Solutions of this sort merely present a sort of "low wall" that must be consciously hopped over.
You can't accidentally, or in a moment of poor judgement, modify a picture. You have to go ahead and make an effort. So it always is. Much of the protocols of police work, as well as other lines of work in all walks of life, is to keep basically honest people honest. The profoundly dishonest cannot, really, be stopped, they can only be caught (sometimes) and punished.