findimagedupes is a command-line utility which performs a rough "visual diff" on two images or a whole tree to detect if any look similar. It can produce output suitable for driving GUI front-ends. It can also export a GQView compatible collection file, so you can deal with the duplicates visually. On common image types, findimagedupes seems to be around 98% accurate.
Release Notes: This release includes bugfixes so findimagedupes now works on Debian and Mandrake 7.2. New features include automatic rescanning if the image database is empty or not present, various performance enhancements, and a new mode that produces output suitable for driving GUI front-end apps.
Release Notes: Initial public release.