[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


-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 228 bytes
Desc: not available
Url : http://lists.freedesktop.org/archives/cairo/attachments/20050201/e2aa9b28/attachment.pgp


More information about the cairo mailing list