I'm making an iPad app and I have this image:
I'd like offer users the option to replace the egg's face with a photo from their own library (assuming I have an egg with a blank space for the head). I was wondering if there was a suitable API for manipulating/overlaying photos or images I can plug in? Any advice much appreciated.
You'll want to look at the CoreImage libraries if you want to do basic image manipulations as you're describing.
First you'll get an image from the users library - you'll present a UIImagePicker modally (in the simplest scenario). This will give you back the selected image.
You'll then proceed to identify a face - CoreImage gives you a CIDetector, and this can be used to obtain a rect containing the face. You'll then grab an image, presumably, from just the rectangle around the face.
Then you take the face image, and place it behind your masked egg.