libjpeg：将Yuv420P图像数据压缩存储为jpeg图像

// outJpegFileName：输出的jpeg文件名称
// yuvData: yuv420格式的数据，其数据存储顺序为：y->u->v
// quaulity: 输出的jpeg图像质量，有效范围为0-100
int Yuv420PToJpeg(const char * outJpegFileName, unsigned char* yuvData, int image_width, int image_height, int quality)
{
	struct jpeg_compress_struct cinfo;
	struct jpeg_error_mgr jerr;
	cinfo.err = jpeg_std_error(&jerr);
	jpeg_create_compress(&cinfo);

	FILE * outfile;    // target file  
	if ((outfile = fopen(outJpegFileName, "wb")) == NULL)
	{
		fprintf(stderr, "can't open %s\n", outJpegFileName);
		exit(1);
	}
	jpeg_stdio_dest(&cinfo, outfile);

	cinfo.image_width = image_width;    
	cinfo.image_height = image_height;
	cinfo.input_components = 3;    // # of color components per pixel  
	cinfo.in_color_space = JCS_YCbCr;  //colorspace of input image  
	jpeg_set_defaults(&cinfo);
	jpeg_set_quality(&cinfo, quality, TRUE);

	//  
	//  cinfo.raw_data_in = TRUE;  
	cinfo.jpeg_color_space = JCS_YCbCr;
	cinfo.comp_info[0].h_samp_factor = 2;
	cinfo.comp_info[0].v_samp_factor = 2;
	/  

	jpeg_start_compress(&cinfo, TRUE);

	JSAMPROW row_pointer[1];

	// 获取y、u、v三个分量各自数据的指针地址
	unsigned char *ybase, *ubase, *vbase;
	ybase = yuvData;
	ubase = yuvData + image_width*image_height;
	vbase = ubase + image_height*image_width / 4;

	unsigned char *yuvLine = new unsigned char[image_width * 3];
	memset(yuvLine, 0, image_width * 3);

	int j = 0;
	while (cinfo.next_scanline < cinfo.image_height)
	{
		int idx = 0;
		for (int i = 0; i<image_width; i++)
		{
			// 分别取y、u、v的数据
			yuvLine[idx++] = ybase[i + j * image_width];
			yuvLine[idx++] = ubase[(j>>1) * image_width/2 + (i>>1) ];
			yuvLine[idx++] = vbase[(j>>1) * image_width/2 + (i>>1) ];
		}
		row_pointer[0] = yuvLine;
		jpeg_write_scanlines(&cinfo, row_pointer, 1);
		j++;
	}
	jpeg_finish_compress(&cinfo);
	jpeg_destroy_compress(&cinfo);
	fclose(outfile);

	delete[]yuvLine;
	return 0;
}