ARM Skia NEON patches - 07 - Equation simplification

ARM Skia NEON patches - 07 - Equation simplification

Misc: simplify the equation of the exclusion Xfermode

The equation can be dramatically simplified. The results with gm are
the same except that the code is faster.

BUG=

Committed: http://code.google.com/p/skia/source/detail?r=10069

[bsalomon, 2013-07-10 14:05:30]

Rik, this seems to be right up your alley. :)

[Rik, 2013-07-10 15:02:22]

On 2013/07/10 14:05:30, bsalomon wrote:
> Rik, this seems to be right up your alley. :)

LGTM

The equation is different from the spec because it does blending and compositing
at the same time and in premultiplied space.
The formula in the spec is just the raw blending formula.

[djsollen, 2013-07-10 15:36:47]

https://codereview.chromium.org/18112016/diff/1/src/core/SkXfermode.cpp
File src/core/SkXfermode.cpp (right):

https://codereview.chromium.org/18112016/diff/1/src/core/SkXfermode.cpp#newco...
src/core/SkXfermode.cpp:403: static inline int exclusion_byte(int sc, int dc,
int sa, int da) {
we should update the signature to remove 'sa' and 'da' now that they aren't
used.

[kevin.petit.not.used.account, 2013-07-11 12:20:48]

On 2013/07/10 15:36:47, djsollen wrote:
> https://codereview.chromium.org/18112016/diff/1/src/core/SkXfermode.cpp
> File src/core/SkXfermode.cpp (right):
> 
>
https://codereview.chromium.org/18112016/diff/1/src/core/SkXfermode.cpp#newco...
> src/core/SkXfermode.cpp:403: static inline int exclusion_byte(int sc, int dc,
> int sa, int da) {
> we should update the signature to remove 'sa' and 'da' now that they aren't
> used.

Agreed. I just uploaded a second patch to do so and also modified the
description
as Rik confirmed the equation was correct.

[djsollen, 2013-07-11 12:39:10]

lgtm

[commit-bot: I haz the power, 2013-07-15 12:13:12]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/kevin.petit.arm@gmail.com/18112016/7001

[commit-bot: I haz the power, 2013-07-15 12:20:38]

Change committed as 10069