Eu encontrei um aplicativo que faz isso; é chamado VisiPics:
VisiPics does more than just look for identical files, it goes beyond checksums to look for similar pictures and does it all with a simple user interface. First, you select the root folder or folders to find and catalogue all of your pictures. It then applies five image comparison filters in order to measure how close pairs of images on the hard drive are.
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All detected duplicates are shown side by side with pertinent information such as file name, type and size being displayed. Its auto-select mode let you choose if you want to keep the higher resolution picture, space-saving filetype, smaller filesize or all of the above. If you are insecure over what you really want to delete you can manually select the images you don't want to keep and delete them yourself.