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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 "include/core/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 {
26 public:
27     /**
28      *  This will construct Perlin noise of the given type (Fractal Noise or Turbulence).
29      *
30      *  Both base frequencies (X and Y) have a usual range of (0..1) and must be non-negative.
31      *
32      *  The number of octaves provided should be fairly small, with a limit of 255 enforced.
33      *  Each octave doubles the frequency, so 10 octaves would produce noise from
34      *  baseFrequency * 1, * 2, * 4, ..., * 512, which quickly yields insignificantly small
35      *  periods and resembles regular unstructured noise rather than Perlin noise.
36      *
37      *  If tileSize isn't NULL or an empty size, the tileSize parameter will be used to modify
38      *  the frequencies so that the noise will be tileable for the given tile size. If tileSize
39      *  is NULL or an empty size, the frequencies will be used as is without modification.
40      */
41     static sk_sp<SkShader> MakeFractalNoise(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
42                                             int numOctaves, SkScalar seed,
43                                             const SkISize* tileSize = nullptr);
44     static sk_sp<SkShader> MakeTurbulence(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
45                                           int numOctaves, SkScalar seed,
46                                           const SkISize* tileSize = nullptr);
47 
48     static void RegisterFlattenables();
49 
50 private:
51     SkPerlinNoiseShader() = delete;
52 };
53 
54 #endif
55