On 01.08.2012 20:59, Michael Meeks wrote:
On Wed, 2012-08-01 at 19:56 +0400, Ivan Timofeev wrote:
I solved the problem by the following change in renderAreaToPix:
cairo_data[x*4+0] * alpha
That appears to me to break the compositing :-) it might happen to
improve things for this case of course.
Well, now I have read about alpha compositing and cairo... :)
We use CAIRO_FORMAT_ARGB32 and the cairo manual says[1]:
Pre-multiplied alpha is used. (That is, 50% transparent red is
0x80800000, not 0x80ff0000.)
so cairo_data elements already multiplied by alpha.
[1]
http://www.cairographics.org/manual/cairo-Image-Surfaces.html#cairo-format-t
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