RaphaŽl Quinet wrote:
On Tue, 16 Dec 2003 10:31:29 -0200, "Joao S. O. Bueno" <[EMAIL PROTECTED]> wrote:

You could maybe just add (or ask someone to add) a "zero-out transparent pixels" on the layers menu.


I do not care (yet) about clearing the transparent pixels, destroying
color data, using pre-multiplied alpha or all the (un)related things
that were mentioned in recent messages.

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

Above you said "I do not care about [...] destroying color data", now you say that the GIMP should be free to destroy RGB data. No offense, but that does make it easier to misunderstand you. After reading many posts about this topic, I'm still not sure I understand what you are saying.

As far as I understand it, I disagree.


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 *really* don't see why. The way I see it is that in general things should be kept orthogonal as much as possible, unless there are good reasons to do otherwise. In RGBA we have four values named R, G, B and A, and it is perfectly possible to change any single one of them without affecting the others. That's orthogonality, and it is a nice feature to have.

What is the advantage of RGB data suddenly being undefined?

"Codito ergo sum"
Roel Schroeven
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