Find Waldo (little pic) in Where is Waldo (large pic)

[Ofnuts]

You can give the two pictures to Gimp, but you should also give it some script that will move the little pic over the big one, compute the difference and stop when it goes below some threshold. But for a small 1000x800 (800.000 pixels), you'll have to do that 400.000 times on the average.