jpeg入门学习笔记

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

int main(int argc,char **argv)
{
	struct jpeg_decompress_struct cinfo;
	struct jpeg_error_mgr jerr;
	FILE * infile;
	
	cinfo.err=jpeg_std_error(&jerr);
	
	jpeg_create_decompress(&cinfo);
	// 指定源文件
	if ((infile = fopen(argv[1], "rb")) == NULL) {
		fprintf(stderr, "can't open %s\n", argv[1]);
		return -1;
	}
	jpeg_stdio_src(&cinfo, infile);

	// 用jpeg_read_header获得jpg信息
	jpeg_read_header(&cinfo, TRUE);;
	/* 源信息 */
	printf("image_width = %d\n", cinfo.image_width);
	printf("image_height = %d\n", cinfo.image_height);
	printf("num_components = %d\n", cinfo.num_components);
	// 设置解压参数,比如放大、缩小

	// 启动解压：jpeg_start_decompress
	jpeg_start_decompress(&cinfo);
	/* 输出的图象的信息 */
	printf("output_width = %d\n", cinfo.output_width);
	printf("output_height = %d\n", cinfo.output_height);
	printf("output_components = %d\n", cinfo.output_components);
	
	// 循环调用jpeg_read_scanlines来一行一行地获得解压的数据

	jpeg_finish_decompress(&cinfo);
	jpeg_destroy_decompress(&cinfo);

	return 0;
	
}