title: Flatten CALayer sublayers into one layer
body: <p>In my app I have one root layer, and many images which are sublayers of rootLayer. I'd like to flatten all the sublayers of rootLayer into one layer/image, that don't have any sublayers. I think I should do this by drawing all sublayers in core graphics context, but I don't know how to do that.</p>
  
  <p>I hope you'll understand me, and sorry for my English.</p>