iOS Perspective Correction

We have an existing iOS application, written for iOS 5.0+. The application crops an image to a polygon (defined by 4 points on the screen - it isn't guaranteed to be rectangular). We require perspective correction on the cropped image, to fill a rectangle that is yet to be defined; it would need to be a stand-alone method that takes in the cropped image and a rectangle, and the cropped vertices if required. We will provide the iOS application so that the code can be integrated in, and tested. This is quite urgent, so the sooner this is achievable, the better.