Crop image to a square according to the size of a UIView/CGRect

Question

I have an implementation of AVCaptureSession and my goal is for the user to take a photo and only save the part of the image within the red square border, as shown below:

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Answer 1

Swift 3:

let imageRef:CGImage = uncroppedImage.cgImage!.cropping(to: bounds)!
let croppedImage:UIImage = UIImage(cgImage: imageRef)