void GrGLAlphaThresholdFragmentProcessor::emitCode(EmitArgs& args) {
    GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
    fInnerThresholdVar = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                                    kFloat_GrSLType, kDefault_GrSLPrecision,
                                                    "inner_threshold");
    fOuterThresholdVar = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                                    kFloat_GrSLType, kDefault_GrSLPrecision,
                                                    "outer_threshold");

    GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
    SkString coords2D = fragBuilder->ensureFSCoords2D(args.fCoords, 0);
    SkString maskCoords2D = fragBuilder->ensureFSCoords2D(args.fCoords, 1);

    fragBuilder->codeAppendf("vec2 coord = %s;", coords2D.c_str());
    fragBuilder->codeAppendf("vec2 mask_coord = %s;", maskCoords2D.c_str());
    fragBuilder->codeAppend("vec4 input_color = ");
    fragBuilder->appendTextureLookup(args.fTexSamplers[0], "coord");
    fragBuilder->codeAppend(";");
    fragBuilder->codeAppend("vec4 mask_color = ");
    fragBuilder->appendTextureLookup(args.fTexSamplers[1], "mask_coord");
    fragBuilder->codeAppend(";");

    fragBuilder->codeAppendf("float inner_thresh = %s;",
                             uniformHandler->getUniformCStr(fInnerThresholdVar));
    fragBuilder->codeAppendf("float outer_thresh = %s;",
                             uniformHandler->getUniformCStr(fOuterThresholdVar));
    fragBuilder->codeAppend("float mask = mask_color.a;");

    fragBuilder->codeAppend("vec4 color = input_color;");
    fragBuilder->codeAppend("if (mask < 0.5) {"
                            "if (color.a > outer_thresh) {"
                            "float scale = outer_thresh / color.a;"
                            "color.rgb *= scale;"
                            "color.a = outer_thresh;"
                            "}"
                            "} else if (color.a < inner_thresh) {"
                            "float scale = inner_thresh / max(0.001, color.a);"
                            "color.rgb *= scale;"
                            "color.a = inner_thresh;"
                            "}");

    fragBuilder->codeAppendf("%s = %s;", args.fOutputColor,
                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr4("color")).c_str());
}
void GrGLMagnifierEffect::emitCode(EmitArgs& args) {
    GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
    fOffsetVar = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                            kVec2f_GrSLType, kDefault_GrSLPrecision,
                                            "Offset");
    fInvZoomVar = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                             kVec2f_GrSLType, kDefault_GrSLPrecision,
                                             "InvZoom");
    fInvInsetVar = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                              kVec2f_GrSLType, kDefault_GrSLPrecision,
                                              "InvInset");
    fBoundsVar = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                            kVec4f_GrSLType, kDefault_GrSLPrecision,
                                            "Bounds");

    GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
    SkString coords2D = fragBuilder->ensureFSCoords2D(args.fCoords, 0);
    fragBuilder->codeAppendf("\t\tvec2 coord = %s;\n", coords2D.c_str());
    fragBuilder->codeAppendf("\t\tvec2 zoom_coord = %s + %s * %s;\n",
                             uniformHandler->getUniformCStr(fOffsetVar),
                             coords2D.c_str(),
                             uniformHandler->getUniformCStr(fInvZoomVar));
    const char* bounds = uniformHandler->getUniformCStr(fBoundsVar);
    fragBuilder->codeAppendf("\t\tvec2 delta = (coord - %s.xy) * %s.zw;\n", bounds, bounds);
    fragBuilder->codeAppendf("\t\tdelta = min(delta, vec2(1.0, 1.0) - delta);\n");
    fragBuilder->codeAppendf("\t\tdelta = delta * %s;\n",
                             uniformHandler->getUniformCStr(fInvInsetVar));

    fragBuilder->codeAppend("\t\tfloat weight = 0.0;\n");
    fragBuilder->codeAppend("\t\tif (delta.s < 2.0 && delta.t < 2.0) {\n");
    fragBuilder->codeAppend("\t\t\tdelta = vec2(2.0, 2.0) - delta;\n");
    fragBuilder->codeAppend("\t\t\tfloat dist = length(delta);\n");
    fragBuilder->codeAppend("\t\t\tdist = max(2.0 - dist, 0.0);\n");
    fragBuilder->codeAppend("\t\t\tweight = min(dist * dist, 1.0);\n");
    fragBuilder->codeAppend("\t\t} else {\n");
    fragBuilder->codeAppend("\t\t\tvec2 delta_squared = delta * delta;\n");
    fragBuilder->codeAppend("\t\t\tweight = min(min(delta_squared.x, delta_squared.y), 1.0);\n");
    fragBuilder->codeAppend("\t\t}\n");

