jpeg3.c

本程序利用linux的GTK

#include <stdio.h>
#include <setjmp.h>
#include "jpeglib.h"
#include "cdjpeg.h"
#include "jversion.h"

struct my_error_mgr {
  struct jpeg_error_mgr pub;	/* "public" fields */
  jmp_buf setjmp_buffer;	/* for return to caller */
};

typedef struct my_error_mgr * my_error_ptr;

METHODDEF(void)
my_error_exit (j_common_ptr cinfo)
{
  my_error_ptr myerr = (my_error_ptr) cinfo->err;
  (*cinfo->err->output_message) (cinfo);
  longjmp(myerr->setjmp_buffer, 1);
}

GLOBAL(int)
read_JPEG_file (char * infn,char *outfn)
{
  struct jpeg_decompress_struct cinfo;
  struct my_error_mgr jerr;
  FILE * infile, *outfile;		/* source file */
  djpeg_dest_ptr dest_mgr = NULL;
  JDIMENSION num_scanlines;
  if ((infile = fopen(infn, "rb")) == NULL) {
    fprintf(stderr, "can't open %s\n", infn);
    return 0;
  }
    if ((outfile = fopen(outfn, "wb+")) == NULL) {
    fprintf(stderr, "can't open %s\n", outfn);
    return 0;
  }
  /* Step 1: allocate and initialize JPEG decompression object */
  cinfo.err = jpeg_std_error(&jerr.pub);
  jerr.pub.error_exit = my_error_exit;
  if (setjmp(jerr.setjmp_buffer)) {
    jpeg_destroy_decompress(&cinfo);
    fclose(infile);
    return 0;
  }
  jpeg_create_decompress(&cinfo);
  /* Step 2: specify data source (eg, a file) */
  jpeg_stdio_src(&cinfo, infile);
  /* Step 3: read file parameters with jpeg_read_header() */
  (void) jpeg_read_header(&cinfo, TRUE);
  
  dest_mgr = jinit_write_bmp(&cinfo, FALSE);
  dest_mgr->output_file = outfile;
  /* Step 4: set parameters for decompression */
  /* In this example, we don't need to change any of the defaults set by
   * jpeg_read_header(), so we do nothing here.
   */
  /* Step 5: Start decompressor */
  (void) jpeg_start_decompress(&cinfo);
  (*dest_mgr->start_output) (&cinfo, dest_mgr);

  /* Step 6: while (scan lines remain to be read) */
  while (cinfo.output_scanline < cinfo.output_height) {
	  num_scanlines = jpeg_read_scanlines(&cinfo, dest_mgr->buffer,
					dest_mgr->buffer_height);
    (*dest_mgr->put_pixel_rows) (&cinfo, dest_mgr, num_scanlines);
  }
    (*dest_mgr->finish_output) (&cinfo, dest_mgr);
  /* Step 7: Finish decompression */
  (void) jpeg_finish_decompress(&cinfo);
  /* Step 8: Release JPEG decompression object */
  jpeg_destroy_decompress(&cinfo);
  fclose(infile);
  fclose(outfile);
  return 1;
}

int main(int argc,char *argv[])
{
	int suc=0;
	if((suc=read_JPEG_file(argv[1],argv[2]))!=1){
		printf("Usage:%s jpegfilename bmpfilename\n",argv[0]);
		printf("Failed to read JPEG...\n");
		return 1;
	}
	else{
		printf("\nSuccessfully read JPEG image!!\n");
		return 0;
	}
}