title: OpenCV: transforming 3 channel image into 4 channel
body: <p>I am trying to change 3-channel image into 4-channel like this: </p>
  
  <pre><code>cv::VideoCapture video;
  video.open("sample.avi");
  cv::Mat source;
  cv::Mat newSrc;
  int from_to = { 0,0, 1,1, 2,2, 3,3 };
  for ( int i = 0; i &lt; 1000; i ++ )
  {
     video &gt;&gt; source;
     cv::mixChannels ( source, 2, newSrc, 1, from_to, 4 );
  }
  </code></pre>
  
  <p>Then I got </p>
  
  <pre><code>too many input arguments in function call
  </code></pre>
  
  <p>for the 'mixChannels' line. Besides, I am not sure whether I am giving the arguments correctly for my goal. Can someone help me? Thank you. </p>