Commandline image conversion

[peteruithoven]

I'd love a quicker way to convert images to the supported palette. Ideally also in a way that eliminates as many possible mistakes as possible.

I've used inky-palette.gpl but didn't get it to work. I had to edit and export the existing backdrop.png. I also want to convert a lot of weather icon images.

Is there any way to execute this conversion through gimp through the command line? (I'm on Linux so any bash, zsh compatible command would work) If this is possible it becomes very easy to convert multiple files.

(I'm going to start looking into this myself, but any tips, experiments are welcome)

[peteruithoven]

Interesting: https://www.gimp.org/tutorials/Basic_Batch/

I've been testing with the following file as it should clearly be changed:

The command gimp-context-set-palette seems what we want?

(define (inky filename)
   (let* ((image (car (gimp-file-load RUN-NONINTERACTIVE filename filename)))
          (drawable (car (gimp-image-get-active-layer image))))
     (gimp-context-set-palette "inky")
     (gimp-file-save RUN-NONINTERACTIVE image drawable filename filename)
     (gimp-image-delete image)))

In my case I've got Gimp installed as flatpak so I had to save this to: ~/.var/app/org.gimp.GIMP/config/GIMP/2.10/scripts

And normally you'd run it like:

gimp -i -b '(inky "icon.png")' -b '(gimp-quit 0)'

Because if flatpak I had to run it like:

/usr/bin/flatpak run --branch=stable --arch=x86_64 --command=gimp-2.10 --file-forwarding org.gimp.GIMP -i -b '(inky "icon.png")' -b '(gimp-quit 0)'

It returns:

batch command executed successfully

It edits the file, but the colours don't change / are not limited.

Looking into gimp-image-convert-indexed next...

[peteruithoven]

gimp-image-convert-indexed seems what I needed.

(define (inky filename)
   (let* ((image (car (gimp-file-load RUN-NONINTERACTIVE filename filename)))
          (drawable (car (gimp-image-get-active-layer image))))
     (gimp-image-convert-indexed
        image
        CONVERT-DITHER-NONE
        CONVERT-PALETTE-CUSTOM
        3
        FALSE
        TRUE
        "inky")
     (gimp-file-save RUN-NONINTERACTIVE image drawable filename filename)
     (gimp-image-delete image)))

Save this script as inky.scm in the GIMP scripts folder. Add the palette to gimp with the name "inky".

Execute by running:

gimp -i -b '(inky "file.png")' -b '(gimp-quit 0)'

This script clearly simplifies the colors into the 3 colors. But white becomes black, the palette might be off? Switching around white with black in the palette doesn't help.

[bablokb]

Why don't you just copy (and modify) the python-code from the Inky-Impression class to a small python-script?