added experimental improved Perlin noise shader

experimental/SkPerlinNoiseShader2/SkPerlinNoiseShader2.h

Index: experimental/SkPerlinNoiseShader2/SkPerlinNoiseShader2.h
diff --git a/include/effects/SkPerlinNoiseShader.h b/experimental/SkPerlinNoiseShader2/SkPerlinNoiseShader2.h
similarity index 72%
copy from include/effects/SkPerlinNoiseShader.h
copy to experimental/SkPerlinNoiseShader2/SkPerlinNoiseShader2.h
index 0cb1b47a9f4b57b12e979ebb81ec41f445e36101..3c02c5de244c546ad39b4f3b15a1882882332c76 100644
--- a/include/effects/SkPerlinNoiseShader.h
+++ b/experimental/SkPerlinNoiseShader2/SkPerlinNoiseShader2.h
@@ -5,14 +5,14 @@
  * found in the LICENSE file.
  */
 
-#ifndef SkPerlinNoiseShader_DEFINED
-#define SkPerlinNoiseShader_DEFINED
+#ifndef SkPerlinNoiseShader2_DEFINED
+#define SkPerlinNoiseShader2_DEFINED
 
 #include "SkShader.h"
 
-/** \class SkPerlinNoiseShader
+/** \class SkPerlinNoiseShader2
 
-    SkPerlinNoiseShader creates an image using the Perlin turbulence function.
+    SkPerlinNoiseShader2 creates an image using the Perlin turbulence function.
 
     It can produce tileable noise if asked to stitch tiles and provided a tile size.
     In order to fill a large area with repeating noise, set the stitchTiles flag to
@@ -22,24 +22,30 @@
     The algorithm used is described here :
     http://www.w3.org/TR/SVG/filters.html#feTurbulenceElement
 */
-class SK_API SkPerlinNoiseShader : public SkShader {
+class SK_API SkPerlinNoiseShader2 : public SkShader {
 public:
     struct StitchData;
     struct PaintingData;
 
     /**
-     *  About the noise types : the difference between the 2 is just minor tweaks to the algorithm,
-     *  they're not 2 entirely different noises. The output looks different, but once the noise is
-     *  generated in the [1, -1] range, the output is brought back in the [0, 1] range by doing :
+     *  About the noise types : the difference between the first 2 is just minor tweaks to the 
+     *  algorithm, they're not 2 entirely different noises. The output looks different, but once the 
+     *  noise is generated in the [1, -1] range, the output is brought back in the [0, 1] range by 
+     *  doing :
      *  kFractalNoise_Type : noise * 0.5 + 0.5
      *  kTurbulence_Type   : abs(noise)
      *  Very little differences between the 2 types, although you can tell the difference visually.
+     *  "Improved" is based on the Improved Perlin Noise algorithm described at
+     *  http://mrl.nyu.edu/~perlin/noise/. It is quite distinct from the other two, and the noise is
+     *  a 2D slice of a 3D noise texture. Minor changes to the Z coordinate will result in minor
+     *  changes to the noise, making it suitable for animated noise.
      */
     enum Type {
         kFractalNoise_Type,
         kTurbulence_Type,
+        kImprovedNoise_Type,
         kFirstType = kFractalNoise_Type,
-        kLastType = kTurbulence_Type
+        kLastType = kImprovedNoise_Type
     };
     /**
      *  This will construct Perlin noise of the given type (Fractal Noise or Turbulence).
@@ -62,6 +68,12 @@ public:
                                      int numOctaves, SkScalar seed,
                                      const SkISize* tileSize = NULL);
     /**
+     * Creates an Improved Perlin Noise shader. The z value is roughly equivalent to the seed of the
+     * other two types, but minor variations to z will only slightly change the noise.
+     */
+    static SkShader* CreateImprovedNoise(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
+                                         int numOctaves, SkScalar z);
+    /**
      * Create alias for CreateTurbulunce until all Skia users changed
      * its code to use the new naming
      */
@@ -76,7 +88,7 @@ public:
 
     class PerlinNoiseShaderContext : public SkShader::Context {
     public:
-        PerlinNoiseShaderContext(const SkPerlinNoiseShader& shader, const ContextRec&);
+        PerlinNoiseShaderContext(const SkPerlinNoiseShader2& shader, const ContextRec&);
         virtual ~PerlinNoiseShaderContext();
 
         void shadeSpan(int x, int y, SkPMColor[], int count) override;
@@ -87,6 +99,7 @@ public:
         SkScalar calculateTurbulenceValueForPoint(
             int channel,
             StitchData& stitchData, const SkPoint& point) const;
+        SkScalar calculateImprovedNoiseValueForPoint(int channel, const SkPoint& point) const;
         SkScalar noise2D(int channel,
                          const StitchData& stitchData, const SkPoint& noiseVector) const;
 
@@ -102,19 +115,19 @@ public:
 #endif
 
     SK_TO_STRING_OVERRIDE()
-    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkPerlinNoiseShader)
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkPerlinNoiseShader2)
 
 protected:
     void flatten(SkWriteBuffer&) const override;
     Context* onCreateContext(const ContextRec&, void* storage) const override;
 
 private:
-    SkPerlinNoiseShader(SkPerlinNoiseShader::Type type, SkScalar baseFrequencyX,
+    SkPerlinNoiseShader2(SkPerlinNoiseShader2::Type type, SkScalar baseFrequencyX,
                         SkScalar baseFrequencyY, int numOctaves, SkScalar seed,
                         const SkISize* tileSize);
-    virtual ~SkPerlinNoiseShader();
+    virtual ~SkPerlinNoiseShader2();
 
-    const SkPerlinNoiseShader::Type fType;
+    const SkPerlinNoiseShader2::Type fType;
     const SkScalar                  fBaseFrequencyX;
     const SkScalar                  fBaseFrequencyY;
     const int                       fNumOctaves;