PastCam

I actually really like this concept. It was almost exactly what I was looking for. But it lacks the ability to select a new photo (having to exit the app to select another photo is highly annoying and inefficient). Also, most comparison photos people like to take are of themselves or with those around them. So, having a function to flip the camera around would definitely help with selfies. :) Would definitely give this a 5 star if new additions are made.

It only lets you use the app in vertical mode. If you try to use an existing horizontal image it crops it into a vertical image and there are no settings that at all so you can't do anything about it. :/

Great way to line up your camera shots using past pics as a framework. Used it with my dog as a puppy and now as an adult