From Black Bilby:
Duplicate Image Detector will hunt through your files and directories, detecting images which are identical or very close to identical. No longer will your hard drive be full of the same image copied over and over. Avoid slowing down your website by making users load the same file multiple times. Duplicate Image Detector will even detect images which are saved in different formats but have the same source. If you have a tiff file which has then been saved using different jpeg compression settings Duplicate Image Detector will find all of those images. Version 1.1.0 add a couple of new features to Duplicate Image Detector. The first is the ability to compare a directory of images to the images that you have already processed with Duplicate Image Detector. Once the comparison is complete you have the option of deleting or applying a finder label to the matched or unmatched images. Also version 1.1.0 brings the ability to save a collection of Images. Also to make the management of a collection of images over time easy the ability to check for new, changed or deleted files has been added. Finally the option to add extra directories of images to collection has also been added.
It seems clumsy, and if it finds a lot of duplicates, it looks like it will take a bunch of time. solve your problem.
when a programer decides to realse a program that he/she is proud of. he releases it complete. But if they think that people who try i, will find that it sucks, they cripple it and make everyone pay BEFORE they find out that it is junk.
Therefore, if you are going to pay for it, i think it is a good idea to see if it works, before it is too late.