src/effects/SkColorMatrixFilter.cpp

/*
 * Copyright 2011 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
#include "SkColorMatrixFilter.h"
#include "SkColorMatrix.h"
#include "SkColorPriv.h"
#include "SkReadBuffer.h"
#include "SkWriteBuffer.h"
#include "SkUnPreMultiply.h"
#include "SkString.h"

static int32_t rowmul4(const int32_t array[], unsigned r, unsigned g,
                          unsigned b, unsigned a) {
    return array[0] * r + array[1] * g  + array[2] * b + array[3] * a + array[4];
}

static int32_t rowmul3(const int32_t array[], unsigned r, unsigned g,
                       unsigned b) {
    return array[0] * r + array[1] * g  + array[2] * b + array[4];
}

static void General(const SkColorMatrixFilter::State& state,
                    unsigned r, unsigned g, unsigned b, unsigned a,
                    int32_t* SK_RESTRICT result) {
    const int32_t* SK_RESTRICT array = state.fArray;
    const int shift = state.fShift;

    result[0] = rowmul4(&array[0], r, g, b, a) >> shift;
    result[1] = rowmul4(&array[5], r, g, b, a) >> shift;
    result[2] = rowmul4(&array[10], r, g, b, a) >> shift;
    result[3] = rowmul4(&array[15], r, g, b, a) >> shift;
}

static void General16(const SkColorMatrixFilter::State& state,
                      unsigned r, unsigned g, unsigned b, unsigned a,
                      int32_t* SK_RESTRICT result) {
    const int32_t* SK_RESTRICT array = state.fArray;

    result[0] = rowmul4(&array[0], r, g, b, a) >> 16;
    result[1] = rowmul4(&array[5], r, g, b, a) >> 16;
    result[2] = rowmul4(&array[10], r, g, b, a) >> 16;
    result[3] = rowmul4(&array[15], r, g, b, a) >> 16;
}

static void AffineAdd(const SkColorMatrixFilter::State& state,
                      unsigned r, unsigned g, unsigned b, unsigned a,
                      int32_t* SK_RESTRICT result) {
    const int32_t* SK_RESTRICT array = state.fArray;
    const int shift = state.fShift;

    result[0] = rowmul3(&array[0], r, g, b) >> shift;
    result[1] = rowmul3(&array[5], r, g, b) >> shift;
    result[2] = rowmul3(&array[10], r, g, b) >> shift;
    result[3] = a;
}

static void AffineAdd16(const SkColorMatrixFilter::State& state,
                        unsigned r, unsigned g, unsigned b, unsigned a,
                        int32_t* SK_RESTRICT result) {
    const int32_t* SK_RESTRICT array = state.fArray;

    result[0] = rowmul3(&array[0], r, g, b) >> 16;
    result[1] = rowmul3(&array[5], r, g, b) >> 16;
    result[2] = rowmul3(&array[10], r, g, b) >> 16;
    result[3] = a;
}

static void ScaleAdd(const SkColorMatrixFilter::State& state,
                     unsigned r, unsigned g, unsigned b, unsigned a,
                     int32_t* SK_RESTRICT result) {
    const int32_t* SK_RESTRICT array = state.fArray;
    const int shift = state.fShift;

    // cast to (int) to keep the expression signed for the shift
    result[0] = (array[SkColorMatrix::kR_Scale] * (int)r + array[4]) >> shift;
    result[1] = (array[SkColorMatrix::kG_Scale] * (int)g + array[9]) >> shift;
    result[2] = (array[SkColorMatrix::kB_Scale] * (int)b + array[14]) >> shift;
    result[3] = a;
}

static void ScaleAdd16(const SkColorMatrixFilter::State& state,
                       unsigned r, unsigned g, unsigned b, unsigned a,
                       int32_t* SK_RESTRICT result) {
    const int32_t* SK_RESTRICT array = state.fArray;

