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* CreateTurbulence(SkScalar baseFrequencyX, SkScalar baseFrequencyY, 62 int numOctaves, SkScalar seed, 63 const SkISize* tileSize = NULL); 64 /** 65 * Create alias for CreateTurbulunce until all Skia users changed 66 * its code to use the new naming 67 */ 68 static SkShader* CreateTubulence(SkScalar baseFrequencyX, SkScalar baseFrequencyY, 69 int numOctaves, SkScalar seed, 70 const SkISize* tileSize = NULL) { 71 return CreateTurbulence(baseFrequencyX, baseFrequencyY, numOctaves, seed, tileSize); 72 } 73 74 75 virtual size_t contextSize() const SK_OVERRIDE; 76 77 class PerlinNoiseShaderContext : public SkShader::Context { 78 public: 79 PerlinNoiseShaderContext(const SkPerlinNoiseShader& shader, const ContextRec&); 80 virtual ~PerlinNoiseShaderContext() {} 81 82 virtual void shadeSpan(int x, int y, SkPMColor[], int count) SK_OVERRIDE; 83 virtual void shadeSpan16(int x, int y, uint16_t[], int count) SK_OVERRIDE; 84 85 private: 86 SkPMColor shade(const SkPoint& point, StitchData& stitchData) const; 87 SkScalar calculateTurbulenceValueForPoint( 88 int channel, const PaintingData& paintingData, 89 StitchData& stitchData, const SkPoint& point) const; 90 SkScalar noise2D(int channel, const PaintingData& paintingData, 91 const StitchData& stitchData, const SkPoint& noiseVector) const; 92 93 SkMatrix fMatrix; 94 95 typedef SkShader::Context INHERITED; 96 }; 97 98 virtual bool asNewEffect(GrContext* context, const SkPaint&, const SkMatrix*, GrColor*, 99 GrEffectRef**) const SK_OVERRIDE; 100 101 SK_TO_STRING_OVERRIDE() 102 SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkPerlinNoiseShader) 103 104 protected: 105 SkPerlinNoiseShader(SkReadBuffer&); 106 virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE; 107 virtual Context* onCreateContext(const ContextRec&, void* storage) const SK_OVERRIDE; 108 109 private: 110 SkPerlinNoiseShader(SkPerlinNoiseShader::Type type, SkScalar baseFrequencyX, 111 SkScalar baseFrequencyY, int numOctaves, SkScalar seed, 112 const SkISize* tileSize); 113 virtual ~SkPerlinNoiseShader(); 114 115 // TODO (scroggo): Once all SkShaders are created from a factory, and we have removed the 116 // constructor that creates SkPerlinNoiseShader from an SkReadBuffer, several fields can 117 // be made constant. 118 /*const*/ SkPerlinNoiseShader::Type fType; 119 /*const*/ SkScalar fBaseFrequencyX; 120 /*const*/ SkScalar fBaseFrequencyY; 121 /*const*/ int fNumOctaves; 122 /*const*/ SkScalar fSeed; 123 /*const*/ SkISize fTileSize; 124 /*const*/ bool fStitchTiles; 125 126 PaintingData* fPaintingData; 127 128 typedef SkShader INHERITED; 129 }; 130 131 #endif 132
