src/shaders/SkPerlinNoiseShader.cpp

/*
 * Copyright 2013 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "include/effects/SkPerlinNoiseShader.h"

#include "include/core/SkColorFilter.h"
#include "include/core/SkShader.h"
#include "include/core/SkString.h"
#include "include/core/SkUnPreMultiply.h"
#include "src/core/SkArenaAlloc.h"
#include "src/core/SkMakeUnique.h"
#include "src/core/SkReadBuffer.h"
#include "src/core/SkWriteBuffer.h"

#if SK_SUPPORT_GPU
#include "include/private/GrRecordingContext.h"
#include "src/gpu/GrCoordTransform.h"
#include "src/gpu/GrRecordingContextPriv.h"
#include "src/gpu/SkGr.h"
#include "src/gpu/effects/generated/GrConstColorProcessor.h"
#include "src/gpu/glsl/GrGLSLFragmentProcessor.h"
#include "src/gpu/glsl/GrGLSLFragmentShaderBuilder.h"
#include "src/gpu/glsl/GrGLSLProgramDataManager.h"
#include "src/gpu/glsl/GrGLSLUniformHandler.h"
#endif

static const int kBlockSize = 256;
static const int kBlockMask = kBlockSize - 1;
static const int kPerlinNoise = 4096;
static const int kRandMaximum = SK_MaxS32; // 2**31 - 1

static uint8_t improved_noise_permutations[] = {
    151, 160, 137,  91,  90,  15, 131,  13, 201,  95,  96,  53, 194, 233,   7, 225, 140,  36, 103,
     30,  69, 142,   8,  99,  37, 240,  21,  10,  23, 190,   6, 148, 247, 120, 234,  75,   0,  26,
    197,  62,  94, 252, 219, 203, 117,  35,  11,  32,  57, 177,  33,  88, 237, 149,  56,  87, 174,
     20, 125, 136, 171, 168,  68, 175,  74, 165,  71, 134, 139,  48,  27, 166,  77, 146, 158, 231,
     83, 111, 229, 122,  60, 211, 133, 230, 220, 105,  92,  41,  55,  46, 245,  40, 244, 102, 143,
     54,  65,  25,  63, 161,   1, 216,  80,  73, 209,  76, 132, 187, 208,  89,  18, 169, 200, 196,
    135, 130, 116, 188, 159,  86, 164, 100, 109, 198, 173, 186,   3,  64,  52, 217, 226, 250, 124,
    123,   5, 202,  38, 147, 118, 126, 255,  82,  85, 212, 207, 206,  59, 227,  47,  16,  58,  17,
    182, 189,  28,  42, 223, 183, 170, 213, 119, 248, 152,   2,  44, 154, 163,  70, 221, 153, 101,
    155, 167,  43, 172,   9, 129,  22,  39, 253,  19,  98, 108, 110,  79, 113, 224, 232, 178, 185,
    112, 104, 218, 246,  97, 228, 251,  34, 242, 193, 238, 210, 144,  12, 191, 179, 162, 241,  81,
     51, 145, 235, 249,  14, 239, 107,  49, 192, 214,  31, 181, 199, 106, 157, 184,  84, 204, 176,
    115, 121,  50,  45, 127,   4, 150, 254, 138, 236, 205,  93, 222, 114,  67,  29,  24,  72, 243,
    141, 128, 195,  78,  66, 215,  61, 156, 180,
    151, 160, 137,  91,  90,  15, 131,  13, 201,  95,  96,  53, 194, 233,   7, 225, 140,  36, 103,
     30,  69, 142,   8,  99,  37, 240,  21,  10,  23, 190,   6, 148, 247, 120, 234,  75,   0,  26,
    197,  62,  94, 252, 219, 203, 117,  35,  11,  32,  57, 177,  33,  88, 237, 149,  56,  87, 174,
     20, 125, 136, 171, 168,  68, 175,  74, 165,  71, 134, 139,  48,  27, 166,  77, 146, 158, 231,
     83, 111, 229, 122,  60, 211, 133, 230, 220, 105,  92,  41,  55,  46, 245,  40, 244, 102, 143,
     54,  65,  25,  63, 161,   1, 216,  80,  73, 209,  76, 132, 187, 208,  89,  18, 169, 200, 196,
    135, 130, 116, 188, 159,  86, 164, 100, 109, 198, 173, 186,   3,  64,  52, 217, 226, 250, 124,
    123,   5, 202,  38, 147, 118, 126, 255,  82,  85, 212, 207, 206,  59, 227,  47,  16,  58,  17,
    182, 189,  28,  42, 223, 183, 170, 213, 119, 248, 152,   2,  44, 154, 163,  70, 221, 153, 101,
    155, 167,  43, 172,   9, 129,  22,  39, 253,  19,  98, 108, 110,  79, 113, 224, 232, 178, 185,
    112, 104, 218, 246,  97, 228, 251,  34, 242, 193, 238, 210, 144,  12, 191, 179, 162, 241,  81,
     51, 145, 235, 249,  14, 239, 107,  49, 192, 214,  31, 181, 199, 106, 157, 184,  84, 204, 176,
    115, 121,  50,  45, 127,   4, 150, 254, 138, 236, 205,  93, 222, 114,  67,  29,  24,  72, 243,
    141, 128, 195,  78,  66, 215,  61, 156, 180
};

class SkPerlinNoiseShaderImpl : public SkShaderBase {
public:
    struct StitchData {
        StitchData()
          : fWidth(0)
          , fWrapX(0)
          , fHeight(0)
          , fWrapY(0)
        {}

        StitchData(SkScalar w, SkScalar h)
          : fWidth(SkTMin(SkScalarRoundToInt(w), SK_MaxS32 - kPerlinNoise))
          , fWrapX(kPerlinNoise + fWidth)
          , fHeight(SkTMin(SkScalarRoundToInt(h), SK_MaxS32 - kPerlinNoise))
          , fWrapY(kPerlinNoise + fHeight) {}

        bool operator==(const StitchData& other) const {
            return fWidth == other.fWidth &&
                   fWrapX == other.fWrapX &&
                   fHeight == other.fHeight &&
                   fWrapY == other.fWrapY;
        }

        int fWidth; // How much to subtract to wrap for stitching.
        int fWrapX; // Minimum value to wrap.
        int fHeight;
        int fWrapY;
    };

    struct PaintingData {
        PaintingData(const SkISize& tileSize, SkScalar seed,
                     SkScalar baseFrequencyX, SkScalar baseFrequencyY,
                     const SkMatrix& matrix)
        {
            SkVector tileVec;
            matrix.mapVector(SkIntToScalar(tileSize.fWidth), SkIntToScalar(tileSize.fHeight),
                             &tileVec);

            SkSize scale;
            if (!matrix.decomposeScale(&scale, nullptr)) {
                scale.set(SK_ScalarNearlyZero, SK_ScalarNearlyZero);
            }
            fBaseFrequency.set(baseFrequencyX * SkScalarInvert(scale.width()),
                               baseFrequencyY * SkScalarInvert(scale.height()));
            fTileSize.set(SkScalarRoundToInt(tileVec.fX), SkScalarRoundToInt(tileVec.fY));
            this->init(seed);
            if (!fTileSize.isEmpty()) {
                this->stitch();
            }

    #if SK_SUPPORT_GPU
            SkImageInfo info = SkImageInfo::MakeA8(kBlockSize, 1);
            SkPixmap permutationsPixmap(info, fLatticeSelector, info.minRowBytes());
            fPermutationsImage = SkImage::MakeFromRaster(permutationsPixmap, nullptr, nullptr);

            info = SkImageInfo::MakeN32Premul(kBlockSize, 4);
            SkPixmap noisePixmap(info, fNoise[0][0], info.minRowBytes());
            fNoiseImage = SkImage::MakeFromRaster(noisePixmap, nullptr, nullptr);

            info = SkImageInfo::MakeA8(256, 1);
            SkPixmap impPermutationsPixmap(info, improved_noise_permutations, info.minRowBytes());
            fImprovedPermutationsImage = SkImage::MakeFromRaster(impPermutationsPixmap, nullptr,
                                                                 nullptr);

            static uint8_t gradients[] = { 2, 2, 1, 0,
                                           0, 2, 1, 0,
                                           2, 0, 1, 0,
                                           0, 0, 1, 0,
                                           2, 1, 2, 0,
                                           0, 1, 2, 0,
                                           2, 1, 0, 0,
                                           0, 1, 0, 0,
                                           1, 2, 2, 0,
                                           1, 0, 2, 0,
                                           1, 2, 0, 0,
                                           1, 0, 0, 0,
                                           2, 2, 1, 0,
                                           1, 0, 2, 0,
                                           0, 2, 1, 0,
                                           1, 0, 0, 0 };
            info = SkImageInfo::MakeN32Premul(16, 1);
            SkPixmap gradPixmap(info, gradients, info.minRowBytes());
            fGradientImage = SkImage::MakeFromRaster(gradPixmap, nullptr, nullptr);
    #endif
        }

    #if SK_SUPPORT_GPU
        PaintingData(const PaintingData& that)
                : fSeed(that.fSeed)
                , fTileSize(that.fTileSize)
                , fBaseFrequency(that.fBaseFrequency)
                , fStitchDataInit(that.fStitchDataInit)
                , fPermutationsImage(that.fPermutationsImage)
                , fNoiseImage(that.fNoiseImage)
                , fImprovedPermutationsImage(that.fImprovedPermutationsImage)
                , fGradientImage(that.fGradientImage) {
            memcpy(fLatticeSelector, that.fLatticeSelector, sizeof(fLatticeSelector));
            memcpy(fNoise, that.fNoise, sizeof(fNoise));
            memcpy(fGradient, that.fGradient, sizeof(fGradient));
        }
    #endif

        int         fSeed;
        uint8_t     fLatticeSelector[kBlockSize];
        uint16_t    fNoise[4][kBlockSize][2];
        SkPoint     fGradient[4][kBlockSize];
        SkISize     fTileSize;
        SkVector    fBaseFrequency;
        StitchData  fStitchDataInit;

    private:

