Given a couple hundred JPEGs, what's the most efficient way, using Free tools, to one of:
-- find the brightest file
-- find the file with the most overall contrast (not all white or all black, but a good mix of both?)
Background: got video thumbnailing working in FotoBilder, but sometimes people's videos start with some black frames at the beginning. Or bright white (presumably?) while their phone/camera CCDs adjust to outdoor sunlight and the user aims at their actual target.
So I'd like to extract the first 20-100 frames and pick the most "interesting" one, for some definition of interesting. But definitely not solid black or white.