root / ImageMagick / trunk / coders / bmp.c

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%                            BBBB   M   M  PPPP                               %
%                            B   B  MM MM  P   P                              %
%                            BBBB   M M M  PPPP                               %
%                            B   B  M   M  P                                  %
%                            BBBB   M   M  P                                  %
%                                                                             %
%                                                                             %
%             Read/Write Microsoft Windows Bitmap Image Format.               %
%                                                                             %
%                              Software Design                                %
%                                John Cristy                                  %
%                            Glenn Randers-Pehrson                            %
%                               December 2001                                 %
%                                                                             %
%                                                                             %
%  Copyright 1999-2008 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/color-private.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/profile.h"
#include "magick/quantum-private.h"
#include "magick/static.h"
#include "magick/string_.h"
#include "magick/module.h"
#include "magick/transform.h"

/*
  Macro definitions (from Windows wingdi.h).
*/
#undef BI_JPEG
#define BI_JPEG  4
#undef BI_PNG
#define BI_PNG  5
#if !defined(__WINDOWS__) || defined(__MINGW32__)
#define BI_RGB  0
#define BI_RLE8  1
#define BI_RLE4  2
#define BI_BITFIELDS  3

#define LCS_CALIBRATED_RBG  0
#define LCS_sRGB  1
#define LCS_WINDOWS_COLOR_SPACE  2
#define PROFILE_LINKED  3
#define PROFILE_EMBEDDED  4

#define LCS_GM_BUSINESS  1  /* Saturation */
#define LCS_GM_GRAPHICS  2  /* Relative */
#define LCS_GM_IMAGES  4  /* Perceptual */
#define LCS_GM_ABS_COLORIMETRIC  8  /* Absolute */
#endif

/*
  Typedef declarations.
*/
typedef struct _BMPInfo
{
  unsigned long
    file_size,
    ba_offset,
    offset_bits,
    size;

  long
    width,
    height;

  unsigned short
    planes,
    bits_per_pixel;

  unsigned long
    compression,
    image_size,
    x_pixels,
    y_pixels,
    number_colors,
    red_mask,
    green_mask,
    blue_mask,
    alpha_mask,
    colors_important;

  long
    colorspace;

  PrimaryInfo
    red_primary,
    green_primary,
    blue_primary,
    gamma_scale;
} BMPInfo;

/*
  Forward declarations.
*/
static MagickBooleanType
  WriteBMPImage(const ImageInfo *,Image *);

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   D e c o d e I m a g e                                                     %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  DecodeImage unpacks the packed image pixels into runlength-encoded
%  pixel packets.
%
%  The format of the DecodeImage method is:
%
%      MagickBooleanType DecodeImage(Image *image,
%        const unsigned long compression,unsigned char *pixels)
%
%  A description of each parameter follows:
%
%    o image: the address of a structure of type Image.
%
%    o compression:  Zero means uncompressed.  A value of 1 means the
%      compressed pixels are runlength encoded for a 256-color bitmap.
%      A value of 2 means a 16-color bitmap.  A value of 3 means bitfields
%      encoding.
%
%    o pixels:  The address of a byte (8 bits) array of pixel data created by
%      the decoding process.
%
*/

static inline long MagickAbsoluteValue(const long x)
{
  if (x < 0)
    return(-x);
  return(x);
}

static inline size_t MagickMax(const size_t x,const size_t y)
{
  if (x > y)
    return(x);
  return(y);
}

static inline long MagickMin(const long x,const long y)
{
  if (x < y)
    return(x);
  return(y);
}

static MagickBooleanType DecodeImage(Image *image,
  const unsigned long compression,unsigned char *pixels)
{
  int
    count;

  long
    y;

  register long
    i,
    x;

  register unsigned char
    *p,
    *q;

  unsigned char
    byte;

