title: Holding an image for runtime updating in OpenCV
body: <p>I have an image I'd like to display using <code>imshow()</code> and to <strong>update</strong> at runtime: say I'd like to run a corner detection algorithm then <strong>display the corner on this same image</strong> - like in MATLAB <code>figure  plot(), hold plot()</code> - the <strong><code>hold</code></strong> keyword hold the previous image/graph and enables a new plot on the same figure.</p>
  
  <p>Is this possible to do with OpenCV? If yes, how can I do it?</p>
  
  <p>thanks  </p>