effects/imagefilters/SkArithmeticImageFilter.cpp

/*
 * Copyright 2016 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/SkArithmeticImageFilter.h"

#include "include/core/SkCanvas.h"
#include "include/effects/SkXfermodeImageFilter.h"
#include "include/private/SkNx.h"
#include "src/core/SkImageFilter_Base.h"
#include "src/core/SkReadBuffer.h"
#include "src/core/SkSpecialImage.h"
#include "src/core/SkSpecialSurface.h"
#include "src/core/SkWriteBuffer.h"
#if SK_SUPPORT_GPU
#include "include/effects/SkRuntimeEffect.h"
#include "include/private/GrRecordingContext.h"
#include "src/gpu/GrClip.h"
#include "src/gpu/GrColorSpaceXform.h"
#include "src/gpu/GrRecordingContextPriv.h"
#include "src/gpu/GrRenderTargetContext.h"
#include "src/gpu/GrTextureProxy.h"
#include "src/gpu/SkGr.h"
#include "src/gpu/effects/GrSkSLFP.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"

GR_FP_SRC_STRING SKSL_ARITHMETIC_SRC = R"(
uniform float4 k;
in bool enforcePMColor;
in fragmentProcessor child;

void main(float2 p, inout half4 color) {
    half4 dst = sample(child, p);
    color = saturate(half(k.x) * color * dst + half(k.y) * color + half(k.z) * dst + half(k.w));
    @if (enforcePMColor) {
        color.rgb = min(color.rgb, color.a);
    }
}
)";
#endif

namespace {

class ArithmeticImageFilterImpl final : public SkImageFilter_Base {
public:
    ArithmeticImageFilterImpl(float k1, float k2, float k3, float k4, bool enforcePMColor,
                              sk_sp<SkImageFilter> inputs[2], const CropRect* cropRect)
            : INHERITED(inputs, 2, cropRect), fInputs{k1, k2, k3, k4, enforcePMColor} {}

protected:
    sk_sp<SkSpecialImage> onFilterImage(const Context&, SkIPoint* offset) const override;

    SkIRect onFilterBounds(const SkIRect&, const SkMatrix& ctm,
                           MapDirection, const SkIRect* inputRect) const override;

#if SK_SUPPORT_GPU
    sk_sp<SkSpecialImage> filterImageGPU(const Context& ctx,
                                         sk_sp<SkSpecialImage> background,
                                         const SkIPoint& backgroundOffset,
                                         sk_sp<SkSpecialImage> foreground,
                                         const SkIPoint& foregroundOffset,
                                         const SkIRect& bounds) const;
#endif

    void flatten(SkWriteBuffer& buffer) const override;

    void drawForeground(SkCanvas* canvas, SkSpecialImage*, const SkIRect&) const;

private:
    friend void SkArithmeticImageFilter::RegisterFlattenables();
    SK_FLATTENABLE_HOOKS(ArithmeticImageFilterImpl)

    bool affectsTransparentBlack() const override { return !SkScalarNearlyZero(fInputs.fK[3]); }

    ArithmeticFPInputs fInputs;

    typedef SkImageFilter_Base INHERITED;
};

}; // end namespace

sk_sp<SkImageFilter> SkArithmeticImageFilter::Make(float k1, float k2, float k3, float k4,
                                                   bool enforcePMColor,
                                                   sk_sp<SkImageFilter> background,
                                                   sk_sp<SkImageFilter> foreground,
                                                   const SkImageFilter::CropRect* crop) {
    if (!SkScalarIsFinite(k1) || !SkScalarIsFinite(k2) || !SkScalarIsFinite(k3) ||
        !SkScalarIsFinite(k4)) {
        return nullptr;
    }

