Hi RaphaŽl,

I think everyone has more or less had their say on the thread -
can I just sum up the salient points?

RaphaŽl 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
RaphalŽl's concerns, while staying true to the principle I


       David Neary,
       Lyon, France
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