non-linear blending first steps

Code:
  - Add a non-linear blending bit and makeNonlinearBlending()
    to SkColorSpace
  - remove enough F16=linear checks to make it possible to
    create surfaces and encode pngs with nonlinear F16

Testing:
  - add "esrgb" software config to DM, run it
  - add "srgbnl" software config, run it
  - deemphasize importance of "srgb" config on bots
  - update unit tests to reflect relaxed F16 constraints
  - add a new unit test file with _really_ basic tests,
    and a new unit test that's not working yet

Bug: skia:7942

Change-Id: I8ac042bdf9f3d791765393b68fd9256375184d83
Reviewed-on: https://skia-review.googlesource.com/127325
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

4 files changed, 18 insertions, 4 deletions

diff --git a/src/core/SkColorSpace.cpp b/src/core/SkColorSpace.cpp
index be399bda6f..b75edcef94 100644
--- a/src/core/SkColorSpace.cpp
+++ b/src/core/SkColorSpace.cpp
@@ -500,6 +500,10 @@ bool SkColorSpace::Equals(const SkColorSpace* src, const SkColorSpace* dst) {
         return false;
     }
 
+    if (src->nonlinearBlending() != dst->nonlinearBlending()) {
+        return false;
+    }
+
     const SkData* srcData = src->onProfileData();
     const SkData* dstData = dst->onProfileData();
     if (srcData || dstData) {
diff --git a/src/core/SkColorSpace_XYZ.cpp b/src/core/SkColorSpace_XYZ.cpp
index 17462a117a..968f01d793 100644
--- a/src/core/SkColorSpace_XYZ.cpp
+++ b/src/core/SkColorSpace_XYZ.cpp
@@ -119,3 +119,13 @@ void SkColorSpace_XYZ::toDstGammaTables(const uint8_t* tables[3], sk_sp<SkData>*
     tables[1] = fToDstGammaTables[1];
     tables[2] = fToDstGammaTables[2];
 }
+
+sk_sp<SkColorSpace> SkColorSpace_XYZ::makeNonlinearBlending() const {
+    if (this->nonlinearBlending()) {
+        return sk_ref_sp(const_cast<SkColorSpace_XYZ*>(this));
+    }
+
+    auto cs = sk_make_sp<SkColorSpace_XYZ>(fGammaNamed, fGammas, fToXYZD50, fProfileData);
+    cs->fNonlinearBlending = true;
+    return cs;
+}
diff --git a/src/core/SkColorSpace_XYZ.h b/src/core/SkColorSpace_XYZ.h
index 2ad2e38b1b..d0984ecd1e 100644
--- a/src/core/SkColorSpace_XYZ.h
+++ b/src/core/SkColorSpace_XYZ.h
@@ -23,12 +23,14 @@ public:
     bool onGammaCloseToSRGB() const override;
     bool onGammaIsLinear() const override;
     bool onIsNumericalTransferFn(SkColorSpaceTransferFn* coeffs) const override;
+    bool nonlinearBlending() const override { return fNonlinearBlending; }
 
     const SkData* onProfileData() const override { return fProfileData.get(); }
 
     sk_sp<SkColorSpace> makeLinearGamma() const override;
     sk_sp<SkColorSpace> makeSRGBGamma() const override;
     sk_sp<SkColorSpace> makeColorSpin() const override;
+    sk_sp<SkColorSpace> makeNonlinearBlending() const override;
 
     SkGammaNamed onGammaNamed() const override { return fGammaNamed; }
 
@@ -56,6 +58,8 @@ private:
     mutable const uint8_t* fToDstGammaTables[3];
     mutable SkOnce         fToDstGammaOnce;
 
+    bool fNonlinearBlending = false;
+
     friend class SkColorSpace;
     friend class ColorSpaceXformTest;
 };
diff --git a/src/core/SkPictureImageGenerator.cpp b/src/core/SkPictureImageGenerator.cpp
index 4b68ffdd93..f17ff647ae 100644
--- a/src/core/SkPictureImageGenerator.cpp
+++ b/src/core/SkPictureImageGenerator.cpp
@@ -23,10 +23,6 @@ SkPictureImageGenerator::Make(const SkISize& size, sk_sp<SkPicture> picture, con
         return nullptr;
     }
 
-    if (SkImage::BitDepth::kF16 == bitDepth && (!colorSpace || !colorSpace->gammaIsLinear())) {
-        return nullptr;
-    }
-
     if (colorSpace && (!colorSpace->gammaCloseToSRGB() && !colorSpace->gammaIsLinear())) {
         return nullptr;
     }