SkPerlinNoiseShader.h revision fd5c9a6e04ba31a82670d281b03b9c4a3f9b6e3c 
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 {
26    struct PaintingData;
27public:
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
75protected:
76    SkPerlinNoiseShader(SkReadBuffer&);
77    virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
78
79private:
80    SkPerlinNoiseShader(SkPerlinNoiseShader::Type type, SkScalar baseFrequencyX,
81                        SkScalar baseFrequencyY, int numOctaves, SkScalar seed,
82                        const SkISize* tileSize);
83    virtual ~SkPerlinNoiseShader();
84
85    SkScalar noise2D(int channel, const PaintingData& paintingData,
86                     const StitchData& stitchData, const SkPoint& noiseVector) const;
87
88    SkScalar calculateTurbulenceValueForPoint(int channel, const PaintingData& paintingData,
89                                              StitchData& stitchData, const SkPoint& point) const;
90
91    SkPMColor shade(const SkPoint& point, StitchData& stitchData) const;
92
93    // TODO (scroggo): Once all SkShaders are created from a factory, and we have removed the
94    // constructor that creates SkPerlinNoiseShader from an SkReadBuffer, several fields can
95    // be made constant.
96    /*const*/ SkPerlinNoiseShader::Type fType;
97    /*const*/ SkScalar                  fBaseFrequencyX;
98    /*const*/ SkScalar                  fBaseFrequencyY;
99    /*const*/ int                       fNumOctaves;
100    /*const*/ SkScalar                  fSeed;
101    /*const*/ SkISize                   fTileSize;
102    /*const*/ bool                      fStitchTiles;
103    // TODO (scroggo): Once setContext creates a new object, place this on that object.
104    SkMatrix fMatrix;
105
106    PaintingData* fPaintingData;
107
108    typedef SkShader INHERITED;
109};
110
111#endif
112