libjpeg学习3：turbojpeg试用

GNU/Linux程序 328 字 次

turbojpeg针对ARM和X86对了优化，宣称其速度是libjpeg的2到4倍。下载其源码，值得称赞的地方是其例子，单元测试很到位。另外是它的注释，或者说是html说明文件，对于宏、函数都有详细的说明。本文就是参考源码的例子和html文档写的简单示例。由于只是试用，并无深入研究，只是在我的虚拟机里运行。对于性能测试，并未进行。

代码示例：

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <setjmp.h>
 
#include "jpeg-utils.h"
 
// jpeg库头文件必须放到stdio.h后面
#include "libjpeg/include/turbojpeg.h"
 
 
int tjpeg_header(unsigned char* jpeg_buffer, int jpeg_size, int* width, int* height, int* subsample, int* colorspace)
{
    tjhandle handle = NULL;
 
    handle = tjInitDecompress();
    tjDecompressHeader3(handle, jpeg_buffer, jpeg_size, width, height, subsample, colorspace);
 
    tjDestroy(handle);
 
    return 0;
}
 
int tjpeg2rgb(unsigned char* jpeg_buffer, int jpeg_size, unsigned char* rgb_buffer, int* size)
{
    tjhandle handle = NULL;
    int width, height, subsample, colorspace;
    int flags = 0;
    int pixelfmt = TJPF_RGB;
 
    handle = tjInitDecompress();
    tjDecompressHeader3(handle, jpeg_buffer, jpeg_size, &width, &height, &subsample, &colorspace);
 
    flags |= 0;
    tjDecompress2(handle, jpeg_buffer, jpeg_size, rgb_buffer, width, 0,
            height, pixelfmt, flags);
 
    tjDestroy(handle);
 
    return 0;
}
 
int trgb2jpeg(unsigned char* rgb_buffer, int width, int height, int quality, unsigned char** jpeg_buffer, unsigned long* jpeg_size)
{
    tjhandle handle = NULL;
    //unsigned long size=0;
    int flags = 0;
    int subsamp = TJSAMP_422;
    int pixelfmt = TJPF_RGB;
 
    handle=tjInitCompress();
    //size=tjBufSize(width, height, subsamp);
    tjCompress2(handle, rgb_buffer, width, 0, height, pixelfmt, jpeg_buffer, jpeg_size, subsamp,
            quality, flags);
 
    tjDestroy(handle);
 
    return 0;
}

李迟 2015.7.7