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#include <config.h>
#include <stdio.h>
#include <math.h>
#include <string.h>
#include <errno.h>
#include "GFile_JPEG.h"
extern "C" {
#include <jpeglib.h>
}
/* GFile (ie. GImage) decendent for reading JPEG files.
*
* Written by: Chris Studholme
* Last Update: 28-May-2000
* Copyright: GPL (http://www.fsf.org/copyleft/gpl.html)
*/
/* ================ GFile_JPEG methods ================ */
GFile_JPEG::GFile_JPEG(const char* filename, bool fast) {
red=green=blue=NULL;
w=h=0;
// allocate and initialize a JPEG compression object
jpeg_decompress_struct cinfo;
jpeg_error_mgr jerr;
cinfo.err = jpeg_std_error(&jerr);
jpeg_create_decompress(&cinfo);
// specify the source for the compressed data
FILE* infile;
if ((infile = fopen(filename, "rb")) == NULL) {
fprintf(stderr, "can't open %s\n", filename);
return;
}
jpeg_stdio_src(&cinfo, infile);
// call jpeg_read_header() to obtain image info
jpeg_read_header(&cinfo, TRUE);
// set parameters for decompression
cinfo.dct_method = JDCT_FLOAT;
// jpeg_start_decompress(...);
jpeg_start_decompress(&cinfo);
w=cinfo.output_width;
h=cinfo.output_height;
if (cinfo.output_components!=3) {
fprintf(stderr,"GFile_JPEG: only full color JPEG images are supported\n");
jpeg_destroy_decompress(&cinfo);
fclose(infile);
return;
}
int row_stride = cinfo.output_width * cinfo.output_components;
/* Make a one-row-high sample array that will go away when done with image */
JSAMPARRAY buffer = (*cinfo.mem->alloc_sarray)
((j_common_ptr) &cinfo, JPOOL_IMAGE, row_stride, 1);
unsigned char* r = new unsigned char[w*h];
unsigned char* g = new unsigned char[w*h];
unsigned char* b = new unsigned char[w*h];
// while (scan lines remain to be read)
for (int y=0; y<h; ++y) {
// jpeg_read_scanlines(...);
jpeg_read_scanlines(&cinfo,buffer,1);
for (int x=0; x<w; ++x) {
r[y*w+x] = buffer[0][3*x+0];
g[y*w+x] = buffer[0][3*x+1];
b[y*w+x] = buffer[0][3*x+2];
}
}
memset(histogram,0,sizeof(histogram));
addToHistogram(histogram,r,w*h);
addToHistogram(histogram,g,w*h);
addToHistogram(histogram,b,w*h);
// jpeg_finish_decompress(...);
jpeg_finish_decompress(&cinfo);
// release the JPEG decompression object
jpeg_destroy_decompress(&cinfo);
fclose(infile);
// create linear mapping
fprintf(stderr,"Initializing linear matrix... ");
red = new GImageComponent0(r,w,h,fast?-1:0);
delete[] r;
fprintf(stderr,"red... ");
green = new GImageComponent0(g,w,h,fast?-1:0);
delete[] g;
fprintf(stderr,"green... ");
blue = new GImageComponent0(b,w,h,fast?-1:0);
delete[] b;
fprintf(stderr,"blue, done.\n");
if (!fast)
fprintf(stderr,"Total Error is %g\n",red->getTotalError()+
green->getTotalError()+blue->getTotalError());
}
GFile_JPEG::~GFile_JPEG() {
if (red)
delete red;
if (green)
delete green;
if (blue)
delete blue;
}
bool GFile_JPEG::supportsFile(FILE* file) {
if (fseek(file,0,SEEK_SET)!=0) {
fprintf(stderr,"GFile_JPEG::supportsFile() fseek() failed %d\n",errno);
return false;
}
unsigned char header[2];
if (fread(header,sizeof(header),1,file)!=1) {
fprintf(stderr,"GFile_JPEG::supportsFile() fread() failed %d\n",errno);
return false;
}
return ((header[0]==0x0FF)&&(header[1]==0x0D8));
}
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