title: Inconsistent window size with OpenCV and namedWindow
body: <p>This code snippet using OpenCV 3.0 and Visual Studio 2013 on Windows 7:</p>
  
  <pre><code>Mat rgb = imread("test.jpeg");
  Mat channel[3];
  
  split(rgb, channel);
  
  namedWindow("Red", WINDOW_NORMAL);
  namedWindow("Green", WINDOW_NORMAL);
  namedWindow("Blue", WINDOW_NORMAL);
  namedWindow("RGB", WINDOW_NORMAL); 
  
  imshow("Blue", channel[0]);
  imshow("Green", channel[1]);
  imshow("Red", channel[2]);
  imshow("RGB", rgb);   
  
  waitKey(0); 
  </code></pre>
  
  <p>displays full screen windows named <em>Blue</em>, <em>Green</em> and <em>Red</em>, but <em>RGB</em> window is only quarter screen size. Shouldn't they all be the same size? </p>