    fragBuilder->codeAppend("\t\tvec2 mix_coord = mix(coord, zoom_coord, weight);\n");
    fragBuilder->codeAppend("\t\tvec4 output_color = ");
    fragBuilder->appendTextureLookup(args.fTexSamplers[0], "mix_coord");
    fragBuilder->codeAppend(";\n");

    fragBuilder->codeAppendf("\t\t%s = output_color;", args.fOutputColor);
    SkString modulate;
    GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
    fragBuilder->codeAppend(modulate.c_str());
}
void GrGLMorphologyEffect::emitCode(EmitArgs& args) {
    const GrMorphologyEffect& me = args.fFp.cast<GrMorphologyEffect>();

    GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
    fPixelSizeUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                               kFloat_GrSLType, kDefault_GrSLPrecision,
                                               "PixelSize");
    const char* pixelSizeInc = uniformHandler->getUniformCStr(fPixelSizeUni);
    fRangeUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                           kVec2f_GrSLType, kDefault_GrSLPrecision,
                                           "Range");
    const char* range = uniformHandler->getUniformCStr(fRangeUni);

    GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
    SkString coords2D = fragBuilder->ensureFSCoords2D(args.fCoords, 0);
    const char* func;
    switch (me.type()) {
        case GrMorphologyEffect::kErode_MorphologyType:
            fragBuilder->codeAppendf("\t\t%s = vec4(1, 1, 1, 1);\n", args.fOutputColor);
            func = "min";
            break;
        case GrMorphologyEffect::kDilate_MorphologyType:
            fragBuilder->codeAppendf("\t\t%s = vec4(0, 0, 0, 0);\n", args.fOutputColor);
            func = "max";
            break;
        default:
            SkFAIL("Unexpected type");
            func = ""; // suppress warning
            break;
    }

    const char* dir;
    switch (me.direction()) {
        case Gr1DKernelEffect::kX_Direction:
            dir = "x";
            break;
        case Gr1DKernelEffect::kY_Direction:
            dir = "y";
            break;
        default:
            SkFAIL("Unknown filter direction.");
            dir = ""; // suppress warning
    }

    int width = GrMorphologyEffect::WidthFromRadius(me.radius());

    // vec2 coord = coord2D;
    fragBuilder->codeAppendf("\t\tvec2 coord = %s;\n", coords2D.c_str());
    // coord.x -= radius * pixelSize;
    fragBuilder->codeAppendf("\t\tcoord.%s -= %d.0 * %s; \n", dir, me.radius(), pixelSizeInc);
    if (me.useRange()) {
        // highBound = min(highBound, coord.x + (width-1) * pixelSize);
        fragBuilder->codeAppendf("\t\tfloat highBound = min(%s.y, coord.%s + %f * %s);",
                                 range, dir, float(width - 1), pixelSizeInc);
        // coord.x = max(lowBound, coord.x);
        fragBuilder->codeAppendf("\t\tcoord.%s = max(%s.x, coord.%s);", dir, range, dir);
    }
    fragBuilder->codeAppendf("\t\tfor (int i = 0; i < %d; i++) {\n", width);
    fragBuilder->codeAppendf("\t\t\t%s = %s(%s, ", args.fOutputColor, func, args.fOutputColor);
    fragBuilder->appendTextureLookup(args.fTexSamplers[0], "coord");
    fragBuilder->codeAppend(");\n");
    // coord.x += pixelSize;
    fragBuilder->codeAppendf("\t\t\tcoord.%s += %s;\n", dir, pixelSizeInc);
    if (me.useRange()) {
        // coord.x = min(highBound, coord.x);
        fragBuilder->codeAppendf("\t\t\tcoord.%s = min(highBound, coord.%s);", dir, dir);
    }
    fragBuilder->codeAppend("\t\t}\n");
    SkString modulate;
    GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
    fragBuilder->codeAppend(modulate.c_str());
}
void GrGLDisplacementMapEffect::emitCode(EmitArgs& args) {
    const GrDisplacementMapEffect& displacementMap = args.fFp.cast<GrDisplacementMapEffect>();
    const GrTextureDomain& domain = displacementMap.domain();

    fScaleUni = args.fUniformHandler->addUniform(kFragment_GrShaderFlag,
                                                 kVec2f_GrSLType, kDefault_GrSLPrecision, "Scale");
    const char* scaleUni = args.fUniformHandler->getUniformCStr(fScaleUni);
    const char* dColor = "dColor";
    const char* cCoords = "cCoords";
    const char* nearZero = "1e-6"; // Since 6.10352e−5 is the smallest half float, use
                                   // a number smaller than that to approximate 0, but
                                   // leave room for 32-bit float GPU rounding errors.

    GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
    fragBuilder->codeAppendf("\t\tvec4 %s = ", dColor);
    fragBuilder->appendTextureLookup(args.fTexSamplers[0], args.fCoords[0].c_str(),
                                   args.fCoords[0].getType());
    fragBuilder->codeAppend(";\n");

    // Unpremultiply the displacement
    fragBuilder->codeAppendf(
        "\t\t%s.rgb = (%s.a < %s) ? vec3(0.0) : clamp(%s.rgb / %s.a, 0.0, 1.0);",
        dColor, dColor, nearZero, dColor, dColor);
    SkString coords2D = fragBuilder->ensureFSCoords2D(args.fCoords, 1);
    fragBuilder->codeAppendf("\t\tvec2 %s = %s + %s*(%s.",
                             cCoords, coords2D.c_str(), scaleUni, dColor);

    switch (displacementMap.xChannelSelector()) {
      case SkDisplacementMapEffect::kR_ChannelSelectorType:
        fragBuilder->codeAppend("r");
        break;
      case SkDisplacementMapEffect::kG_ChannelSelectorType:
        fragBuilder->codeAppend("g");
        break;
      case SkDisplacementMapEffect::kB_ChannelSelectorType:
        fragBuilder->codeAppend("b");
        break;
      case SkDisplacementMapEffect::kA_ChannelSelectorType:
        fragBuilder->codeAppend("a");
        break;
      case SkDisplacementMapEffect::kUnknown_ChannelSelectorType:
      default:
        SkDEBUGFAIL("Unknown X channel selector");
    }

    switch (displacementMap.yChannelSelector()) {
      case SkDisplacementMapEffect::kR_ChannelSelectorType:
        fragBuilder->codeAppend("r");
        break;
      case SkDisplacementMapEffect::kG_ChannelSelectorType:
        fragBuilder->codeAppend("g");
        break;
      case SkDisplacementMapEffect::kB_ChannelSelectorType:
        fragBuilder->codeAppend("b");
        break;
      case SkDisplacementMapEffect::kA_ChannelSelectorType:
        fragBuilder->codeAppend("a");
        break;
      case SkDisplacementMapEffect::kUnknown_ChannelSelectorType:
      default:
        SkDEBUGFAIL("Unknown Y channel selector");
    }
    fragBuilder->codeAppend("-vec2(0.5));\t\t");

    fGLDomain.sampleTexture(fragBuilder,
                            args.fUniformHandler,
                            args.fGLSLCaps,
                            domain,
                            args.fOutputColor,
                            SkString(cCoords),
                            args.fTexSamplers[1]);
    fragBuilder->codeAppend(";\n");
}
void GrGLBicubicEffect::emitCode(EmitArgs& args) {
    const GrTextureDomain& domain = args.fFp.cast<GrBicubicEffect>().domain();

    GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
    fCoefficientsUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
                       kMat44f_GrSLType, kDefault_GrSLPrecision,
                       "Coefficients");
    fImageIncrementUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
                         kVec2f_GrSLType, kDefault_GrSLPrecision,
                         "ImageIncrement");

    const char* imgInc = uniformHandler->getUniformCStr(fImageIncrementUni);
    const char* coeff = uniformHandler->getUniformCStr(fCoefficientsUni);

    SkString cubicBlendName;

