OpenCV和FFMpeg图片转换对比

    /* OpenCV */
    cv::Mat srcimg, dstimg;
    srcimg.create(height*3/2, width, CV_8UC1);
    FILE* fp = fopen(yuvf, "rb");
    fread(srcimg.data, 1, height*width*3/2, fp);
    // 需要进行一次转化
    cv::cvtColor(srcimg, dstimg, cv::COLOR_YUV2BGR_NV12);
    // 文件保存，目前已经测试jpg和png文件可行
    cv::imwrite(fout, dstimg);

/* libavcodec */
  1     AVCodec* codec;
  2     AVCodecContext* codecCtx;
  3     struct SwsContext* swsCtx;
  4     FILE* fp;
  5     int inSz, tmpSz;
  6     uint8_t *inbuff, *tmpbuff;
  7     size_t rd;
  8     int got_output = 0;
  9     int ret = 0;
 10     AVFrame *frame = NULL;
 11     AVPacket  pkt;
 12     if (width < 1 || height < 1 || !in || !out)
 13         return -1;
 14 
 15     // 准备转换环境
 16     av_register_all(); // 必须调用，否则 avcodec_find_encoder 会失败
 17     codec = avcodec_find_encoder(AV_CODEC_ID_MJPEG);
 18     if (NULL == codec) {
 19         return -2;
 20     }
 21     codecCtx = avcodec_alloc_context3(codec);
 22     if (NULL == codecCtx) {
 23         ret = -3;
 24         goto codecctx_errout;
 25     }
 26     codecCtx->bit_rate = 4000000;
 27     codecCtx->width =width;
 28     codecCtx->height = height;
 29     codecCtx->time_base = (AVRational){ 1, 25 };
 30     codecCtx->pix_fmt = AV_PIX_FMT_YUVJ420P;
 31     if (avcodec_open2(codecCtx, codec, NULL) < 0) {
 32         ret = -4;
 33         goto codecctx_errout;
 34     }
 35     frame = av_frame_alloc(); 
 36     av_init_packet(&pkt);
 37     pkt.data = NULL;
 38     pkt.size = 0;
 39 
 40     // 加载源文件
 41     fp = fopen(in, "rb");
 42     if (NULL == fp) {
 43         ret = -5;
 44         goto out;
 45     }
 46 
 47     inSz = av_image_get_buffer_size(infmt, width, height, 1);
 48     if (inSz <= 0) {
 49         ret = -6;
 50         goto out;
 51     }
 52     inbuff = (uint8_t*)malloc(inSz);
 53     if (NULL == inbuff) {
 54         ret = -7;
 55         goto out;
 56     }
 57     rd = fread(inbuff, 1, inSz, fp);
 58     if (rd != (size_t)inSz) {
 59         fclose(fp);
 60         ret = -8;
 61         goto allout;
 62     }
 63     fclose(fp);
 64 
 65     // 转换格式为YUV420P
 66     if (infmt != AV_PIX_FMT_YUVJ420P && infmt != AV_PIX_FMT_YUV420P) {
 67         swsCtx = sws_getContext(width, height, infmt, width, height, AV_PIX_FMT_YUV420P, SWS_BILINEAR, 0, 0, 0);
 68         if (NULL == swsCtx) {
 69             ret = -9;
 70             goto allout;
 71         }
 72         tmpSz = av_image_get_buffer_size(AV_PIX_FMT_YUV420P, width, height, 1);
 73         tmpbuff = (uint8_t*)malloc(tmpSz);
 74         if (NULL == tmpbuff) {
 75             ret = -9;
 76             goto allout;
 77         }
 78 
 79         AVFrame FrIn, FrOut;
 80         av_image_fill_linesizes(FrIn.linesize, infmt, width);
 81         av_image_fill_pointers(FrIn.data, infmt, height, inbuff, FrIn.linesize);
 82         av_image_fill_linesizes(FrOut.linesize, AV_PIX_FMT_YUV420P, width);
 83         av_image_fill_pointers(FrOut.data, AV_PIX_FMT_YUV420P, height, tmpbuff, FrOut.linesize);
 84 
 85         sws_scale(swsCtx, (const uint8_t* const*)FrIn.data, FrIn.linesize, 0, height, FrOut.data, FrOut.linesize);
 86         // 使用新的buffer
 87         free(inbuff);
 88         inbuff = tmpbuff;
 89     }
 90     // 填充AVFrame
 91     frame->format = codecCtx->pix_fmt;
 92     frame->width = width;
 93     frame->height = height;
 94 
 95     // 转换
 96     av_image_fill_linesizes(frame->linesize, codecCtx->pix_fmt, width);
 97     av_image_fill_pointers(frame->data, codecCtx->pix_fmt, height, inbuff, frame->linesize);
 98     if (avcodec_send_frame(codecCtx, frame) < 0) {
 99         ret = -10;
100         goto allout;
101     }
102     if (0 == avcodec_receive_packet(codecCtx, &pkt)) {
103         fp = fopen(out, "wb");
104         if (fp) {
105             fwrite(pkt.data, 1, pkt.size, fp);
106             fclose(fp);
107         }
108         else {
109             ret = 12;
110         }
111         av_packet_unref(&pkt);
112     }
113 
114     // 环境回收
115 allout:
116     free(inbuff);
117 out:
118     sws_freeContext(swsCtx);
119     av_frame_free(&frame); 
120 codecctx_errout:
121     avcodec_close(codecCtx);
122     av_free(codecCtx);
123 errout:
124     return ret;