Date: Sat, 4 May 2013 22:04:41 +0200
Subject: Re: [Gimp-user] How to make transparency gradiate?

    On 05/04/2013 03:54 PM, Richard
      Gitschlag wrote:



          You can also achieve the same result using paint tools.


        1 - Eyedrop the background color.

        2 - Switch to the Paintbrush and the "color erase" blending
        mode.  Color erase is also a color-to-alpha transition.

        3 - Start painting the background.


    Hmm... this begs the question: what is the difference between
    "Colors/Color-to-alpha" and the bucket-fill tool in color-erase



For starters, Color to Alpha is a plugin, color erase is part of the program 

Color erase can be used "on the fly" with any drawing tool, and it can benefit 
from all the tool's options (such as brush hardness and mouse/tablet dynamics). 
 Combine it with the "Behind" blending mode (its exact opposite) it's almost 
like having a different Eraser tool.

To cite some of my personal experience, when I create a traditional color 
pencil drawing, I typically want to clean up the background paper.  Not the 
paper grain (it mostly washes out anyway and is not an issue), but things like 
stray pencil flecks and so on.  I also wanted to be able to digitally tint the 
background (say, by gradient), so I needed to erase the background.  The 
problem is you can't use the eraser to do this - you have a flat layer with RGB 
values gradiating from color RGB to white background so you can't just erase 
out the alpha channel (leaving the RGB values otherwise unchanged); you need a 
Color to Alpha transition.

So, for a while what I did was I copied the layer, performed a Color to Alpha 
transition (relative to white) on the lower copy, then used the Eraser on the 
upper copy.  But once I wrapped my head around what the "color erase" blending 
mode actually IS, I realized that was a much more efficient way of doing the 
same thing.  I didn't have to duplicate the layer; I could just paint over it 
in "Color Erase" mode; any mistakes I can just paint over again in "Behind" 
mode.  The only downside is not having a way to easily toggle between these two 

-- Stratadrake
Numbers may not lie, but neither do they tell the whole truth.

gimp-user-list mailing list

Reply via email to