I’m open to using GIMP or a web-based online tool

I’d like to take a source image and posterize it, but instead of letting the application pick the resulting colors, I’d like to pick them manually. So for every pixel, the app would change the color to one of my chosen colors

  • tal@lemmy.todayEnglish
    11·
    2 days ago

    I don’t know if it’s identical to the posterize effect, but in GIMP, you can reduce an image to indexed color using a fixed, user-specified palette and then back to RGB.

    Image->Mode->Indexed…

    Select your palette. Set dithering to None. Hit OK.

    Image->Mode->RGB

    You might try adding a subsequent despeckle…I think that Posterize might do something along those lines as well.

    EDIT: Okay, after running a test image in GIMP, and then examining histograms on the output is that it looks like what Posterize does in GIMP is to take a “number of levels” input, then strictly divide each channel evenly along those lines (e.g. for “3”, you’ll have 0%, 50% brightness, and 100% brightness for each of red, green, and blue channels), and then it reduces the number of colors using only those colors. I don’t think that it does a despeckle. I used to enjoy making “more-poster-like” images than Posterize did, and usually did a despeckle to simplify them before running outlines on it, stuff like this:

    But looking at a test image from GIMP posterization, it clearly has single-color single pixel regions, so Posterize isn’t doing any sort of despeckling: