[cairo] alpha blending

[James Cloos]

There was an interesting bug report this week on fdo referencing alpha
blending algorithms.

It advocates:   blend(x,y) = sqrt((x^2+y^2)/2)

Ie, hypot() normalized so that inputs in [0,1] result in outputs in [0,1].

Evidently at least one BigName platform uses that.

I don't know how it interacts with all of the Porter-Duff ops, but as I
recall cairo currently just does linear for the alphas, yes?

Any thoughts on whether switch the alpha blending to that normalized
hypot would benefit cairo?

-JimC
-- 
James Cloos <cloos at jhcloos.com>         OpenPGP: 0x997A9F17ED7DAEA6