  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  assert(pixels != (unsigned char *) NULL);
  (void) ResetMagickMemory(pixels,0,(size_t) image->columns*image->rows*
    sizeof(*pixels));
  byte=0;
  x=0;
  p=pixels;
  q=pixels+(size_t) image->columns*image->rows;
  for (y=0; y < (long) image->rows; )
  {
    if ((p < pixels) || (p >= q))
      break;
    count=ReadBlobByte(image);
    if (count == EOF)
      break;
    if (count != 0)
      {
        /*
          Encoded mode.
        */
        count=MagickMin(count,(int) (q-p));
        byte=(unsigned char) ReadBlobByte(image);
        if (compression == BI_RLE8)
          {
            for (i=0; i < count; i++)
              *p++=(unsigned char) byte;
          }
        else
          {
            for (i=0; i < count; i++)
              *p++=(unsigned char)
                ((i & 0x01) != 0 ? (byte & 0x0f) : ((byte >> 4) & 0x0f));
          }
        x+=count;
      }
    else
      {
        /*
          Escape mode.
        */
        count=ReadBlobByte(image);
        if (count == 0x01)
          return(MagickTrue);
        switch (count)
        {
          case 0x00:
          {
            /*
              End of line.
            */
            x=0;
            y++;
            p=pixels+y*image->columns;
            break;
          }
          case 0x02:
          {
            /*
              Delta mode.
            */
            x+=ReadBlobByte(image);
            y+=ReadBlobByte(image);
            p=pixels+y*image->columns+x;
            break;
          }
          default:
          {
            /*
              Absolute mode.
            */
            count=MagickMin(count,(int) (q-p));
            if (compression == BI_RLE8)
              for (i=0; i < count; i++)
                *p++=(unsigned char) ReadBlobByte(image);
            else
              for (i=0; i < count; i++)
              {
                if ((i & 0x01) == 0)
                  byte=(unsigned char) ReadBlobByte(image);
                *p++=(unsigned char)
                  ((i & 0x01) != 0 ? (byte & 0x0f) : ((byte >> 4) & 0x0f));
              }
            x+=count;
            /*
              Read pad byte.
            */
            if (compression == BI_RLE8)
              {
                if ((count & 0x01) != 0)
                  (void) ReadBlobByte(image);
              }
            else
              if (((count & 0x03) == 1) || ((count & 0x03) == 2))
                (void) ReadBlobByte(image);
            break;
          }
        }
      }
    if (SetImageProgress(image,LoadImageTag,y,image->rows) == MagickFalse)
      break;
  }
  (void) ReadBlobByte(image);  /* end of line */
  (void) ReadBlobByte(image);
  return(MagickTrue);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   E n c o d e I m a g e                                                     %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  EncodeImage compresses pixels using a runlength encoded format.
%
%  The format of the EncodeImage method is:
%
%    static MagickBooleanType EncodeImage(Image *image,
%      const unsigned long bytes_per_line,const unsigned char *pixels,
%      unsigned char *compressed_pixels)
%
%  A description of each parameter follows:
%
%    o image:  The image.
%
%    o bytes_per_line: the number of bytes in a scanline of compressed pixels
%
%    o pixels:  The address of a byte (8 bits) array of pixel data created by
%      the compression process.
%
%    o compressed_pixels:  The address of a byte (8 bits) array of compressed
%      pixel data.
%
*/
static size_t EncodeImage(Image *image,const unsigned long bytes_per_line,
  const unsigned char *pixels,unsigned char *compressed_pixels)
{
  long
    y;

  MagickBooleanType
    status;

  register const unsigned char
    *p;

  register long
    i,
    x;

  register unsigned char
    *q;

