Batch replace colors

[EagleEye559]

Hey everyone,

I'm working on an image up-scaling project, with a massive amount of texture files; however, I've ran into an issue where the placeholder colors on the texture palette cause interference with the up-scaling software.

Placeholder colors, and the effect they have can be seen here:
https://gyazo.com/d087759e04450d144e14c757cb773d95

I am not as knowledgeable about GIMP's more advanced features, but I'd want to develop a process to batch process a folder of images, and replace the impacting colors with another to resolve the issue.

How would I go about this process? Explain like I am five / don't know anything about GIMP's functionality. Any help would be greatly appreciated!

EDIT: I've started using Color to Alpha, which seems to work for this purpose. Just applying this as a Batch to the whole set is now the challenge.

[rich2005]

(08-07-2020, 02:00 PM)EagleEye559 Wrote: ..snip...
EDIT: I've started using Color to Alpha, which seems to work for this purpose. Just applying this as a Batch to the whole set is now the challenge.

Without delving into the mysteries of Gimp scripting for a starter you could try the batch plugin BIMP https://alessandrofrancesconi.it/projects/bimp/

Choose other Gimp procedure, search for colortoalpha, and set the colour.

   

...but it is a bit of a blunt tool. It will remove the colour from everything. 
If that works you can add a scaling procedure. Otherwise hopefully more suggestions.

[EagleEye559]

Thanks for the advice, I've done some quick testing with that method, and I seem to have made an error, as all the files now have a green tint applied. I'll change the approach slightly, but this appears to be a method to pursue for now.

Regardless of the color being converted to Alpha, the rest of the image has it's color shifted.
https://gyazo.com/281090f29317dc15090582304b4bd3d1

[rich2005]

That is what I meant about C2A being a blunt tool.

Example: An image with a mixture of red-green-blue (as most images are) 
Remove one element - in this case a primary - blue and the remaining red and green combine and you also get semi-transparency.

   

You need some other method
You need to give more information. 
What are these 'placeholder colours'? 
You mentioned a texture palette, what is that ? 
Best if you upload a couple of typical  images, maybe zipped into a file on dropbox or similar.

[EagleEye559]

(08-07-2020, 03:47 PM)rich2005 Wrote: That is what I meant about C2A being a blunt tool.

Example: An image with a mixture of red-green-blue (as most images are) 
Remove one element - in this case a primary - blue and the remaining red and green combine and you also get semi-transparency.



You need some other method
You need to give more information. 
What are these 'placeholder colours'? 
You mentioned a texture palette, what is that ? 
Best if you upload a couple of typical  images, maybe zipped into a file on dropbox or similar.

You can see an example of the textures here:
https://easyupload.io/xc5um7

As each model or surface references an image, not all sectors in the image are used. Anything not used, will feature a void of color. Some of these colors directly interfere with up-scaling tools, as they border the texture. The affected outcome, is a green tint.

Removing any variants of red from these placeholder voids, resolves the issues during the process.

[rich2005]

I do not have a solution, but can I restate (as I see it) the question.

Lots of individual png images, with transparency.
Some with solid blocks of a colour (red?) to remove.
Blocks of this colour, different sizes, different locations.
Keep anything else that has a red component 'as-is'

   

Obviously one-at-a-time with fuzzy select works. 
Needs a script that can search for those individual blocks.

[Ofnuts]

(08-07-2020, 06:02 PM)rich2005 Wrote: I do not have a solution, but can I restate (as I see it) the question.

Lots of individual png images, with transparency.
Some with solid blocks of a colour (red?) to remove.
Blocks of this colour, different sizes, different locations.
Keep anything else that has a red component 'as-is'



Obviously one-at-a-time with fuzzy select works. 
Needs a script that can search for those individual blocks.

Assuming the placeholder color has been picked because it doesn't occur anywhere in the textures, a color selection with a very low threshold would select all the blocks. It is also possible to select only on hue.

[rich2005]

Quote: Assuming the placeholder color has been picked because it doesn't occur anywhere in the textures, a color selection with a very low threshold would select all the blocks. It is also possible to select only on hue.

I do not know. The 'red' placeholder is RGB 240,40,48  and some of the image elements do contain a fair proportion of red.


Individually, not a problem, For batch, the best I get is with the gmic plugin http://www.gmic.eu using a gmic command in BIMP

Code:

fx_select_color 0,0,0,0,240,40,48,255,2,255,255,255,0,0,50,50

Maybe not 100% , you can see from the insets. Big block removed but tiny block remains (edit: ah just checked, different red)

   

Tried through the 55 images provided. No earth shattering records broken. Took about 45 seconds. (from the first post, "massive amount of texture files" I wonder how massive is massive)