I was wondering what's a good library or some code to find the similarities between one image and another image/images. I have some software I'm writing where the user has a set of images and he/she wants to compare one image to the rest and then output the similarities into an image file to visually see the differences. I've used code before to do very simple compares but they're not detailed enough and I have no clue how to output the similarities or differences into and image file. Does anyone have any ideas?