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rename to bt709_luminance_or_luma_to_alpha

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We conflate luminance (dot of linear r,g,b) and luma (dot of
gamma-encoded r',g',b') all over the place in Skia.  This one is
possibly the most confusing of any of them, in that the dot-product
coefficients for BT.709 luma were somewhat arbitrarily chosen to be the
same as the coefficients for luminance.

So, big old ridiculously new long name to make it clear it works
for both luma and luminance, but that it's hardcoded to BT.709.

My quick reference when I forget things:
https://en.wikipedia.org/wiki/Luma_(video)

Change-Id: I5a6567de296795f558acc5dd3c39974b8035234e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/226762
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
This commit is contained in:
Mike Klein 2019-07-11 07:38:31 -05:00 committed by Skia Commit-Bot
parent b5c69a4a46
commit da69d5929d
4 changed files with 5 additions and 5 deletions
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2
src/core/SkRasterPipeline.cpp
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@ -244,7 +244,7 @@ void SkRasterPipeline::append_store(SkColorType ct, const SkRasterPipeline_Memor
this->append(store_1010102, ctx);
break;
case kGray_8_SkColorType: this->append(luminance_to_alpha);
case kGray_8_SkColorType: this->append(bt709_luminance_or_luma_to_alpha);
this->append(store_a8, ctx);
break;

2
src/core/SkRasterPipeline.h
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@ -56,7 +56,7 @@
M(load_rg1616) M(store_rg1616) \
M(load_16161616) M(store_16161616) \
M(load_1010102) M(load_1010102_dst) M(store_1010102) M(gather_1010102) \
M(alpha_to_gray) M(alpha_to_gray_dst) M(luminance_to_alpha) \
M(alpha_to_gray) M(alpha_to_gray_dst) M(bt709_luminance_or_luma_to_alpha) \
M(bilerp_clamp_8888) \
M(store_u16_be) \
M(load_src) M(store_src) M(load_dst) M(store_dst) \

2
src/effects/SkLumaColorFilter.cpp
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@ -19,7 +19,7 @@
#endif
bool SkLumaColorFilter::onAppendStages(const SkStageRec& rec, bool shaderIsOpaque) const {
rec.fPipeline->append(SkRasterPipeline::luminance_to_alpha);
rec.fPipeline->append(SkRasterPipeline::bt709_luminance_or_luma_to_alpha);
rec.fPipeline->append(SkRasterPipeline::clamp_0);
rec.fPipeline->append(SkRasterPipeline::clamp_1);
return true;

4
src/opts/SkRasterPipeline_opts.h
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@ -2224,7 +2224,7 @@ STAGE(alpha_to_gray_dst, Ctx::None) {
dr = dg = db = da;
da = 1;
}
STAGE(luminance_to_alpha, Ctx::None) {
STAGE(bt709_luminance_or_luma_to_alpha, Ctx::None) {
a = r*0.2126f + g*0.7152f + b*0.0722f;
r = g = b = 0;
}
@ -3507,7 +3507,7 @@ STAGE_PP(alpha_to_gray_dst, Ctx::None) {
dr = dg = db = da;
da = 255;
}
STAGE_PP(luminance_to_alpha, Ctx::None) {
STAGE_PP(bt709_luminance_or_luma_to_alpha, Ctx::None) {
a = (r*54 + g*183 + b*19)/256; // 0.2126, 0.7152, 0.0722 with 256 denominator.
r = g = b = 0;
}