    #if SK_SUPPORT_GPU
        sk_sp<SkImage> fPermutationsImage;
        sk_sp<SkImage> fNoiseImage;
        sk_sp<SkImage> fImprovedPermutationsImage;
        sk_sp<SkImage> fGradientImage;
    #endif

        inline int random()  {
            static const int gRandAmplitude = 16807; // 7**5; primitive root of m
            static const int gRandQ = 127773; // m / a
            static const int gRandR = 2836; // m % a

            int result = gRandAmplitude * (fSeed % gRandQ) - gRandR * (fSeed / gRandQ);
            if (result <= 0)
                result += kRandMaximum;
            fSeed = result;
            return result;
        }

        // Only called once. Could be part of the constructor.
        void init(SkScalar seed)
        {
            static const SkScalar gInvBlockSizef = SkScalarInvert(SkIntToScalar(kBlockSize));

            // According to the SVG spec, we must truncate (not round) the seed value.
            fSeed = SkScalarTruncToInt(seed);
            // The seed value clamp to the range [1, kRandMaximum - 1].
            if (fSeed <= 0) {
                fSeed = -(fSeed % (kRandMaximum - 1)) + 1;
            }
            if (fSeed > kRandMaximum - 1) {
                fSeed = kRandMaximum - 1;
            }
            for (int channel = 0; channel < 4; ++channel) {
                for (int i = 0; i < kBlockSize; ++i) {
                    fLatticeSelector[i] = i;
                    fNoise[channel][i][0] = (random() % (2 * kBlockSize));
                    fNoise[channel][i][1] = (random() % (2 * kBlockSize));
                }
            }
            for (int i = kBlockSize - 1; i > 0; --i) {
                int k = fLatticeSelector[i];
                int j = random() % kBlockSize;
                SkASSERT(j >= 0);
                SkASSERT(j < kBlockSize);
                fLatticeSelector[i] = fLatticeSelector[j];
                fLatticeSelector[j] = k;
            }

            // Perform the permutations now
            {
                // Copy noise data
                uint16_t noise[4][kBlockSize][2];
                for (int i = 0; i < kBlockSize; ++i) {
                    for (int channel = 0; channel < 4; ++channel) {
                        for (int j = 0; j < 2; ++j) {
                            noise[channel][i][j] = fNoise[channel][i][j];
                        }
                    }
                }
                // Do permutations on noise data
                for (int i = 0; i < kBlockSize; ++i) {
                    for (int channel = 0; channel < 4; ++channel) {
                        for (int j = 0; j < 2; ++j) {
                            fNoise[channel][i][j] = noise[channel][fLatticeSelector[i]][j];
                        }
                    }
                }
            }

            // Half of the largest possible value for 16 bit unsigned int
            static const SkScalar gHalfMax16bits = 32767.5f;

            // Compute gradients from permutated noise data
            for (int channel = 0; channel < 4; ++channel) {
                for (int i = 0; i < kBlockSize; ++i) {
                    fGradient[channel][i] = SkPoint::Make(
                        (fNoise[channel][i][0] - kBlockSize) * gInvBlockSizef,
                        (fNoise[channel][i][1] - kBlockSize) * gInvBlockSizef);
                    fGradient[channel][i].normalize();
                    // Put the normalized gradient back into the noise data
                    fNoise[channel][i][0] = SkScalarRoundToInt(
                                                   (fGradient[channel][i].fX + 1) * gHalfMax16bits);
                    fNoise[channel][i][1] = SkScalarRoundToInt(
                                                   (fGradient[channel][i].fY + 1) * gHalfMax16bits);
                }
            }
        }

        // Only called once. Could be part of the constructor.
        void stitch() {
            SkScalar tileWidth  = SkIntToScalar(fTileSize.width());
            SkScalar tileHeight = SkIntToScalar(fTileSize.height());
            SkASSERT(tileWidth > 0 && tileHeight > 0);
            // When stitching tiled turbulence, the frequencies must be adjusted
            // so that the tile borders will be continuous.
            if (fBaseFrequency.fX) {
                SkScalar lowFrequencx =
                    SkScalarFloorToScalar(tileWidth * fBaseFrequency.fX) / tileWidth;
                SkScalar highFrequencx =
                    SkScalarCeilToScalar(tileWidth * fBaseFrequency.fX) / tileWidth;
                // BaseFrequency should be non-negative according to the standard.
                // lowFrequencx can be 0 if fBaseFrequency.fX is very small.
                if (sk_ieee_float_divide(fBaseFrequency.fX, lowFrequencx) < highFrequencx / fBaseFrequency.fX) {
                    fBaseFrequency.fX = lowFrequencx;
                } else {
                    fBaseFrequency.fX = highFrequencx;
                }
            }
            if (fBaseFrequency.fY) {
                SkScalar lowFrequency =
                    SkScalarFloorToScalar(tileHeight * fBaseFrequency.fY) / tileHeight;
                SkScalar highFrequency =
                    SkScalarCeilToScalar(tileHeight * fBaseFrequency.fY) / tileHeight;
                // lowFrequency can be 0 if fBaseFrequency.fY is very small.
                if (sk_ieee_float_divide(fBaseFrequency.fY, lowFrequency) < highFrequency / fBaseFrequency.fY) {
                    fBaseFrequency.fY = lowFrequency;
                } else {
                    fBaseFrequency.fY = highFrequency;
                }
            }
            // Set up TurbulenceInitial stitch values.
            fStitchDataInit = StitchData(tileWidth * fBaseFrequency.fX,
                                         tileHeight * fBaseFrequency.fY);
        }

    public:

#if SK_SUPPORT_GPU
        const sk_sp<SkImage> getPermutationsImage() const { return fPermutationsImage; }

        const sk_sp<SkImage> getNoiseImage() const { return fNoiseImage; }

        const sk_sp<SkImage> getImprovedPermutationsImage() const {
            return fImprovedPermutationsImage;
        }

        const sk_sp<SkImage> getGradientImage() const { return fGradientImage; }
#endif
    };

    /**
     *  About the noise types : the difference between the first 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.
     *  "Improved" is based on the Improved Perlin Noise algorithm described at
     *  http://mrl.nyu.edu/~perlin/noise/. It is quite distinct from the other two, and the noise is
     *  a 2D slice of a 3D noise texture. Minor changes to the Z coordinate will result in minor
     *  changes to the noise, making it suitable for animated noise.
     */
    enum Type {
        kFractalNoise_Type,
        kTurbulence_Type,
        kImprovedNoise_Type,
        kLast_Type = kImprovedNoise_Type
    };

    static const int kMaxOctaves = 255; // numOctaves must be <= 0 and <= kMaxOctaves

    SkPerlinNoiseShaderImpl(SkPerlinNoiseShaderImpl::Type type, SkScalar baseFrequencyX,
                      SkScalar baseFrequencyY, int numOctaves, SkScalar seed,
                      const SkISize* tileSize);

    class PerlinNoiseShaderContext : public Context {
    public:
        PerlinNoiseShaderContext(const SkPerlinNoiseShaderImpl& shader, const ContextRec&);

        void shadeSpan(int x, int y, SkPMColor[], int count) override;

    private:
        SkPMColor shade(const SkPoint& point, StitchData& stitchData) const;
        SkScalar calculateTurbulenceValueForPoint(
                                                  int channel,
                                                  StitchData& stitchData, const SkPoint& point) const;
        SkScalar calculateImprovedNoiseValueForPoint(int channel, const SkPoint& point) const;
        SkScalar noise2D(int channel,
                         const StitchData& stitchData, const SkPoint& noiseVector) const;

        SkMatrix     fMatrix;
        PaintingData fPaintingData;

        typedef Context INHERITED;
    };

#if SK_SUPPORT_GPU
    std::unique_ptr<GrFragmentProcessor> asFragmentProcessor(const GrFPArgs&) const override;
#endif

protected:
    void flatten(SkWriteBuffer&) const override;
#ifdef SK_ENABLE_LEGACY_SHADERCONTEXT
    Context* onMakeContext(const ContextRec&, SkArenaAlloc*) const override;
#endif

private:
    SK_FLATTENABLE_HOOKS(SkPerlinNoiseShaderImpl)

    const SkPerlinNoiseShaderImpl::Type fType;
    const SkScalar                  fBaseFrequencyX;
    const SkScalar                  fBaseFrequencyY;
    const int                       fNumOctaves;
    const SkScalar                  fSeed;
    const SkISize                   fTileSize;
    const bool                      fStitchTiles;

    friend class ::SkPerlinNoiseShader;

    typedef SkShaderBase INHERITED;
};

namespace {

// noiseValue is the color component's value (or color)
// limitValue is the maximum perlin noise array index value allowed
// newValue is the current noise dimension (either width or height)
inline int checkNoise(int noiseValue, int limitValue, int newValue) {
    // If the noise value would bring us out of bounds of the current noise array while we are
    // stiching noise tiles together, wrap the noise around the current dimension of the noise to
    // stay within the array bounds in a continuous fashion (so that tiling lines are not visible)
    if (noiseValue >= limitValue) {
        noiseValue -= newValue;
    }
    return noiseValue;
}

inline SkScalar smoothCurve(SkScalar t) {
    return t * t * (3 - 2 * t);
}

} // end namespace

SkPerlinNoiseShaderImpl::SkPerlinNoiseShaderImpl(SkPerlinNoiseShaderImpl::Type type,
                                                 SkScalar baseFrequencyX,
                                                 SkScalar baseFrequencyY,
                                                 int numOctaves,
                                                 SkScalar seed,
                                                 const SkISize* tileSize)
  : fType(type)
  , fBaseFrequencyX(baseFrequencyX)
  , fBaseFrequencyY(baseFrequencyY)
  , fNumOctaves(numOctaves > kMaxOctaves ? kMaxOctaves : numOctaves/*[0,255] octaves allowed*/)
  , fSeed(seed)
  , fTileSize(nullptr == tileSize ? SkISize::Make(0, 0) : *tileSize)
  , fStitchTiles(!fTileSize.isEmpty())
{
    SkASSERT(numOctaves >= 0 && numOctaves <= kMaxOctaves);
    SkASSERT(fBaseFrequencyX >= 0);
    SkASSERT(fBaseFrequencyY >= 0);
}

sk_sp<SkFlattenable> SkPerlinNoiseShaderImpl::CreateProc(SkReadBuffer& buffer) {
    Type type = buffer.read32LE(kLast_Type);

