[cairo] Operator optimization based on source or dest opacity

Antoine Azar cairo at antoineazar.com
Wed Feb 27 12:41:08 PST 2008

At 12:57 PM 2/27/2008, Vladimir Vukicevic wrote:

>One thing to be aware of... while the perf gains are significant, it 
>means that the test suite isn't actually exercising painting an 
>image with alpha transparency with OVER since the images are all 
>opaque.  You should probably replace the images so that the actual 
>OVER compositing path is being tested :)  (Or maybe create new 
>tests, though I don't think there's much value in doing lots and 
>lots of tests with the OVER-to-SOURCE optimization.)

The extra tests are already in the perf suite, with:
{ set_source_image_surface_rgba, "image_rgba" },

I didn't include those tests in my perf sample as they don't get any 
benefit from the optimization. I've just run them myself to make sure 
there's no perf regression and the numbers pre/post optimization are 
+ / - 2%. So someone running the full perf suite will see the OVER 
compositing path be tested with the RGBA source images.

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