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libjpeg学习3:turbojpeg试用
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:
#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