How to capture image merged by the camera ouput and its cameraOverlay in iphone

I want to capture the the image of camera taken, and this 开发者_Python百科image should come with its camera overlay image, how to do that?

And It seems that UIGetScreenImage() could not pass the appstore review.

use AVCaptureSession and related classes in the AV Foundation Framework

see this official thread in Apple Developer Forums: UIGetScreenImage() Thread