Hi Raphaël,
I think everyone has more or less had their say on the thread -
can I just sum up the salient points?
Raphaël Quinet wrote:
> I agree. This is what the GIMP does and I was definitely not
> suggesting to change this, so I think that you misunderstood what I
> wrote. The GIMP will keep on using post-multiplied alpha in the
> future, and this is a good thing.
>
> The whole point of this discussion was based on the fact that because
> we use post-multiplied alpha, there is some ambiguity about whether
> the average user is supposed to know and rely on the RGB values of
> transparent pixels. If we had been using pre-multiplied alpha, then
> there would be no reason for any debate, because all transparent
> pixels would have R, G and B = 0.
You believe that allowing the RGB data behind transparent pixels to
be exposed might be confusing to some users - so far in the
thread you are the only one who has asserted this.
You consider that in certain circumstances this behaviour could
be considered a bug.
Others have stated that there are several applications where
transparent data is stored across sessions, and that this data is
indeed useful, and not at all undefined.
Personally I have stated that we should never destroy or modify
data without explicit user action to that effect.
For the moment, unless I am mistaken, you are the only person to
have stated that they consider the current behaviour wrt
transparency flawed.
Can I propose, then, that we keep the current behaviour? Perhaps
we could have a filter that pre-multiplies layers by their alpha
channel? That would be trivial to write, and would address
Raphalël's concerns, while staying true to the principle I
outlined.
Cheers,
Dave.
--
David Neary,
Lyon, France
E-Mail: bolsh@xxxxxxxx
