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 SkPerlinNoiseShader2_DEFINED
9#define SkPerlinNoiseShader2_DEFINED
10
11#include "SkShader.h"
12
13/** \class SkPerlinNoiseShader2
14
15    SkPerlinNoiseShader2 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*/
25class SK_API SkPerlinNoiseShader2 : public SkShader {
26public:
27    struct StitchData;
28    struct PaintingData;
29
30    /**
31     *  About the noise types : the difference between the first 2 is just minor tweaks to the
32     *  algorithm, they're not 2 entirely different noises. The output looks different, but once the
33     *  noise is generated in the [1, -1] range, the output is brought back in the [0, 1] range by
34     *  doing :
35     *  kFractalNoise_Type : noise * 0.5 + 0.5
36     *  kTurbulence_Type   : abs(noise)
37     *  Very little differences between the 2 types, although you can tell the difference visually.
38     *  "Improved" is based on the Improved Perlin Noise algorithm described at
39     *  http://mrl.nyu.edu/~perlin/noise/. It is quite distinct from the other two, and the noise is
40     *  a 2D slice of a 3D noise texture. Minor changes to the Z coordinate will result in minor
41     *  changes to the noise, making it suitable for animated noise.
42     */
43    enum Type {
44        kFractalNoise_Type,
45        kTurbulence_Type,
46        kImprovedNoise_Type,
47        kFirstType = kFractalNoise_Type,
48        kLastType = kImprovedNoise_Type
49    };
50    /**
51     *  This will construct Perlin noise of the given type (Fractal Noise or Turbulence).
52     *
53     *  Both base frequencies (X and Y) have a usual range of (0..1).
54     *
55     *  The number of octaves provided should be fairly small, although no limit is enforced.
56     *  Each octave doubles the frequency, so 10 octaves would produce noise from
57     *  baseFrequency * 1, * 2, * 4, ..., * 512, which quickly yields insignificantly small
58     *  periods and resembles regular unstructured noise rather than Perlin noise.
59     *
60     *  If tileSize isn't NULL or an empty size, the tileSize parameter will be used to modify
61     *  the frequencies so that the noise will be tileable for the given tile size. If tileSize
62     *  is NULL or an empty size, the frequencies will be used as is without modification.
63     */
64    static SkShader* CreateFractalNoise(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
65                                        int numOctaves, SkScalar seed,
66                                        const SkISize* tileSize = NULL);
67    static SkShader* CreateTurbulence(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
68                                     int numOctaves, SkScalar seed,
69                                     const SkISize* tileSize = NULL);
70    /**
71     * Creates an Improved Perlin Noise shader. The z value is roughly equivalent to the seed of the
72     * other two types, but minor variations to z will only slightly change the noise.
73     */
74    static SkShader* CreateImprovedNoise(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
75                                         int numOctaves, SkScalar z);
76    /**
77     * Create alias for CreateTurbulunce until all Skia users changed
78     * its code to use the new naming
79     */
80    static SkShader* CreateTubulence(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
81                                     int numOctaves, SkScalar seed,
82                                     const SkISize* tileSize = NULL) {
83    return CreateTurbulence(baseFrequencyX, baseFrequencyY, numOctaves, seed, tileSize);
84    }
85
86
87    size_t contextSize(const ContextRec&) const override;
88
89    class PerlinNoiseShaderContext : public SkShader::Context {
90    public:
91        PerlinNoiseShaderContext(const SkPerlinNoiseShader2& shader, const ContextRec&);
92        virtual ~PerlinNoiseShaderContext();
93
94        void shadeSpan(int x, int y, SkPMColor[], int count) override;
95
96    private:
97        SkPMColor shade(const SkPoint& point, StitchData& stitchData) const;
98        SkScalar calculateTurbulenceValueForPoint(
99            int channel,
100            StitchData& stitchData, const SkPoint& point) const;
101        SkScalar calculateImprovedNoiseValueForPoint(int channel, const SkPoint& point) const;
102        SkScalar noise2D(int channel,
103                         const StitchData& stitchData, const SkPoint& noiseVector) const;
104
105        SkMatrix fMatrix;
106        PaintingData* fPaintingData;
107
108        typedef SkShader::Context INHERITED;
109    };
110
111#if SK_SUPPORT_GPU
112    const GrFragmentProcessor* asFragmentProcessor(GrContext* context, const SkMatrix& viewM,
113                                                   const SkMatrix*, SkFilterQuality) const override;
114#endif
115
116    SK_TO_STRING_OVERRIDE()
117    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkPerlinNoiseShader2)
118
119protected:
120    void flatten(SkWriteBuffer&) const override;
121    Context* onCreateContext(const ContextRec&, void* storage) const override;
122
123private:
124    SkPerlinNoiseShader2(SkPerlinNoiseShader2::Type type, SkScalar baseFrequencyX,
125                        SkScalar baseFrequencyY, int numOctaves, SkScalar seed,
126                        const SkISize* tileSize);
127    virtual ~SkPerlinNoiseShader2();
128
129    const SkPerlinNoiseShader2::Type fType;
130    const SkScalar                  fBaseFrequencyX;
131    const SkScalar                  fBaseFrequencyY;
132    const int                       fNumOctaves;
133    const SkScalar                  fSeed;
134    const SkISize                   fTileSize;
135    const bool                      fStitchTiles;
136
137    typedef SkShader INHERITED;
138};
139
140#endif
141