How to add CIFilter to AVCaptureDeferredPhotoProxy

Hello, I m trying to implement deferred photo processing in my photo capture app. After I take a photo, I pass it through a CIFilter, now with the Deferred Photo Processing where would I pass the resulting photo through the CIFilter? Since there is no way for me to know when the system has finished processing a photo. If I have to do it in my app foreground every time, how do I prevent a scenario, where the user takes a photo, heads straight to the Photos App and sees the image without the filter?