hmm, i'd expect there is software that will compare, but I won't expect it to be cheap. Its very complex for a computer to decide against something like that since it can be from different angles, and so isn't as simple as spot the difference, and a computer would find it hard to play that game anyway.
i found this:
http://www.bolidesoft.com/imagecomparer.html
now this won't help you, as it only compares the same image and tells you if its on the computer already to help web servers, and deletes them if it finds one, and this kind of thing woudl be easier than what you are getting it to do.
What you want to do is get a program that will basically look at the letters and numbers and register them as data over the image, and that means image recognition..
and just like voice recognition, its harder to do for computers.
I'm finding it very hard to find a specific program i'm afraid
I know there would be some, but i know for sure they wouldn't be cheap.
I hope someone can help you