On Mon, Sep 18, 2000 at 05:24:20PM -0400, Garry R. Osgood wrote:
> Nick Lamb wrote:
> > Pre-multiplying is a performance hack only, please don't let people
> > think of it as something that will cure "black fringes" -- it won't.
> > Perhaps that wasn't your intention, but in any case...
> Perhaps a later Gimp will know how to consume premultiplied alpha
> (you'll have to throw some switches) the 1.x Gimps of the next
> two years or so won't know how to do it.

This is exactly what I was worried about -- Gimp already DOES convert
premultiplied alpha from the one source I'm sure uses it, TIFF. It
is trivial (though perhaps sometimes costly) to convert TIFFs during
loading so we (almost) always do.

Support _internally_ in Gimp (which you're proposing for 2.0) is
orthogonal to loading external data correctly. If someone finds me
an MS internal document dictating that BMP uses pre-multiplied alpha
I'll add the conversion functions in days -- to the BMP loader.

For undisciplined formats a load-time option is not a sensible way
to go, we'll probably have to provide a plug-in which does the
conversion and include help that explains what it's for / how to use
it to handle either case, some heuristics in the plug-in can help.

I'm not willing to write such a plug-in not only because I'm already
too busy, but because I think the film/ rendering communities
brought this on themselves. I've seen too much evidence that says
they don't care about standards, or interoperability.


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