    // cast to (int) to keep the expression signed for the shift
    result[0] = (array[SkColorMatrix::kR_Scale] * (int)r + array[4]) >> 16;
    result[1] = (array[SkColorMatrix::kG_Scale] * (int)g + array[9]) >> 16;
    result[2] = (array[SkColorMatrix::kB_Scale] * (int)b + array[14]) >> 16;
    result[3] = a;
}

static void Add(const SkColorMatrixFilter::State& state,
                unsigned r, unsigned g, unsigned b, unsigned a,
                int32_t* SK_RESTRICT result) {
    const int32_t* SK_RESTRICT array = state.fArray;
    const int shift = state.fShift;

    result[0] = r + (array[SkColorMatrix::kR_Trans] >> shift);
    result[1] = g + (array[SkColorMatrix::kG_Trans] >> shift);
    result[2] = b + (array[SkColorMatrix::kB_Trans] >> shift);
    result[3] = a;
}

static void Add16(const SkColorMatrixFilter::State& state,
                  unsigned r, unsigned g, unsigned b, unsigned a,
                  int32_t* SK_RESTRICT result) {
    const int32_t* SK_RESTRICT array = state.fArray;

    result[0] = r + (array[SkColorMatrix::kR_Trans] >> 16);
    result[1] = g + (array[SkColorMatrix::kG_Trans] >> 16);
    result[2] = b + (array[SkColorMatrix::kB_Trans] >> 16);
    result[3] = a;
}

#define kNO_ALPHA_FLAGS (SkColorFilter::kAlphaUnchanged_Flag |  \
                         SkColorFilter::kHasFilter16_Flag)

// src is [20] but some compilers won't accept __restrict__ on anything
// but an raw pointer or reference
void SkColorMatrixFilter::initState(const SkScalar* SK_RESTRICT src) {
    int32_t* array = fState.fArray;
    SkFixed max = 0;
    for (int i = 0; i < 20; i++) {
        SkFixed value = SkScalarToFixed(src[i]);
        array[i] = value;
        value = SkAbs32(value);
        max = SkMax32(max, value);
    }

    /*  All of fArray[] values must fit in 23 bits, to safely allow me to
        multiply them by 8bit unsigned values, and get a signed answer without
        overflow. This means clz needs to be 9 or bigger
    */
    int bits = SkCLZ(max);
    int32_t one = SK_Fixed1;

    fState.fShift = 16; // we are starting out as fixed 16.16
    if (bits < 9) {
        bits = 9 - bits;
        fState.fShift -= bits;
        for (int i = 0; i < 20; i++) {
            array[i] >>= bits;
        }
        one >>= bits;
    }

    // check if we have to munge Alpha
    int32_t changesAlpha = (array[15] | array[16] | array[17] |
                            (array[18] - one) | array[19]);
    int32_t usesAlpha = (array[3] | array[8] | array[13]);
    bool shiftIs16 = (16 == fState.fShift);

    if (changesAlpha | usesAlpha) {
        fProc = shiftIs16 ? General16 : General;
        fFlags = changesAlpha ? 0 : SkColorFilter::kAlphaUnchanged_Flag;
    } else {
        fFlags = kNO_ALPHA_FLAGS;

        int32_t needsScale = (array[SkColorMatrix::kR_Scale] - one) |
                             (array[SkColorMatrix::kG_Scale] - one) |
                             (array[SkColorMatrix::kB_Scale] - one);

        int32_t needs3x3 =  array[1] | array[2] |     // red off-axis
                            array[5] | array[7] |     // green off-axis
                            array[10] | array[11];    // blue off-axis

        if (needs3x3) {
            fProc = shiftIs16 ? AffineAdd16 : AffineAdd;
        } else if (needsScale) {
            fProc = shiftIs16 ? ScaleAdd16 : ScaleAdd;
        } else if (array[SkColorMatrix::kR_Trans] |
                   array[SkColorMatrix::kG_Trans] |
                   array[SkColorMatrix::kB_Trans]) {
            fProc = shiftIs16 ? Add16 : Add;
        } else {
            fProc = NULL;   // identity
        }
    }

