Solution for the grayscale selections

[Cyrille Berger]

On Tue, 25 Sep 2012 11:23:16 +0200 (CEST), Boudewijn Rempt
<boud at valdyas.org> wrote:
> But all that is not necessary, I think. We create dabs in the colorspace

> of the target device, so no conversion is needed, nor is it needed to
have 
> a composite op that can handle two different colorspaces.
> 
> The only thing we need to do is make sure that the dab is created 
> correctly and that the gray colorspace can properly compose the dab's 
> pixels with the target pixels.

The problem is that the dab is made of two part, the colour and the
transparency channel, and there is no way around that. So if we want to
follow a single channel mask (for CPU/Memory saving), we need a way to
compose pure greyscale with greyscale+alpha.

-- 
Cyrille Berger