Date: Sat, 4 May 2013 22:04:41 +0200
From:
ofnuts laposte net
To:
gimp-user-list gnome org
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 mode?
_______________________________________________
For starters, Color to Alpha is a plugin, color erase is part of
the program core.
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 modes.
-- Stratadrake
strata_ranger hotmail com
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Numbers may not lie, but neither do they tell the whole truth.
