iOS: UIImagePickerController Overlay property Detects CameraSource Change
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**Background:** I am implementing a face mask to help people focus their camera and to produce a uniform result across every picture. Sadly, the face mask needs to adjust its size while switching between front and back facing camera to provide a great guideline for people. 

**Problem:** I have been trying to detect this switch between camera to adjust my face mask accordingly. I have not yet found how to detect it. 

**Additional Info:** I have tried looking into delegate and/or subclassing the pickerController. There are no methods visible for this detection. My last resort would be having a thread keep on checking camera source and adjust if needed. I welcome anything better :)