[cairo] draw lines on only one channel

M Joonas Pihlaja jpihlaja at cc.helsinki.fi
Wed Mar 3 06:21:34 PST 2010


On Wed, 3 Mar 2010, Tz-Huan Huang wrote:

> For example, when I draw a line on red channel (suppose
> the color is (1.0, 0.0, 0.0)), then draw a line on blue channel
> (suppose the color is (0.0, 0.0, 1.0)), I hope the intersect is
> purple (1.0, 0.0, 1.0) not blue.

It sounds like you want to use CAIRO_OPERATOR_ADD rather than the 


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