    SkScalar freqX = buffer.readScalar();
    SkScalar freqY = buffer.readScalar();
    int octaves = buffer.read32LE<int>(kMaxOctaves);

    SkScalar seed = buffer.readScalar();
    SkISize tileSize;
    tileSize.fWidth = buffer.readInt();
    tileSize.fHeight = buffer.readInt();

    switch (type) {
        case kFractalNoise_Type:
            return SkPerlinNoiseShader::MakeFractalNoise(freqX, freqY, octaves, seed, &tileSize);
        case kTurbulence_Type:
            return SkPerlinNoiseShader::MakeTurbulence(freqX, freqY, octaves, seed, &tileSize);
        case kImprovedNoise_Type:
            return SkPerlinNoiseShader::MakeImprovedNoise(freqX, freqY, octaves, seed);
        default:
            // Really shouldn't get here b.c. of earlier check on type
            buffer.validate(false);
            return nullptr;
    }
}

void SkPerlinNoiseShaderImpl::flatten(SkWriteBuffer& buffer) const {
    buffer.writeInt((int) fType);
    buffer.writeScalar(fBaseFrequencyX);
    buffer.writeScalar(fBaseFrequencyY);
    buffer.writeInt(fNumOctaves);
    buffer.writeScalar(fSeed);
    buffer.writeInt(fTileSize.fWidth);
    buffer.writeInt(fTileSize.fHeight);
}

SkScalar SkPerlinNoiseShaderImpl::PerlinNoiseShaderContext::noise2D(
        int channel, const StitchData& stitchData, const SkPoint& noiseVector) const {
    struct Noise {
        int noisePositionIntegerValue;
        int nextNoisePositionIntegerValue;
        SkScalar noisePositionFractionValue;
        Noise(SkScalar component)
        {
            SkScalar position = component + kPerlinNoise;
            noisePositionIntegerValue = SkScalarFloorToInt(position);
            noisePositionFractionValue = position - SkIntToScalar(noisePositionIntegerValue);
            nextNoisePositionIntegerValue = noisePositionIntegerValue + 1;
        }
    };
    Noise noiseX(noiseVector.x());
    Noise noiseY(noiseVector.y());
    SkScalar u, v;
    const SkPerlinNoiseShaderImpl& perlinNoiseShader = static_cast<const SkPerlinNoiseShaderImpl&>(fShader);
    // If stitching, adjust lattice points accordingly.
    if (perlinNoiseShader.fStitchTiles) {
        noiseX.noisePositionIntegerValue =
            checkNoise(noiseX.noisePositionIntegerValue, stitchData.fWrapX, stitchData.fWidth);
        noiseY.noisePositionIntegerValue =
            checkNoise(noiseY.noisePositionIntegerValue, stitchData.fWrapY, stitchData.fHeight);
        noiseX.nextNoisePositionIntegerValue =
            checkNoise(noiseX.nextNoisePositionIntegerValue, stitchData.fWrapX, stitchData.fWidth);
        noiseY.nextNoisePositionIntegerValue =
            checkNoise(noiseY.nextNoisePositionIntegerValue, stitchData.fWrapY, stitchData.fHeight);
    }
    noiseX.noisePositionIntegerValue &= kBlockMask;
    noiseY.noisePositionIntegerValue &= kBlockMask;
    noiseX.nextNoisePositionIntegerValue &= kBlockMask;
    noiseY.nextNoisePositionIntegerValue &= kBlockMask;
    int i = fPaintingData.fLatticeSelector[noiseX.noisePositionIntegerValue];
    int j = fPaintingData.fLatticeSelector[noiseX.nextNoisePositionIntegerValue];
    int b00 = (i + noiseY.noisePositionIntegerValue) & kBlockMask;
    int b10 = (j + noiseY.noisePositionIntegerValue) & kBlockMask;
    int b01 = (i + noiseY.nextNoisePositionIntegerValue) & kBlockMask;
    int b11 = (j + noiseY.nextNoisePositionIntegerValue) & kBlockMask;
    SkScalar sx = smoothCurve(noiseX.noisePositionFractionValue);
    SkScalar sy = smoothCurve(noiseY.noisePositionFractionValue);

    if (sx < 0 || sy < 0 || sx > 1 || sy > 1) {
        return 0;  // Check for pathological inputs.
    }

    // This is taken 1:1 from SVG spec: http://www.w3.org/TR/SVG11/filters.html#feTurbulenceElement
    SkPoint fractionValue = SkPoint::Make(noiseX.noisePositionFractionValue,
                                          noiseY.noisePositionFractionValue); // Offset (0,0)
    u = fPaintingData.fGradient[channel][b00].dot(fractionValue);
    fractionValue.fX -= SK_Scalar1; // Offset (-1,0)
    v = fPaintingData.fGradient[channel][b10].dot(fractionValue);
    SkScalar a = SkScalarInterp(u, v, sx);
    fractionValue.fY -= SK_Scalar1; // Offset (-1,-1)
    v = fPaintingData.fGradient[channel][b11].dot(fractionValue);
    fractionValue.fX = noiseX.noisePositionFractionValue; // Offset (0,-1)
    u = fPaintingData.fGradient[channel][b01].dot(fractionValue);
    SkScalar b = SkScalarInterp(u, v, sx);
    return SkScalarInterp(a, b, sy);
}

SkScalar SkPerlinNoiseShaderImpl::PerlinNoiseShaderContext::calculateTurbulenceValueForPoint(
        int channel, StitchData& stitchData, const SkPoint& point) const {
    const SkPerlinNoiseShaderImpl& perlinNoiseShader = static_cast<const SkPerlinNoiseShaderImpl&>(fShader);
    if (perlinNoiseShader.fStitchTiles) {
        // Set up TurbulenceInitial stitch values.
        stitchData = fPaintingData.fStitchDataInit;
    }
    SkScalar turbulenceFunctionResult = 0;
    SkPoint noiseVector(SkPoint::Make(point.x() * fPaintingData.fBaseFrequency.fX,
                                      point.y() * fPaintingData.fBaseFrequency.fY));
    SkScalar ratio = SK_Scalar1;
    for (int octave = 0; octave < perlinNoiseShader.fNumOctaves; ++octave) {
        SkScalar noise = noise2D(channel, stitchData, noiseVector);
        SkScalar numer = (perlinNoiseShader.fType == kFractalNoise_Type) ?
                            noise : SkScalarAbs(noise);
        turbulenceFunctionResult += numer / ratio;
        noiseVector.fX *= 2;
        noiseVector.fY *= 2;
        ratio *= 2;
        if (perlinNoiseShader.fStitchTiles) {
            // Update stitch values
            stitchData = StitchData(SkIntToScalar(stitchData.fWidth)  * 2,
                                    SkIntToScalar(stitchData.fHeight) * 2);
        }
    }

    // The value of turbulenceFunctionResult comes from ((turbulenceFunctionResult) + 1) / 2
    // by fractalNoise and (turbulenceFunctionResult) by turbulence.
    if (perlinNoiseShader.fType == kFractalNoise_Type) {
        turbulenceFunctionResult = SkScalarHalf(turbulenceFunctionResult + 1);
    }

    if (channel == 3) { // Scale alpha by paint value
        turbulenceFunctionResult *= SkIntToScalar(getPaintAlpha()) / 255;
    }

    // Clamp result
    return SkScalarPin(turbulenceFunctionResult, 0, SK_Scalar1);
}

////////////////////////////////////////////////////////////////////////////////////////////////////
// Improved Perlin Noise based on Java implementation found at http://mrl.nyu.edu/~perlin/noise/
static SkScalar fade(SkScalar t) {
    return t * t * t * (t * (t * 6 - 15) + 10);
}

static SkScalar lerp(SkScalar t, SkScalar a, SkScalar b) {
    return a + t * (b - a);
}

static SkScalar grad(int hash, SkScalar x, SkScalar y, SkScalar z) {
    int h = hash & 15;
    SkScalar u = h < 8 ? x : y;
    SkScalar v = h < 4 ? y : h == 12 || h == 14 ? x : z;
    return ((h & 1) == 0 ? u : -u) + ((h & 2) == 0 ? v : -v);
}