  /*
    Runlength encode pixels.
  */
  assert(image != (Image *) NULL);
  assert(image->signature == MagickSignature);
  if (image->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
  assert(pixels != (const unsigned char *) NULL);
  assert(compressed_pixels != (unsigned char *) NULL);
  p=pixels;
  q=compressed_pixels;
  i=0;
  for (y=0; y < (long) image->rows; y++)
  {
    for (x=0; x < (long) bytes_per_line; x+=i)
    {
      /*
        Determine runlength.
      */
      for (i=1; ((x+i) < (long) bytes_per_line); i++)
        if ((i == 255) || (*(p+i) != *p))
          break;
      *q++=(unsigned char) i;
      *q++=(*p);
      p+=i;
    }
    /*
      End of line.
    */
    *q++=(unsigned char) 0x00;
    *q++=(unsigned char) 0x00;
    status=SetImageProgress(image,SaveImageTag,y,image->rows);
    if (status == MagickFalse)
      break;
  }
  /*
    End of bitmap.
  */
  *q++=(unsigned char) 0x00;
  *q++=(unsigned char) 0x01;
  return((size_t) (q-compressed_pixels));
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   I s B M P                                                                 %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  IsBMP() returns MagickTrue if the image format type, identified by the
%  magick string, is BMP.
%
%  The format of the IsBMP method is:
%
%      MagickBooleanType IsBMP(const unsigned char *magick,const size_t length)
%
%  A description of each parameter follows:
%
%    o magick: This string is generally the first few bytes of an image file
%      or blob.
%
%    o length: Specifies the length of the magick string.
%
*/
static MagickBooleanType IsBMP(const unsigned char *magick,const size_t length)
{
  if (length < 2)
    return(MagickFalse);
  if ((LocaleNCompare((char *) magick,"BA",2) == 0) ||
      (LocaleNCompare((char *) magick,"BM",2) == 0) ||
      (LocaleNCompare((char *) magick,"IC",2) == 0) ||
      (LocaleNCompare((char *) magick,"PI",2) == 0) ||
      (LocaleNCompare((char *) magick,"CI",2) == 0) ||
      (LocaleNCompare((char *) magick,"CP",2) == 0))
    return(MagickTrue);
  return(MagickFalse);
}

/*
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                                                             %
%                                                                             %
%                                                                             %
%   R e a d B M P I m a g e                                                   %
%                                                                             %
%                                                                             %
%                                                                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  ReadBMPImage() reads a Microsoft Windows bitmap image file, Version
%  2, 3 (for Windows or NT), or 4, 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 ReadBMPImage method is:
%
%      image=ReadBMPImage(image_info)
%
%  A description of each parameter follows:
%
%    o image_info: the image info.
%
%    o exception: return any errors or warnings in this structure.
%
*/

static Image *ReadBMPImage(const ImageInfo *image_info,ExceptionInfo *exception)
{
  BMPInfo
    bmp_info;

  Image
    *image;

  IndexPacket
    index;

  long
    y;

  MagickBooleanType
    status;

  MagickOffsetType
    offset,
    start_position;

  register IndexPacket
    *indexes;

  register long
    x;

  register PixelPacket
    *q;

  register long
    i;

  register unsigned char
    *p;

  ssize_t
    count;

  size_t
    length;

  unsigned char
    magick[12],
    *pixels;

  unsigned long
    bit,
    blue,
    bytes_per_line,
    green,
    opacity,
    red;

  /*
    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);
    }
  /*
    Determine if this a BMP file.
  */
  (void) ResetMagickMemory(&bmp_info,0,sizeof(bmp_info));
  bmp_info.ba_offset=0;
  start_position=0;
  count=ReadBlob(image,2,magick);
  do
  {
    LongPixelPacket
      shift;

    PixelPacket
      quantum_bits;

    unsigned long
      profile_data,
      profile_size;

