Add SkColorSpaceTransferFn to SkColorSpace

include/core/SkColorSpace.h

Index: include/core/SkColorSpace.h
diff --git a/include/core/SkColorSpace.h b/include/core/SkColorSpace.h
index 9b990da966dcac73912ed36ae1cb23423524e85f..b1daf4f232692898514f63f57ddb9f383d3ce793 100644
--- a/include/core/SkColorSpace.h
+++ b/include/core/SkColorSpace.h
@@ -29,6 +29,27 @@ struct SK_API SkColorSpacePrimaries {
     bool toXYZD50(SkMatrix44* toXYZD50) const;
 };
 
+/**
+ *  Contains the coefficients for a common transfer function equation, specified as
+ *  a transformation from a curved space to linear.
+ *
+ *  LinearVal = E*InputVal + F        , for 0.0f <= InputVal <  D
+ *  LinearVal = (A*InputVal + B)^G + C, for D    <= InputVal <= 1.0f
+ *
+ *  Function is undefined if InputVal is not in [ 0.0f, 1.0f ].
+ *  Resulting LinearVals must be in [ 0.0f, 1.0f ].
+ *  Function must be positive and increasing.
+ */
+struct SK_API SkColorSpaceTransferFn {
+    float fG;
+    float fA;
+    float fB;
+    float fC;
+    float fD;
+    float fE;
+    float fF;
+};
+
 class SK_API SkColorSpace : public SkRefCnt {
 public:
 
@@ -68,10 +89,12 @@ public:
     /**
      *  Create an SkColorSpace from a transfer function and a color gamut.
      *
-     *  Transfer function is specified as linear or sRGB.
+     *  Transfer function can be specified as a render target or as the coefficients to an equation.
      *  Gamut is specified using the matrix transformation to XYZ D50.
      */
     static sk_sp<SkColorSpace> NewRGB(RenderTargetGamma gamma, const SkMatrix44& toXYZD50);
+    static sk_sp<SkColorSpace> NewRGB(const SkColorSpaceTransferFn& coeffs,
+                                      const SkMatrix44& toXYZD50);
 
     /**
      *  Create a common, named SkColorSpace.