[cairo] four-channel alpha and destination alpha
Keith Packard
keithp at keithp.com
Tue Feb 1 09:06:18 PST 2005
Around 10 o'clock on Feb 1, Owen Taylor wrote:
> And the obvious question was "how do you compute the right value for the A
> channel of the mask".
Xft uses the middle sub-pixel (green, in the existing cases), mostly
because it doesn't matter for normal usage.
> - You get super-luminous pixels like the above mentioned
> 88AA0000. pixman handles that OK, but it's conceivable that
> hardware-accelerated compositing paths would have difficulty.
I think any hardware that can handle GL will be able to manage this
without trouble; it can happen with a regular ADD operation.
-keith
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