[SOLVED] GIMP - Drawing white on mask - brush very weak or non-functional [solved]

Grobe

Distinguished
Hi

First of all, I just figured out (did a user mistake of course), but since many searches on web haven't provided any idea for solution I try to explain here.

I have an non-transparent icon that I opted to use Gimp for in order to make it transparent. The color that was supposed to be transparent was kind of gray (just refered to as gray'ish hereafter), and therefore I needed to take some extra steps.
  • Create a new layer below with background color similar to the gray'ish color.
  • Then duplicate original layer and make it invisible (will work on this later)
  • The original layer changes mode from normal to difference. This make all colors that differ from the gray'ish to stand out.
  • Then copy visible and paste as copy of layer (this have wrong colors, but that's ok as it represent the upcoming image transparency)
  • Then adding layer mask to copy of layer, and choose to use "Greyscale copy of layer" This make the image properly transparent, but has to be transferred to the new original image (the duplicate layer from #2 )
  • Make "Mask to selection" (right click on copy of layer)
Now it's time to make the original layer transparent:
  • Select duplicate of original layer (from step #2 ), make it visible (all other layers can now be made invisible for not disturbing, and if wanted, a bottom layer with some solid color - not the grey'ish - may be crated so that the final result is easier to see when working).
  • When duplicate of original layer is selected, Add layer mask, choose "Selection"
Then - it will be necessary to adjust the transparency map (layer mask), so one may want to use paint brush tool for that.

Then the problem
It turns out that most painting tools act as they're incredible weak. Painting by use a white color paint brush tool have almost no effect, no matter what setting I try.

And the stupid mistake
Have a look at step #6. It turns out that I didn't remember to get rid of the selection mask. And in Gimp, the selection mask control in detail how much a tool can affect any pixel.
So by select nothing, the problem was gone and I could draw normally again.

Hope this can be helpful for somebody else as well. Gimp is an awesome tool 🆒
 

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