title: Separate hsv channels in opencv
body: <p>I am having an hsv mat file in opencv and I want to separate the channels. I found  cvSplit( hsv, h, s, v, NULL ), but it doesn't work with Mat files. How is it then, to keep just the first channel h of  from the Mat image file??
  My result is the above. Basically is the image that I convert, I can see the face but in weird tones.</p>
  
  <p><img src="https://i.stack.imgur.com/kzQOH.png" alt="h channel"></p>
  
  <p>The code used:</p>
  
  <pre><code>    cvtColor(cropped_rgb, cropped_hsv, CV_BGR2HSV);
      split(cropped_hsv, channels);
      cropped_hsv = channels[0]; 
      imshow("cropped_hsv", cropped_hsv);
  </code></pre>