
      {
        for (i = 0; i < 4; i++)
        {
          if ((x + i) < (ssize_t) dds_info->width && (y + j) < (ssize_t) dds_info->height)
            {
              code = (bits >> ((4*j+i)*2)) & 0x3;
              SetPixelRed(q,ScaleCharToQuantum(colors.r[code]));
              SetPixelGreen(q,ScaleCharToQuantum(colors.g[code]));
              SetPixelBlue(q,ScaleCharToQuantum(colors.b[code]));
              /*
                Extract alpha value: multiply 0..15 by 17 to get range 0..255
              */
              if (j < 2)
                alpha = 17U * (unsigned char) ((a0 >> (4*(4*j+i))) & 0xf);
              else
                alpha = 17U * (unsigned char) ((a1 >> (4*(4*(j-2)+i))) & 0xf);
              SetPixelAlpha(q,ScaleCharToQuantum((unsigned char)
                alpha));
              q++;
            }
        }
      }

      if (SyncAuthenticPixels(image,exception) == MagickFalse)
        return MagickFalse;
    }
  }

  SkipDXTMipmaps(image, dds_info, 16);

  return MagickTrue;
}

static MagickBooleanType ReadDXT5(Image *image, DDSInfo *dds_info)
{
  DDSColors
    colors;

  ExceptionInfo
    *exception;

  ssize_t
    j,
    y;

  MagickSizeType
    alpha_bits;

  PixelPacket
    *q;

  register ssize_t
    i,
    x;

  unsigned char
    a0,
    a1;

  size_t
    alpha,
    bits,
    code,
    alpha_code;

  unsigned short
    c0,
    c1;

  exception=(&image->exception);
  for (y = 0; y < (ssize_t) dds_info->height; y += 4)
  {
    for (x = 0; x < (ssize_t) dds_info->width; x += 4)
    {
      /* Get 4x4 patch of pixels to write on */
      q = QueueAuthenticPixels(image, x, y, Min(4, dds_info->width - x),
                         Min(4, dds_info->height - y),exception);

      if (q == (PixelPacket *) NULL)
        return MagickFalse;

      /* Read alpha values (8 bytes) */
      a0 = (unsigned char) ReadBlobByte(image);
      a1 = (unsigned char) ReadBlobByte(image);

      alpha_bits = (MagickSizeType)ReadBlobLSBLong(image);
      alpha_bits = alpha_bits | ((MagickSizeType)ReadBlobLSBShort(image) << 32);

      /* Read 8 bytes of data from the image */
      c0 = ReadBlobLSBShort(image);
      c1 = ReadBlobLSBShort(image);
      bits = ReadBlobLSBLong(image);

      CalculateColors(c0, c1, &colors, MagickTrue);

      /* Write the pixels */
      for (j = 0; j < 4; j++)
      {
        for (i = 0; i < 4; i++)
        {
          if ((x + i) < (ssize_t) dds_info->width && (y + j) < (ssize_t) dds_info->height)
            {
              code = (bits >> ((4*j+i)*2)) & 0x3;
              SetPixelRed(q,ScaleCharToQuantum(colors.r[code]));
              SetPixelGreen(q,ScaleCharToQuantum(colors.g[code]));
              SetPixelBlue(q,ScaleCharToQuantum(colors.b[code]));
              /* Extract alpha value */
              alpha_code = (size_t) (alpha_bits >> (3*(4*j+i))) & 0x7;
              if (alpha_code == 0)
                alpha = a0;
              else if (alpha_code == 1)
                alpha = a1;
              else if (a0 > a1)
                alpha = ((8-alpha_code) * a0 + (alpha_code-1) * a1) / 7;
              else if (alpha_code == 6)
                alpha = 0;
              else if (alpha_code == 7)
                alpha = 255;
              else
                alpha = (((6-alpha_code) * a0 + (alpha_code-1) * a1) / 5);
              SetPixelAlpha(q,ScaleCharToQuantum((unsigned char)
                alpha));
              q++;
            }
        }
      }

      if (SyncAuthenticPixels(image,exception) == MagickFalse)
        return MagickFalse;
    }
  }

  SkipDXTMipmaps(image, dds_info, 16);

  return MagickTrue;
}

static MagickBooleanType ReadUncompressedRGB(Image *image, DDSInfo *dds_info)
{
  ExceptionInfo
    *exception;

  ssize_t
    x, y;

  PixelPacket
    *q;

  exception=(&image->exception);
  for (y = 0; y < (ssize_t) dds_info->height; y++)
  {
    q = QueueAuthenticPixels(image, 0, y, dds_info->width, 1,exception);

    if (q == (PixelPacket *) NULL)
      return MagickFalse;

    for (x = 0; x < (ssize_t) dds_info->width; x++)
    {
      SetPixelBlue(q,ScaleCharToQuantum((unsigned char)
        ReadBlobByte(image)));
      SetPixelGreen(q,ScaleCharToQuantum((unsigned char)
        ReadBlobByte(image)));
      SetPixelRed(q,ScaleCharToQuantum((unsigned char)
        ReadBlobByte(image)));
      if (dds_info->pixelformat.rgb_bitcount == 32)
        (void) ReadBlobByte(image);
      q++;
    }
 
    if (SyncAuthenticPixels(image,exception) == MagickFalse)
      return MagickFalse;
  }