    /*  preround our add values so we get a rounded shift. We do this after we
        analyze the array, so we don't miss the case where the caller has zeros
        which could make us accidentally take the General or Add case.
    */
    if (NULL != fProc) {
        int32_t add = 1 << (fState.fShift - 1);
        array[4] += add;
        array[9] += add;
        array[14] += add;
        array[19] += add;
    }
}

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

static int32_t pin(int32_t value, int32_t max) {
    if (value < 0) {
        value = 0;
    }
    if (value > max) {
        value = max;
    }
    return value;
}

SkColorMatrixFilter::SkColorMatrixFilter(const SkColorMatrix& cm) : fMatrix(cm) {
    this->initState(cm.fMat);
}

SkColorMatrixFilter::SkColorMatrixFilter(const SkScalar array[20]) {
    memcpy(fMatrix.fMat, array, 20 * sizeof(SkScalar));
    this->initState(array);
}

uint32_t SkColorMatrixFilter::getFlags() const {
    return this->INHERITED::getFlags() | fFlags;
}

void SkColorMatrixFilter::filterSpan(const SkPMColor src[], int count,
                                     SkPMColor dst[]) const {
    Proc proc = fProc;
    const State& state = fState;
    int32_t result[4];

    if (NULL == proc) {
        if (src != dst) {
            memcpy(dst, src, count * sizeof(SkPMColor));
        }
        return;
    }

    const SkUnPreMultiply::Scale* table = SkUnPreMultiply::GetScaleTable();

    for (int i = 0; i < count; i++) {
        SkPMColor c = src[i];

        unsigned r = SkGetPackedR32(c);
        unsigned g = SkGetPackedG32(c);
        unsigned b = SkGetPackedB32(c);
        unsigned a = SkGetPackedA32(c);

        // need our components to be un-premultiplied
        if (255 != a) {
            SkUnPreMultiply::Scale scale = table[a];
            r = SkUnPreMultiply::ApplyScale(scale, r);
            g = SkUnPreMultiply::ApplyScale(scale, g);
            b = SkUnPreMultiply::ApplyScale(scale, b);

            SkASSERT(r <= 255);
            SkASSERT(g <= 255);
            SkASSERT(b <= 255);
        }

        proc(state, r, g, b, a, result);

        r = pin(result[0], SK_R32_MASK);
        g = pin(result[1], SK_G32_MASK);
        b = pin(result[2], SK_B32_MASK);
        a = pin(result[3], SK_A32_MASK);
        // re-prepremultiply if needed
        dst[i] = SkPremultiplyARGBInline(a, r, g, b);
    }
}

void SkColorMatrixFilter::filterSpan16(const uint16_t src[], int count,
                                       uint16_t dst[]) const {
    SkASSERT(fFlags & SkColorFilter::kHasFilter16_Flag);

    Proc   proc = fProc;
    const State& state = fState;
    int32_t result[4];

    if (NULL == proc) {
        if (src != dst) {
            memcpy(dst, src, count * sizeof(uint16_t));
        }
        return;
    }

    for (int i = 0; i < count; i++) {
        uint16_t c = src[i];

        // expand to 8bit components (since our matrix translate is 8bit biased
        unsigned r = SkPacked16ToR32(c);
        unsigned g = SkPacked16ToG32(c);
        unsigned b = SkPacked16ToB32(c);

        proc(state, r, g, b, 0, result);

        r = pin(result[0], SK_R32_MASK);
        g = pin(result[1], SK_G32_MASK);
        b = pin(result[2], SK_B32_MASK);

        // now packed it back down to 16bits (hmmm, could dither...)
        dst[i] = SkPack888ToRGB16(r, g, b);
    }
}

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

void SkColorMatrixFilter::flatten(SkWriteBuffer& buffer) const {
    this->INHERITED::flatten(buffer);
    SkASSERT(sizeof(fMatrix.fMat)/sizeof(SkScalar) == 20);
    buffer.writeScalarArray(fMatrix.fMat, 20);
}

