img_gif.c

#include <gif_lib.h>
#undef TRUE
#undef FALSE

static BOOL decGif_start (const char * file, IMGINFO info);
static BOOL decGif_read  (IMGINFO, CHAR * buffer);
static void decGif_quit  (IMGINFO);

static DECODER _decoder_gif = {
	DECODER_CHAIN,
	{ MIME_IMG_GIF, 0 },
	decGif_start
};
#undef  DECODER_CHAIN
#define DECODER_CHAIN &_decoder_gif

#if defined(GIFLIB_MAJOR) 
static void _PrintGifError(GifFileType *gif)
{
	const char *err = GifErrorString(gif->Error);
	if (err != NULL)
		fprintf(stderr, "\nGIF-LIB error: %s.\n", err);
	else
		fprintf(stderr, "\nGIF-LIB undefined error %d.\n", gif->Error);
}
#define PrintGifError() _PrintGifError(gif)
#endif


/*----------------------------------------------------------------------------*/
static BOOL
decGif_start (const char * file, IMGINFO info)
{
	short interlace = 0;
	short transpar  = -1;
	short img_w     = 0;
	short img_h     = 0;
	
	ColorMapObject * map = NULL;
#if defined(GIFLIB_MAJOR)
	int gif_error;
	GifFileType    * gif = DGifOpenFileName (file, &gif_error);
#else
	GifFileType    * gif = DGifOpenFileName (file);
#endif
	if (!gif) {
		return FALSE;
	} else {
		GifRecordType rec;
		do {
			if (DGifGetRecordType (gif, &rec) == GIF_ERROR) {
				fprintf (stderr, "DGifGetRecordType() ");
				PrintGifError();
				break;
			
			} else if (rec == IMAGE_DESC_RECORD_TYPE) {
				if (DGifGetImageDesc(gif) == GIF_ERROR) {
					fprintf (stderr, "DGifGetImageDesc() ");
					PrintGifError();
					break;
				
				} else {
					GifImageDesc * dsc = &gif->Image;
					map = (dsc->ColorMap ? dsc->ColorMap : gif->SColorMap);
					img_w = dsc->Width;
					img_h = dsc->Height;
					if (dsc->Interlace) {
						interlace = 8;
					}
				}
				break;
			} else if (rec == EXTENSION_RECORD_TYPE) {
				int           code;
				GifByteType * block;
				if (DGifGetExtension (gif, &code, &block) == GIF_ERROR) {
					fprintf (stderr, "DGifGetExtension() ");
					PrintGifError();
					break;
				
				} else while (block != NULL) {
					if (code == 0xF9 && (block[1] & 1)) {
						transpar = (short)block[4];
					}
					if (DGifGetExtensionNext (gif, &block) == GIF_ERROR) {
						fprintf (stderr, "DGifGetExtensionNext() ");
						PrintGifError();
						break;
					}
				}
			} else {
				fprintf (stderr, "other: %i \n", rec);
				break;
			}
		} while (rec != TERMINATE_RECORD_TYPE);
	}
	
	if (!map || img_w <= 0 || img_w >= 4096 || img_h <= 0 || img_h >= 4096) {
#if defined(GIFLIB_MAJOR)
		DGifCloseFile (gif, NULL);
#else
		DGifCloseFile (gif);
#endif
		return TRUE;
	}
	
	info->_priv_data = gif;
/*	info->_priv_more = NULL; */
/*	info->_priv_file = NULL; */
	info->read       = decGif_read;
	info->quit       = decGif_quit;
	info->ImgWidth   = img_w;
	info->ImgHeight  = img_h;
	info->NumComps   = 1;
	info->BitDepth   = map->BitsPerPixel;
	info->NumColors  = map->ColorCount;
	if ((info->Palette = &map->Colors->Red) != NULL) {
		GifColorType * rgb = NULL;
		info->PalRpos = (unsigned)&rgb->Red;
		info->PalGpos = (unsigned)&rgb->Green;
		info->PalBpos = (unsigned)&rgb->Blue;
		info->PalStep = (unsigned)&rgb[1];
	}
	info->Transp     = transpar;
	info->Interlace  = interlace;
	
	return TRUE;
}

/*----------------------------------------------------------------------------*/
static BOOL
decGif_read (IMGINFO info, CHAR * buffer)
{
	return (DGifGetLine (info->_priv_data, (void *)buffer, info->ImgWidth) == GIF_OK);
}

/*----------------------------------------------------------------------------*/
static void
decGif_quit (IMGINFO info)
{
	if (info->_priv_data) {
#if defined(GIFLIB_MAJOR)
		DGifCloseFile (info->_priv_data, NULL);
#else
		DGifCloseFile (info->_priv_data);
#endif
		info->_priv_data = NULL;
	}
}