title: convert QVideoFrame to QImage
body: <p>I want to get every frames from a <code>QMediaPlayer</code> and convert it to <code>QImage</code> (or <code>cv::Mat</code>)</p>
  
  <p>so I used   <code>videoFrameProbed</code> signal from <code>QVideoProbe</code>:</p>
  
  <pre><code>connect(&amp;video_probe_, &amp;QVideoProbe::videoFrameProbed, 
           [this](const QVideoFrame&amp; currentFrame){
     //QImage img = ??
  }
  </code></pre>
  
  <p>But I didn't find any way for getting <code>QImage</code> from <code>QVideoFrame</code>!</p>
  
  <p>How can I convert <code>QVideoFrame</code> to <code>QImage</code> ?!</p>