Structures

In version 1.0, there's only one structure: GIF_INFO. It is used by every function in the GIFLIB. You should have one structure for each GIF you decode.

struc TGifInfo  {
  .GIFVersion      rb    3
  .dwLSWidth       dd    ?
  .dwLSHeight      dd    ?
  .lpColorTable    dd    ?
  .ColorCount      dd    ?
  .dwImageWidth    dd    ?
  .dwImageHeight   dd    ?
  .lpImageData     dd    ?
  .dwImageFormat   dd    ?
  .lpGIFData       dd    ?
  .dwGIFDataSize   dd    ?
; INTERNAL DATA
  .lpLZWTable      dd    ?
  .dwLZWTableSize  dd    ?
  .dwLZWTableCount dd    ?
  .fGlobalCTable   db    ?
  .dbGCTableSize   db    ?
  .fLocalCTable    db    ?
  .dbLCTableSize   db    ?
  .lpGIFImage      dd    ?
  .lpCurrentByte   dd    ?
  .dbBitsAvailable db    ?
  .dbCurBitSize    db    ?
  .dbInitBitSize   db    ?
  .lpLastEOSB      dd    ?
  .dwLZWClear      dd    ?
  .CurrentBits     dd    ?
  .IsFirstCode     db    ?
  .PixelCounter    dd    ?
}
GIFVersion These are the second 3 bytes of the file, that indicate the version number of the GIF File, like "87a" or "89a".
dwLSWidth Logical screen width (see GIF format)
dwLSHeight Logical screen height (see GIF format)
lpColorTable Pointer to the GIF color table (RR GG BB RR GG BB format)
ColorCount Number of colors in the GIF
dwImageWidth Actual image width (use this one to get the image dimensions)
dwImageHeight Actual image height (use this one to get the image dimensions)
lpImageData

Output buffer for decoded data (in the format specified by dwImageFormat).
Data is outputted as windows bitmap data, in one of the following three formats: 1-bit monochrome, 4-bit 16-color or 8-bit 256 color. Scanlines are aligned to dwords (see the bitmap documentation in the win32 programmer's reference)

dwImageFormat Specifies the image format (IMAGEFORMAT_XXXX constants). You can use a format that has a higher maximum number of colors than the original GIF, but lower is not supported (256 color output from a 16 color gif is allowed, 16 color output from a 256 color gif is NOT).
lpGIFData Points to the actual GIF data (in the GIF file format).
dwGIFDataSize Size of the data pointed to by lpGIFData
InternalData Data that is used internally by GIFLIB.