[cairo] [Pixman] pixman: New ARM NEON optimizations

[Bill Spitzak]

Siarhei Siamashka wrote:

>> I agree with Soeren that treating one-channel images as though
>> r==g==b==a (ie it is a white premultiplied image) is much more useful
>> than as a black premultiplied image and should be done.
> 
> I was worried about the 'component alpha would become completely regular with
> no need for the "component_alpha" bit in pictures' part. It sounded like this
> case of 'using a 4-channel image as a mask is the same as using the alpha
> channel' was considered to be dropped.

If an image is used as component alpha mask then it has to have 3 
channels, not 4. I believe if there are 4 channels then the intention is 
to use the alpha channel only, rather than ignore it.