[cairo] render in grayscale
hermansson.per at bredband.net
Tue Sep 22 11:01:25 PDT 2009
Behdad Esfahbod wrote:
> On 09/22/2009 01:00 PM, Bill Spitzak wrote:
>> I think the original poster wants to render not the alpha, but something
>> like (r+g+b)/3 of the image as grayscale.
> That's exactly what the solution Kalle and I proposed does. Though,
> one typically wants a non-uniform combination of rgb for grayscale,
> with green getting a larger multiplier.
So if I understand correctly rendering with the alpha surface as mask
should work to get all colors replaced with different gray values?
After I applied the suggested changes, with the following code:
cairo_set_source_rgb(cr, 0, 0, 0);
pattern = cairo_pattern_create_for_surface(target);
I only get a white background with a filled black rectangle, how is the
transparency supposed to work?
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