I have been searching through the webs for a long time for a good, easy to use tool for recoloring pixel art to a specified color palette. The perfect tool should make it easy and fast to test out different palettes for a provided bitmap image or a sprite sheet, but it should also make it possible to fine tune the color mappings and add new colors to the palette if needed.
This has provided to be a rather challenging task. Photoshop and other similar graphics programs do have the possibility to switch to indexed color which lets you force the image to a new color palette, but I find that workflow to be rather tedious and time consuming. Illustrator has the recolor artwork tool, but it works only with vector images.
Here are some of the tools that I did find:
Recolouriser (Aseprite extension):
https://community.aseprite.org/t/extension-recolouriser/12011
-Requires Aseprite, which is not a free program (unless you are willing to compile it from source), Aseprite is not very expensive though, but in a school environment free tools are always easier to adopt (no need for a complex purchasing/licensing process).
Pixel Palette Tool
https://withthelove.itch.io/pixelpalettetool
This is the tool that I have been experimenting with a lot recently. It’s free, easy to use and seems to tick all the boxes. It does hang for a while when recoloring large images though.
Repixel app
This app looks interesting but unfortunately the link seems to be down and I couldn’t figure out a way of contacting the author in order to inquire about the availability and status of this software.
Deep Learning
There are certainly very interesting possibilities in the realm of deep learning and neural networks regarding this topic. I have successfully used Image Palettizer earlier https://github.com/PureAsbestos/Image-palettizer. Unfortunately the most recent GUI version of program keep crashing and giving me a fatal error.
At the moment Pixel Palette Tool seems to be the best option, so if you want to test out different color palettes for your pixel art sprites, I recommend giving it a go!