    /*
      Verify BMP identifier.
    */
    if (bmp_info.ba_offset == 0)
      start_position=TellBlob(image)-2;
    bmp_info.ba_offset=0;
    while (LocaleNCompare((char *) magick,"BA",2) == 0)
    {
      bmp_info.file_size=ReadBlobLSBLong(image);
      bmp_info.ba_offset=ReadBlobLSBLong(image);
      bmp_info.offset_bits=ReadBlobLSBLong(image);
      count=ReadBlob(image,2,magick);
      if (count != 2)
        break;
    }
    if (image->debug != MagickFalse)
      (void) LogMagickEvent(CoderEvent,GetMagickModule(),"  Magick: %c%c",
        magick[0],magick[1]);
    if ((count == 0) || ((LocaleNCompare((char *) magick,"BM",2) != 0) &&
        (LocaleNCompare((char *) magick,"CI",2) != 0)))
      ThrowReaderException(CorruptImageError,"ImproperImageHeader");
    bmp_info.file_size=ReadBlobLSBLong(image);
    (void) ReadBlobLSBLong(image);
    bmp_info.offset_bits=ReadBlobLSBLong(image);
    bmp_info.size=ReadBlobLSBLong(image);
    if (image->debug != MagickFalse)
      (void) LogMagickEvent(CoderEvent,GetMagickModule(),"  BMP size: %lu",
        bmp_info.size);
    if (bmp_info.size == 12)
      {
        /*
          OS/2 BMP image file.
        */
        bmp_info.width=(short) ReadBlobLSBShort(image);
        bmp_info.height=(short) ReadBlobLSBShort(image);
        bmp_info.planes=ReadBlobLSBShort(image);
        bmp_info.bits_per_pixel=ReadBlobLSBShort(image);
        bmp_info.x_pixels=0;
        bmp_info.y_pixels=0;
        bmp_info.number_colors=0;
        bmp_info.compression=BI_RGB;
        bmp_info.image_size=0;
        bmp_info.alpha_mask=0;
        if (image->debug != MagickFalse)
          {
            (void) LogMagickEvent(CoderEvent,GetMagickModule(),
              "  Format: OS/2 Bitmap");
            (void) LogMagickEvent(CoderEvent,GetMagickModule(),
              "  Geometry: %ldx%ld",bmp_info.width,bmp_info.height);
          }
      }
    else
      {
        /*
          Microsoft Windows BMP image file.
        */
        if (bmp_info.size < 40)
          ThrowReaderException(CorruptImageError,"NonOS2HeaderSizeError");
        bmp_info.width=(long) ReadBlobLSBLong(image);
        bmp_info.height=(long) ReadBlobLSBLong(image);
        bmp_info.planes=ReadBlobLSBShort(image);
        bmp_info.bits_per_pixel=ReadBlobLSBShort(image);
        bmp_info.compression=ReadBlobLSBLong(image);
        bmp_info.image_size=ReadBlobLSBLong(image);
        bmp_info.x_pixels=ReadBlobLSBLong(image);
        bmp_info.y_pixels=ReadBlobLSBLong(image);
        bmp_info.number_colors=ReadBlobLSBLong(image);
        bmp_info.colors_important=ReadBlobLSBLong(image);
        profile_data=0;
        profile_size=0;
        if (image->debug != MagickFalse)
          {
            (void) LogMagickEvent(CoderEvent,GetMagickModule(),
              "  Format: MS Windows bitmap");
            (void) LogMagickEvent(CoderEvent,GetMagickModule(),
              "  Geometry: %ldx%ld",bmp_info.width,bmp_info.height);
            (void) LogMagickEvent(CoderEvent,GetMagickModule(),
              "  Bits per pixel: %d",bmp_info.bits_per_pixel);
            switch ((int) bmp_info.compression)
            {
              case BI_RGB:
              {
                (void) LogMagickEvent(CoderEvent,GetMagickModule(),
                  "  Compression: BI_RGB");
                break;
              }
              case BI_RLE4:
              {
                (void) LogMagickEvent(CoderEvent,GetMagickModule(),
                  "  Compression: BI_RLE4");
                break;
              }
              case BI_RLE8:
              {
                (void) LogMagickEvent(CoderEvent,GetMagickModule(),
                  "  Compression: BI_RLE8");
                break;
              }
              case BI_BITFIELDS:
              {
                (void) LogMagickEvent(CoderEvent,GetMagickModule(),
                  "  Compression: BI_BITFIELDS");
                break;
              }
              case BI_PNG:
              {
                (void) LogMagickEvent(CoderEvent,GetMagickModule(),
                  "  Compression: BI_PNG");
                break;
              }
              case BI_JPEG:
              {
                (void) LogMagickEvent(CoderEvent,GetMagickModule(),
                  "  Compression: BI_JPEG");
                break;
              }
              default:
              {
                (void) LogMagickEvent(CoderEvent,GetMagickModule(),
                  "  Compression: UNKNOWN (%lu)",bmp_info.compression);
              }
            }
            (void) LogMagickEvent(CoderEvent,GetMagickModule(),
              "  Number of colors: %lu",bmp_info.number_colors);
          }
        bmp_info.red_mask=ReadBlobLSBLong(image);
        bmp_info.green_mask=ReadBlobLSBLong(image);
        bmp_info.blue_mask=ReadBlobLSBLong(image);
        if (bmp_info.size > 40)
          {
            double
              sum;

