How can I avoid the outlines of removed colors?

[Zydelum]

Hello,

With Gimp, I select one or more colors by color > Color tab > Color to Alpha.

Starting with this image:
[attachment=13626]

I can eliminate the yellow and blue without the outlines getting in the way:
[attachment=13624]

From another image:
[attachment=13623]

I can remove the yellow and red, but the old outlines remain:
[attachment=13625]

With Gimp, I can no longer reproduce the first technique and avoid the second technique.

Can someone explain why?




Thank you for your help.

[Ofnuts]

Because there are soft edges with "anti-aliasing" pixels, so there are more colors than meets the eye.

See https://www.gimp-forum.net/Thread-Backgr...r-graphics

[vitforlinux]

When I want to remove a color with Color to Alpha, I first make a selection of the color, then I expand it by one or two pixels, then I use Color to Alpha, and the result is clean.

But I have to repeat this for every color I want to remove.

Otherwise Color to Alpha 'eats' the color... even where I would like it to remain.