starter kit for colorspaces

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"
+
+struct SkFloat3 {
+    float fVec[3];
+
+    void dump() const;
+};
+
+struct SkFloat3x3 {
+    float fMat[9];
+
+    void dump() const;
+};
+
+struct SkPM4f;
+void SkApply3x3ToPM4f(const SkFloat3x3&, const SkPM4f src[], SkPM4f dst[], int count);
+
+class SkColorSpace : public SkRefCnt {
+public:
+    enum Named {
+        kUnknown_Named,
+        kDevice_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 SkColorSpace* NewRGB(const SkFloat3x3& toXYZD50, const SkFloat3& gamma);
+
+    static SkColorSpace* NewNamed(Named);
+    static SkColorSpace* NewICC(const void*, size_t);
+
+    SkFloat3 gamma() const { return fGamma; }
+    Named named() const { return fNamed; }
+    uint32_t uniqueID() const { return fUniqueID; }
+
+    enum Result {
+        kFailure_Result,
+        kIdentity_Result,
+        kNormal_Result,
+    };
+
+    /**
+     *  Given a src and dst colorspace, return the 3x3 matrix that will convert src_linear_RGB
+     *  values into dst_linear_RGB values.
+     */
+    static Result Concat(const SkColorSpace* src, const SkColorSpace* dst, SkFloat3x3* result);
+
+    static void Test();
+    void dump() const;
+
+protected:
+    SkColorSpace(const SkFloat3x3& toXYZ, const SkFloat3& gamma, Named);
+
+private:
+    const SkFloat3x3 fToXYZD50;
+    const SkFloat3   fGamma;
+    const uint32_t   fUniqueID;
+    const Named      fNamed;
+};
+
+#endif