            /*
              Read color management information.
            */
            bmp_info.alpha_mask=ReadBlobLSBLong(image);
            bmp_info.colorspace=(long) ReadBlobLSBLong(image);
            /*
              Decode 2^30 fixed point formatted CIE primaries.
            */
            bmp_info.red_primary.x=(double) ReadBlobLSBLong(image)/0x3ffffff;
            bmp_info.red_primary.y=(double) ReadBlobLSBLong(image)/0x3ffffff;
            bmp_info.red_primary.z=(double) ReadBlobLSBLong(image)/0x3ffffff;
            bmp_info.green_primary.x=(double) ReadBlobLSBLong(image)/0x3ffffff;
            bmp_info.green_primary.y=(double) ReadBlobLSBLong(image)/0x3ffffff;
            bmp_info.green_primary.z=(double) ReadBlobLSBLong(image)/0x3ffffff;
            bmp_info.blue_primary.x=(double) ReadBlobLSBLong(image)/0x3ffffff;
            bmp_info.blue_primary.y=(double) ReadBlobLSBLong(image)/0x3ffffff;
            bmp_info.blue_primary.z=(double) ReadBlobLSBLong(image)/0x3ffffff;
            sum=bmp_info.red_primary.x+bmp_info.red_primary.x+
              bmp_info.red_primary.z;
            image->chromaticity.red_primary.x/=sum;
            image->chromaticity.red_primary.y/=sum;
            sum=bmp_info.green_primary.x+bmp_info.green_primary.x+
              bmp_info.green_primary.z;
            image->chromaticity.green_primary.x/=sum;
            image->chromaticity.green_primary.y/=sum;
            sum=bmp_info.blue_primary.x+bmp_info.blue_primary.x+
              bmp_info.blue_primary.z;
            image->chromaticity.blue_primary.x/=sum;
            image->chromaticity.blue_primary.y/=sum;
            /*
              Decode 16^16 fixed point formatted gamma_scales.
            */
            bmp_info.gamma_scale.x=(double) ReadBlobLSBLong(image)/0xffff;
            bmp_info.gamma_scale.y=(double) ReadBlobLSBLong(image)/0xffff;
            bmp_info.gamma_scale.z=(double) ReadBlobLSBLong(image)/0xffff;
            /*
              Compute a single gamma from the BMP 3-channel gamma.
            */
            image->gamma=(bmp_info.gamma_scale.x+bmp_info.gamma_scale.y+
              bmp_info.gamma_scale.z)/3.0;
          }
        if (bmp_info.size > 108)
          {
            unsigned long
              intent;

