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*/
25class SK_API SkPerlinNoiseShader : public SkShader {
26public:
27    struct StitchData;
28    struct PaintingData;
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 sk_sp<SkShader> MakeFractalNoise(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
59                                            int numOctaves, SkScalar seed,
60                                            const SkISize* tileSize = nullptr);
61    static sk_sp<SkShader> MakeTurbulence(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
62                                          int numOctaves, SkScalar seed,
63                                          const SkISize* tileSize = nullptr);
64
65    class PerlinNoiseShaderContext : public SkShader::Context {
66    public:
67        PerlinNoiseShaderContext(const SkPerlinNoiseShader& shader, const ContextRec&);
68        ~PerlinNoiseShaderContext() override;
69
70        void shadeSpan(int x, int y, SkPMColor[], int count) override;
71
72    private:
73        SkPMColor shade(const SkPoint& point, StitchData& stitchData) const;
74        SkScalar calculateTurbulenceValueForPoint(
75            int channel,
76            StitchData& stitchData, const SkPoint& point) const;
77        SkScalar noise2D(int channel,
78                         const StitchData& stitchData, const SkPoint& noiseVector) const;
79
80        SkMatrix fMatrix;
81        PaintingData* fPaintingData;
82
83        typedef SkShader::Context INHERITED;
84    };
85
86#if SK_SUPPORT_GPU
87    sk_sp<GrFragmentProcessor> asFragmentProcessor(const AsFPArgs&) const override;
88#endif
89
90    SK_TO_STRING_OVERRIDE()
91    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkPerlinNoiseShader)
92
93protected:
94    void flatten(SkWriteBuffer&) const override;
95    Context* onMakeContext(const ContextRec&, SkArenaAlloc* storage) const override;
96
97private:
98    SkPerlinNoiseShader(SkPerlinNoiseShader::Type type, SkScalar baseFrequencyX,
99                        SkScalar baseFrequencyY, int numOctaves, SkScalar seed,
100                        const SkISize* tileSize);
101    ~SkPerlinNoiseShader() override;
102
103    const SkPerlinNoiseShader::Type fType;
104    const SkScalar                  fBaseFrequencyX;
105    const SkScalar                  fBaseFrequencyY;
106    const int                       fNumOctaves;
107    const SkScalar                  fSeed;
108    const SkISize                   fTileSize;
109    const bool                      fStitchTiles;
110
111    typedef SkShader INHERITED;
112};
113
114#endif
115