SkColorMatrixFilter::SkColorMatrixFilter(SkReadBuffer& buffer)
        : INHERITED(buffer) {
    SkASSERT(buffer.getArrayCount() == 20);
    if (buffer.readScalarArray(fMatrix.fMat, 20)) {
        this->initState(fMatrix.fMat);
    }
}

bool SkColorMatrixFilter::asColorMatrix(SkScalar matrix[20]) const {
    if (matrix) {
        memcpy(matrix, fMatrix.fMat, 20 * sizeof(SkScalar));
    }
    return true;
}

#if SK_SUPPORT_GPU
#include "GrEffect.h"
#include "GrTBackendEffectFactory.h"
#include "gl/GrGLEffect.h"
#include "gl/GrGLShaderBuilder.h"

class ColorMatrixEffect : public GrEffect {
public:
    static GrEffect* Create(const SkColorMatrix& matrix) {
        return SkNEW_ARGS(ColorMatrixEffect, (matrix));
    }

    static const char* Name() { return "Color Matrix"; }

    virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE {
        return GrTBackendEffectFactory<ColorMatrixEffect>::getInstance();
    }

    virtual void getConstantColorComponents(GrColor* color,
                                            uint32_t* validFlags) const SK_OVERRIDE {
        // We only bother to check whether the alpha channel will be constant. If SkColorMatrix had
        // type flags it might be worth checking the other components.

        // The matrix is defined such the 4th row determines the output alpha. The first four
        // columns of that row multiply the input r, g, b, and a, respectively, and the last column
        // is the "translation".
        static const uint32_t kRGBAFlags[] = {
            kR_GrColorComponentFlag,
            kG_GrColorComponentFlag,
            kB_GrColorComponentFlag,
            kA_GrColorComponentFlag
        };
        static const int kShifts[] = {
            GrColor_SHIFT_R, GrColor_SHIFT_G, GrColor_SHIFT_B, GrColor_SHIFT_A,
        };
        enum {
            kAlphaRowStartIdx = 15,
            kAlphaRowTranslateIdx = 19,
        };

        SkScalar outputA = 0;
        for (int i = 0; i < 4; ++i) {
            // If any relevant component of the color to be passed through the matrix is non-const
            // then we can't know the final result.
            if (0 != fMatrix.fMat[kAlphaRowStartIdx + i]) {
                if (!(*validFlags & kRGBAFlags[i])) {
                    *validFlags = 0;
                    return;
                } else {
                    uint32_t component = (*color >> kShifts[i]) & 0xFF;
                    outputA += fMatrix.fMat[kAlphaRowStartIdx + i] * component;
                }
            }
        }
        outputA += fMatrix.fMat[kAlphaRowTranslateIdx];
        *validFlags = kA_GrColorComponentFlag;
        // We pin the color to [0,1]. This would happen to the *final* color output from the frag
        // shader but currently the effect does not pin its own output. So in the case of over/
        // underflow this may deviate from the actual result. Maybe the effect should pin its
        // result if the matrix could over/underflow for any component?
        *color = static_cast<uint8_t>(SkScalarPin(outputA, 0, 255)) << GrColor_SHIFT_A;
    }

    GR_DECLARE_EFFECT_TEST;

    class GLEffect : public GrGLEffect {
    public:
        // this class always generates the same code.
        static EffectKey GenKey(const GrDrawEffect&, const GrGLCaps&) { return 0; }

