[Pixman] [cairo] Gradient rendering seriously broken

[Soeren Sandmann]

Krzysztof Kosiński <tweenk.pl at gmail.com> writes:

> Hello
> 
> My port of Inkscape to Cairo is running into more problems. While the
> image resampling problem only decreases quality, there are problems
> with gradients that cause completely wrong rendering. The problem is
> described in more detail (with images) on the bug tracker:
> https://bugs.freedesktop.org/show_bug.cgi?id=29470

For the aliasing issue, the solution is the same as the image
downscaling: add supersampling to pixman. The various image fetchers
should fetch a grid of subpixels for each output pixel and then
compute the average before storing the result in the output buffer.

(The fact that supersampling applies to both gradients and sampled
images (and to a future polygon image) is one of the main reasons to
use it rather than more sophisticated area sampling techniques).


Soren