Algorithm for soft-light blend mode

Hey,

I'm in the process of implementing bend modes in the Cairo imaging
library[1]. As Cairo is used as the renderer for a wide variety of
formats, I wanted to have an as comprehensive list of blend modes as
possible. And it turns out that the blend mode algorithms used are
almost always equal. However, there is one exception: soft-light. The
latest SVG draft specifies a different algorithm than PDF.

So I was wondering if it was possible to change the algorithm in SVG
to match the one of PDF, as that would solve a lot of problems.

Cheers,
Benjamin


1: http://www.cairographics.org