[cairo] issue with blend modes in pixman

[Adrian Johnson]

On 01/01/13 07:35, Rik Cabanier wrote:
> Some of the blend modes are not producing correct results.
> You can find a diff with the incorrect results
> here: https://bugs.webkit.org/show_bug.cgi?id=105074
> 
> Looking at the formulas, I can see what's wrong but I don't know who to
> contact.

Could you tell us what specifically is wrong with the formula?

The webkit bug suggests there is a difference between the SVG and PDF
formulas. At the time the blend modes were added to pixman the formulas
were based on the PDF specification and the SVG working group said the
SVG formulas should match PDF [1]. Are the PDF formulas wrong? Or do we
need CAIRO_OPERATOR_COLOR_BURN and CAIRO_OPERATOR_COLOR_BURN_SVG if we
are to support both PDF and SVG renderers?

[1] http://lists.cairographics.org/archives/cairo/2008-October/015362.html