title: How to get a subimage of a subimage using getImageData in HTML5 canvas
body: <p>With HTML5 canvas you can get a subimage of an image with no difficulty. Like follows:</p>
  
  <p>var imageData = context.getImageData(5, 5, 10, 10);
  var d = imageData.data</p>
  
  <p>However, there does not appear to be a way to get another subimage of this data.</p>
  
  <p>Say I wanted to do this:
  var imageData = context.getImageData(0, 0, 2, 2) of the previously returned subimage.</p>
  
  <p>This would effectively be (5, 5, 2, 2);</p>
  
  <p>Drilling down recursively into an image with subimages is possible with most graphics libraries.  Does canvas have something similar?</p>