From kde-kimageshop  Wed Sep 15 13:59:53 2004
From: Boudewijn Rempt <boud () valdyas ! org>
Date: Wed, 15 Sep 2004 13:59:53 +0000
To: kde-kimageshop
Subject: Re: always an alpha channel
Message-Id: <200409151559.57737.boud () valdyas ! org>
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On Wednesday 15 September 2004 15:30, Casper Boemann wrote:

>
> Case 1 problems might be overcome, if we think of a "normal layer" as a
> "color layer" and an "alpha layer" always combined. The "normal layer"
> would then have the responsibillity of combining the two. But what happens
> when we use paintdevices that are not layers - wouldn't we still want alp=
ha
> for those?

Of course. Otherwise you won't be able to do antialiased brushes. Before=20
painting a brush stroke, the brush mask is first converted to a paint devic=
e.

>
> My suggestion would be more in the like of a RGB colorstrategy, a RGBA
> colorstrategy, a RAGABA colorstrategy and so fourth with CMYK, CMYKA etc.
> To avoid code duplication we could have an AlphaColorstrategyTrait and let
> RGBA inherit from both RGBColorStrategy and AlphaColorstrateyTrait. The
> trait could be reused for CMYK with alpha.

Yes, that could be the way to go, I think. But the current API is confusing
with its myriad ways of discovering whether there's an alpha channel, and n=
o=20
way to add one that's missing...

On the other hand, once onvererting between RGB and RGBA would become=20
possible, having an in-band alpha would slow things down. The advantage of=
=20
using a separate alpha 'layer' that's always associated with a paint device=
=20
is that it becomes really easy to add or remove an alpha channel.

Oh, well -- I'll add some templates first, fix the selections workflow &=20
paste/past into and move, and look into the weird scaling artefacts for=20
images that are partly obscured by the UI. And there are composition=20
artefacts that show up in the selection code.

=2D-=20
Boudewijn Rempt | "Geef mij maar zuurtjes."
http://www.valdyas.org/fading/index.cgi

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