[cairo] pixman box filtering code prototype

[Jeff Muizelaar]

On Tue, Nov 04, 2008 at 05:37:51PM -0500, Jeff Muizelaar wrote:
> Here's an update. It should be basically correct at this time (although
> it doesn't filter masks yet...). It still needs cleanup and
> optimization.

And another update. This version is pretty much feature complete and I
gave it a basic run through with firefox. (there's still a rounding
problem...).

I've also done some quick performance tests compared to the current
bilinear downscaling:
scale:.8 speed: 2x faster
scale:.4 speed: a little faster
scale:.2 speed: slower

The speed gains currently come at a cost. The image quality when scaling
between 1. and .5 is lower than the current filtering because we use a
combination of two integer box sizes which causes some blockiness. It's
possible to fix this by using a non-integer box-filter but that will
probably have a performance impact.

-Jeff