[Pixman] sRGB processing for pixman

Søren Sandmann sandmann at cs.au.dk
Mon Jun 25 10:47:29 PDT 2012

Bill Spitzak <spitzak at gmail.com> writes:

> A problem is the pseudo-random starting point. This is necessary so
> that you do not get vertical stripes when the rows have the same
> data. But if you want your composites to not change, it has to be
> deterministic. I'm not sure but perhaps a hash of the y coordinate of
> the source will work, or that hash plus the color of a pixel at x==0.

Error diffusion is a good idea in principle, but the problem you
describe above is quite tricky to deal with. A hash of the source y
coordinate won't work in the case where the source is a solid color and
the coordinates are simply (0, 0). A hash of the destination y
coordinate is not going to work either, because it would cause stripes
when scrolling.

I think we just need to fix the bug and make the transformed paths use
the wide pipeline when wide formats are involved.


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