gd_gif_in.c

Linux/Unix下的绘图函数库（Graphic Drawing Library）

#include <stdio.h>
#include <math.h>
#include <string.h>
#include <stdlib.h>
#include "gd.h"

/* Used only when debugging GIF compression code */
/* #define DEBUGGING_ENVARS */

#ifdef DEBUGGING_ENVARS

static int verbose_set = 0;
static int verbose;
#define VERBOSE (verbose_set?verbose:set_verbose())

static int set_verbose(void)
{
 verbose = !!getenv("GIF_VERBOSE");
 verbose_set = 1;
 return(verbose);
}

#else

#define VERBOSE 0

#endif


#define        MAXCOLORMAPSIZE         256

#define        TRUE    1
#define        FALSE   0

#define CM_RED         0
#define CM_GREEN       1
#define CM_BLUE                2

#define        MAX_LWZ_BITS            12

#define INTERLACE              0x40
#define LOCALCOLORMAP  0x80
#define BitSet(byte, bit)      (((byte) & (bit)) == (bit))

#define        ReadOK(file,buffer,len) (gdGetBuf(buffer, len, file) != 0)

#define LM_to_uint(a,b)                        (((b)<<8)|(a))

/* We may eventually want to use this information, but def it out for now */
#if 0
static struct {
       unsigned int    Width;
       unsigned int    Height;
       unsigned char   ColorMap[3][MAXCOLORMAPSIZE];
       unsigned int    BitPixel;
       unsigned int    ColorResolution;
       unsigned int    Background;
       unsigned int    AspectRatio;
} GifScreen;
#endif

#if 0
static struct {
       int     transparent;
       int     delayTime;
       int     inputFlag;
       int     disposal;
} Gif89 = { -1, -1, -1, 0 };
#endif

static int ReadColorMap (gdIOCtx *fd, int number, unsigned char (*buffer)[256]);
static int DoExtension (gdIOCtx *fd, int label, int *Transparent, int *ZeroDataBlockP);
static int GetDataBlock (gdIOCtx *fd, unsigned char *buf, int *ZeroDataBlockP);
static int GetCode (gdIOCtx *fd, int code_size, int flag, int *ZeroDataBlockP);
static int LWZReadByte (gdIOCtx *fd, int flag, int input_code_size, int *ZeroDataBlockP);

static void ReadImage (gdImagePtr im, gdIOCtx *fd, int len, int height, unsigned char (*cmap)[256], int interlace, int *ZeroDataBlockP); /*1.4//, int ignore); */

BGD_DECLARE(gdImagePtr) gdImageCreateFromGif(FILE *fdFile)
{
        gdIOCtx		*fd = gdNewFileCtx(fdFile);
        gdImagePtr    	im = 0;

        im = gdImageCreateFromGifCtx(fd);

        fd->gd_free(fd);

        return im;
}

BGD_DECLARE(gdImagePtr) gdImageCreateFromGifPtr (int size, void *data)
{
  gdImagePtr im;
  gdIOCtx *in = gdNewDynamicCtxEx (size, data, 0);
  im = gdImageCreateFromGifCtx (in);
  in->gd_free (in);
  return im;
}

BGD_DECLARE(gdImagePtr) gdImageCreateFromGifCtx(gdIOCtxPtr fd)
{
       int BitPixel;
#if 0
       int ColorResolution;
       int Background;
       int AspectRatio;
#endif
       int Transparent = (-1);
       unsigned char   buf[16];
       unsigned char   c;
       unsigned char   ColorMap[3][MAXCOLORMAPSIZE];
       unsigned char   localColorMap[3][MAXCOLORMAPSIZE];
       int             imw, imh;
       int             useGlobalColormap;
       int             bitPixel;
       int	       i;
       /*1.4//int             imageCount = 0; */
       char            version[4];
       /* 2.0.28: threadsafe storage */
       int ZeroDataBlock = FALSE;

       gdImagePtr im = 0;
       if (! ReadOK(fd,buf,6)) {
		return 0;
	}
       if (strncmp((char *)buf,"GIF",3) != 0) {
		return 0;
	}
       strncpy(version, (char *)buf + 3, 3);
       version[3] = '\0';

