[Pixman] Op. when compositing

Eric Nicolas erik.nicolas at gmail.com
Wed Jun 11 01:16:46 PDT 2014

I have a question about the OP modes when compositing with Pixman. I had a look at the source code, but this part of the code is quite complex, so I couldn’t find the answer there.
What I would like to do is :
-          Use a plain color via a pixman_image_create_solid_fill on a RGBA color ;
-          Use a PIXMAN_a8 mask ;
-          Modify a target PIXMAN_r8g8b8a8 image.
So I do a pixman_image_composite(OP, fill, mask, target, …).
My problem is that I cannot find an OP which would allow me to blend fill and mask together into target. I mean if ‘fill’ color has an alpha (for instance 0x80), mask is also an alpha (for instance 0x80), I expect the target to be blent with the color modified with an alpha of 0x40 (full fill color x mask alpha => blent to target).

The closest I found is PIXMAN_OP_ATOP, but it always use the RGB from the fill color and the A from the mask, it never blends the color with the mask before compositing onto the target.
Any help would be appreciated.
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