Combine color levels with indexed conversion with single preview

[bicyclesonthemoon]

Hello.
This is my first message on this forum.
I'm looking for an answer which could improve my workflow in Gimp (2.10)

I'm making a story consisting of 580x410 PNG or GIF pictures and some text below the picture.
I'm drawing on paper, scanning, and then making the individual pictures in GIMP.

When making new pictures my workflow always starts the same way:
First step is adjusting the colour levels. (colors -> levels).
Next step is converting to an indexed colour palette (image -> mode -> indexed).
I select one of some palettes I prepared earlier, most have 4 colours. Sometimes I use dithering.

This is less straightforward than it could be because of lack of preview.
The color level adjustment step does have a preview, good.
The palette and dithering choice doesn't have a preview.
What I would really like is a single preview for a combined operation of both steps.
In a single window I would choose both colour levels and palette settings and see a preview of the total result.

Because right now it is like this:
I choose levels which I thing will be good,
then I convert to the indexed palette,
then I see that it does not look as good as I thought.
So I have to revert,
adjust levels again,
convert to indexed palette again,
and see if it looks better now.
I repeat this multiple times until I get a result which looks good enough.
This takes some time.

If I had the option to do it in a single step with preview it would improve my work a lot.

Is it possible to achieve this in GIMP?
How can I achieve in in GIMP?
If not in GIMP, then is there an alternative software where I can go this and then do rest of the work in GIMP?

[rich2005]

For a color indexed image, if you open the colormap dock Windows -> Dockable Dialogues -> Colormap you can edit the indexed colors directly Like this demo: https://i.imgur.com/LZikSHu.mp4

So if you have say 4 or 5 standard colours, you select and use from the colour selector.

Just a possibility.

[Ofnuts]

(03-20-2023, 02:41 PM)bicyclesonthemoon Wrote: Hello.
This is my first message on this forum.
I'm looking for an answer which could improve my workflow in Gimp (2.10)

I'm making a story consisting of 580x410 PNG or GIF pictures and some text below the picture.
I'm drawing on paper, scanning, and then making the individual pictures in GIMP.

When making new pictures my workflow always starts the same way:
First step is adjusting the colour levels. (colors -> levels).
Next step is converting to an indexed colour palette (image -> mode -> indexed).
I select one of some palettes I prepared earlier, most have 4 colours. Sometimes I use dithering.

This is less straightforward than it could be because of lack of preview.
The color level adjustment step does have a preview, good.
The palette and dithering choice doesn't have a preview.
What I would really like is a single preview for a combined operation of both steps.
In a single window I would choose both colour levels and palette settings and see a preview of the total result.

Because right now it is like this:
I choose levels which I thing will be good,
then I convert to the indexed palette,
then I see that it does not look as good as I thought.
So I have to revert,
adjust levels again,
convert to indexed palette again,
and see if it looks better now.
I repeat this multiple times until I get a result which looks good enough.
This takes some time.

If I had the option to do it in a single step with preview it would improve my work a lot.

Is it possible to achieve this in GIMP?
How can I achieve in in GIMP?
If not in GIMP, then is there an alternative software where I can go this and then do rest of the work in GIMP?

No good way I can think of. However, maybe you can come up with rules about the output of Levels (using the Histogram dialog in particular, such as a minimum ratio of pixels in a given range...) that can make you quite certain that the color indexing will work well. Still trial an error, but a much more educated trial.

[bicyclesonthemoon]

Thank you for the answers.
I know how to edit colormaps.
I'm using color palettes which I have already prepared before.
So I don't choose the individual colors but I only select which color palette I will use.
Adjusting the levels effectively changes where will be the threshold between the colours in the palette.
And I would really like to have a preview for this.
I would like to eliminate the trial and error from this part of the workflow.
Could this be achieved using scripts, plugins, etc?

[PixLab]

(03-21-2023, 09:00 PM)bicyclesonthemoon Wrote: And I would really like to have a preview for this.
.....//.....
Could this be achieved using scripts, plugins, etc?

Maybe a GEGL plugin can do the things you would like all at once, that might be possible, Beaver can tell you, he does do GEGL plugins, for example > https://www.gimp-forum.net/Thread-GEGL-S...new-plugin  
The big advantage of GEGL is it has preview and splitscreen preview directly on the canvas, and maybe sooner that expected > non destructive abilities

Maybe you don't need a plugin, but just few lines of code in the GEGL graph (Filters > Generic > GEGL Graph...) to write something like this:
   

[bicyclesonthemoon]

Thanks again for answer.
I checked today the Gegl graph option,
this is an useful tool but not in this case, as converting an image to indexed is not a Gegl operation.

So I would have to look into the plugin option.

Is there a place where I can ask to hire someone who would be willing to make a plugin?

What I would like to have the combined options from both dialogs, with preview.
as shown:
(I marked which parts are necessary for me)