The subject matter of said images isn’t important, I just want to perform some image processing techniques later and possibly even share them.
Edit: I’ll await any particular suggestions for another day or so, but I see a number of wonderful possible candidate pictures here to dabble with.
I’ll check back tomorrow. My goal is to experiment with my old 16 color palette reduction code, custom palette for each image.
Wikimedia Commons is a great place to start, everything is public domain or freely-licensed. Searching for “color” brings up some good ones, like these:
They run monthly photo contests (which I’ve been meaning to post here) that can get weirdly specific, and which might be useful to you. For example, One Stands Out might be a good test of image processing techniques:
https://commons.wikimedia.org/wiki/Commons:Photo_challenge#June_2025
The Wiki Science Competition gets some really interesting photos, the winners are collected here:
https://www.wikisciencecompetition.org/
You can see the current list here and past years here:
https://commons.wikimedia.org/wiki/Commons:Wiki_Science_Competition_2025
That first example you posted actually ought to be a great test of my palette reduction algorithm! I can actually run the algorithm for as many colors as I want, 16, 256, any arbitrary number really, until I stop it anyways. But it gets exponentially slower the more colors it’s gotta detect.
Anyways, piddling around with my old code for a 16 color palette, I tested and posted this image…
I tested the second example there with the 20 colored pencils in a circle…