        GLEffect(const GrBackendEffectFactory& factory,
                 const GrDrawEffect&)
        : INHERITED(factory) {
        }

        virtual void emitCode(GrGLShaderBuilder* builder,
                              const GrDrawEffect&,
                              EffectKey,
                              const char* outputColor,
                              const char* inputColor,
                              const TransformedCoordsArray&,
                              const TextureSamplerArray&) SK_OVERRIDE {
            fMatrixHandle = builder->addUniform(GrGLShaderBuilder::kFragment_Visibility,
                                                kMat44f_GrSLType,
                                                "ColorMatrix");
            fVectorHandle = builder->addUniform(GrGLShaderBuilder::kFragment_Visibility,
                                                kVec4f_GrSLType,
                                                "ColorMatrixVector");

            if (NULL == inputColor) {
                // could optimize this case, but we aren't for now.
                inputColor = "vec4(1)";
            }
            // The max() is to guard against 0 / 0 during unpremul when the incoming color is
            // transparent black.
            builder->fsCodeAppendf("\tfloat nonZeroAlpha = max(%s.a, 0.00001);\n", inputColor);
            builder->fsCodeAppendf("\t%s = %s * vec4(%s.rgb / nonZeroAlpha, nonZeroAlpha) + %s;\n",
                                   outputColor,
                                   builder->getUniformCStr(fMatrixHandle),
                                   inputColor,
                                   builder->getUniformCStr(fVectorHandle));
            builder->fsCodeAppendf("\t%s = clamp(%s, 0.0, 1.0);\n", outputColor, outputColor);
            builder->fsCodeAppendf("\t%s.rgb *= %s.a;\n", outputColor, outputColor);
        }

        virtual void setData(const GrGLUniformManager& uniManager,
                             const GrDrawEffect& drawEffect) SK_OVERRIDE {
            const ColorMatrixEffect& cme = drawEffect.castEffect<ColorMatrixEffect>();
            const float* m = cme.fMatrix.fMat;
            // The GL matrix is transposed from SkColorMatrix.
            GrGLfloat mt[]  = {
                m[0], m[5], m[10], m[15],
                m[1], m[6], m[11], m[16],
                m[2], m[7], m[12], m[17],
                m[3], m[8], m[13], m[18],
            };
            static const float kScale = 1.0f / 255.0f;
            GrGLfloat vec[] = {
                m[4] * kScale, m[9] * kScale, m[14] * kScale, m[19] * kScale,
            };
            uniManager.setMatrix4fv(fMatrixHandle, 1, mt);
            uniManager.set4fv(fVectorHandle, 1, vec);
        }

    private:
        GrGLUniformManager::UniformHandle fMatrixHandle;
        GrGLUniformManager::UniformHandle fVectorHandle;

        typedef GrGLEffect INHERITED;
    };

private:
    ColorMatrixEffect(const SkColorMatrix& matrix) : fMatrix(matrix) {}

    virtual bool onIsEqual(const GrEffect& s) const {
        const ColorMatrixEffect& cme = CastEffect<ColorMatrixEffect>(s);
        return cme.fMatrix == fMatrix;
    }

    SkColorMatrix fMatrix;

    typedef GrEffect INHERITED;
};

GR_DEFINE_EFFECT_TEST(ColorMatrixEffect);

GrEffect* ColorMatrixEffect::TestCreate(SkRandom* random,
                                        GrContext*,
                                        const GrDrawTargetCaps&,
                                        GrTexture* dummyTextures[2]) {
    SkColorMatrix colorMatrix;
    for (size_t i = 0; i < SK_ARRAY_COUNT(colorMatrix.fMat); ++i) {
        colorMatrix.fMat[i] = random->nextSScalar1();
    }
    return ColorMatrixEffect::Create(colorMatrix);
}

GrEffect* SkColorMatrixFilter::asNewEffect(GrContext*) const {
    return ColorMatrixEffect::Create(fMatrix);
}

#endif

#ifndef SK_IGNORE_TO_STRING
void SkColorMatrixFilter::toString(SkString* str) const {
    str->append("SkColorMatrixFilter: ");

    str->append("matrix: (");
    for (int i = 0; i < 20; ++i) {
        str->appendScalar(fMatrix.fMat[i]);
        if (i < 19) {
            str->append(", ");
        }
    }
    str->append(")");
}
#endif