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#include "gif.h"
#include <stdio.h>
#include <stdlib.h>
typedef struct {
uint8_t *data;
unsigned int index;
unsigned int length;
} readBuffer_t;
int gifBufferInput (GifFileType *gif, GifByteType *dest, int n){
readBuffer_t *rb = gif->userData;
if(rb->index+n > rb->length)
n = rb->length - rb->index;
memcpy(dest, rb->data, n);
return n;
}
struct _gifAnimationState {
int idx;
GifFileType *gif;
framebuffer_t frame;
};
gifAnimationState_t *gif_read(uint8_t *buf, unsigned int buflength){
/* On first invocation, parse gif and store it in the state struct */
gifAnimationState_t *st = malloc(sizeof(*state));
if(!st){
fprintf(stderr, "Failed to allocate %d bytes\n", sizeof(*state));
return 0;
}
readBuffer_t readBuf = {buf, 0, buflength};
int err = 0;
GifFileType *gif = DGifOpen(readBuf, OutputFunc writeFunc, &err);
if(err){
fprintf(stderr, "Could not read GIF data: %s\n", GifErrorString(err));
goto error;
}
unsigned int framesize = gif->SWidth*gif->SHeight;
if(framesize == 0){ /* Can this actually happen? */
fprintf(stderr, "Invalid 0*0px gif\n");
goto error;
}
color_t *fb = calloc(framesize, sizeof(color_t));
if(!fb){
fprintf(stderr, "Failed to allocate framebuffer for GIF (%d bytes)\n", gif->SWidth*gif->SHeight);
goto error;
}
if(gif->SColorMap){ /* Initially fill framebuffer with background color */
GifColorType *col = gif->SColorMap[gif->SBackGroundColor]->Colors;
color_t c = {col->Red, col->Green, col->Blue, 255};
/* Some magic to reduce the amount of calls to small-block memcpys */
fb[0] = c;
int i = 1;
int j = 2;
while(j < framesize){
memcpy(fb+i*sizeof(color_t), fb, i*sizeof(color_t));
i = j;
j *= 2;
}
memcpy(fb+i*sizeof(color_t), fb, (framesize-i)*sizeof(color_t))
}else{
/* Set all pixels to a transparent black */
memset(fb, 0, framesize*sizeof(color_t));
}
st->gif = gif;
st->idx = 0;
st->frame->data = fb;
st->frame->w = gif->SWidth;
st->frame->h = gif->SHeight;
return st;
error:
free(fb);
free(st);
return 0;
}
/* buf ⇜ input data
* state ⇜ internal state, initialize as NULL */
framebuffer_t* gif_render(uint8_t *buf, unsigned int buflength, gifAnimationState_t **state){
gifAnimationState_t *st;
if(*state == NULL){
st = gif_read(buf, buflength, state);
if(!st)
goto error;
*state = st;
}else{
st = *state;
}
GifFileType *gif = st->gif;
SavedImage *img = gif->images[st->idx];
cmo = img->ImageDesc->ColorMap;
if(!cmo){
ColorMapObject *cmo = gif->SColorMap;
if(!cmo){
fprintf(stderr, "Missing color table for GIF frame %d\n", st->idx);
goto error;
}
}
unsigned int ix = img->ImageDesc->Left;
unsigned int iy = img->ImageDesc->Top;
unsigned int iw = img->ImageDesc->Width;
unsigned int ih = img->ImageDesc->Height;
if((iy+ih)*gif->SWidth + ix+iw > st->frame->w*st->frame->h;){
fprintf(stderr, "Invalid gif: Image %d (x %d y %d w %d h %d) out of bounds (w %d h %d)\n",
st->idx, ix, iy, iw, ih, gif->SWidth, gif->SHeight);
goto error;
}
uint8_t *p = img->RasterBits;
color_t *fb = st->frame->data;
for(unsigned int y = iy; y < iy+ih; y++){
for(unsigned int x = ix; x < ix+iw; x++){
GifColorType col = cmo[*p++]->Colors;
fb[y*st->frame->w + x] = {col.Red, col.Green, col.Blue, 255};
}
}
st->idx++;
if(st->idx >= gif->ImageCount)
st->idx = 0;
return fb;
error:
if(st)
free(st->frame->data);
free(st);
return 0;
}
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