Mapping touch to picture help?

[adamj]

Hi All,

I'm having a terrible time trying to figure out how to map a touch that is fired from my UIImagePicker cameraOverlayView onto the picture that is captured by [picker takePicture].

Ultimately I want to crop a small rectangle underneath the finger of the touch....which I originally thought would be simply, but I found out that it's not.

What's messing me up is the UIImageOrientation, the different aspect ratio (3:2 for screen, 4:3 for picture) and the scale. I know that the easiest way (programatically) to do this is to transform the image to fit the screen size and orientation and keep the touch point as is, but this is very slow to execute.

I'd prefer to reorient the point to fit the picture, however I really don't know where to start on this (googled like crazy). Can anyone point me in the direction of some good websites that might cover this, or share some code snippet or advice?

All I want to do is crop a 100x100 square under the touch point from the picture, I had no idea it was going to be so complex!

Cheers
Adam