    static const GrGLSLShaderVar gCubicBlendArgs[] = {
        GrGLSLShaderVar("coefficients",  kMat44f_GrSLType),
        GrGLSLShaderVar("t",             kFloat_GrSLType),
        GrGLSLShaderVar("c0",            kVec4f_GrSLType),
        GrGLSLShaderVar("c1",            kVec4f_GrSLType),
        GrGLSLShaderVar("c2",            kVec4f_GrSLType),
        GrGLSLShaderVar("c3",            kVec4f_GrSLType),
    };
    GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
    SkString coords2D = fragBuilder->ensureFSCoords2D(args.fCoords, 0);
    fragBuilder->emitFunction(kVec4f_GrSLType,
                              "cubicBlend",
                              SK_ARRAY_COUNT(gCubicBlendArgs),
                              gCubicBlendArgs,
                              "\tvec4 ts = vec4(1.0, t, t * t, t * t * t);\n"
                              "\tvec4 c = coefficients * ts;\n"
                              "\treturn c.x * c0 + c.y * c1 + c.z * c2 + c.w * c3;\n",
                              &cubicBlendName);
    fragBuilder->codeAppendf("\tvec2 coord = %s - %s * vec2(0.5);\n", coords2D.c_str(), imgInc);
    // We unnormalize the coord in order to determine our fractional offset (f) within the texel
    // We then snap coord to a texel center and renormalize. The snap prevents cases where the
    // starting coords are near a texel boundary and accumulations of imgInc would cause us to skip/
    // double hit a texel.
    fragBuilder->codeAppendf("\tcoord /= %s;\n", imgInc);
    fragBuilder->codeAppend("\tvec2 f = fract(coord);\n");
    fragBuilder->codeAppendf("\tcoord = (coord - f + vec2(0.5)) * %s;\n", imgInc);
    fragBuilder->codeAppend("\tvec4 rowColors[4];\n");
    for (int y = 0; y < 4; ++y) {
        for (int x = 0; x < 4; ++x) {
            SkString coord;
            coord.printf("coord + %s * vec2(%d, %d)", imgInc, x - 1, y - 1);
            SkString sampleVar;
            sampleVar.printf("rowColors[%d]", x);
            fDomain.sampleTexture(fragBuilder,
                                  args.fUniformHandler,
                                  args.fGLSLCaps,
                                  domain,
                                  sampleVar.c_str(),
                                  coord,
                                  args.fTexSamplers[0]);
        }
        fragBuilder->codeAppendf(
            "\tvec4 s%d = %s(%s, f.x, rowColors[0], rowColors[1], rowColors[2], rowColors[3]);\n",
            y, cubicBlendName.c_str(), coeff);
    }
    SkString bicubicColor;
    bicubicColor.printf("%s(%s, f.y, s0, s1, s2, s3)", cubicBlendName.c_str(), coeff);
    fragBuilder->codeAppendf("\t%s = %s;\n",
                             args.fOutputColor, (GrGLSLExpr4(bicubicColor.c_str()) *
                                     GrGLSLExpr4(args.fInputColor)).c_str());
}
void GrGLPerlinNoise::emitCode(EmitArgs& args) {
    const GrPerlinNoiseEffect& pne = args.fFp.cast<GrPerlinNoiseEffect>();

    GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
    GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
    SkString vCoords = fragBuilder->ensureFSCoords2D(args.fCoords, 0);

    fBaseFrequencyUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                                   kVec2f_GrSLType, kDefault_GrSLPrecision,
                                                   "baseFrequency");
    const char* baseFrequencyUni = uniformHandler->getUniformCStr(fBaseFrequencyUni);

    const char* stitchDataUni = nullptr;
    if (pne.stitchTiles()) {
        fStitchDataUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                                    kVec2f_GrSLType, kDefault_GrSLPrecision,
                                                    "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 * vec2(%s)) * vec2(2.0) - vec2(1.0)), %s);";

    // Add noise function
    static const GrGLSLShaderVar gPerlinNoiseArgs[] =  {
        GrGLSLShaderVar(chanCoord, kFloat_GrSLType),
        GrGLSLShaderVar(noiseVec, kVec2f_GrSLType)
    };

    static const GrGLSLShaderVar gPerlinNoiseStitchArgs[] =  {
        GrGLSLShaderVar(chanCoord, kFloat_GrSLType),
        GrGLSLShaderVar(noiseVec, kVec2f_GrSLType),
        GrGLSLShaderVar(stitchData, kVec2f_GrSLType)
    };

    SkString noiseCode;

    noiseCode.appendf("\tvec4 %s;\n", floorVal);
    noiseCode.appendf("\t%s.xy = floor(%s);\n", floorVal, noiseVec);
    noiseCode.appendf("\t%s.zw = %s.xy + vec2(1.0);\n", floorVal, floorVal);
    noiseCode.appendf("\tvec2 %s = fract(%s);\n", fractVal, noiseVec);

    // smooth curve : t * t * (3 - 2 * t)
    noiseCode.appendf("\n\tvec2 %s = %s * %s * (vec2(3.0) - vec2(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)) / vec4(256.0));\n",
                      floorVal, floorVal);

    // Get permutation for x
    {
        SkString xCoords("");
        xCoords.appendf("vec2(%s.x, 0.5)", floorVal);

        noiseCode.appendf("\n\tvec2 %s;\n\t%s.x = ", latticeIdx, latticeIdx);
        fragBuilder->appendTextureLookup(&noiseCode, args.fTexSamplers[0], xCoords.c_str(),
                                         kVec2f_GrSLType);
        noiseCode.append(".r;");
    }

