[cairo] Frame Buffer and Special Pixel Formats

[Carl Worth]

On Mon, 4 Dec 2006 09:58:48 +0100 (CET), Klaus Stehle wrote:
> > My understanding is that we don't want to clutter the image-backend API.

It's not just a question of avoiding API clutter. I think a bigger
issue is the desire to have an optimized software rendering
implementation. With the very small number of image formats that cairo
provides, (as well as the rich set of operators), there's already
fairly large combinatorial explosion going on inside the rendering
code.

So it doesn't make sense to add new image formats unless we're also
committed to implementing as much optimization in the rendering for
those as we plan to implement for all other image formats.

If instead, the idea is to just add some conversion before and after
each operation, then it doesn't make sense to provide this as a
"supported" image format in cairo. It would be more efficient to delay
the conversion until an entire set of operations is performed, (such
as a complete frame in an animated sequence). And doing conversion at
that point should be possible with the interfaces in cairo
already. (One thing that might be needed is a way to find out the
region that is dirtied by a sequence of operations so that no more
data is converted/copied than necessary).

Does that make sense?

-Carl
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