For a photo, you might have to be a bit fuzzier than that, given that things like jpeg recompression can change a lot of that. I assume there are techniques to

For a photo, you might have to be a bit fuzzier than that, given that things like jpeg recompression can change a lot of that. I assume there are techniques to get around that sort of thing, though, and major software vendors like Google & Microsoft ought to have the sort of people who can solve that problem.