SkScalar SkPerlinNoiseShaderImpl::PerlinNoiseShaderContext::calculateImprovedNoiseValueForPoint(
        int channel, const SkPoint& point) const {
    const SkPerlinNoiseShaderImpl& perlinNoiseShader = static_cast<const SkPerlinNoiseShaderImpl&>(fShader);
    SkScalar x = point.fX * perlinNoiseShader.fBaseFrequencyX;
    SkScalar y = point.fY * perlinNoiseShader.fBaseFrequencyY;
    // z offset between different channels, chosen arbitrarily
    static const SkScalar CHANNEL_DELTA = 1000.0f;
    SkScalar z = channel * CHANNEL_DELTA + perlinNoiseShader.fSeed;
    SkScalar result = 0;
    SkScalar ratio = SK_Scalar1;
    for (int i = 0; i < perlinNoiseShader.fNumOctaves; i++) {
        int X = SkScalarFloorToInt(x) & 255;
        int Y = SkScalarFloorToInt(y) & 255;
        int Z = SkScalarFloorToInt(z) & 255;
        SkScalar px = x - SkScalarFloorToScalar(x);
        SkScalar py = y - SkScalarFloorToScalar(y);
        SkScalar pz = z - SkScalarFloorToScalar(z);
        SkScalar u = fade(px);
        SkScalar v = fade(py);
        SkScalar w = fade(pz);
        uint8_t* permutations = improved_noise_permutations;
        int A  = permutations[X] + Y;
        int AA = permutations[A] + Z;
        int AB = permutations[A + 1] + Z;
        int B  = permutations[X + 1] + Y;
        int BA = permutations[B] + Z;
        int BB = permutations[B + 1] + Z;
        result += lerp(w, lerp(v, lerp(u, grad(permutations[AA    ], px    , py    , pz    ),
                                          grad(permutations[BA    ], px - 1, py    , pz    )),
                                  lerp(u, grad(permutations[AB    ], px    , py - 1, pz    ),
                                          grad(permutations[BB    ], px - 1, py - 1, pz    ))),
                          lerp(v, lerp(u, grad(permutations[AA + 1], px    , py    , pz - 1),
                                          grad(permutations[BA + 1], px - 1, py    , pz - 1)),
                                  lerp(u, grad(permutations[AB + 1], px    , py - 1, pz - 1),
                                          grad(permutations[BB + 1], px - 1, py - 1, pz - 1)))) /
                   ratio;
        x *= 2;
        y *= 2;
        ratio *= 2;
    }
    result = SkScalarClampMax((result + 1.0f) / 2.0f, 1.0f);
    return result;
}
////////////////////////////////////////////////////////////////////////////////////////////////////

SkPMColor SkPerlinNoiseShaderImpl::PerlinNoiseShaderContext::shade(
        const SkPoint& point, StitchData& stitchData) const {
    const SkPerlinNoiseShaderImpl& perlinNoiseShader = static_cast<const SkPerlinNoiseShaderImpl&>(fShader);
    SkPoint newPoint;
    fMatrix.mapPoints(&newPoint, &point, 1);
    newPoint.fX = SkScalarRoundToScalar(newPoint.fX);
    newPoint.fY = SkScalarRoundToScalar(newPoint.fY);

    U8CPU rgba[4];
    for (int channel = 3; channel >= 0; --channel) {
        SkScalar value;
        if (perlinNoiseShader.fType == kImprovedNoise_Type) {
            value = calculateImprovedNoiseValueForPoint(channel, newPoint);
        }
        else {
            value = calculateTurbulenceValueForPoint(channel, stitchData, newPoint);
        }
        rgba[channel] = SkScalarFloorToInt(255 * value);
    }
    return SkPreMultiplyARGB(rgba[3], rgba[0], rgba[1], rgba[2]);
}

#ifdef SK_ENABLE_LEGACY_SHADERCONTEXT
SkShaderBase::Context* SkPerlinNoiseShaderImpl::onMakeContext(const ContextRec& rec,
                                                              SkArenaAlloc* alloc) const {
    // should we pay attention to rec's device-colorspace?
    return alloc->make<PerlinNoiseShaderContext>(*this, rec);
}
#endif

static inline SkMatrix total_matrix(const SkShaderBase::ContextRec& rec,
                                    const SkShaderBase& shader) {
    SkMatrix matrix = SkMatrix::Concat(*rec.fMatrix, shader.getLocalMatrix());
    if (rec.fLocalMatrix) {
        matrix.preConcat(*rec.fLocalMatrix);
    }

    return matrix;
}

SkPerlinNoiseShaderImpl::PerlinNoiseShaderContext::PerlinNoiseShaderContext(
        const SkPerlinNoiseShaderImpl& shader, const ContextRec& rec)
    : INHERITED(shader, rec)
    , fMatrix(total_matrix(rec, shader)) // used for temp storage, adjusted below
    , fPaintingData(shader.fTileSize, shader.fSeed, shader.fBaseFrequencyX,
                    shader.fBaseFrequencyY, fMatrix)
{
    // This (1,1) translation is due to WebKit's 1 based coordinates for the noise
    // (as opposed to 0 based, usually). The same adjustment is in the setData() function.
    fMatrix.setTranslate(-fMatrix.getTranslateX() + SK_Scalar1,
                         -fMatrix.getTranslateY() + SK_Scalar1);
}

void SkPerlinNoiseShaderImpl::PerlinNoiseShaderContext::shadeSpan(
        int x, int y, SkPMColor result[], int count) {
    SkPoint point = SkPoint::Make(SkIntToScalar(x), SkIntToScalar(y));
    StitchData stitchData;
    for (int i = 0; i < count; ++i) {
        result[i] = shade(point, stitchData);
        point.fX += SK_Scalar1;
    }
}

/////////////////////////////////////////////////////////////////////

#if SK_SUPPORT_GPU

class GrGLPerlinNoise : public GrGLSLFragmentProcessor {
public:
    void emitCode(EmitArgs&) override;

    static inline void GenKey(const GrProcessor&, const GrShaderCaps&, GrProcessorKeyBuilder* b);

protected:
    void onSetData(const GrGLSLProgramDataManager&, const GrFragmentProcessor&) override;

private:
    GrGLSLProgramDataManager::UniformHandle fStitchDataUni;
    GrGLSLProgramDataManager::UniformHandle fBaseFrequencyUni;

    typedef GrGLSLFragmentProcessor INHERITED;
};

/////////////////////////////////////////////////////////////////////

class GrPerlinNoise2Effect : public GrFragmentProcessor {
public:
    static std::unique_ptr<GrFragmentProcessor> Make(
            SkPerlinNoiseShaderImpl::Type type, int numOctaves, bool stitchTiles,
            std::unique_ptr<SkPerlinNoiseShaderImpl::PaintingData> paintingData,
            sk_sp<GrTextureProxy> permutationsProxy, sk_sp<GrTextureProxy> noiseProxy,
            const SkMatrix& matrix) {
        return std::unique_ptr<GrFragmentProcessor>(new GrPerlinNoise2Effect(
                type, numOctaves, stitchTiles, std::move(paintingData),
                std::move(permutationsProxy), std::move(noiseProxy), matrix));
    }

    const char* name() const override { return "PerlinNoise"; }

    std::unique_ptr<GrFragmentProcessor> clone() const override {
        return std::unique_ptr<GrFragmentProcessor>(new GrPerlinNoise2Effect(*this));
    }

    const SkPerlinNoiseShaderImpl::StitchData& stitchData() const { return fPaintingData->fStitchDataInit; }

    SkPerlinNoiseShaderImpl::Type type() const { return fType; }
    bool stitchTiles() const { return fStitchTiles; }
    const SkVector& baseFrequency() const { return fPaintingData->fBaseFrequency; }
    int numOctaves() const { return fNumOctaves; }
    const SkMatrix& matrix() const { return fCoordTransform.matrix(); }

private:
    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override {
        return new GrGLPerlinNoise;
    }

    virtual void onGetGLSLProcessorKey(const GrShaderCaps& caps,
                                       GrProcessorKeyBuilder* b) const override {
        GrGLPerlinNoise::GenKey(*this, caps, b);
    }

    bool onIsEqual(const GrFragmentProcessor& sBase) const override {
        const GrPerlinNoise2Effect& s = sBase.cast<GrPerlinNoise2Effect>();
        return fType == s.fType &&
               fPaintingData->fBaseFrequency == s.fPaintingData->fBaseFrequency &&
               fNumOctaves == s.fNumOctaves &&
               fStitchTiles == s.fStitchTiles &&
               fPaintingData->fStitchDataInit == s.fPaintingData->fStitchDataInit;
    }

    GrPerlinNoise2Effect(SkPerlinNoiseShaderImpl::Type type, int numOctaves, bool stitchTiles,
                         std::unique_ptr<SkPerlinNoiseShaderImpl::PaintingData> paintingData,
                         sk_sp<GrTextureProxy> permutationsProxy,
                         sk_sp<GrTextureProxy> noiseProxy,
                         const SkMatrix& matrix)
            : INHERITED(kGrPerlinNoise2Effect_ClassID, kNone_OptimizationFlags)
            , fType(type)
            , fNumOctaves(numOctaves)
            , fStitchTiles(stitchTiles)
            , fPermutationsSampler(std::move(permutationsProxy))
            , fNoiseSampler(std::move(noiseProxy))
            , fPaintingData(std::move(paintingData)) {
        this->setTextureSamplerCnt(2);
        fCoordTransform = GrCoordTransform(matrix);
        this->addCoordTransform(&fCoordTransform);
    }

    GrPerlinNoise2Effect(const GrPerlinNoise2Effect& that)
            : INHERITED(kGrPerlinNoise2Effect_ClassID, kNone_OptimizationFlags)
            , fType(that.fType)
            , fCoordTransform(that.fCoordTransform)
            , fNumOctaves(that.fNumOctaves)
            , fStitchTiles(that.fStitchTiles)
            , fPermutationsSampler(that.fPermutationsSampler)
            , fNoiseSampler(that.fNoiseSampler)
            , fPaintingData(new SkPerlinNoiseShaderImpl::PaintingData(*that.fPaintingData)) {
        this->setTextureSamplerCnt(2);
        this->addCoordTransform(&fCoordTransform);
    }

    const TextureSampler& onTextureSampler(int i) const override {
        return IthTextureSampler(i, fPermutationsSampler, fNoiseSampler);
    }

