static Image *ReadGROUP4Image(const ImageInfo *image_info,
  ExceptionInfo *exception)
{
  char
    filename[MagickPathExtent];

  FILE
    *file;

  Image
    *image;

  ImageInfo
    *read_info;

  int
    c,
    unique_file;

  MagickBooleanType
    status;

  size_t
    length;

  ssize_t
    offset,
    strip_offset;

  /*
    Open image file.
  */
  assert(image_info != (const ImageInfo *) NULL);
  assert(image_info->signature == MagickCoreSignature);
  if (image_info->debug != MagickFalse)
    (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
      image_info->filename);
  assert(exception != (ExceptionInfo *) NULL);
  assert(exception->signature == MagickCoreSignature);
  image=AcquireImage(image_info,exception);
  status=OpenBlob(image_info,image,ReadBinaryBlobMode,exception);
  if (status == MagickFalse)
    {
      image=DestroyImageList(image);
      return((Image *) NULL);
    }
  /*
    Write raw CCITT Group 4 wrapped as a TIFF image file.
  */
  file=(FILE *) NULL;
  unique_file=AcquireUniqueFileResource(filename);
  if (unique_file != -1)
    file=fdopen(unique_file,"wb");
  if ((unique_file == -1) || (file == (FILE *) NULL))
    ThrowImageException(FileOpenError,"UnableToCreateTemporaryFile");
  length=fwrite("\111\111\052\000\010\000\000\000\016\000",1,10,file);
  if (length != 10)
    ThrowReaderException(CorruptImageError,"UnexpectedEndOfFile");
  length=fwrite("\376\000\003\000\001\000\000\000\000\000\000\000",1,12,file);
  length=fwrite("\000\001\004\000\001\000\000\000",1,8,file);
  length=WriteLSBLong(file,(unsigned int) image->columns);
  length=fwrite("\001\001\004\000\001\000\000\000",1,8,file);
  length=WriteLSBLong(file,(unsigned int) image->rows);
  length=fwrite("\002\001\003\000\001\000\000\000\001\000\000\000",1,12,file);
  length=fwrite("\003\001\003\000\001\000\000\000\004\000\000\000",1,12,file);
  length=fwrite("\006\001\003\000\001\000\000\000\000\000\000\000",1,12,file);
  length=fwrite("\021\001\003\000\001\000\000\000",1,8,file);
  strip_offset=10+(12*14)+4+8;
  length=WriteLSBLong(file,(unsigned int) strip_offset);
  length=fwrite("\022\001\003\000\001\000\000\000",1,8,file);
  length=WriteLSBLong(file,(unsigned int) image_info->orientation);
  length=fwrite("\025\001\003\000\001\000\000\000\001\000\000\000",1,12,file);
  length=fwrite("\026\001\004\000\001\000\000\000",1,8,file);
  length=WriteLSBLong(file,(unsigned int) image->rows);
  length=fwrite("\027\001\004\000\001\000\000\000\000\000\000\000",1,12,file);
  offset=(ssize_t) ftell(file)-4;
  length=fwrite("\032\001\005\000\001\000\000\000",1,8,file);
  length=WriteLSBLong(file,(unsigned int) (strip_offset-8));
  length=fwrite("\033\001\005\000\001\000\000\000",1,8,file);
  length=WriteLSBLong(file,(unsigned int) (strip_offset-8));
  length=fwrite("\050\001\003\000\001\000\000\000\002\000\000\000",1,12,file);
  length=fwrite("\000\000\000\000",1,4,file);
  length=WriteLSBLong(file,(unsigned int) image->resolution.x);
  length=WriteLSBLong(file,1);
  status=MagickTrue;
  for (length=0; (c=ReadBlobByte(image)) != EOF; length++)
    if (fputc(c,file) != c)
      status=MagickFalse;
  offset=(ssize_t) fseek(file,(ssize_t) offset,SEEK_SET);
  length=WriteLSBLong(file,(unsigned int) length);
  if (ferror(file) != 0)
    {
      (void) fclose(file);
      ThrowImageException(FileOpenError,"UnableToCreateTemporaryFile");
    }
  (void) fclose(file);
  (void) CloseBlob(image);
  image=DestroyImage(image);
  /*
    Read TIFF image.
  */
  read_info=CloneImageInfo((ImageInfo *) NULL);
  (void) FormatLocaleString(read_info->filename,MagickPathExtent,"%s",filename);
  image=ReadTIFFImage(read_info,exception);
  read_info=DestroyImageInfo(read_info);
  if (image != (Image *) NULL)
    {
      (void) CopyMagickString(image->filename,image_info->filename,
        MagickPathExtent);
      (void) CopyMagickString(image->magick_filename,image_info->filename,
        MagickPathExtent);
      (void) CopyMagickString(image->magick,"GROUP4",MagickPathExtent);
    }
  (void) RelinquishUniqueFileResource(filename);
  if (status == MagickFalse)
    image=DestroyImage(image);
  return(image);
}

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.