            /*
              Read BMP Version 5 color management information.
            */
            intent=ReadBlobLSBLong(image);
            switch ((int) intent)
            {
              case LCS_GM_BUSINESS:
              {
                image->rendering_intent=SaturationIntent;
                break;
              }
              case LCS_GM_GRAPHICS:
              {
                image->rendering_intent=RelativeIntent;
                break;
              }
              case LCS_GM_IMAGES:
              {
                image->rendering_intent=PerceptualIntent;
                break;
              }
              case LCS_GM_ABS_COLORIMETRIC:
              {
                image->rendering_intent=AbsoluteIntent;
                break;
              }
            }
            profile_data=ReadBlobLSBLong(image);
            profile_size=ReadBlobLSBLong(image);
            (void) ReadBlobLSBLong(image);  /* Reserved byte */
          }
      }
    if ((bmp_info.compression != BI_RGB) &&
        ((MagickSizeType) bmp_info.file_size != GetBlobSize(image)))
      (void) ThrowMagickException(exception,GetMagickModule(),CorruptImageError,
        "LengthAndFilesizeDoNotMatch","`%s'",image->filename);
    if (bmp_info.width <= 0)
      ThrowReaderException(CorruptImageError,"NegativeOrZeroImageSize");
    if (bmp_info.height == 0)
      ThrowReaderException(CorruptImageError,"NegativeOrZeroImageSize");
    if (bmp_info.planes != 1)
      ThrowReaderException(CorruptImageError,"StaticPlanesValueNotEqualToOne");
    if ((bmp_info.bits_per_pixel != 1) && (bmp_info.bits_per_pixel != 4) &&
        (bmp_info.bits_per_pixel != 8) && (bmp_info.bits_per_pixel != 16) &&
        (bmp_info.bits_per_pixel != 24) && (bmp_info.bits_per_pixel != 32))
      ThrowReaderException(CorruptImageError,"UnrecognizedBitsPerPixel");
    if (bmp_info.number_colors > (1UL << bmp_info.bits_per_pixel))
      {
        if (bmp_info.bits_per_pixel < 24)
          ThrowReaderException(CorruptImageError,"UnrecognizedNumberOfColors");
        bmp_info.number_colors=0;
      }
    if (bmp_info.compression > 3)
      ThrowReaderException(CorruptImageError,"UnrecognizedImageCompression");
    if ((bmp_info.compression == 1) && (bmp_info.bits_per_pixel != 8))
      ThrowReaderException(CorruptImageError,"UnrecognizedBitsPerPixel");
    if ((bmp_info.compression == 2) && (bmp_info.bits_per_pixel != 4))
      ThrowReaderException(CorruptImageError,"UnrecognizedBitsPerPixel");
    if ((bmp_info.compression == 3) && (bmp_info.bits_per_pixel < 16))
      ThrowReaderException(CorruptImageError,"UnrecognizedBitsPerPixel");
    switch (bmp_info.compression)
    {
      case BI_RGB:
      case BI_RLE8:
      case BI_RLE4:
      case BI_BITFIELDS:
        break;
      case BI_JPEG:
        ThrowReaderException(CoderError,"JPEGCompressNotSupported");
      case BI_PNG:
        ThrowReaderException(CoderError,"PNGCompressNotSupported");
      default:
        ThrowReaderException(CorruptImageError,"UnrecognizedImageCompression");
    }
    image->columns=(unsigned long) MagickAbsoluteValue(bmp_info.width);
    image->rows=(unsigned long) MagickAbsoluteValue(bmp_info.height);
    image->depth=8;
    image->matte=bmp_info.alpha_mask != 0 ? MagickTrue : MagickFalse;
    if ((bmp_info.number_colors != 0) || (bmp_info.bits_per_pixel < 16))
      {
        image->storage_class=PseudoClass;
        image->colors=bmp_info.number_colors;
        if (image->colors == 0)
          image->colors=1L << bmp_info.bits_per_pixel;
      }
    if (image->storage_class == PseudoClass)
      {
        unsigned char
          *bmp_colormap;

        size_t
          packet_size;

