使用libjpeg库将yuv420数据转换为jpg图片

使用libjpeg库转换yuv数据 为jpg时的步骤与RGB数据基本相同，对原始代码稍作修改即可使用。
源数据格式， yuv420， 存储格式为 yyyy....uu..vv， 转换成jpg图片文件。
yuv.bmp，yuv420测试数据，大小为960*540,  分量排列格式为yyyy....uu..vv..
程序代码：

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1. int yuv420sp_to_jpg(char *filename, int width, int height, unsigned char *pYUVBuffer)
   
2. {
   
3.     FILE *fJpg;
   
4.     struct jpeg_compress_struct cinfo;
   
5.     struct jpeg_error_mgr jerr;
   
6.     JSAMPROW row_pointer[1];
   
7.     int row_stride;
   
8.     int i = 0, j = 0;
   
9.     unsigned char yuvbuf[width * 3];
   
10.     unsigned char *pY, *pU, *pV;
    
11.     int ulen;
    
12. 
    
13.     ulen = width * height / 4;
    
14. 
    
15.     if(pYUVBuffer == NULL){
    
16.         debugE("pBGRBuffer is NULL!\n");
    
17.         return -1;
    
18.     }
    
19. 
    
20.     cinfo.err = jpeg_std_error(&jerr);
    
21.     jpeg_create_compress(&cinfo);
    
22.     fJpg = fopen(filename, "wb");
    
23.     if(fJpg == NULL){
    
24.         debugE("Cannot open file %s, %s\n", filename, strerror(errno));
    
25.         jpeg_destroy_compress(&cinfo);
    
26.         return -1;
    
27.     }
    
28. 
    
29.     jpeg_stdio_dest(&cinfo, fJpg);
    
30.     cinfo.image_width = width;
    
31.     cinfo.image_height = height;
    
32.     cinfo.input_components = 3;
    
33.     cinfo.in_color_space = JCS_YCbCr;
    
34.     cinfo.dct_method = JDCT_ISLOW;
    
35.     jpeg_set_defaults(&cinfo);
    
36. 
    
37. 
    
38.     jpeg_set_quality(&cinfo, 99, TRUE);
    
39. 
    
40.     jpeg_start_compress(&cinfo, TRUE);
    
41.     row_stride = cinfo.image_width * 3; /* JSAMPLEs per row in image_buffer */
    
42.     
    
43.     pY = pYUVBuffer;
    
44.     pU = pYUVBuffer + width*height;
    
45.     pV = pYUVBuffer + width*height + ulen;
    
46.     j = 1;
    
47.     while (cinfo.next_scanline < cinfo.image_height) {
    
48.         /* jpeg_write_scanlines expects an array of pointers to scanlines.
    
49.          * Here the array is only one element long, but you could pass
    
50.          * more than one scanline at a time if that's more convenient.
    
51.          */
    
52. 
    
53.         /*Test yuv buffer serial is : yyyy...uu..vv*/
    
54.         if(j % 2 == 1 && j > 1){
    
55.             pU = pYUVBuffer + width*height + width / 2 * (j / 2);
    
56.             pV = pYUVBuffer + width*height * 5 / 4 + width / 2 *(j / 2);
    
57.         }
    
58.         for(i = 0; i < width; i += 2){
    
59.             yuvbuf[i*3] = *pY++;
    
60.             yuvbuf[i*3 + 1] = *pU;
    
61.             yuvbuf[i*3 + 2] = *pV;
    
62. 
    
63.             yuvbuf[i*3 + 3] = *pY++;
    
64.             yuvbuf[i*3 + 4] = *pU++;
    
65.             yuvbuf[i*3 + 5] = *pV++;
    
66.         }
    
67. 
    
68.         row_pointer[0] = yuvbuf;
    
69.         (void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
    
70.         j++;
    
71.     }
    
72. 
    
73.     jpeg_finish_compress(&cinfo);
    
74. 
    
75.     jpeg_destroy_compress(&cinfo);
    
76.     fclose(fJpg);
    
77. 
    
78.     return 0;
    
79. }

说明一下，由于yuv420格式问题，我们需要用前两行的y分量共享第一行的uv分量，代码:54-57。
转换效果图如下：