Add SkColorSpaceXform to the public API

include/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 SkColorSpace;
+
 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);

[reed1, 2016/10/04 14:54:43]

Do you copy or ref or neither these two pointers (for the life of the returned
xform)?

[msarett, 2016/10/04 23:21:58]

Neither.  I actually used to make this take sk_sps just in case...  I think this
is how we want it, of course now I'm worried I might change my mind.

 
     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.
      *
+     *  F16 and F32 are only supported as dst color formats, and only when the dst color space
+     *  is linear.  This function will assert on invalid or unsupported uses.
+     *
      *  @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
      *
      */

[reed1, 2016/10/04 14:54:43]

consider making apply non-virtual, and just dispatch to a (new) virtual under
the hood. Makes it clearer that this is intended to be a closed set of
subclasses.

[msarett, 2016/10/04 23:21:58]

Done.

     virtual void apply(void* dst, const uint32_t* src, int len, ColorFormat dstColorFormat,

[reed1, 2016/10/04 14:54:43]

why is src uint32* and dst void* if both have a format descriptor?

[reed1, 2016/10/04 14:54:43]

nit: more common is use "count" when counting logical objects in skia

[msarett, 2016/10/04 23:21:58]

I think it is cleaner to make both void*.  I'm changing this.

FWIW, (as of right now) only RBGA888 and BGRA8888 are supported as inputs, so
uint32_t* is somewhat accurate.

[msarett, 2016/10/04 23:21:58]

Done.

                        ColorFormat srcColorFormat, SkAlphaType alphaType) const = 0;

[reed1, 2016/10/04 14:54:43]

Its tricky to see how the params group... what about:

apply(DstFormat, dst, SrcFormat, src, count, alpha) ?

[msarett, 2016/10/04 23:21:58]

Done.

 
     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