    // Get permutation for x + 1
    {
        SkString xCoords("");
        xCoords.appendf("vec2(%s.z, 0.5)", floorVal);

        noiseCode.appendf("\n\t%s.y = ", latticeIdx);
        fragBuilder->appendTextureLookup(&noiseCode, args.fTexSamplers[0], xCoords.c_str(),
                                         kVec2f_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 * vec2(255.0) + vec2(0.5)) * vec2(0.003921569);",
                      latticeIdx, latticeIdx);
#endif

    // Get (x,y) coordinates with the permutated x
    noiseCode.appendf("\n\tvec4 %s = fract(%s.xyxy + %s.yyww);", bcoords, latticeIdx, floorVal);

    noiseCode.appendf("\n\n\tvec2 %s;", uv);
    // Compute u, at offset (0,0)
    {
        SkString latticeCoords("");
        latticeCoords.appendf("vec2(%s.x, %s)", bcoords, chanCoord);
        noiseCode.appendf("\n\tvec4 %s = ", lattice);
        fragBuilder->appendTextureLookup(&noiseCode, args.fTexSamplers[1], latticeCoords.c_str(),
                                         kVec2f_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("vec2(%s.y, %s)", bcoords, chanCoord);
        noiseCode.append("\n\tlattice = ");
        fragBuilder->appendTextureLookup(&noiseCode, args.fTexSamplers[1], latticeCoords.c_str(),
                                         kVec2f_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\tvec2 %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("vec2(%s.w, %s)", bcoords, chanCoord);
        noiseCode.append("\n\tlattice = ");
        fragBuilder->appendTextureLookup(&noiseCode, args.fTexSamplers[1], latticeCoords.c_str(),
                                         kVec2f_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("vec2(%s.z, %s)", bcoords, chanCoord);
        noiseCode.append("\n\tlattice = ");
        fragBuilder->appendTextureLookup(&noiseCode, args.fTexSamplers[1], latticeCoords.c_str(),
                                         kVec2f_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(kFloat_GrSLType,
                                  "perlinnoise", SK_ARRAY_COUNT(gPerlinNoiseStitchArgs),
                                  gPerlinNoiseStitchArgs, noiseCode.c_str(), &noiseFuncName);
    } else {
        fragBuilder->emitFunction(kFloat_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\tvec2 %s = floor(%s.xy) * %s;",
                             noiseVec, vCoords.c_str(), baseFrequencyUni);

    // Clear the color accumulator
    fragBuilder->codeAppendf("\n\t\t%s = vec4(0.0);", args.fOutputColor);

    if (pne.stitchTiles()) {
        // Set up TurbulenceInitial stitch values.
        fragBuilder->codeAppendf("vec2 %s = %s;", stitchData, stitchDataUni);
    }

    fragBuilder->codeAppendf("float %s = 1.0;", ratio);

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

    fragBuilder->codeAppendf("%s += ", args.fOutputColor);
    if (pne.type() != SkPerlinNoiseShader::kFractalNoise_Type) {
        fragBuilder->codeAppend("abs(");
    }
    if (pne.stitchTiles()) {
        fragBuilder->codeAppendf(
            "vec4(\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(
            "vec4(\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() != SkPerlinNoiseShader::kFractalNoise_Type) {
        fragBuilder->codeAppendf(")"); // end of "abs("
    }
    fragBuilder->codeAppendf(" * %s;", ratio);

    fragBuilder->codeAppendf("\n\t\t\t%s *= vec2(2.0);", noiseVec);
    fragBuilder->codeAppendf("\n\t\t\t%s *= 0.5;", ratio);

    if (pne.stitchTiles()) {
        fragBuilder->codeAppendf("\n\t\t\t%s *= vec2(2.0);", stitchData);
    }
    fragBuilder->codeAppend("\n\t\t}"); // end of the for loop on octaves

    if (pne.type() == SkPerlinNoiseShader::kFractalNoise_Type) {
        // The value of turbulenceFunctionResult comes from ((turbulenceFunctionResult) + 1) / 2
        // by fractalNoise and (turbulenceFunctionResult) by turbulence.
        fragBuilder->codeAppendf("\n\t\t%s = %s * vec4(0.5) + vec4(0.5);",
                                 args.fOutputColor,args.fOutputColor);
    }

    // Clamp values
    fragBuilder->codeAppendf("\n\t\t%s = clamp(%s, 0.0, 1.0);", args.fOutputColor, args.fOutputColor);

    // Pre-multiply the result
    fragBuilder->codeAppendf("\n\t\t%s = vec4(%s.rgb * %s.aaa, %s.a);\n",
                             args.fOutputColor, args.fOutputColor,
                             args.fOutputColor, args.fOutputColor);
}