Ffmpeg avframe to cv:: mat

//AVFrame  turn  cv::mat 
cv::Mat frame_to_mat(const AVFrame * frame) {
    
    int width = frame->width;
    int height = frame->height;

    cv::Mat image(height, width, CV_8UC3);
    int cvLinesizes[1];
    cvLinesizes[0] = image.step1();
    if( NULL == _swsContext) {
    
        _swsContext = sws_getContext(width, height,
            (AVPixelFormat)frame->format, width, height,
            AVPixelFormat::AV_PIX_FMT_BGR24, SWS_FAST_BILINEAR, NULL, NULL, NULL);
    }

    sws_scale(_swsContext, frame->data, 
        frame->linesize, 0, height, &image.data, cvLinesizes);
    
    return image;
}

The parameters passed in by the above function frame Image format in , It can be YUV, RGB , wait ,,
after sws_scale（） After the transformation , write in cv::Mat Data area .

There's another way Is directly to the AVFrame Medium RGB The data is assigned to cv::Mat

cv::Mat img;
img = cv::Mat(height, width, CV_8UC3);
img.data =  _rgb_frame->data[0];