[Pixman] font rendering

Gerd Hoffmann kraxel at redhat.com
Thu Mar 7 23:00:50 PST 2013

On 03/07/13 17:52, Søren Sandmann wrote:
> Gerd Hoffmann <kraxel at redhat.com> writes:
>> Is there documentation somewhere describing what the pixman ops exactly do?
> Unfortunately, pixman doesn't have as much documentation as it should.

>> What I'm trying now is this:
>>     pixman_image_composite(PIXMAN_OP_SRC, bg, NULL, vgafb, ...);
>>     pixman_image_composite(PIXMAN_OP_OVER, fg, glyph, vgafb, ...);
>> So the first op fills with the background color, and the second renders
>> the character.  Comes close to what I want.  Except that the second
>> blends the foreground color with the background color instead of
>> replacing it.
> If I understand correctly, what you are doing now should work. Blending
> of the foreground and background colors should only happen if the
> foreground color has alpha != 0xff, or if a glyph pixel has alpha that
> is neither 0x00 nor 0xff. In either case, blending is presumably what
> you want?

Yes, I'm pretty sure bleeding is what I need here as I want keep the
background pixels as-is.

Found it:  Dropping the pixman_image_set_component_alpha() call I've
copy+pasted from one of the pixman test apps fixed it.  Guess it somehow
overwrote what I had placed in the alpha channel of the mask image.


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