extend SkShader to report a luminance-color to be used for gamma correction

extend SkShader to report a luminance-color to be used for gamma correction

BUG=skia:590
Committed: https://skia.googlesource.com/skia/+/8367b8cb7a6b2f163ee41365323cb219b7049b15

[reed1, 2014-08-21 01:45:31]

need to modify ColorShader as well

[bungeman-skia, 2014-08-21 14:15:43]

https://codereview.chromium.org/492963002/diff/1/gm/aaclip.cpp
File gm/aaclip.cpp (right):

https://codereview.chromium.org/492963002/diff/1/gm/aaclip.cpp#newcode126
gm/aaclip.cpp:126: if (true) { test_gamma(canvas); return; }
I'm supposing this needs to be updated.

https://codereview.chromium.org/492963002/diff/1/src/effects/gradients/SkGrad...
File src/effects/gradients/SkGradientShader.cpp (right):

https://codereview.chromium.org/492963002/diff/1/src/effects/gradients/SkGrad...
src/effects/gradients/SkGradientShader.cpp:254: static unsigned
rndivbyte(unsigned numer, unsigned denom) {
rounded_divide?

It isn't totally clear that the 'd' is part of 'rnd' (which also suggests
'random') and 'div'. Not sure of a better way of getting 'assert is byte, but
returned unsigned' into the name and also short enough to keep your one liner
below.

[reed1, 2014-08-21 20:07:39]

https://codereview.chromium.org/492963002/diff/1/gm/aaclip.cpp
File gm/aaclip.cpp (right):

https://codereview.chromium.org/492963002/diff/1/gm/aaclip.cpp#newcode126
gm/aaclip.cpp:126: if (true) { test_gamma(canvas); return; }
On 2014/08/21 14:15:43, bungeman1 wrote:
> I'm supposing this needs to be updated.

Done.

https://codereview.chromium.org/492963002/diff/1/src/effects/gradients/SkGrad...
File src/effects/gradients/SkGradientShader.cpp (right):

https://codereview.chromium.org/492963002/diff/1/src/effects/gradients/SkGrad...
src/effects/gradients/SkGradientShader.cpp:254: static unsigned
rndivbyte(unsigned numer, unsigned denom) {
On 2014/08/21 14:15:43, bungeman1 wrote:
> rounded_divide?
> 
> It isn't totally clear that the 'd' is part of 'rnd' (which also suggests
> 'random') and 'div'. Not sure of a better way of getting 'assert is byte, but
> returned unsigned' into the name and also short enough to keep your one liner
> below.

Done.

[reed1, 2014-08-21 20:24:21]

The CQ bit was checked by reed@google.com

[commit-bot: I haz the power, 2014-08-21 20:25:09]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/reed@google.com/492963002/40001

[commit-bot: I haz the power, 2014-08-21 20:25:10]

Note for Reviewers:
The CQ is waiting for an approval.
If you believe that the CL is not ready yet, or if you would like to L-G-T-M
with comments then please uncheck the CQ checkbox.

Waiting for LGTM from a valid reviewer till 2014-08-22 02:25 UTC

[commit-bot: I haz the power, 2014-08-21 20:38:09]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  Test-Ubuntu13.10-GCE-NoGPU-x86_64-Debug-Trybot on tryserver.skia
(http://108.170.220.120:10117/builders/Test-Ubuntu13.10-GCE-NoGPU-x86_64-Debug...)

[reed1, 2014-08-21 20:41:06]

The CQ bit was unchecked by reed@google.com

[reed1, 2014-08-21 21:29:41]

waiting on 565 Blend fix (CL in the works)

[bungeman-skia, 2014-08-21 22:29:15]

lgtm

[reed1, 2014-08-22 15:21:19]

The CQ bit was checked by reed@google.com

[commit-bot: I haz the power, 2014-08-22 15:21:45]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/reed@google.com/492963002/40001

[commit-bot: I haz the power, 2014-08-22 15:30:26]

Committed patchset #3 (40001) as 8367b8cb7a6b2f163ee41365323cb219b7049b15

[tomhudson, 2014-08-29 22:52:42]

tomhudson@google.com changed reviewers:
+ tomhudson@google.com

[tomhudson, 2014-08-29 22:52:43]

https://codereview.chromium.org/492963002/diff/40001/src/effects/gradients/Sk...
File src/effects/gradients/SkGradientShader.cpp (right):

https://codereview.chromium.org/492963002/diff/40001/src/effects/gradients/Sk...
src/effects/gradients/SkGradientShader.cpp:341: for (int i = 0; i < n; ++i) {
Seems like this works well for the trivial case (2 colors, or equidistant color
samples), but would need weighting to look representative for several
non-uniformly-spaced color stops?

[reed1, 2014-09-02 13:52:55]

https://codereview.chromium.org/492963002/diff/40001/src/effects/gradients/Sk...
File src/effects/gradients/SkGradientShader.cpp (right):

https://codereview.chromium.org/492963002/diff/40001/src/effects/gradients/Sk...
src/effects/gradients/SkGradientShader.cpp:341: for (int i = 0; i < n; ++i) {
On 2014/08/29 22:52:43, tomhudson wrote:
> Seems like this works well for the trivial case (2 colors, or equidistant
color
> samples), but would need weighting to look representative for several
> non-uniformly-spaced color stops?

Agreed. I have a comment to that effect just above.