Raphaël 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.
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