https://github.com/ImageMagick/ImageMagick/issues/573
static Image *ReadMAPImage(const ImageInfo *image_info,ExceptionInfo *exception)
{
  Image
    *image;

  IndexPacket
    index;

  MagickBooleanType
    status;

  register IndexPacket
    *indexes;

  register ssize_t
    x;

  register PixelPacket
    *q;

  register ssize_t
    i;

  register unsigned char
    *p;

  size_t
    depth,
    packet_size,
    quantum;

  ssize_t
    count,
    y;

  unsigned char
    *colormap,
    *pixels;

  /*
    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);
  if ((image->columns == 0) || (image->rows == 0))
    ThrowReaderException(OptionError,"MustSpecifyImageSize");
  status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
  if (status == MagickFalse)
    {
      image=DestroyImageList(image);
      return((Image *) NULL);
    }
  /*
    Initialize image structure.
  */
  image->storage_class=PseudoClass;
  status=AcquireImageColormap(image,(size_t)
    (image->offset != 0 ? image->offset : 256));
  if (status == MagickFalse)
    ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
  depth=GetImageQuantumDepth(image,MagickTrue);
  packet_size=(size_t) (depth/8);
  pixels=(unsigned char *) AcquireQuantumMemory(image->columns,packet_size*
    sizeof(*pixels));
  packet_size=(size_t) (image->colors > 256 ? 6UL : 3UL);
  colormap=(unsigned char *) AcquireQuantumMemory(image->colors,packet_size*
    sizeof(*colormap));
  if ((pixels == (unsigned char *) NULL) ||
      (colormap == (unsigned char *) NULL))
    ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
  /*
    Read image colormap.
  */
  count=ReadBlob(image,packet_size*image->colors,colormap);
  if (count != (ssize_t) (packet_size*image->colors))
    ThrowReaderException(CorruptImageError,"InsufficientImageDataInFile");
  p=colormap;
  if (image->depth <= 8)
    for (i=0; i < (ssize_t) image->colors; i++)
    {
      image->colormap[i].red=ScaleCharToQuantum(*p++);
      image->colormap[i].green=ScaleCharToQuantum(*p++);
      image->colormap[i].blue=ScaleCharToQuantum(*p++);
    }
  else
    for (i=0; i < (ssize_t) image->colors; i++)
    {
      quantum=(*p++ << 8);
      quantum|=(*p++);
      image->colormap[i].red=(Quantum) quantum;
      quantum=(*p++ << 8);
      quantum|=(*p++);
      image->colormap[i].green=(Quantum) quantum;
      quantum=(*p++ << 8);
      quantum|=(*p++);
      image->colormap[i].blue=(Quantum) quantum;
    }
  colormap=(unsigned char *) RelinquishMagickMemory(colormap);
  if (image_info->ping != MagickFalse)
    {
      (void) CloseBlob(image);
      return(GetFirstImageInList(image));
    }
  status=SetImageExtent(image,image->columns,image->rows);
  if (status == MagickFalse)
    {
      InheritException(exception,&image->exception);
      return(DestroyImageList(image));
    }
  /*
    Read image pixels.
  */
  packet_size=(size_t) (depth/8);
  for (y=0; y < (ssize_t) image->rows; y++)
  {
    p=pixels;
    q=QueueAuthenticPixels(image,0,y,image->columns,1,exception);
    if (q == (PixelPacket *) NULL)
      break;
    indexes=GetAuthenticIndexQueue(image);
    count=ReadBlob(image,(size_t) packet_size*image->columns,pixels);
    if (count != (ssize_t) (packet_size*image->columns))
      break;
    for (x=0; x < (ssize_t) image->columns; x++)
    {
      index=ConstrainColormapIndex(image,*p);
      p++;
      if (image->colors > 256)
        {
          index=ConstrainColormapIndex(image,((size_t) index << 8)+(*p));
          p++;
        }
      SetPixelIndex(indexes+x,index);
      SetPixelRGBO(q,image->colormap+(ssize_t) index);
    }
    if (SyncAuthenticPixels(image,exception) == MagickFalse)
      break;
  }
  pixels=(unsigned char *) RelinquishMagickMemory(pixels);
  if (y < (ssize_t) image->rows)
    ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",
      image->filename);
  (void) CloseBlob(image);
  return(GetFirstImageInList(image));
}

