Introduce SkGammas type to represent ICC gamma curves

src/core/SkColorSpace.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkColorSpace_DEFINED
 #define SkColorSpace_DEFINED
 
 // Some terms
 //
 //  PCS : Profile Connection Space : where color number values have an absolute meaning.
 //        Part of the work float is to convert colors to and from this space...
 //        src_linear_unit_floats --> PCS --> PCS' --> dst_linear_unit_floats
 //
 // Some nice documents
 //
 // http://www.cambridgeincolour.com/tutorials/color-space-conversion.htm
 // https://www.w3.org/Graphics/Color/srgb
 // http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html
 //
 
 #include "SkRefCnt.h"
+#include "SkTArray.h"
 
 struct SkFloat3 {
     float fVec[3];
 
     void dump() const;
 };
 
 struct SkFloat3x3 {
     float fMat[9];
 
     void dump() const;
 };
 
+struct SkGammaCurve {
+    bool isValue() const { return 0.0f != fValue; }
+    bool isTable() const { return 0 != fTableSize; }
+    bool isParametric() const { return false; }
+
+    // We have three different ways to represent gamma.
+    // (1) A single value:
+    float                    fValue;
+
+    // (2) A lookup table:
+    uint32_t                 fTableSize;
+    std::unique_ptr<float[]> fTable;
+
+    // (3) Parameters for a curve:
+    // FIXME (msarett): Handle parametric curves.
+
+    SkGammaCurve() {
+        memset(this, 0, sizeof(struct SkGammaCurve));
+    }
+
+    SkGammaCurve(float value)
+        : fValue(value)
+        , fTableSize(0)
+        , fTable(nullptr)
+    {}
+};
+
+struct SkGammas {
+    SkGammaCurve fRed;
+    SkGammaCurve fGreen;
+    SkGammaCurve fBlue;
+};
+
 struct SkColorLookUpTable {
     static const uint8_t kMaxChannels = 16;
 
     uint8_t                  fInputChannels;
     uint8_t                  fOutputChannels;
     uint8_t                  fGridPoints[kMaxChannels];
     std::unique_ptr<float[]> fTable;
 
     SkColorLookUpTable() {
         memset(this, 0, sizeof(struct SkColorLookUpTable));
     }
-
-    SkColorLookUpTable(SkColorLookUpTable&& that)

[msarett, 2016/04/28 21:26:48]

Now that we are on VS 2015, I think that this is no longer necessary.  Should be
implicit.

-        : fInputChannels(that.fInputChannels)
-        , fOutputChannels(that.fOutputChannels)
-        , fTable(std::move(that.fTable))
-    {
-        memcpy(fGridPoints, that.fGridPoints, kMaxChannels);
-    }
 };
 
 class SkColorSpace : public SkRefCnt {
 public:
     enum Named {
         kUnknown_Named,
         kSRGB_Named,
     };
 
     /**
      *  Return a colorspace instance, given a 3x3 transform from linear_RGB to D50_XYZ
      *  and the src-gamma, return a ColorSpace
      */
-    static sk_sp<SkColorSpace> NewRGB(const SkFloat3x3& toXYZD50, const SkFloat3& gamma);
+    static sk_sp<SkColorSpace> NewRGB(const SkFloat3x3& toXYZD50, SkGammas gammas);
 
     static sk_sp<SkColorSpace> NewNamed(Named);
     static sk_sp<SkColorSpace> NewICC(const void*, size_t);
 
-    SkFloat3 gamma() const { return fGamma; }
+    const SkGammas& gammas() const { return fGammas; }
     SkFloat3x3 xyz() const { return fToXYZD50; }
     SkFloat3 xyzOffset() const { return fToXYZOffset; }
     Named named() const { return fNamed; }
     uint32_t uniqueID() const { return fUniqueID; }
 
 private:
-    SkColorSpace(const SkFloat3& gamma, const SkFloat3x3& toXYZ, Named);
+    SkColorSpace(SkGammas gammas, const SkFloat3x3& toXYZ, Named);
 
-    SkColorSpace(SkColorLookUpTable colorLUT, const SkFloat3& gamma, const SkFloat3x3& toXYZ,
-                 const SkFloat3& toXYZOffset);
+    SkColorSpace(SkColorLookUpTable colorLUT, SkGammas gammas,
+                 const SkFloat3x3& toXYZ, const SkFloat3& toXYZOffset);
 
     const SkColorLookUpTable fColorLUT;
-    const SkFloat3           fGamma;
+    const SkGammas           fGammas;
     const SkFloat3x3         fToXYZD50;
     const SkFloat3           fToXYZOffset;
 
     const uint32_t           fUniqueID;
     const Named              fNamed;
 };
 
 #endif