if you have GEGL 0.4 or higher rather use Tools -> GEGL Opereation -> Color Reduction
- 3-bit RGB 2 colors per channel 8 colors in total
- 6-bit RGB 4 colors per channel 64 colors in total
- 9-bit RGB 8 colors per channel 512 colors in total
- 12-bit RGB 16 colors per channel 4,096 colors in total
- 15-bit RGB 32 colors per channel 32,768 colors in total
- 18-bit RGB 64 colors per channel 262,144 colors in total
- change any number of colors per channel 2-256 colors
- 3-3-2 bit RGB 8 8 4 colors, 256 colors in total
- 5-6-5 bit RGB 32 64 32 colors, 65,536 colors in total (16-bit RGB)
- 3-level RGB 3 3 3 colors, 27 colors in total
- greyscale (can be simulated by first converting to Greyscale and then to RGB.
- intensity (cannot do 4-bit RGBI)
- dithering
- custom palettes
- maximum simultaneous colors
- copy palette_change.py to your ~/.gimp-2.8/plug-ins directory.
- make sure that palette_change.py is marked as executable (sudo chmod +x palette_change.py)