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