New SVG turbulence in Skia
This cl contains the code for both CPU and GPU generation of noise. Both codepaths yield equivalent results.
TEST:Added 'perlinnoise' gm
Review URL: https://codereview.appspot.com/7322060
git-svn-id: http://skia.googlecode.com/svn/trunk/include@8313 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/effects/SkPerlinNoiseShader.h b/effects/SkPerlinNoiseShader.h
new file mode 100644
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+++ b/effects/SkPerlinNoiseShader.h
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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 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
