In gimp just right click the layer, choose add layer mask, then pick from layer’s alpha channel. You now have a mask layer you can paint on.
I’m not trying to make a painting with a drawing tablet, though. I just want to edit the alpha values of an image.
purplemonkeymad@programming.dev 10 hours ago
kestrel7_7@lemmy.world 5 hours ago
Krita is designed for painting, but you don’t have to use it for that…