Re: Applying to a surface the alpha of other

Krzysztof Kosiński <[email protected]>
Newsgroups gmane.comp.lib.cairo
Message-ID <CAFLw2WR_Xu0xvaQnnjTyMBMhzA8CaYDd+VgfeMDiqGNdM2CcFw@mail.gmail.com>
2012/10/22 Bill Spitzak <[email protected]>:
> He does not want to un-premultiply.

I'm not so sure about this. Without un-premultiplication, the result
is equivalent to painting the image with CAIRO_OPERATOR_OVER onto a
black surface. With un-premultiplication, the result is as if the
alpha was reset to zero while keeping the color intact.

Regards, Krzysztof
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