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/SkRefCnt.h" 12 #include "include/core/SkScalar.h" 13 #include "include/core/SkShader.h" // IWYU pragma: keep 14 #include "include/private/base/SkAPI.h" 15 16 struct SkISize; 17 18 /** \class SkPerlinNoiseShader 19 20 SkPerlinNoiseShader creates an image using the Perlin turbulence function. 21 22 It can produce tileable noise if asked to stitch tiles and provided a tile size. 23 In order to fill a large area with repeating noise, set the stitchTiles flag to 24 true, and render exactly a single tile of noise. Without this flag, the result 25 will contain visible seams between tiles. 26 27 The algorithm used is described here : 28 http://www.w3.org/TR/SVG/filters.html#feTurbulenceElement 29 */ 30 namespace SkShaders { 31 /** 32 * This will construct Perlin noise of the given type (Fractal Noise or Turbulence). 33 * 34 * Both base frequencies (X and Y) have a usual range of (0..1) and must be non-negative. 35 * 36 * The number of octaves provided should be fairly small, with a limit of 255 enforced. 37 * Each octave doubles the frequency, so 10 octaves would produce noise from 38 * baseFrequency * 1, * 2, * 4, ..., * 512, which quickly yields insignificantly small 39 * periods and resembles regular unstructured noise rather than Perlin noise. 40 * 41 * If tileSize isn't NULL or an empty size, the tileSize parameter will be used to modify 42 * the frequencies so that the noise will be tileable for the given tile size. If tileSize 43 * is NULL or an empty size, the frequencies will be used as is without modification. 44 */ 45 SK_API sk_sp<SkShader> MakeFractalNoise(SkScalar baseFrequencyX, SkScalar baseFrequencyY, 46 int numOctaves, SkScalar seed, 47 const SkISize* tileSize = nullptr); 48 SK_API sk_sp<SkShader> MakeTurbulence(SkScalar baseFrequencyX, SkScalar baseFrequencyY, 49 int numOctaves, SkScalar seed, 50 const SkISize* tileSize = nullptr); 51 } // namespace SkShaders 52 53 #endif 54