    GR_DECLARE_FRAGMENT_PROCESSOR_TEST

    SkPerlinNoiseShaderImpl::Type       fType;
    GrCoordTransform                    fCoordTransform;
    int                                 fNumOctaves;
    bool                                fStitchTiles;
    TextureSampler                      fPermutationsSampler;
    TextureSampler                      fNoiseSampler;
    std::unique_ptr<SkPerlinNoiseShaderImpl::PaintingData> fPaintingData;

    typedef GrFragmentProcessor INHERITED;
};

/////////////////////////////////////////////////////////////////////
GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrPerlinNoise2Effect);

#if GR_TEST_UTILS
std::unique_ptr<GrFragmentProcessor> GrPerlinNoise2Effect::TestCreate(GrProcessorTestData* d) {
    int      numOctaves = d->fRandom->nextRangeU(2, 10);
    bool     stitchTiles = d->fRandom->nextBool();
    SkScalar seed = SkIntToScalar(d->fRandom->nextU());
    SkISize  tileSize = SkISize::Make(d->fRandom->nextRangeU(4, 4096),
                                      d->fRandom->nextRangeU(4, 4096));
    SkScalar baseFrequencyX = d->fRandom->nextRangeScalar(0.01f,
                                                          0.99f);
    SkScalar baseFrequencyY = d->fRandom->nextRangeScalar(0.01f,
                                                          0.99f);

    sk_sp<SkShader> shader(d->fRandom->nextBool() ?
        SkPerlinNoiseShader::MakeFractalNoise(baseFrequencyX, baseFrequencyY, numOctaves, seed,
                                               stitchTiles ? &tileSize : nullptr) :
        SkPerlinNoiseShader::MakeTurbulence(baseFrequencyX, baseFrequencyY, numOctaves, seed,
                                             stitchTiles ? &tileSize : nullptr));

    GrTest::TestAsFPArgs asFPArgs(d);
    return as_SB(shader)->asFragmentProcessor(asFPArgs.args());
}
#endif

void GrGLPerlinNoise::emitCode(EmitArgs& args) {
    const GrPerlinNoise2Effect& pne = args.fFp.cast<GrPerlinNoise2Effect>();

    GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
    GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
    SkString vCoords = fragBuilder->ensureCoords2D(args.fTransformedCoords[0].fVaryingPoint);

    fBaseFrequencyUni = uniformHandler->addUniform(kFragment_GrShaderFlag, kHalf2_GrSLType,
                                                   "baseFrequency");
    const char* baseFrequencyUni = uniformHandler->getUniformCStr(fBaseFrequencyUni);

    const char* stitchDataUni = nullptr;
    if (pne.stitchTiles()) {
        fStitchDataUni = uniformHandler->addUniform(kFragment_GrShaderFlag, kHalf2_GrSLType,
                                                    "stitchData");
        stitchDataUni = uniformHandler->getUniformCStr(fStitchDataUni);
    }

    // There are 4 lines, so the center of each line is 1/8, 3/8, 5/8 and 7/8
    const char* chanCoordR  = "0.125";
    const char* chanCoordG  = "0.375";
    const char* chanCoordB  = "0.625";
    const char* chanCoordA  = "0.875";
    const char* chanCoord   = "chanCoord";
    const char* stitchData  = "stitchData";
    const char* ratio       = "ratio";
    const char* noiseVec    = "noiseVec";
    const char* noiseSmooth = "noiseSmooth";
    const char* floorVal    = "floorVal";
    const char* fractVal    = "fractVal";
    const char* uv          = "uv";
    const char* ab          = "ab";
    const char* latticeIdx  = "latticeIdx";
    const char* bcoords     = "bcoords";
    const char* lattice     = "lattice";
    const char* inc8bit     = "0.00390625";  // 1.0 / 256.0
    // This is the math to convert the two 16bit integer packed into rgba 8 bit input into a
    // [-1,1] vector and perform a dot product between that vector and the provided vector.
    const char* dotLattice  = "dot(((%s.ga + %s.rb * half2(%s)) * half2(2.0) - half2(1.0)), %s);";

    // Add noise function
    const GrShaderVar gPerlinNoiseArgs[] =  {
        GrShaderVar(chanCoord, kHalf_GrSLType),
        GrShaderVar(noiseVec, kHalf2_GrSLType)
    };

    const GrShaderVar gPerlinNoiseStitchArgs[] =  {
        GrShaderVar(chanCoord, kHalf_GrSLType),
        GrShaderVar(noiseVec, kHalf2_GrSLType),
        GrShaderVar(stitchData, kHalf2_GrSLType)
    };

    SkString noiseCode;

    noiseCode.appendf("\thalf4 %s;\n", floorVal);
    noiseCode.appendf("\t%s.xy = floor(%s);\n", floorVal, noiseVec);
    noiseCode.appendf("\t%s.zw = %s.xy + half2(1.0);\n", floorVal, floorVal);
    noiseCode.appendf("\thalf2 %s = fract(%s);\n", fractVal, noiseVec);

    // smooth curve : t * t * (3 - 2 * t)
    noiseCode.appendf("\n\thalf2 %s = %s * %s * (half2(3.0) - half2(2.0) * %s);",
        noiseSmooth, fractVal, fractVal, fractVal);

    // Adjust frequencies if we're stitching tiles
    if (pne.stitchTiles()) {
        noiseCode.appendf("\n\tif(%s.x >= %s.x) { %s.x -= %s.x; }",
            floorVal, stitchData, floorVal, stitchData);
        noiseCode.appendf("\n\tif(%s.y >= %s.y) { %s.y -= %s.y; }",
            floorVal, stitchData, floorVal, stitchData);
        noiseCode.appendf("\n\tif(%s.z >= %s.x) { %s.z -= %s.x; }",
            floorVal, stitchData, floorVal, stitchData);
        noiseCode.appendf("\n\tif(%s.w >= %s.y) { %s.w -= %s.y; }",
            floorVal, stitchData, floorVal, stitchData);
    }

    // Get texture coordinates and normalize
    noiseCode.appendf("\n\t%s = fract(floor(mod(%s, 256.0)) / half4(256.0));\n",
        floorVal, floorVal);

    // Get permutation for x
    {
        SkString xCoords("");
        xCoords.appendf("half2(%s.x, 0.5)", floorVal);

        noiseCode.appendf("\n\thalf2 %s;\n\t%s.x = ", latticeIdx, latticeIdx);
        fragBuilder->appendTextureLookup(&noiseCode, args.fTexSamplers[0], xCoords.c_str(),
                                         kHalf2_GrSLType);
        noiseCode.append(".r;");
    }

    // Get permutation for x + 1
    {
        SkString xCoords("");
        xCoords.appendf("half2(%s.z, 0.5)", floorVal);

        noiseCode.appendf("\n\t%s.y = ", latticeIdx);
        fragBuilder->appendTextureLookup(&noiseCode, args.fTexSamplers[0], xCoords.c_str(),
                                         kHalf2_GrSLType);
        noiseCode.append(".r;");
    }

#if defined(SK_BUILD_FOR_ANDROID)
    // Android rounding for Tegra devices, like, for example: Xoom (Tegra 2), Nexus 7 (Tegra 3).
    // The issue is that colors aren't accurate enough on Tegra devices. For example, if an 8 bit
    // value of 124 (or 0.486275 here) is entered, we can get a texture value of 123.513725
    // (or 0.484368 here). The following rounding operation prevents these precision issues from
    // affecting the result of the noise by making sure that we only have multiples of 1/255.
    // (Note that 1/255 is about 0.003921569, which is the value used here).
    noiseCode.appendf("\n\t%s = floor(%s * half2(255.0) + half2(0.5)) * half2(0.003921569);",
                      latticeIdx, latticeIdx);
#endif

    // Get (x,y) coordinates with the permutated x
    noiseCode.appendf("\n\thalf4 %s = fract(%s.xyxy + %s.yyww);", bcoords, latticeIdx, floorVal);

    noiseCode.appendf("\n\n\thalf2 %s;", uv);
    // Compute u, at offset (0,0)
    {
        SkString latticeCoords("");
        latticeCoords.appendf("half2(%s.x, %s)", bcoords, chanCoord);
        noiseCode.appendf("\n\thalf4 %s = ", lattice);
        fragBuilder->appendTextureLookup(&noiseCode, args.fTexSamplers[1], latticeCoords.c_str(),
                                         kHalf2_GrSLType);
        noiseCode.appendf(".bgra;\n\t%s.x = ", uv);
        noiseCode.appendf(dotLattice, lattice, lattice, inc8bit, fractVal);
    }

    noiseCode.appendf("\n\t%s.x -= 1.0;", fractVal);
    // Compute v, at offset (-1,0)
    {
        SkString latticeCoords("");
        latticeCoords.appendf("half2(%s.y, %s)", bcoords, chanCoord);
        noiseCode.append("\n\tlattice = ");
        fragBuilder->appendTextureLookup(&noiseCode, args.fTexSamplers[1], latticeCoords.c_str(),
                                         kHalf2_GrSLType);
        noiseCode.appendf(".bgra;\n\t%s.y = ", uv);
        noiseCode.appendf(dotLattice, lattice, lattice, inc8bit, fractVal);
    }

