title: Copy CGContext into another CGContext
body: <p>I am performing some CG drawing operations into a CGContext that I created for an MKMapOverlayView.  After drawing into my context, I create an image and paste it into the context that MapKit provided.</p>
  
  <pre><code>- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context {
      CGColorSpaceRef colorRef = CGColorSpaceCreateDeviceRGB();
      CGContextRef myContext = CGBitmapContextCreate(NULL, kTileSize, kTileSize, 8, 0, colorRef, kCGImageAlphaPremultipliedLast);
      CGColorSpaceRelease(colorRef);
      CGContextSetAllowsAntialiasing(myContext, TRUE);
      //...cut out drawing operations...
      CGImageRef image = CGBitmapContextCreateImage(myContext);
      CGContextDrawImage(context, [self rectForMapRect:mapRect], image);
      CGImageRelease(image);
      CGContextRelease(myContext);
  }
  </code></pre>
  
  <p>Is there a way to simply copy <code>myContext</code> into <code>context</code> without having to create an image?</p>
  
  <p>I realize that some of you will say "why not just draw directly into the context that MapKit provides".  Unfortunately, we're experiencing a drawing glitch when rendering into <code>context</code> directly.  Apple is currently investigating this issue for us, but in the meantime we need to get a workaround in place.  This workaround I presented above is my "best" shot, but it is a bit on the slow side.</p>
  
  <p><strong>P.S.</strong> I have started a bounty since I'm looking for an answer here too. Specifically I'm targeting OS X. So the answer should work there. The OP was looking for an answer on iOS.</p>