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#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <setjmp.h>
#include <string.h>
#include "jpeglib.h"
#include "meh.h"
struct error_mgr{
struct jpeg_error_mgr pub;
jmp_buf jmp_buffer;
};
static void error_exit(j_common_ptr cinfo){
(void) cinfo;
printf("\nerror!\n");
exit(1);
}
struct jpeg_t{
struct image img;
FILE *f;
struct jpeg_decompress_struct cinfo;
struct error_mgr jerr;
};
static struct image *jpeg_open(FILE *f){
struct jpeg_t *j;
rewind(f);
if(getc(f) != 0xff || getc(f) != 0xd8)
return NULL;
j = malloc(sizeof(struct jpeg_t));
j->f = f;
rewind(f);
j->cinfo.err = jpeg_std_error(&j->jerr.pub);
j->jerr.pub.error_exit = error_exit;
jpeg_create_decompress(&j->cinfo);
jpeg_stdio_src(&j->cinfo, f);
jpeg_read_header(&j->cinfo, TRUE);
/* parameters */
j->cinfo.do_fancy_upsampling = 0;
j->cinfo.do_block_smoothing = 0;
j->cinfo.quantize_colors = 0;
j->cinfo.dct_method = JDCT_IFAST;
jpeg_calc_output_dimensions(&j->cinfo);
j->img.width = j->cinfo.output_width;
j->img.height = j->cinfo.output_height;
return (struct image *)j;
}
static int jpeg_read(struct image *img){
struct jpeg_t *j = (struct jpeg_t *)img;
JSAMPARRAY buffer;
int row_stride;
int a = 0, b;
unsigned int x, y;
row_stride = j->cinfo.output_width * j->cinfo.output_components;
buffer = (*j->cinfo.mem->alloc_sarray)((j_common_ptr)&j->cinfo, JPOOL_IMAGE, row_stride, 4);
jpeg_start_decompress(&j->cinfo);
if(j->cinfo.output_components == 3){
for(y = 0; y < j->cinfo.output_height; ){
int n = jpeg_read_scanlines(&j->cinfo, buffer, 4);
for(b = 0; b < n; b++){
memcpy(&img->buf[a], buffer[b], row_stride);
a += row_stride;
}
y += n;
}
}else if(j->cinfo.output_components == 1){
for(y = 0; y < j->cinfo.output_height; ){
int n = jpeg_read_scanlines(&j->cinfo, buffer, 4);
for(b = 0; b < n; b++){
for(x = 0; x < j->cinfo.output_width; x++){
img->buf[a++] = buffer[b][x];
img->buf[a++] = buffer[b][x];
img->buf[a++] = buffer[b][x];
}
}
y += n;
}
}
jpeg_finish_decompress(&j->cinfo);
jpeg_destroy_decompress(&j->cinfo);
return 0;
}
struct imageformat jpeg = {
jpeg_open,
jpeg_read
};
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