Any way to reduce colors in an image? How to shift hues?

[sitebender]

Say I have a 256 grayscale image that I want to turn into a 4 color image. I don't mean the color pallet. I can make a 4 color pallet, but I want to reduce the amount of colors in the image itself. Imagine turning a NES color pallet sprite into a GameBoy color pallet sprite with a function.

The easiest way I can think of now to do it is do a color replace for each individual color and turn them the 4 colors that I want. It seems like a long process. I suppose I can use it with a higher tolerance to expedite the process.

Also while I'm here, is there any way to shift the hue of a color tone? I know there's a way to replace colors, but that seems to work for individual colors like #FF0000 can become #00FF00 when I want all reds to become greens.

[Shirsh]

For automatic turning into different palette you can try this: create new file with your preferred colours, make sure it's set to indexed and just paste any other picture, pasted one will appear only in palette colours. Not sure if it will works good when it's 256->4 though: I tried it with two different city environment pics, palette was automaticly created from one of them, and it was like ~30 into ~16 colours, conversion from one to another was great.

upd: There's a preset for nes and gameboy actually, in "preset" menu right above palette, if sprite set to indexed, loading a palette makes auto conversion. Same with loading palette and setting to indexed later.

[sitebender]

Its almost a year later. I still need this feature. Sure there's a reduce color palette, but I'd like something that would reduce the images use of color based on the color palette. The image itself still has 256 colors when I'd like it to have 4 or whatever. I guess there's always replace color > tolerance.

[jpaugh]

You can do this with GIMP. Go to the Image menu, then Mode > Indexed. Set the maximum number of colors and, Voila!

[BossGalaga]

Originally posted by jpaugh:

You can do this with GIMP. Go to the Image menu, then Mode > Indexed. Set the maximum number of colors and, Voila!

I'm not sure why you're bumping a thread from 3 years ago to suggest using another program because you can literally do this easily in Aseprite. Load the image. Load the color palette that you want to convert the image to. Sprite-Color Mode-Indexed. Boom. Done.

[Luke S]

First make sure your colour mode is currently RGB. Next delete all but the four colours you want to use, Your palette should only have four colours. Next change colour mode to Indexed. Sprite>Colour Mode>Indexed. Your image will now be 4 colours, Move or change the colours in the palette to alter the image to your liking.

I don't visit the forum much.

[Dyzinel]

Originally posted by BossGalaga:

Originally posted by jpaugh:

You can do this with GIMP. Go to the Image menu, then Mode > Indexed. Set the maximum number of colors and, Voila!

I'm not sure why you're bumping a thread from 3 years ago to suggest using another program because you can literally do this easily in Aseprite. Load the image. Load the color palette that you want to convert the image to. Sprite-Color Mode-Indexed. Boom. Done.

Aside from "Menu > Mode" being actually "Image > Mode", his answer was the only one that could help me. I just arrived here with the same problem as op, and his solution worked perfectly. I wanted some sprites of Flandre to automatically have a few less colors, whilst still maintaining her core appearance. When I used that option in Gimp, her colorful gems which were of a unique color, were left absolutely alone and unaltered, but her red dress, which had various variations of red, were merged into a single red. This is the kind of thing I wanted to do and is also probably what op wanted to do too. An option that merges colors that are very similar to each other but leaves alone the others that are not repeating. Then I brought the sprite back to Aseprite after finishing the process successfully.

[Nescius]

besides (1. be in RGB mode, 2. add/delete colors to/from palette, 3. switch to indexed mode)
there's also the response to issue 1099 on Aseprite's github: http://imgur.com/IfrVyfd