    // Compute 'a' as a linear interpolation of 'u' and 'v'
    noiseCode.appendf("\n\thalf2 %s;", ab);
    noiseCode.appendf("\n\t%s.x = mix(%s.x, %s.y, %s.x);", ab, uv, uv, noiseSmooth);

    noiseCode.appendf("\n\t%s.y -= 1.0;", fractVal);
    // Compute v, at offset (-1,-1)
    {
        SkString latticeCoords("");
        latticeCoords.appendf("half2(%s.w, %s)", bcoords, chanCoord);
        noiseCode.append("\n\tlattice = ");
        fragBuilder->appendTextureLookup(&noiseCode, args.fTexSamplers[1], latticeCoords.c_str(),
                                         kHalf2_GrSLType);
        noiseCode.appendf(".bgra;\n\t%s.y = ", uv);
        noiseCode.appendf(dotLattice, lattice, lattice, inc8bit, fractVal);
    }

    noiseCode.appendf("\n\t%s.x += 1.0;", fractVal);
    // Compute u, at offset (0,-1)
    {
        SkString latticeCoords("");
        latticeCoords.appendf("half2(%s.z, %s)", bcoords, chanCoord);
        noiseCode.append("\n\tlattice = ");
        fragBuilder->appendTextureLookup(&noiseCode, args.fTexSamplers[1], latticeCoords.c_str(),
                                         kHalf2_GrSLType);
        noiseCode.appendf(".bgra;\n\t%s.x = ", uv);
        noiseCode.appendf(dotLattice, lattice, lattice, inc8bit, fractVal);
    }

    // Compute 'b' as a linear interpolation of 'u' and 'v'
    noiseCode.appendf("\n\t%s.y = mix(%s.x, %s.y, %s.x);", ab, uv, uv, noiseSmooth);
    // Compute the noise as a linear interpolation of 'a' and 'b'
    noiseCode.appendf("\n\treturn mix(%s.x, %s.y, %s.y);\n", ab, ab, noiseSmooth);

    SkString noiseFuncName;
    if (pne.stitchTiles()) {
        fragBuilder->emitFunction(kHalf_GrSLType,
                                  "perlinnoise", SK_ARRAY_COUNT(gPerlinNoiseStitchArgs),
                                  gPerlinNoiseStitchArgs, noiseCode.c_str(), &noiseFuncName);
    } else {
        fragBuilder->emitFunction(kHalf_GrSLType,
                                  "perlinnoise", SK_ARRAY_COUNT(gPerlinNoiseArgs),
                                  gPerlinNoiseArgs, noiseCode.c_str(), &noiseFuncName);
    }

    // There are rounding errors if the floor operation is not performed here
    fragBuilder->codeAppendf("\n\t\thalf2 %s = half2(floor(%s.xy) * %s);",
                             noiseVec, vCoords.c_str(), baseFrequencyUni);

    // Clear the color accumulator
    fragBuilder->codeAppendf("\n\t\t%s = half4(0.0);", args.fOutputColor);

    if (pne.stitchTiles()) {
        // Set up TurbulenceInitial stitch values.
        fragBuilder->codeAppendf("\n\t\thalf2 %s = %s;", stitchData, stitchDataUni);
    }

    fragBuilder->codeAppendf("\n\t\thalf %s = 1.0;", ratio);

    // Loop over all octaves
    fragBuilder->codeAppendf("for (int octave = 0; octave < %d; ++octave) {", pne.numOctaves());

    fragBuilder->codeAppendf("\n\t\t\t%s += ", args.fOutputColor);
    if (pne.type() != SkPerlinNoiseShaderImpl::kFractalNoise_Type) {
        fragBuilder->codeAppend("abs(");
    }
    if (pne.stitchTiles()) {
        fragBuilder->codeAppendf(
            "half4(\n\t\t\t\t%s(%s, %s, %s),\n\t\t\t\t%s(%s, %s, %s),"
                 "\n\t\t\t\t%s(%s, %s, %s),\n\t\t\t\t%s(%s, %s, %s))",
            noiseFuncName.c_str(), chanCoordR, noiseVec, stitchData,
            noiseFuncName.c_str(), chanCoordG, noiseVec, stitchData,
            noiseFuncName.c_str(), chanCoordB, noiseVec, stitchData,
            noiseFuncName.c_str(), chanCoordA, noiseVec, stitchData);
    } else {
        fragBuilder->codeAppendf(
            "half4(\n\t\t\t\t%s(%s, %s),\n\t\t\t\t%s(%s, %s),"
                 "\n\t\t\t\t%s(%s, %s),\n\t\t\t\t%s(%s, %s))",
            noiseFuncName.c_str(), chanCoordR, noiseVec,
            noiseFuncName.c_str(), chanCoordG, noiseVec,
            noiseFuncName.c_str(), chanCoordB, noiseVec,
            noiseFuncName.c_str(), chanCoordA, noiseVec);
    }
    if (pne.type() != SkPerlinNoiseShaderImpl::kFractalNoise_Type) {
        fragBuilder->codeAppendf(")"); // end of "abs("
    }
    fragBuilder->codeAppendf(" * %s;", ratio);

    fragBuilder->codeAppendf("\n\t\t\t%s *= half2(2.0);", noiseVec);
    fragBuilder->codeAppendf("\n\t\t\t%s *= 0.5;", ratio);

    if (pne.stitchTiles()) {
        fragBuilder->codeAppendf("\n\t\t\t%s *= half2(2.0);", stitchData);
    }
    fragBuilder->codeAppend("\n\t\t}"); // end of the for loop on octaves

    if (pne.type() == SkPerlinNoiseShaderImpl::kFractalNoise_Type) {
        // The value of turbulenceFunctionResult comes from ((turbulenceFunctionResult) + 1) / 2
        // by fractalNoise and (turbulenceFunctionResult) by turbulence.
        fragBuilder->codeAppendf("\n\t\t%s = %s * half4(0.5) + half4(0.5);",
                               args.fOutputColor,args.fOutputColor);
    }

    // Clamp values
    fragBuilder->codeAppendf("\n\t\t%s = saturate(%s);", args.fOutputColor, args.fOutputColor);

    // Pre-multiply the result
    fragBuilder->codeAppendf("\n\t\t%s = half4(%s.rgb * %s.aaa, %s.a);\n",
                             args.fOutputColor, args.fOutputColor,
                             args.fOutputColor, args.fOutputColor);
}

void GrGLPerlinNoise::GenKey(const GrProcessor& processor, const GrShaderCaps&,
                             GrProcessorKeyBuilder* b) {
    const GrPerlinNoise2Effect& turbulence = processor.cast<GrPerlinNoise2Effect>();

    uint32_t key = turbulence.numOctaves();

    key = key << 3; // Make room for next 3 bits

    switch (turbulence.type()) {
        case SkPerlinNoiseShaderImpl::kFractalNoise_Type:
            key |= 0x1;
            break;
        case SkPerlinNoiseShaderImpl::kTurbulence_Type:
            key |= 0x2;
            break;
        default:
            // leave key at 0
            break;
    }

    if (turbulence.stitchTiles()) {
        key |= 0x4; // Flip the 3rd bit if tile stitching is on
    }

    b->add32(key);
}

void GrGLPerlinNoise::onSetData(const GrGLSLProgramDataManager& pdman,
                                const GrFragmentProcessor& processor) {
    INHERITED::onSetData(pdman, processor);

    const GrPerlinNoise2Effect& turbulence = processor.cast<GrPerlinNoise2Effect>();

    const SkVector& baseFrequency = turbulence.baseFrequency();
    pdman.set2f(fBaseFrequencyUni, baseFrequency.fX, baseFrequency.fY);

    if (turbulence.stitchTiles()) {
        const SkPerlinNoiseShaderImpl::StitchData& stitchData = turbulence.stitchData();
        pdman.set2f(fStitchDataUni, SkIntToScalar(stitchData.fWidth),
                                   SkIntToScalar(stitchData.fHeight));
    }
}

/////////////////////////////////////////////////////////////////////

class GrGLImprovedPerlinNoise : public GrGLSLFragmentProcessor {
public:
    void emitCode(EmitArgs&) override;

    static inline void GenKey(const GrProcessor&, const GrShaderCaps&, GrProcessorKeyBuilder*);

protected:
    void onSetData(const GrGLSLProgramDataManager&, const GrFragmentProcessor&) override;

private:
    GrGLSLProgramDataManager::UniformHandle fZUni;
    GrGLSLProgramDataManager::UniformHandle fBaseFrequencyUni;

    typedef GrGLSLFragmentProcessor INHERITED;
};

/////////////////////////////////////////////////////////////////////

class GrImprovedPerlinNoiseEffect : public GrFragmentProcessor {
public:
    static std::unique_ptr<GrFragmentProcessor> Make(
            int octaves, SkScalar z,
            std::unique_ptr<SkPerlinNoiseShaderImpl::PaintingData> paintingData,
            sk_sp<GrTextureProxy> permutationsProxy, sk_sp<GrTextureProxy> gradientProxy,
            const SkMatrix& matrix) {
        return std::unique_ptr<GrFragmentProcessor>(new GrImprovedPerlinNoiseEffect(
                octaves, z, std::move(paintingData), std::move(permutationsProxy),
                std::move(gradientProxy), matrix));
    }

    const char* name() const override { return "ImprovedPerlinNoise"; }

    std::unique_ptr<GrFragmentProcessor> clone() const override {
        return std::unique_ptr<GrFragmentProcessor>(new GrImprovedPerlinNoiseEffect(*this));
    }

    const SkVector& baseFrequency() const { return fPaintingData->fBaseFrequency; }
    SkScalar z() const { return fZ; }
    int octaves() const { return fOctaves; }
    const SkMatrix& matrix() const { return fCoordTransform.matrix(); }

private:
    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override {
        return new GrGLImprovedPerlinNoise;
    }

    void onGetGLSLProcessorKey(const GrShaderCaps& caps, GrProcessorKeyBuilder* b) const override {
        GrGLImprovedPerlinNoise::GenKey(*this, caps, b);
    }

    bool onIsEqual(const GrFragmentProcessor& sBase) const override {
        const GrImprovedPerlinNoiseEffect& s = sBase.cast<GrImprovedPerlinNoiseEffect>();
        return fZ == fZ &&
               fPaintingData->fBaseFrequency == s.fPaintingData->fBaseFrequency;
    }

