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55 lines
2.2 KiB
55 lines
2.2 KiB
/*
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* Copyright 2013 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkPerlinNoiseShader_DEFINED
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#define SkPerlinNoiseShader_DEFINED
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#include "include/core/SkShader.h"
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/** \class SkPerlinNoiseShader
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SkPerlinNoiseShader creates an image using the Perlin turbulence function.
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It can produce tileable noise if asked to stitch tiles and provided a tile size.
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In order to fill a large area with repeating noise, set the stitchTiles flag to
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true, and render exactly a single tile of noise. Without this flag, the result
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will contain visible seams between tiles.
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The algorithm used is described here :
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http://www.w3.org/TR/SVG/filters.html#feTurbulenceElement
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*/
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class SK_API SkPerlinNoiseShader {
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public:
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/**
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* This will construct Perlin noise of the given type (Fractal Noise or Turbulence).
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*
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* Both base frequencies (X and Y) have a usual range of (0..1) and must be non-negative.
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*
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* The number of octaves provided should be fairly small, with a limit of 255 enforced.
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* Each octave doubles the frequency, so 10 octaves would produce noise from
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* baseFrequency * 1, * 2, * 4, ..., * 512, which quickly yields insignificantly small
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* periods and resembles regular unstructured noise rather than Perlin noise.
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*
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* If tileSize isn't NULL or an empty size, the tileSize parameter will be used to modify
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* the frequencies so that the noise will be tileable for the given tile size. If tileSize
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* is NULL or an empty size, the frequencies will be used as is without modification.
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*/
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static sk_sp<SkShader> MakeFractalNoise(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
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int numOctaves, SkScalar seed,
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const SkISize* tileSize = nullptr);
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static sk_sp<SkShader> MakeTurbulence(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
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int numOctaves, SkScalar seed,
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const SkISize* tileSize = nullptr);
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static void RegisterFlattenables();
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private:
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SkPerlinNoiseShader() = delete;
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};
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#endif
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