Cropping a large collection of .PNG screenshots

["Kevin O'Gorman" <kogorman@gmail.com>]

I have a few hundred screen shots I want to put on a web page, but
they are all full-screen and I want to crop to the real contents.
This is an identical region in all cases.  So I want to script it.

So, 2 questions:
A) What's the best tool for the job?  Gimp, irfanview, or something else?
B) Is there a script already in existence where I can just change the
crop rectangle?  I really don't want to learn a new language for a
one-time job.

-- 
Kevin O'Gorman

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