simon.thum at gmx.de
Fri Jan 23 13:15:38 PST 2009
Soeren Sandmann wrote:
> Just in case someone gets bored over the Thanksgiving holiday.
I looked at your page more or less accidentally, and I'd like to take
the chance to comment on it.
The issues I mean are:
> Higher Quality Image Filtering
> Add better filtering, especially for downscaling transformations.
> Color Management/Gamma Correction
> Find out what color management support is needed in cairo, XRender, and pixman.
I'd just like t point out there is a close relation often overlooked.
Basically, if you scale down using 'super sampling' (I didn't find it in
pixman, but it's a likely choice. Also called a box filter.) quality
suffers more the more you scale down.
However, when you implement super sampling with respect to gamma, the
quality loss drops to nearly zero. I'd say typically you need no more
strange "higher quality" filters when that's done.
I extensively researched that during my diploma, and if you can point me
to the right spots in pixman, I may be able to draw up a patch.
As for gamma correction in general, It's an extensive work and change.
Basically, you need to check every single pixel-level computation
whether it is gamma-invariant, if not, make it so. I devised a small
calculus allowing to judge that matter. Maybe I can find it again, if
That said, it would certainly be worth to do it. However I'm far from
having the time to do so.
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