RaphaŽl Quinet wrote:

I care about the message that we are giving to the user about the
alpha channel: the correct way to present the alpha channel is that a
pixel with alpha=0 has an undefined color.  The GIMP should be free to
keep the RGB data of transparent pixels intact or to destroy it if
necessary.  Hackers may be aware of whether the GIMP will keep the RGB
data or not for such and such operation, but we should avoid adding
features that explicitely require one or the other to happen.

Firstly, I'd strongly debate the idea that only 'Hackers' need that RGB data that's hidden by the alpha plane.

Anyone who paints textures to apply to 3D models is going to need those
RGB values to be in good shape when the file is written out.

With the increasing prevelence of games that are user-customisable, I
think an increasing proportion of GIMP users will care greatly about
this feature.

Either way, having to keep a mental image of what operations will screw
up my texture to the point of unusability and which ones will preserve
it is not something that I could live with.  I've been a user (and
sometimes - author) of paint programs since the Quantel Paintbox back
in the early 1980's - so I'm guessing I fit your idea of a power user.

IMHO, Alpha should be treated just exactly like R, G and B (or C, M, Y and
K) are treated.  I should be able to paint into the alpha plane (which is
in effect what the GIMP eraser tool does).

I think the way that the alpha plane is treated as special is a large
part of the problem here.

Basically, the model that we should promote is:
- layer mask    => hiding mechanism, reversible
- alpha channel => pixels that are cleared have undefined RGB data,
                   not reversible (except for undo)

Breaking this model should be avoided, except in very special cases
(i.e. obscure features for hackers).

I don't think painting texture maps should be considered an obscure or special case undertaken only by deep guru's.

If you think of this as an operation that many of your users will be
doing, your argument falls to the ground.

The second law of Frisbee throwing states: "Never precede any maneuver
by a comment more predictive than "Watch this!"...it turns out that
this also applies to writing Fragment Shaders.
Steve Baker                      (817)619-2657 (Vox/Vox-Mail)
L3Com/Link Simulation & Training (817)619-2466 (Fax)
Work: [EMAIL PROTECTED]           http://www.link.com
Home: [EMAIL PROTECTED]       http://www.sjbaker.org

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