Add SkColorSpaceXform to the public API

src/core/SkColorSpaceXform.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 SkColorSpaceXform_DEFINED
-#define SkColorSpaceXform_DEFINED
-
-#include "SkColorSpace.h"
-#include "SkColorSpace_Base.h"
-#include "SkImageInfo.h"
-
-class SkColorSpaceXform : SkNoncopyable {
-public:
-
-    /**
-     *  Create an object to handle color space conversions.
-     *
-     *  @param srcSpace The encoded color space.
-     *  @param dstSpace The destination color space.
-     *
-     */
-    static std::unique_ptr<SkColorSpaceXform> New(SkColorSpace* srcSpace, SkColorSpace* dstSpace);
-
-    enum ColorFormat : uint8_t {
-        kRGBA_8888_ColorFormat,
-        kBGRA_8888_ColorFormat,
-        kRGBA_F16_ColorFormat,
-        kRGBA_F32_ColorFormat,
-    };
-
-    /**
-     *  Apply the color conversion to a |src| buffer, storing the output in the |dst| buffer.
-     *
-     *  @param dst            Stored in the format described by |dstColorFormat|
-     *  @param src            Stored in the format described by |srcColorFormat|
-     *  @param len            Number of pixels in the buffers
-     *  @param dstColorFormat Describes color format of |dst|
-     *  @param srcColorFormat Describes color format of |src|
-     *                        Must be kRGBA_8888 or kBGRA_8888
-     *  @param alphaType      Describes alpha properties of the |dst| (and |src|)
-     *                        kUnpremul preserves input alpha values
-     *                        kPremul   performs a premultiplication and also preserves alpha values
-     *                        kOpaque   optimization hint, |dst| alphas set to 1
-     *
-     */
-    virtual void apply(void* dst, const uint32_t* src, int len, ColorFormat dstColorFormat,
-                       ColorFormat srcColorFormat, SkAlphaType alphaType) const = 0;
-
-    virtual ~SkColorSpaceXform() {}
-};
-
-enum SrcGamma {
-    kLinear_SrcGamma,
-    kTable_SrcGamma,
-};
-
-enum DstGamma {
-    kLinear_DstGamma,
-    kSRGB_DstGamma,
-    k2Dot2_DstGamma,
-    kTable_DstGamma,
-};
-
-enum ColorSpaceMatch {
-    kNone_ColorSpaceMatch,
-    kGamut_ColorSpaceMatch,
-    kFull_ColorSpaceMatch,
-};
-
-template <SrcGamma kSrc, DstGamma kDst, ColorSpaceMatch kCSM>
-class SkColorSpaceXform_Base : public SkColorSpaceXform {
-public:
-
-    void apply(void* dst, const uint32_t* src, int len, ColorFormat dstColorFormat,
-               ColorFormat srcColorFormat, SkAlphaType alphaType) const override;
-
-    static constexpr int      kDstGammaTableSize = 1024;
-
-private:
-    SkColorSpaceXform_Base(SkColorSpace* srcSpace, const SkMatrix44& srcToDst,
-                           SkColorSpace* dstSpace);
-
-    sk_sp<SkColorLookUpTable> fColorLUT;
-
-    // Contain pointers into storage or pointers into precomputed tables.
-    const float*              fSrcGammaTables[3];
-    const uint8_t*            fDstGammaTables[3];
-    SkAutoMalloc              fStorage;
-
-    float                     fSrcToDst[16];
-
-    friend class SkColorSpaceXform;
-    friend std::unique_ptr<SkColorSpaceXform> SlowIdentityXform(SkColorSpace* space);
-};
-
-// For testing.  Bypasses opts for when src and dst color spaces are equal.
-std::unique_ptr<SkColorSpaceXform> SlowIdentityXform(SkColorSpace* space);
-
-#endif