[cairo] transparency with alpha channel RGBA
M Joonas Pihlaja
jpihlaja at cc.helsinki.fi
Wed Oct 28 14:00:01 PDT 2009
On Tue, 27 Oct 2009, uray meiviar wrote:
> how do I get, non-premultiplied color so my openGL texture will have
> correct alpha channel values?
I believe you can use premultiplied textures with OpenGL by
configuring the right blend function. For the cases where using
unpremultiplied data is unavoidable you'll need to convert the
premultiplied data yourself before uploading the textures. Various
implementations of unpremultipliers are available here:
Generally the overhead from unpremultiplication is fairly low as long
as you don't implement it using three divisions per pixel.
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