        /*
          Read BMP raster colormap.
        */
        if (image->debug != MagickFalse)
          (void) LogMagickEvent(CoderEvent,GetMagickModule(),
            "  Reading colormap of %ld colors",image->colors);
        if (AcquireImageColormap(image,image->colors) == MagickFalse)
          ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
        bmp_colormap=(unsigned char *) AcquireQuantumMemory((size_t)
          image->colors,4*sizeof(*bmp_colormap));
        if (bmp_colormap == (unsigned char *) NULL)
          ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
        if ((bmp_info.size == 12) || (bmp_info.size == 64))
          packet_size=3;
        else
          packet_size=4;
        offset=SeekBlob(image,start_position+14+bmp_info.size,SEEK_SET);
        if (offset < 0)
          ThrowReaderException(CorruptImageError,"ImproperImageHeader");
        count=ReadBlob(image,packet_size*image->colors,bmp_colormap);
        if (count != (ssize_t) (packet_size*image->colors))
          ThrowReaderException(CorruptImageError,"InsufficientImageDataInFile");
        p=bmp_colormap;
        for (i=0; i < (long) image->colors; i++)
        {
          image->colormap[i].blue=ScaleCharToQuantum(*p++);
          image->colormap[i].green=ScaleCharToQuantum(*p++);
          image->colormap[i].red=ScaleCharToQuantum(*p++);
          if (packet_size == 4)
            p++;
        }
        bmp_colormap=(unsigned char *) RelinquishMagickMemory(bmp_colormap);
      }
    if ((image_info->ping != MagickFalse) && (image_info->number_scenes != 0))
      if (image->scene >= (image_info->scene+image_info->number_scenes-1))
        break;
    /*
      Read image data.
    */
    if (SetImageExtent(image,0,0) == MagickFalse)
      {
        InheritException(exception,&image->exception);
        return(DestroyImageList(image));
      }
    offset=SeekBlob(image,start_position+bmp_info.offset_bits,SEEK_SET);
    if (offset < 0)
      ThrowReaderException(CorruptImageError,"ImproperImageHeader");
    if (bmp_info.compression == BI_RLE4)
      bmp_info.bits_per_pixel<<=1;
    bytes_per_line=4*((image->columns*bmp_info.bits_per_pixel+31)/32);
    length=(size_t) bytes_per_line*image->rows;
    pixels=(unsigned char *) AcquireQuantumMemory((size_t) image->rows,
      MagickMax(bytes_per_line,image->columns+256UL)*sizeof(*pixels));
    if (pixels == (unsigned char *) NULL)
      ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
    if ((bmp_info.compression == BI_RGB) ||
        (bmp_info.compression == BI_BITFIELDS))
      {
        if (image->debug != MagickFalse)
          (void) LogMagickEvent(CoderEvent,GetMagickModule(),
            "  Reading pixels (%ld bytes)",(long) length);
        count=ReadBlob(image,length,pixels);
        if (count != (ssize_t) length)
          ThrowReaderException(CorruptImageError,"InsufficientImageDataInFile");
      }
    else
      {
        /*
          Convert run-length encoded raster pixels.
        */
        status=DecodeImage(image,bmp_info.compression,pixels);
        if (status == MagickFalse)
          ThrowReaderException(CorruptImageError,
            "UnableToRunlengthDecodeImage");
      }
    /*
      Initialize image structure.
    */
    image->x_resolution=(double) bmp_info.x_pixels/100.0;
    image->y_resolution=(double) bmp_info.y_pixels/100.0;
    image->units=PixelsPerCentimeterResolution;
    /*
      Convert BMP raster image to pixel packets.
    */
    if (bmp_info.compression == BI_RGB)
      {
        bmp_info.alpha_mask=0;
        bmp_info.red_mask=0x00ff0000UL;
        bmp_info.green_mask=0x0000ff00UL;
        bmp_info.blue_mask=0x000000ffUL;
        if (bmp_info.bits_per_pixel == 16)
          {
            /*
              RGB555.
            */
            bmp_info.red_mask=0x00007c00UL;
            bmp_info.green_mask=0x000003e0UL;
            bmp_info.blue_mask=0x0000001fUL;
          }
      }
    if ((bmp_info.bits_per_pixel == 16) || (bmp_info.bits_per_pixel == 32))
      {
        register unsigned long
          sample;

        /*
          Get shift and quantum bits info from bitfield masks.
        */
        (void) ResetMagickMemory(&shift,0,sizeof(shift));
        (void) ResetMagickMemory(&quantum_bits,0,sizeof(quantum_bits));
        if (bmp_info.red_mask != 0)
          while (((bmp_info.red_mask << shift.red) & 0x80000000UL) == 0)
            shift.red++;
        if (bmp_info.green_mask != 0)
          while (((bmp_info.green_mask << shift.green) & 0x80000000UL) == 0)
            shift.green++;
        if (bmp_info.blue_mask != 0)
          while (((bmp_info.blue_mask << shift.blue) & 0x80000000UL) == 0)
            shift.blue++;
        if (bmp_info.alpha_mask != 0)
          while (((bmp_info.alpha_mask << shift.opacity) & 0x80000000UL) == 0)
            shift.opacity++;
        sample=shift.red;
        while (((bmp_info.red_mask << sample) & 0x80000000UL) != 0)
          sample++;
        quantum_bits.red=(Quantum) (sample-shift.red);
        sample=shift.green;
        while (((bmp_info.green_mask << sample) & 0x80000000UL) != 0)