       if ((strcmp(version, "87a") != 0) && (strcmp(version, "89a") != 0)) {
		return 0;
	}
       if (! ReadOK(fd,buf,7)) {
		return 0;
	}
       BitPixel        = 2<<(buf[4]&0x07);
#if 0
       ColorResolution = (int) (((buf[4]&0x70)>>3)+1);
       Background      = buf[5];
       AspectRatio     = buf[6];
#endif

       if (BitSet(buf[4], LOCALCOLORMAP)) {    /* Global Colormap */
               if (ReadColorMap(fd, BitPixel, ColorMap)) {
			return 0;
		}
       }
       for (;;) {
               if (! ReadOK(fd,&c,1)) {
                       return 0;
               }
               if (c == ';') {         /* GIF terminator */
			goto terminated;
	       }

               if (c == '!') {         /* Extension */
                       if (! ReadOK(fd,&c,1)) {
                               return 0;
                       }
                       DoExtension(fd, c, &Transparent, &ZeroDataBlock);
                       continue;
               }

               if (c != ',') {         /* Not a valid start character */
                       continue;
               }

               /*1.4//++imageCount; */

               if (! ReadOK(fd,buf,9)) {
	               return 0;
               }

               useGlobalColormap = ! BitSet(buf[8], LOCALCOLORMAP);

               bitPixel = 1<<((buf[8]&0x07)+1);

               imw = LM_to_uint(buf[4],buf[5]);
               imh = LM_to_uint(buf[6],buf[7]);
	       if (!(im = gdImageCreate(imw, imh))) {
			 return 0;
	       }
               im->interlace = BitSet(buf[8], INTERLACE);
               if (! useGlobalColormap) {
                       if (ReadColorMap(fd, bitPixel, localColorMap)) { 
                                 return 0;
                       }
                       ReadImage(im, fd, imw, imh, localColorMap, 
                                 BitSet(buf[8], INTERLACE), &ZeroDataBlock); 
               } else {
                       ReadImage(im, fd, imw, imh,
                                 ColorMap, 
                                 BitSet(buf[8], INTERLACE), &ZeroDataBlock);
               }
               if (Transparent != (-1)) {
                       gdImageColorTransparent(im, Transparent);
               }	   
	       goto terminated;
       }

terminated:
       /* Terminator before any image was declared! */
       if (!im) {
		return 0;
       }
       /* Check for open colors at the end, so
          we can reduce colorsTotal and ultimately
          BitsPerPixel */
       for (i=((im->colorsTotal-1)); (i>=0); i--) {
		if (im->open[i]) {
                	im->colorsTotal--;
                } else {
                	break;
                }
       } 
       return im;
}

static int
ReadColorMap(gdIOCtx *fd, int number, unsigned char (*buffer)[256])
{
       int             i;
       unsigned char   rgb[3];


       for (i = 0; i < number; ++i) {
               if (! ReadOK(fd, rgb, sizeof(rgb))) {
                       return TRUE;
               }
               buffer[CM_RED][i] = rgb[0] ;
               buffer[CM_GREEN][i] = rgb[1] ;
               buffer[CM_BLUE][i] = rgb[2] ;
       }


       return FALSE;
}

static int
DoExtension(gdIOCtx *fd, int label, int *Transparent, int *ZeroDataBlockP)
{
       static unsigned char     buf[256];

       switch (label) {
       case 0xf9:              /* Graphic Control Extension */
               (void) GetDataBlock(fd, (unsigned char*) buf, ZeroDataBlockP);
#if 0
               Gif89.disposal    = (buf[0] >> 2) & 0x7;
               Gif89.inputFlag   = (buf[0] >> 1) & 0x1;
               Gif89.delayTime   = LM_to_uint(buf[1],buf[2]);
#endif
               if ((buf[0] & 0x1) != 0)
                       *Transparent = buf[3];

               while (GetDataBlock(fd, (unsigned char*) buf, ZeroDataBlockP) != 0)
                       ;
               return FALSE;
       default:
               break;
       }
       while (GetDataBlock(fd, (unsigned char*) buf, ZeroDataBlockP) != 0)
               ;

       return FALSE;
}

static int
GetDataBlock_(gdIOCtx *fd, unsigned char *buf, int *ZeroDataBlockP)
{
       unsigned char   count;

       if (! ReadOK(fd,&count,1)) {
               return -1;
       }

       *ZeroDataBlockP = count == 0;

       if ((count != 0) && (! ReadOK(fd, buf, count))) {
               return -1;
       }

       return count;
}