GAH!!! Just reading that bug report makes me want to tear my eyes out.

The other thing that doesn't seem to be mentioned in there is that the bilinear filtering method that cairo uses is wildly inappropriate even in a lot of downscaling operations. It blurs the hell out of images. This is conjecture but I suspect that a highly "optimised" algorythm may be in effect. After so much time, and then this. I think  I'm switching to something else permanently.