    GrImprovedPerlinNoiseEffect(int octaves, SkScalar z,
                                std::unique_ptr<SkPerlinNoiseShaderImpl::PaintingData> paintingData,
                                sk_sp<GrTextureProxy> permutationsProxy,
                                sk_sp<GrTextureProxy> gradientProxy,
                                const SkMatrix& matrix)
            : INHERITED(kGrImprovedPerlinNoiseEffect_ClassID, kNone_OptimizationFlags)
            , fOctaves(octaves)
            , fZ(z)
            , fPermutationsSampler(std::move(permutationsProxy))
            , fGradientSampler(std::move(gradientProxy))
            , fPaintingData(std::move(paintingData)) {
        this->setTextureSamplerCnt(2);
        fCoordTransform = GrCoordTransform(matrix);
        this->addCoordTransform(&fCoordTransform);
    }

    GrImprovedPerlinNoiseEffect(const GrImprovedPerlinNoiseEffect& that)
            : INHERITED(kGrImprovedPerlinNoiseEffect_ClassID, kNone_OptimizationFlags)
            , fCoordTransform(that.fCoordTransform)
            , fOctaves(that.fOctaves)
            , fZ(that.fZ)
            , fPermutationsSampler(that.fPermutationsSampler)
            , fGradientSampler(that.fGradientSampler)
            , fPaintingData(new SkPerlinNoiseShaderImpl::PaintingData(*that.fPaintingData)) {
        this->setTextureSamplerCnt(2);
        this->addCoordTransform(&fCoordTransform);
    }

    const TextureSampler& onTextureSampler(int i) const override {
        return IthTextureSampler(i, fPermutationsSampler, fGradientSampler);
    }

    GR_DECLARE_FRAGMENT_PROCESSOR_TEST

    GrCoordTransform                    fCoordTransform;
    int                                 fOctaves;
    SkScalar                            fZ;
    TextureSampler                      fPermutationsSampler;
    TextureSampler                      fGradientSampler;
    std::unique_ptr<SkPerlinNoiseShaderImpl::PaintingData> fPaintingData;

    typedef GrFragmentProcessor INHERITED;
};

/////////////////////////////////////////////////////////////////////
GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrImprovedPerlinNoiseEffect);

#if GR_TEST_UTILS
std::unique_ptr<GrFragmentProcessor> GrImprovedPerlinNoiseEffect::TestCreate(
        GrProcessorTestData* d) {
    SkScalar baseFrequencyX = d->fRandom->nextRangeScalar(0.01f,
                                                          0.99f);
    SkScalar baseFrequencyY = d->fRandom->nextRangeScalar(0.01f,
                                                          0.99f);
    int numOctaves = d->fRandom->nextRangeU(2, 10);
    SkScalar z = SkIntToScalar(d->fRandom->nextU());

    sk_sp<SkShader> shader(SkPerlinNoiseShader::MakeImprovedNoise(baseFrequencyX,
                                                                   baseFrequencyY,
                                                                   numOctaves,
                                                                   z));

    GrTest::TestAsFPArgs asFPArgs(d);
    return as_SB(shader)->asFragmentProcessor(asFPArgs.args());
}
#endif

void GrGLImprovedPerlinNoise::emitCode(EmitArgs& args) {
    const GrImprovedPerlinNoiseEffect& pne = args.fFp.cast<GrImprovedPerlinNoiseEffect>();
    GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
    GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
    SkString vCoords = fragBuilder->ensureCoords2D(args.fTransformedCoords[0].fVaryingPoint);

    fBaseFrequencyUni = uniformHandler->addUniform(kFragment_GrShaderFlag, kHalf2_GrSLType,
                                                   "baseFrequency");
    const char* baseFrequencyUni = uniformHandler->getUniformCStr(fBaseFrequencyUni);

    fZUni = uniformHandler->addUniform(kFragment_GrShaderFlag, kHalf_GrSLType, "z");
    const char* zUni = uniformHandler->getUniformCStr(fZUni);

    // fade function
    const GrShaderVar fadeArgs[] =  {
        GrShaderVar("t", kHalf3_GrSLType)
    };
    SkString fadeFuncName;
    fragBuilder->emitFunction(kHalf3_GrSLType, "fade", SK_ARRAY_COUNT(fadeArgs),
                              fadeArgs,
                              "return t * t * t * (t * (t * 6.0 - 15.0) + 10.0);",
                              &fadeFuncName);

    // perm function
    const GrShaderVar permArgs[] =  {
        GrShaderVar("x", kHalf_GrSLType)
    };
    SkString permFuncName;
    SkString permCode("return ");
    // FIXME even though I'm creating these textures with kRepeat_TileMode, they're clamped. Not
    // sure why. Using fract() (here and the next texture lookup) as a workaround.
    fragBuilder->appendTextureLookup(&permCode, args.fTexSamplers[0], "float2(fract(x / 256.0), 0.0)",
                                     kHalf2_GrSLType);
    permCode.append(".r * 255.0;");
    fragBuilder->emitFunction(kHalf_GrSLType, "perm", SK_ARRAY_COUNT(permArgs), permArgs,
                              permCode.c_str(), &permFuncName);

    // grad function
    const GrShaderVar gradArgs[] =  {
        GrShaderVar("x", kHalf_GrSLType),
        GrShaderVar("p", kHalf3_GrSLType)
    };
    SkString gradFuncName;
    SkString gradCode("return half(dot(");
    fragBuilder->appendTextureLookup(&gradCode, args.fTexSamplers[1], "float2(fract(x / 16.0), 0.0)",
                                     kHalf2_GrSLType);
    gradCode.append(".rgb * 255.0 - float3(1.0), p));");
    fragBuilder->emitFunction(kHalf_GrSLType, "grad", SK_ARRAY_COUNT(gradArgs), gradArgs,
                              gradCode.c_str(), &gradFuncName);

    // lerp function
    const GrShaderVar lerpArgs[] =  {
        GrShaderVar("a", kHalf_GrSLType),
        GrShaderVar("b", kHalf_GrSLType),
        GrShaderVar("w", kHalf_GrSLType)
    };
    SkString lerpFuncName;
    fragBuilder->emitFunction(kHalf_GrSLType, "lerp", SK_ARRAY_COUNT(lerpArgs), lerpArgs,
                              "return a + w * (b - a);", &lerpFuncName);

    // noise function
    const GrShaderVar noiseArgs[] =  {
        GrShaderVar("p", kHalf3_GrSLType),
    };
    SkString noiseFuncName;
    SkString noiseCode;
    noiseCode.append("half3 P = mod(floor(p), 256.0);");
    noiseCode.append("p -= floor(p);");
    noiseCode.appendf("half3 f = %s(p);", fadeFuncName.c_str());
    noiseCode.appendf("half A = %s(P.x) + P.y;", permFuncName.c_str());
    noiseCode.appendf("half AA = %s(A) + P.z;", permFuncName.c_str());
    noiseCode.appendf("half AB = %s(A + 1.0) + P.z;", permFuncName.c_str());
    noiseCode.appendf("half B =  %s(P.x + 1.0) + P.y;", permFuncName.c_str());
    noiseCode.appendf("half BA = %s(B) + P.z;", permFuncName.c_str());
    noiseCode.appendf("half BB = %s(B + 1.0) + P.z;", permFuncName.c_str());
    noiseCode.appendf("half result = %s(", lerpFuncName.c_str());
    noiseCode.appendf("%s(%s(%s(%s(AA), p),", lerpFuncName.c_str(), lerpFuncName.c_str(),
                      gradFuncName.c_str(), permFuncName.c_str());
    noiseCode.appendf("%s(%s(BA), p + half3(-1.0, 0.0, 0.0)), f.x),", gradFuncName.c_str(),
                      permFuncName.c_str());
    noiseCode.appendf("%s(%s(%s(AB), p + half3(0.0, -1.0, 0.0)),", lerpFuncName.c_str(),
                      gradFuncName.c_str(), permFuncName.c_str());
    noiseCode.appendf("%s(%s(BB), p + half3(-1.0, -1.0, 0.0)), f.x), f.y),",
                      gradFuncName.c_str(), permFuncName.c_str());
    noiseCode.appendf("%s(%s(%s(%s(AA + 1.0), p + half3(0.0, 0.0, -1.0)),",
                      lerpFuncName.c_str(), lerpFuncName.c_str(), gradFuncName.c_str(),
                      permFuncName.c_str());
    noiseCode.appendf("%s(%s(BA + 1.0), p + half3(-1.0, 0.0, -1.0)), f.x),",
                      gradFuncName.c_str(), permFuncName.c_str());
    noiseCode.appendf("%s(%s(%s(AB + 1.0), p + half3(0.0, -1.0, -1.0)),",
                      lerpFuncName.c_str(), gradFuncName.c_str(), permFuncName.c_str());
    noiseCode.appendf("%s(%s(BB + 1.0), p + half3(-1.0, -1.0, -1.0)), f.x), f.y), f.z);",
                      gradFuncName.c_str(), permFuncName.c_str());
    noiseCode.append("return result;");
    fragBuilder->emitFunction(kHalf_GrSLType, "noise", SK_ARRAY_COUNT(noiseArgs), noiseArgs,
                              noiseCode.c_str(), &noiseFuncName);