  SkipRGBMipmaps(image, dds_info, 3);

  return MagickTrue;
}

static MagickBooleanType ReadUncompressedRGBA(Image *image, DDSInfo *dds_info)
{
  ExceptionInfo
    *exception;

  ssize_t
    x, y;

  PixelPacket
    *q;

  exception=(&image->exception);
  for (y = 0; y < (ssize_t) dds_info->height; y++)
  {
    q = QueueAuthenticPixels(image, 0, y, dds_info->width, 1,exception);

    if (q == (PixelPacket *) NULL)
      return MagickFalse;

    for (x = 0; x < (ssize_t) dds_info->width; x++)
    {
      SetPixelBlue(q,ScaleCharToQuantum((unsigned char)
        ReadBlobByte(image)));
      SetPixelGreen(q,ScaleCharToQuantum((unsigned char)
        ReadBlobByte(image)));
      SetPixelRed(q,ScaleCharToQuantum((unsigned char)
        ReadBlobByte(image)));
      SetPixelAlpha(q,ScaleCharToQuantum((unsigned char)
        ReadBlobByte(image)));
      q++;
    }

    if (SyncAuthenticPixels(image,exception) == MagickFalse)
      return MagickFalse;
  }

  SkipRGBMipmaps(image, dds_info, 4);

  return MagickTrue;
}

/*
  Skip the mipmap images for compressed (DXTn) dds files
*/
static void SkipDXTMipmaps(Image *image, DDSInfo *dds_info, int texel_size)
{
  register ssize_t
    i;

  MagickOffsetType
    offset;

  size_t
    h,
    w;

  /*
    Only skip mipmaps for textures and cube maps
  */
  if (dds_info->ddscaps1 & DDSCAPS_MIPMAP
      && (dds_info->ddscaps1 & DDSCAPS_TEXTURE
          || dds_info->ddscaps2 & DDSCAPS2_CUBEMAP))
    {
      w = DIV2(dds_info->width);
      h = DIV2(dds_info->height);

      /*
        Mipmapcount includes the main image, so start from one
      */
      for (i = 1; (i < (ssize_t) dds_info->mipmapcount) && w && h; i++)
      {
        offset = (MagickOffsetType) ((w + 3) / 4) * ((h + 3) / 4) * texel_size;
        (void) SeekBlob(image, offset, SEEK_CUR);

        w = DIV2(w);
        h = DIV2(h);
      }
    }
}

/*
  Skip the mipmap images for uncompressed (RGB or RGBA) dds files
*/
static void SkipRGBMipmaps(Image *image, DDSInfo *dds_info, int pixel_size)
{
  MagickOffsetType
    offset;

  register ssize_t
    i;

  size_t
    h,
    w;

  /*
    Only skip mipmaps for textures and cube maps
  */
  if (dds_info->ddscaps1 & DDSCAPS_MIPMAP
      && (dds_info->ddscaps1 & DDSCAPS_TEXTURE
          || dds_info->ddscaps2 & DDSCAPS2_CUBEMAP))
    {
      w = DIV2(dds_info->width);
      h = DIV2(dds_info->height);

      /*
        Mipmapcount includes the main image, so start from one
      */
      for (i=1; (i < (ssize_t) dds_info->mipmapcount) && w && h; i++)
      {
        offset = (MagickOffsetType) w * h * pixel_size;
        (void) SeekBlob(image, offset, SEEK_CUR);

        w = DIV2(w);
        h = DIV2(h);
      }
    }
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   I s D D S                                                                 %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  IsDDS() returns MagickTrue if the image format type, identified by the
%  magick string, is DDS.
%
%  The format of the IsDDS method is:
%
%      MagickBooleanType IsDDS(const unsigned char *magick,const size_t length)
%
%  A description of each parameter follows:
%
%    o magick: compare image format pattern against these bytes.
%
%    o length: Specifies the length of the magick string.
%
*/
static MagickBooleanType IsDDS(const unsigned char *magick,const size_t length)
{
  if (length < 4)
    return(MagickFalse);
  if (LocaleNCompare((char *) magick,"DDS ", 4) == 0)
    return(MagickTrue);
  return(MagickFalse);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   R e g i s t e r D D S I m a g e                                           %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  RegisterDDSImage() adds attributes for the DDS image format to
%  the list of supported formats.  The attributes include the image format
%  tag, a method to read and/or write the format, whether the format
%  supports the saving of more than one frame to the same file or blob,
%  whether the format supports native in-memory I/O, and a brief
%  description of the format.
%
%  The format of the RegisterDDSImage method is:
%
%      RegisterDDSImage(void)
%
*/
ModuleExport size_t RegisterDDSImage(void)
{
  MagickInfo
    *entry;

  entry = SetMagickInfo("DDS");
  entry->decoder = (DecodeImageHandler *) ReadDDSImage;
  entry->magick = (IsImageFormatHandler *) IsDDS;
  entry->seekable_stream=MagickTrue;
  entry->description = ConstantString("Microsoft DirectDraw Surface");
  entry->module = ConstantString("DDS");
  (void) RegisterMagickInfo(entry);
  return(MagickImageCoderSignature);
}


/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   U n r e g i s t e r D D S I m a g e                                       %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  UnregisterDDSImage() removes format registrations made by the
%  DDS module from the list of supported formats.
%
%  The format of the UnregisterDDSImage method is:
%
%      UnregisterDDSImage(void)
%
*/
ModuleExport void UnregisterDDSImage(void)
{
  (void) UnregisterMagickInfo("DDS");
}


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