Color exchange not working

[rich2005]

@ All users: It really does help if the correct OS and Gimp versions are stated. Please correct your profile.

You could try Tools -> GEGL Operation -> Color Warp  10 down in the drop down menu.  Looks like this

   

[She]

(11-21-2019, 02:50 PM)rich2005 Wrote: @ All users: It really does help if the correct OS and Gimp versions are stated. Please correct your profile.

You could try Tools -> GEGL Operation -> Color Warp  10 down in the drop down menu.  Looks like this

Thanks so much for your help. This is exactly what I need and it is an amazing tool and so easy to use.

[chaslinux]

(11-21-2019, 01:26 AM)She Wrote: Hello

I am new to gimp. I'm trying to use colour exchange and nothing is happening. I use the colour selector within colour exchange to select 'from' and 'to' colours (as in: https://infofreund.de/gimp-replace-color/). Absolutely nothing happens. Why is this?

I suspect you probably did what I did and converted the image from RGB to Indexed. In my case I converted by image from RGB to 4 a colour index and I kept trying to use Colors > Map > Color Exchange. How can you swap 4 colours in a palette if only those 4 colours exist in the palette?

Converting the image back to RGB did it for me. Now when I try swapping the colours it lets me swap the colours I have in the image with the colour palette.

Very late reply, I found this forum looking for the solution to this and then it occurred to me the reason why.

[Aronaya]

OK, that helped with my question, too, made some progress and was finally able to get color exchange to work somewhat - from black to turquoise color.

But I'm trying to exchange black for white. I can't get the controls to make the target color anywhere close to white. The hex 'FFFFFF' does nothing useful.

Also mostly a rookie, been using GIMP for years, at the lowest level of competence. Not a graphic designer, all the jargon mystifies me.

How can I exchange all black line drawing to all white (PNG transparent background)?

MacOS Big Sure 11.4 with GIMP 2.10

[rich2005]

All black on transparent to all white on transparent. Do not use the color exchange tools.

Make sure the image is in RGB mode Image -> Mode -> RGB
Enable the alpha lock top of the layers dock
Bucket fill the canvas with white, (bucket fill tool, select all)
Toggle the alpha lock off.

example (linux not MacOS) https://i.imgur.com/iGtTvOD.mp4

[PixLab]

It seems you did not "catch" how the color exchange is working
To understand it, Put those 3 sliders at FULL throttle first!
   
Then 1 by 1 put them down to zero, you will see it's just working fine
You have to play with those 3 sliders to get what you want

Those 3 sliders are the RGB channels (Red, Green, and Blue), thus those threshold are about the amount of a specific color you want to swap in each channel)