Design some software to be used with Android , compare two similar images, find differences

I need a basic app designed. The app will take two photos and identify changes/ differences. For example. I take a photo of a room, then I removed the chair, i take a second photo and compare the differences the app will highlight area where the chair use to be. Programming should consider the two images wont have an exact reference point (because user will take the photos and wont be precisely same position) for comparison so it must be able to find its reference point to do the comparison correctly.