libjpeg-turbo是一个效率很高的图片处理的C库，所以严格来说放在Go这里不太妥当，但是之后我们会把它封装成Go可以调用的类库。据说libjpeg-turbo在处理jpeg格式图片时比ImageMagick库效率高了三倍，参照示例代码写了一个缩略图的功能：

1 // 2 //  main.cpp 3 //  libjpegturbo 4 // 5 //  Created by 张皓然 on 2018/4/17. 6 //  Copyright © 2018年 张皓然. All rights reserved. 7 // 8  9 #include 
     
      10 #include "/opt/libjpeg-turbo/include/jpeglib.h"11 12 using namespace std;13 14 int compress_JPEG_file(string strImageName, string strDstImageName, int quality, int scale_num, int scale_denom) {15     //创建必要变量，后缀in是源图片信息，out是目标图片信息，buffer是缓冲区16     struct jpeg_decompress_struct cinfo_in;17     struct jpeg_compress_struct cinfo_out;18     struct jpeg_error_mgr jerr_in, jerr_out;19     FILE *infile, *outfile;20     JSAMPARRAY buffer;21     //表示每行的宽度，为width*components22     int row_stride;23     24     //初始化对象25     jpeg_create_decompress(&cinfo_in);26     jpeg_create_compress(&cinfo_out);27     //绑定错误结构28     cinfo_in.err = jpeg_std_error(&jerr_in);29     cinfo_out.err = jpeg_std_error(&jerr_out);30     //C库方式打开图片文件，并填入cinfo对象31     if((infile = fopen(strImageName.c_str(), "rb")) == NULL) {32         fprintf(stderr, "can't open %s\n", strImageName.c_str());33         return -1;34     }35     if((outfile = fopen(strDstImageName.c_str(), "wb")) == NULL) {36         fprintf(stderr, "can't open %s\n", strDstImageName.c_str());37         return -1;38     }39     jpeg_stdio_src(&cinfo_in, infile);40     jpeg_stdio_dest(&cinfo_out, outfile);41     //读取文件信息42     jpeg_read_header(&cinfo_in, TRUE);43     44     //设定文件压缩比例，M/N45     cinfo_in.scale_num = scale_num;46     cinfo_in.scale_denom = scale_denom;47     48     //开始解压缩49     jpeg_start_decompress(&cinfo_in);50     51     //将压缩后的信息存入cinfo_out中作为新图片的参数52     cinfo_out.image_height = cinfo_in.output_height;53     cinfo_out.image_width = cinfo_in.output_width;54     cinfo_out.input_components = 3;55     cinfo_out.in_color_space = JCS_RGB;56     jpeg_set_defaults(&cinfo_out);57     //设置图片质量58     jpeg_set_quality(&cinfo_out, quality, TRUE);59     //开始压缩60     jpeg_start_compress(&cinfo_out, TRUE);61     62     //设定每行的宽度准备写入，并分配缓冲区空间63     row_stride = cinfo_in.output_width * cinfo_in.output_components;64     buffer = (*cinfo_in.mem -> alloc_sarray)((j_common_ptr)&cinfo_in, JPOOL_IMAGE, row_stride, 1);65     66     while(cinfo_in.output_scanline < cinfo_in.output_height) {67         //从in中读取数据并写入out中68         jpeg_read_scanlines(&cinfo_in, buffer, 1);69         jpeg_write_scanlines(&cinfo_out, buffer, 1);70     }71     72     //结束，释放变量73     jpeg_finish_decompress(&cinfo_in);74     jpeg_destroy_decompress(&cinfo_in);75     76     jpeg_finish_compress(&cinfo_out);77     jpeg_destroy_compress(&cinfo_out);78     79     fclose(infile);80     fclose(outfile);81     82     return 0;83 }84 85 int main() {86     clock_t start, finish;87     start = clock();88     for(int i = 0; i < 100; i ++) compress_JPEG_file("/Users/zhanghaoran/Desktop/abc.jpg", "/Users/zhanghaoran/Desktop/abc_compress.jpg", 80, 1, 2);89     finish = clock();90     cout << "Total : " << (double)(finish - start) / CLOCKS_PER_SEC << endl;91 }