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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 "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 SkShader {
struct PaintingData;
public:
struct StitchData;
/**
* About the noise types : the difference between the 2 is just minor tweaks to the algorithm,
* they're not 2 entirely different noises. The output looks different, but once the noise is
* generated in the [1, -1] range, the output is brought back in the [0, 1] range by doing :
* kFractalNoise_Type : noise * 0.5 + 0.5
* kTurbulence_Type : abs(noise)
* Very little differences between the 2 types, although you can tell the difference visually.
*/
enum Type {
kFractalNoise_Type,
kTurbulence_Type,
kFirstType = kFractalNoise_Type,
kLastType = kTurbulence_Type
};
/**
* 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).
*
* The number of octaves provided should be fairly small, although no limit is 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 SkShader* CreateFractalNoise(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
int numOctaves, SkScalar seed,
const SkISize* tileSize = NULL);
static SkShader* CreateTubulence(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
int numOctaves, SkScalar seed,
const SkISize* tileSize = NULL);
virtual bool setContext(const SkBitmap& device, const SkPaint& paint,
const SkMatrix& matrix);
virtual void shadeSpan(int x, int y, SkPMColor[], int count) SK_OVERRIDE;
virtual void shadeSpan16(int x, int y, uint16_t[], int count) SK_OVERRIDE;
virtual GrEffectRef* asNewEffect(GrContext* context, const SkPaint&) const SK_OVERRIDE;
SK_DEVELOPER_TO_STRING()
SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkPerlinNoiseShader)
protected:
SkPerlinNoiseShader(SkFlattenableReadBuffer&);
virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
private:
SkPerlinNoiseShader(SkPerlinNoiseShader::Type type, SkScalar baseFrequencyX,
SkScalar baseFrequencyY, int numOctaves, SkScalar seed,
const SkISize* tileSize = NULL);
virtual ~SkPerlinNoiseShader();
void setTileSize(const SkISize&);
void initPaint(PaintingData& paintingData);
SkScalar noise2D(int channel, const PaintingData& paintingData,
const StitchData& stitchData, const SkPoint& noiseVector);
SkScalar calculateTurbulenceValueForPoint(int channel, const PaintingData& paintingData,
StitchData& stitchData, const SkPoint& point);
SkPMColor shade(const SkPoint& point, StitchData& stitchData);
SkPerlinNoiseShader::Type fType;
SkScalar fBaseFrequencyX;
SkScalar fBaseFrequencyY;
int fNumOctaves;
SkScalar fSeed;
SkISize fTileSize;
bool fStitchTiles;
SkMatrix fMatrix;
PaintingData* fPaintingData;
typedef SkShader INHERITED;
};
#endif
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