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#include <stdio.h>
#include <string.h>
#include "meh.h"
#define GIF87a 0
#define GIF89a 1
unsigned char *loadgif(FILE *infile, int *bufwidth, int *bufheight){
int version;
unsigned char *palette;
int pallen;
unsigned char *buf;
unsigned int bpp;
{
/* Read header*/
unsigned char packed;
unsigned char header[13];
if(fread(header, 1, 13, infile) != 13)
return NULL;
if(!memcmp("GIF89a", header, 6))
version = GIF89a;
else if(!memcmp("GIF87a", header, 6))
version = GIF87a;
else
return NULL;
*bufwidth = header[6] | header[7] << 8;
*bufheight = header[8] | header[9] << 8;
packed = header[10];
bpp = (packed & 7) + 1;
/* Read colormap */
if(packed & 0x80){
printf("Reading palette\n");
pallen = 1 << bpp;
printf("pallen: %i\n", pallen);
palette = malloc(3 * pallen);
fread(palette, 1, 3 * pallen, infile);
}
}
{
int blocktype;
while((blocktype = fgetc(infile)) != EOF){
if(blocktype == ';'){
printf("end of file\n");
break;
}else if(blocktype == '!'){
int bytecount, fncode;
if((fncode = fgetc(infile)) == EOF)
return NULL;
while(1){
bytecount = fgetc(infile);
printf("Skipping extblock 0x%x\n", fncode);
if(bytecount == EOF)
return NULL;
else if(bytecount > 0)
fseek(infile, bytecount, SEEK_CUR);
else
break;
}
}else if(blocktype == ','){
int imagex, imagey, imagew, imageh;
unsigned char imagedesc[9];
if(fread(imagedesc, 1, 9, infile) != 9)
return NULL;
if(imagedesc[8] & 0x80){
printf("ERROR: local palettes not supported\n");
return NULL;
}
if(imagedesc[8] & 0x40){
printf("ERROR: interlaced images\n");
return NULL;
}
imagex = imagedesc[0] | imagedesc[1] << 8;
imagey = imagedesc[2] | imagedesc[3] << 8;
imagew = imagedesc[4] | imagedesc[5] << 8;
imageh = imagedesc[6] | imagedesc[7] << 8;
if(imagex != 0 || imagey != 0 || imagew != *bufwidth || imageh != *bufheight){
printf("%ix%i %ix%i\n", imagex, imagey, imagew, imageh);
printf("TODO: allow this sort of thing\n");
return NULL;
}
{
int initcodesize, curcodesize;
initcodesize = fgetc(infile);
if(initcodesize < 1 || initcodesize > 9){
printf("bad code size %i\n", initcodesize);
return NULL;
}
curcodesize = initcodesize + 1;
}
break;
}else{
printf("Unknown block type %i\n", blocktype);
return NULL;
}
}
}
printf("end\n");
return NULL;
}
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