src/core/SkMatrixColorFilter.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 "src/core/SkMatrixColorFilter.h"

#include "include/core/SkColorFilter.h"
#include "include/core/SkRefCnt.h"
#include "include/core/SkScalar.h"
#include "include/effects/SkColorMatrix.h"
#include "include/private/base/SkAssert.h"
#include "include/private/base/SkFloatingPoint.h"
#include "src/core/SkColorFilterBase.h"
#include "src/core/SkEffectPriv.h"
#include "src/core/SkRasterPipeline.h"
#include "src/core/SkRasterPipelineOpList.h"
#include "src/core/SkReadBuffer.h"
#include "src/core/SkWriteBuffer.h"

#include <array>
#include <cstring>

#if defined(SK_GRAPHITE)
#include "src/gpu/graphite/KeyHelpers.h"
#include "src/gpu/graphite/PaintParamsKey.h"
#endif  // SK_GRAPHITE

static bool is_alpha_unchanged(const float matrix[20]) {
    const float* srcA = matrix + 15;

    return SkScalarNearlyZero(srcA[0]) && SkScalarNearlyZero(srcA[1]) &&
           SkScalarNearlyZero(srcA[2]) && SkScalarNearlyEqual(srcA[3], 1) &&
           SkScalarNearlyZero(srcA[4]);
}

SkMatrixColorFilter::SkMatrixColorFilter(const float array[20], Domain domain)
        : fAlphaIsUnchanged(is_alpha_unchanged(array)), fDomain(domain) {
    memcpy(fMatrix, array, 20 * sizeof(float));
}

void SkMatrixColorFilter::flatten(SkWriteBuffer& buffer) const {
    SkASSERT(sizeof(fMatrix) / sizeof(float) == 20);
    buffer.writeScalarArray(fMatrix, 20);

    // RGBA flag
    buffer.writeBool(fDomain == Domain::kRGBA);
}

sk_sp<SkFlattenable> SkMatrixColorFilter::CreateProc(SkReadBuffer& buffer) {
    float matrix[20];
    if (!buffer.readScalarArray(matrix, 20)) {
        return nullptr;
    }

    auto is_rgba = buffer.readBool();
    return is_rgba ? SkColorFilters::Matrix(matrix) : SkColorFilters::HSLAMatrix(matrix);
}

bool SkMatrixColorFilter::onAsAColorMatrix(float matrix[20]) const {
    if (matrix) {
        memcpy(matrix, fMatrix, 20 * sizeof(float));
    }
    return true;
}

bool SkMatrixColorFilter::appendStages(const SkStageRec& rec, bool shaderIsOpaque) const {
    const bool willStayOpaque = shaderIsOpaque && fAlphaIsUnchanged,
               hsla = fDomain == Domain::kHSLA;

    SkRasterPipeline* p = rec.fPipeline;
    if (!shaderIsOpaque) {
        p->append(SkRasterPipelineOp::unpremul);
    }
    if (hsla) {
        p->append(SkRasterPipelineOp::rgb_to_hsl);
    }
    if (true) {
        p->append(SkRasterPipelineOp::matrix_4x5, fMatrix);
    }
    if (hsla) {
        p->append(SkRasterPipelineOp::hsl_to_rgb);
    }
    if (true) {
        p->append(SkRasterPipelineOp::clamp_01);
    }
    if (!willStayOpaque) {
        p->append(SkRasterPipelineOp::premul);
    }
    return true;
}

#if defined(SK_ENABLE_SKVM)
skvm::Color SkMatrixColorFilter::onProgram(skvm::Builder* p,
                                           skvm::Color c,
                                           const SkColorInfo& /*dst*/,
                                           skvm::Uniforms* uniforms,
                                           SkArenaAlloc*) const {
    auto apply_matrix = [&](auto xyzw) {
        auto dot = [&](int j) {
            auto custom_mad = [&](float f, skvm::F32 m, skvm::F32 a) {
                // skvm::Builder won't fold f*0 == 0, but we shouldn't encounter NaN here.
                // While looking, also simplify f == ±1.  Anything else becomes a uniform.
                return f == 0.0f
                               ? a
                               : f == +1.0f ? a + m
                                            : f == -1.0f ? a - m
                                                         : m * p->uniformF(uniforms->pushF(f)) + a;
            };

            // Similarly, let skvm::Builder fold away the additive bias when zero.
            const float b = fMatrix[4 + j * 5];
            skvm::F32 bias = b == 0.0f ? p->splat(0.0f) : p->uniformF(uniforms->pushF(b));

            auto [x, y, z, w] = xyzw;
            return custom_mad(fMatrix[0 + j * 5],
                              x,
                              custom_mad(fMatrix[1 + j * 5],
                                         y,
                                         custom_mad(fMatrix[2 + j * 5],
                                                    z,
                                                    custom_mad(fMatrix[3 + j * 5], w, bias))));
        };
        return std::make_tuple(dot(0), dot(1), dot(2), dot(3));
    };

    c = unpremul(c);

    if (fDomain == Domain::kHSLA) {
        auto [h, s, l, a] = apply_matrix(p->to_hsla(c));
        c = p->to_rgba({h, s, l, a});
    } else {
        auto [r, g, b, a] = apply_matrix(c);
        c = {r, g, b, a};
    }

    return premul(clamp01(c));
}
#endif

#if defined(SK_GRAPHITE)
void SkMatrixColorFilter::addToKey(const skgpu::graphite::KeyContext& keyContext,
                                   skgpu::graphite::PaintParamsKeyBuilder* builder,
                                   skgpu::graphite::PipelineDataGatherer* gatherer) const {
    using namespace skgpu::graphite;

    MatrixColorFilterBlock::MatrixColorFilterData matrixCFData(fMatrix, fDomain == Domain::kHSLA);

    MatrixColorFilterBlock::BeginBlock(keyContext, builder, gatherer, &matrixCFData);
    builder->endBlock();
}
#endif  // SK_GRAPHITE

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

static sk_sp<SkColorFilter> MakeMatrix(const float array[20], SkMatrixColorFilter::Domain domain) {
    if (!sk_floats_are_finite(array, 20)) {
        return nullptr;
    }
    return sk_make_sp<SkMatrixColorFilter>(array, domain);
}

sk_sp<SkColorFilter> SkColorFilters::Matrix(const float array[20]) {
    return MakeMatrix(array, SkMatrixColorFilter::Domain::kRGBA);
}

sk_sp<SkColorFilter> SkColorFilters::Matrix(const SkColorMatrix& cm) {
    return MakeMatrix(cm.fMat.data(), SkMatrixColorFilter::Domain::kRGBA);
}

sk_sp<SkColorFilter> SkColorFilters::HSLAMatrix(const float array[20]) {
    return MakeMatrix(array, SkMatrixColorFilter::Domain::kHSLA);
}

sk_sp<SkColorFilter> SkColorFilters::HSLAMatrix(const SkColorMatrix& cm) {
    return MakeMatrix(cm.fMat.data(), SkMatrixColorFilter::Domain::kHSLA);
}

void SkRegisterMatrixColorFilterFlattenable() {
    SK_REGISTER_FLATTENABLE(SkMatrixColorFilter);
    // Previous name
    SkFlattenable::Register("SkColorFilter_Matrix", SkMatrixColorFilter::CreateProc);
}