Masking the Google Map in iOS

In my app I have displayed some custom overlay on google map using MKOverlay with the help of TileMap sample code. My requirement is, I need to mask the entire google map underneath the overlay.That is, I want rest of the开发者_运维技巧 map area to appear to be in gray except my custom overlay. Could anyone give me direction on how to achieve this?

Thanks in advance,

I don't know all the calls that you'd need to cover but I know how to find out. In the TileMap example code provided by Apple they show how the MKMapView will call for tiles. All you'd need to do is swap out the code that finds files on disk and swap in some code that always returns a grey square every time.

However this won't remove the Google logo or stop the app from downloading the map tiles from Google in the background. If you find out how to stop that please let me know.