I have something that does a similar job, however it works
in a slightly different way. First of all the assumption is
that the exact size of the image gives a quicker hint than the checksum so it keeps a hash that translates file
sizes into a list of names and only looks at the contents
when possible matches are detected.
This lets me specify a root directory, find candidates for
cleaning up and interactively delete them using Tk.
To answer the other question I am running this under Windows
(and I am not allowed to install a real environment) so diff is not available.