    // noiseOctaves function
    const GrShaderVar noiseOctavesArgs[] =  {
        GrShaderVar("p", kHalf3_GrSLType)
    };
    SkString noiseOctavesFuncName;
    SkString noiseOctavesCode;
    noiseOctavesCode.append("half result = 0.0;");
    noiseOctavesCode.append("half ratio = 1.0;");
    noiseOctavesCode.appendf("for (half i = 0.0; i < %d; i++) {", pne.octaves());
    noiseOctavesCode.appendf("result += %s(p) / ratio;", noiseFuncName.c_str());
    noiseOctavesCode.append("p *= 2.0;");
    noiseOctavesCode.append("ratio *= 2.0;");
    noiseOctavesCode.append("}");
    noiseOctavesCode.append("return (result + 1.0) / 2.0;");
    fragBuilder->emitFunction(kHalf_GrSLType, "noiseOctaves", SK_ARRAY_COUNT(noiseOctavesArgs),
                              noiseOctavesArgs, noiseOctavesCode.c_str(), &noiseOctavesFuncName);

    fragBuilder->codeAppendf("half2 coords = half2(%s * %s);", vCoords.c_str(), baseFrequencyUni);
    fragBuilder->codeAppendf("half r = %s(half3(coords, %s));", noiseOctavesFuncName.c_str(),
                             zUni);
    fragBuilder->codeAppendf("half g = %s(half3(coords, %s + 0000.0));",
                             noiseOctavesFuncName.c_str(), zUni);
    fragBuilder->codeAppendf("half b = %s(half3(coords, %s + 0000.0));",
                             noiseOctavesFuncName.c_str(), zUni);
    fragBuilder->codeAppendf("half a = %s(half3(coords, %s + 0000.0));",
                             noiseOctavesFuncName.c_str(), zUni);
    fragBuilder->codeAppendf("%s = half4(r, g, b, a);", args.fOutputColor);

    // Clamp values
    fragBuilder->codeAppendf("%s = saturate(%s);", args.fOutputColor, args.fOutputColor);

    // Pre-multiply the result
    fragBuilder->codeAppendf("\n\t\t%s = half4(%s.rgb * %s.aaa, %s.a);\n",
                             args.fOutputColor, args.fOutputColor,
                             args.fOutputColor, args.fOutputColor);
}

void GrGLImprovedPerlinNoise::GenKey(const GrProcessor& processor, const GrShaderCaps&,
                                     GrProcessorKeyBuilder* b) {
    const GrImprovedPerlinNoiseEffect& pne = processor.cast<GrImprovedPerlinNoiseEffect>();
    b->add32(pne.octaves());
}

void GrGLImprovedPerlinNoise::onSetData(const GrGLSLProgramDataManager& pdman,
                                        const GrFragmentProcessor& processor) {
    INHERITED::onSetData(pdman, processor);

    const GrImprovedPerlinNoiseEffect& noise = processor.cast<GrImprovedPerlinNoiseEffect>();

    const SkVector& baseFrequency = noise.baseFrequency();
    pdman.set2f(fBaseFrequencyUni, baseFrequency.fX, baseFrequency.fY);

    pdman.set1f(fZUni, noise.z());
}

/////////////////////////////////////////////////////////////////////
std::unique_ptr<GrFragmentProcessor> SkPerlinNoiseShaderImpl::asFragmentProcessor(
        const GrFPArgs& args) const {
    SkASSERT(args.fContext);

    const auto localMatrix = this->totalLocalMatrix(args.fPreLocalMatrix, args.fPostLocalMatrix);
    const auto paintMatrix = SkMatrix::Concat(*args.fViewMatrix, *localMatrix);

    // Either we don't stitch tiles, either we have a valid tile size
    SkASSERT(!fStitchTiles || !fTileSize.isEmpty());

    std::unique_ptr<SkPerlinNoiseShaderImpl::PaintingData> paintingData =
        skstd::make_unique<SkPerlinNoiseShaderImpl::PaintingData>(fTileSize,
                                                                  fSeed,
                                                                  fBaseFrequencyX,
                                                                  fBaseFrequencyY,
                                                                  paintMatrix);

    SkMatrix m = *args.fViewMatrix;
    m.setTranslateX(-localMatrix->getTranslateX() + SK_Scalar1);
    m.setTranslateY(-localMatrix->getTranslateY() + SK_Scalar1);

    auto proxyProvider = args.fContext->priv().proxyProvider();
    if (fType == kImprovedNoise_Type) {
        // Need to assert that the textures we'll create are power of 2 so a copy isn't needed.
        // We also know that we will not be using mipmaps. If things things weren't true we should
        // go through GrBitmapTextureMaker to handle needed copies.
        const sk_sp<SkImage> permutationsImage = paintingData->getImprovedPermutationsImage();
        SkASSERT(SkIsPow2(permutationsImage->width()) && SkIsPow2(permutationsImage->height()));
        sk_sp<GrTextureProxy> permutationsTexture(
                GrMakeCachedImageProxy(proxyProvider, std::move(permutationsImage)));

        const sk_sp<SkImage> gradientImage = paintingData->getGradientImage();
        SkASSERT(SkIsPow2(gradientImage->width()) && SkIsPow2(gradientImage->height()));
        sk_sp<GrTextureProxy> gradientTexture(
                GrMakeCachedImageProxy(proxyProvider, std::move(gradientImage)));
        return GrImprovedPerlinNoiseEffect::Make(fNumOctaves, fSeed, std::move(paintingData),
                                                 std::move(permutationsTexture),
                                                 std::move(gradientTexture), m);
    }

    if (0 == fNumOctaves) {
        if (kFractalNoise_Type == fType) {
            // Extract the incoming alpha and emit rgba = (a/4, a/4, a/4, a/2)
            // TODO: Either treat the output of this shader as sRGB or allow client to specify a
            // color space of the noise. Either way, this case (and the GLSL) need to convert to
            // the destination.
            auto inner =
                    GrConstColorProcessor::Make(SkPMColor4f::FromBytes_RGBA(0x80404040),
                                                GrConstColorProcessor::InputMode::kModulateRGBA);
            return GrFragmentProcessor::MulChildByInputAlpha(std::move(inner));
        }
        // Emit zero.
        return GrConstColorProcessor::Make(SK_PMColor4fTRANSPARENT,
                                           GrConstColorProcessor::InputMode::kIgnore);
    }

    // Need to assert that the textures we'll create are power of 2 so that now copy is needed. We
    // also know that we will not be using mipmaps. If things things weren't true we should go
    // through GrBitmapTextureMaker to handle needed copies.
    const sk_sp<SkImage> permutationsImage = paintingData->getPermutationsImage();
    SkASSERT(SkIsPow2(permutationsImage->width()) && SkIsPow2(permutationsImage->height()));
    sk_sp<GrTextureProxy> permutationsProxy = GrMakeCachedImageProxy(proxyProvider,
                                                                     std::move(permutationsImage));

    const sk_sp<SkImage> noiseImage = paintingData->getNoiseImage();
    SkASSERT(SkIsPow2(noiseImage->width()) && SkIsPow2(noiseImage->height()));
    sk_sp<GrTextureProxy> noiseProxy = GrMakeCachedImageProxy(proxyProvider,
                                                              std::move(noiseImage));

    if (permutationsProxy && noiseProxy) {
        auto inner = GrPerlinNoise2Effect::Make(fType,
                                                fNumOctaves,
                                                fStitchTiles,
                                                std::move(paintingData),
                                                std::move(permutationsProxy),
                                                std::move(noiseProxy),
                                                m);
        return GrFragmentProcessor::MulChildByInputAlpha(std::move(inner));
    }
    return nullptr;
}

#endif

///////////////////////////////////////////////////////////////////////////////////////////////////

static bool valid_input(SkScalar baseX, SkScalar baseY, int numOctaves, const SkISize* tileSize,
                        SkScalar seed) {
    if (!(baseX >= 0 && baseY >= 0)) {
        return false;
    }
    if (!(numOctaves >= 0 && numOctaves <= SkPerlinNoiseShaderImpl::kMaxOctaves)) {
        return false;
    }
    if (tileSize && !(tileSize->width() >= 0 && tileSize->height() >= 0)) {
        return false;
    }
    if (!SkScalarIsFinite(seed)) {
        return false;
    }
    return true;
}

sk_sp<SkShader> SkPerlinNoiseShader::MakeFractalNoise(SkScalar baseFrequencyX,
                                                      SkScalar baseFrequencyY,
                                                      int numOctaves, SkScalar seed,
                                                      const SkISize* tileSize) {
    if (!valid_input(baseFrequencyX, baseFrequencyY, numOctaves, tileSize, seed)) {
        return nullptr;
    }
    return sk_sp<SkShader>(new SkPerlinNoiseShaderImpl(SkPerlinNoiseShaderImpl::kFractalNoise_Type,
                                                 baseFrequencyX, baseFrequencyY, numOctaves, seed,
                                                 tileSize));
}

sk_sp<SkShader> SkPerlinNoiseShader::MakeTurbulence(SkScalar baseFrequencyX,
                                                    SkScalar baseFrequencyY,
                                                    int numOctaves, SkScalar seed,
                                                    const SkISize* tileSize) {
    if (!valid_input(baseFrequencyX, baseFrequencyY, numOctaves, tileSize, seed)) {
        return nullptr;
    }
    return sk_sp<SkShader>(new SkPerlinNoiseShaderImpl(SkPerlinNoiseShaderImpl::kTurbulence_Type,
                                                 baseFrequencyX, baseFrequencyY, numOctaves, seed,
                                                 tileSize));
}

sk_sp<SkShader> SkPerlinNoiseShader::MakeImprovedNoise(SkScalar baseFrequencyX,
                                                       SkScalar baseFrequencyY,
                                                       int numOctaves, SkScalar z) {
    if (!valid_input(baseFrequencyX, baseFrequencyY, numOctaves, nullptr, z)) {
        return nullptr;
    }
    return sk_sp<SkShader>(new SkPerlinNoiseShaderImpl(SkPerlinNoiseShaderImpl::kImprovedNoise_Type,
                                                 baseFrequencyX, baseFrequencyY, numOctaves, z,
                                                 nullptr));
}

void SkPerlinNoiseShader::RegisterFlattenables() {
    SK_REGISTER_FLATTENABLE(SkPerlinNoiseShaderImpl);
}