title: MKAnnotation image offset with custom pin image
body: <p>I have a MKAnnotation with an custom pin image. However the pin(MKAnnotationView) centers the image in relation to the specified coordinate. I want to set the point of the coordinate at the bottom center of the image, not center.</p>
  
  <p>I've tried using <code>annView.centerOffset = CGPointMake(-12, -28);</code>. But the problem is that <code>centerOffset</code> isn't relevant to the maps zoom level. </p>
  
  <p>One can do this both in the JS API and in Android. Is there any possibility to do this in objective-c?</p>
  
  <p>..fredrik</p>