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

  IndexPacket
    index;

  MagickBooleanType
    status;

  register IndexPacket
    *indexes;

  register ssize_t
    x;

  register PixelPacket
    *q;

  register ssize_t
    i;

  register unsigned char
    *p;

  size_t
    depth,
    packet_size,
    quantum;

  ssize_t
    count,
    y;

  unsigned char
    *colormap,
    *pixels;

  /*
    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);
  if ((image->columns == 0) || (image->rows == 0))
    ThrowReaderException(OptionError,"MustSpecifyImageSize");
  status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
  if (status == MagickFalse)
    {
      image=DestroyImageList(image);
      return((Image *) NULL);
    }
  /*
    Initialize image structure.
  */
  image->storage_class=PseudoClass;
  status=AcquireImageColormap(image,(size_t)
    (image->offset != 0 ? image->offset : 256));
  if (status == MagickFalse)
    ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
  depth=GetImageQuantumDepth(image,MagickTrue);
  packet_size=(size_t) (depth/8);
  pixels=(unsigned char *) AcquireQuantumMemory(image->columns,packet_size*
    sizeof(*pixels));
  packet_size=(size_t) (image->colors > 256 ? 6UL : 3UL);
  colormap=(unsigned char *) AcquireQuantumMemory(image->colors,packet_size*
    sizeof(*colormap));
  if ((pixels == (unsigned char *) NULL) ||
      (colormap == (unsigned char *) NULL))
    ThrowReaderException(ResourceLimitError,"MemoryAllocationFailed");
  /*
    Read image colormap.
  */
  count=ReadBlob(image,packet_size*image->colors,colormap);
  if (count != (ssize_t) (packet_size*image->colors))
    ThrowReaderException(CorruptImageError,"InsufficientImageDataInFile");
  p=colormap;
  if (image->depth <= 8)
    for (i=0; i < (ssize_t) image->colors; i++)
    {
      image->colormap[i].red=ScaleCharToQuantum(*p++);
      image->colormap[i].green=ScaleCharToQuantum(*p++);
      image->colormap[i].blue=ScaleCharToQuantum(*p++);
    }
  else
    for (i=0; i < (ssize_t) image->colors; i++)
    {
      quantum=(*p++ << 8);
      quantum|=(*p++);
      image->colormap[i].red=(Quantum) quantum;
      quantum=(*p++ << 8);
      quantum|=(*p++);
      image->colormap[i].green=(Quantum) quantum;
      quantum=(*p++ << 8);
      quantum|=(*p++);
      image->colormap[i].blue=(Quantum) quantum;
    }
  colormap=(unsigned char *) RelinquishMagickMemory(colormap);
  if (image_info->ping != MagickFalse)
    {
      (void) CloseBlob(image);
      return(GetFirstImageInList(image));
    }
  status=SetImageExtent(image,image->columns,image->rows);
  if (status == MagickFalse)
    {
      InheritException(exception,&image->exception);
      return(DestroyImageList(image));
    }
  /*
    Read image pixels.
  */
  packet_size=(size_t) (depth/8);
  for (y=0; y < (ssize_t) image->rows; y++)
  {
    p=pixels;
    q=QueueAuthenticPixels(image,0,y,image->columns,1,exception);
    if (q == (PixelPacket *) NULL)
      break;
    indexes=GetAuthenticIndexQueue(image);
    count=ReadBlob(image,(size_t) packet_size*image->columns,pixels);
    if (count != (ssize_t) (packet_size*image->columns))
      break;
    for (x=0; x < (ssize_t) image->columns; x++)
    {
      index=ConstrainColormapIndex(image,*p);
      p++;
      if (image->colors > 256)
        {
          index=ConstrainColormapIndex(image,((size_t) index << 8)+(*p));
          p++;
        }
      SetPixelIndex(indexes+x,index);
      SetPixelRGBO(q,image->colormap+(ssize_t) index);
    }
    if (SyncAuthenticPixels(image,exception) == MagickFalse)
      break;
  }
  pixels=(unsigned char *) RelinquishMagickMemory(pixels);
  if (y < (ssize_t) image->rows)
    ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",
      image->filename);
  (void) CloseBlob(image);
  return(GetFirstImageInList(image));
}
