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      1 /*
      2  * Copyright 2013 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #ifndef SkPerlinNoiseShader_DEFINED
      9 #define SkPerlinNoiseShader_DEFINED
     10 
     11 #include "SkShader.h"
     12 
     13 /** \class SkPerlinNoiseShader
     14 
     15     SkPerlinNoiseShader creates an image using the Perlin turbulence function.
     16 
     17     It can produce tileable noise if asked to stitch tiles and provided a tile size.
     18     In order to fill a large area with repeating noise, set the stitchTiles flag to
     19     true, and render exactly a single tile of noise. Without this flag, the result
     20     will contain visible seams between tiles.
     21 
     22     The algorithm used is described here :
     23     http://www.w3.org/TR/SVG/filters.html#feTurbulenceElement
     24 */
     25 class SK_API SkPerlinNoiseShader : public SkShader {
     26     struct PaintingData;
     27 public:
     28     struct StitchData;
     29 
     30     /**
     31      *  About the noise types : the difference between the 2 is just minor tweaks to the algorithm,
     32      *  they're not 2 entirely different noises. The output looks different, but once the noise is
     33      *  generated in the [1, -1] range, the output is brought back in the [0, 1] range by doing :
     34      *  kFractalNoise_Type : noise * 0.5 + 0.5
     35      *  kTurbulence_Type   : abs(noise)
     36      *  Very little differences between the 2 types, although you can tell the difference visually.
     37      */
     38     enum Type {
     39         kFractalNoise_Type,
     40         kTurbulence_Type,
     41         kFirstType = kFractalNoise_Type,
     42         kLastType = kTurbulence_Type
     43     };
     44     /**
     45      *  This will construct Perlin noise of the given type (Fractal Noise or Turbulence).
     46      *
     47      *  Both base frequencies (X and Y) have a usual range of (0..1).
     48      *
     49      *  The number of octaves provided should be fairly small, although no limit is enforced.
     50      *  Each octave doubles the frequency, so 10 octaves would produce noise from
     51      *  baseFrequency * 1, * 2, * 4, ..., * 512, which quickly yields insignificantly small
     52      *  periods and resembles regular unstructured noise rather than Perlin noise.
     53      *
     54      *  If tileSize isn't NULL or an empty size, the tileSize parameter will be used to modify
     55      *  the frequencies so that the noise will be tileable for the given tile size. If tileSize
     56      *  is NULL or an empty size, the frequencies will be used as is without modification.
     57      */
     58     static SkShader* CreateFractalNoise(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
     59                                         int numOctaves, SkScalar seed,
     60                                         const SkISize* tileSize = NULL);
     61     static SkShader* CreateTubulence(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
     62                                      int numOctaves, SkScalar seed,
     63                                      const SkISize* tileSize = NULL);
     64 
     65     virtual bool setContext(const SkBitmap& device, const SkPaint& paint,
     66                             const SkMatrix& matrix);
     67     virtual void shadeSpan(int x, int y, SkPMColor[], int count) SK_OVERRIDE;
     68     virtual void shadeSpan16(int x, int y, uint16_t[], int count) SK_OVERRIDE;
     69 
     70     virtual GrEffectRef* asNewEffect(GrContext* context, const SkPaint&) const SK_OVERRIDE;
     71 
     72     SK_DEVELOPER_TO_STRING()
     73     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkPerlinNoiseShader)
     74 
     75 protected:
     76     SkPerlinNoiseShader(SkFlattenableReadBuffer&);
     77     virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
     78 
     79 private:
     80     SkPerlinNoiseShader(SkPerlinNoiseShader::Type type, SkScalar baseFrequencyX,
     81                         SkScalar baseFrequencyY, int numOctaves, SkScalar seed,
     82                         const SkISize* tileSize = NULL);
     83     virtual ~SkPerlinNoiseShader();
     84 
     85     void setTileSize(const SkISize&);
     86 
     87     void initPaint(PaintingData& paintingData);
     88 
     89     SkScalar noise2D(int channel, const PaintingData& paintingData,
     90                      const StitchData& stitchData, const SkPoint& noiseVector);
     91 
     92     SkScalar calculateTurbulenceValueForPoint(int channel, const PaintingData& paintingData,
     93                                               StitchData& stitchData, const SkPoint& point);
     94 
     95     SkPMColor shade(const SkPoint& point, StitchData& stitchData);
     96 
     97     SkPerlinNoiseShader::Type fType;
     98     SkScalar fBaseFrequencyX;
     99     SkScalar fBaseFrequencyY;
    100     int fNumOctaves;
    101     SkScalar fSeed;
    102     SkISize fTileSize;
    103     bool fStitchTiles;
    104     SkMatrix fMatrix;
    105 
    106     PaintingData* fPaintingData;
    107 
    108     typedef SkShader INHERITED;
    109 };
    110 
    111 #endif
    112