    // are we nearly some other "std" mode?
    int mode = -1;  // illegal mode
    if (SkScalarNearlyZero(k1) && SkScalarNearlyEqual(k2, SK_Scalar1) && SkScalarNearlyZero(k3) &&
        SkScalarNearlyZero(k4)) {
        mode = (int)SkBlendMode::kSrc;
    } else if (SkScalarNearlyZero(k1) && SkScalarNearlyZero(k2) &&
               SkScalarNearlyEqual(k3, SK_Scalar1) && SkScalarNearlyZero(k4)) {
        mode = (int)SkBlendMode::kDst;
    } else if (SkScalarNearlyZero(k1) && SkScalarNearlyZero(k2) && SkScalarNearlyZero(k3) &&
               SkScalarNearlyZero(k4)) {
        mode = (int)SkBlendMode::kClear;
    }
    if (mode >= 0) {
        return SkXfermodeImageFilter::Make((SkBlendMode)mode, std::move(background),
                                           std::move(foreground), crop);
    }

    sk_sp<SkImageFilter> inputs[2] = {std::move(background), std::move(foreground)};
    return sk_sp<SkImageFilter>(
            new ArithmeticImageFilterImpl(k1, k2, k3, k4, enforcePMColor, inputs, crop));
}

void SkArithmeticImageFilter::RegisterFlattenables() {
    SK_REGISTER_FLATTENABLE(ArithmeticImageFilterImpl);
}

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

sk_sp<SkFlattenable> ArithmeticImageFilterImpl::CreateProc(SkReadBuffer& buffer) {
    SK_IMAGEFILTER_UNFLATTEN_COMMON(common, 2);
    float k[4];
    for (int i = 0; i < 4; ++i) {
        k[i] = buffer.readScalar();
    }
    const bool enforcePMColor = buffer.readBool();
    if (!buffer.isValid()) {
        return nullptr;
    }
    return SkArithmeticImageFilter::Make(k[0], k[1], k[2], k[3], enforcePMColor, common.getInput(0),
                                         common.getInput(1), &common.cropRect());
}

void ArithmeticImageFilterImpl::flatten(SkWriteBuffer& buffer) const {
    this->INHERITED::flatten(buffer);
    for (int i = 0; i < 4; ++i) {
        buffer.writeScalar(fInputs.fK[i]);
    }
    buffer.writeBool(fInputs.fEnforcePMColor);
}

static Sk4f pin(float min, const Sk4f& val, float max) {
    return Sk4f::Max(min, Sk4f::Min(val, max));
}

template <bool EnforcePMColor>
void arith_span(const float k[], SkPMColor dst[], const SkPMColor src[], int count) {
    const Sk4f k1 = k[0] * (1/255.0f),
               k2 = k[1],
               k3 = k[2],
               k4 = k[3] * 255.0f + 0.5f;

    for (int i = 0; i < count; i++) {
        Sk4f s = SkNx_cast<float>(Sk4b::Load(src+i)),
             d = SkNx_cast<float>(Sk4b::Load(dst+i)),
             r = pin(0, k1*s*d + k2*s + k3*d + k4, 255);
        if (EnforcePMColor) {
            Sk4f a = SkNx_shuffle<3,3,3,3>(r);
            r = Sk4f::Min(a, r);
        }
        SkNx_cast<uint8_t>(r).store(dst+i);
    }
}

// apply mode to src==transparent (0)
template<bool EnforcePMColor> void arith_transparent(const float k[], SkPMColor dst[], int count) {
    const Sk4f k3 = k[2],
               k4 = k[3] * 255.0f + 0.5f;

    for (int i = 0; i < count; i++) {
        Sk4f d = SkNx_cast<float>(Sk4b::Load(dst+i)),
             r = pin(0, k3*d + k4, 255);
        if (EnforcePMColor) {
            Sk4f a = SkNx_shuffle<3,3,3,3>(r);
            r = Sk4f::Min(a, r);
        }
        SkNx_cast<uint8_t>(r).store(dst+i);
    }
}

static bool intersect(SkPixmap* dst, SkPixmap* src, int srcDx, int srcDy) {
    SkIRect dstR = SkIRect::MakeWH(dst->width(), dst->height());
    SkIRect srcR = SkIRect::MakeXYWH(srcDx, srcDy, src->width(), src->height());
    SkIRect sect;
    if (!sect.intersect(dstR, srcR)) {
        return false;
    }
    *dst = SkPixmap(dst->info().makeDimensions(sect.size()),
                    dst->addr(sect.fLeft, sect.fTop),
                    dst->rowBytes());
    *src = SkPixmap(src->info().makeDimensions(sect.size()),
                    src->addr(std::max(0, -srcDx), std::max(0, -srcDy)),
                    src->rowBytes());
    return true;
}

sk_sp<SkSpecialImage> ArithmeticImageFilterImpl::onFilterImage(const Context& ctx,
                                                               SkIPoint* offset) const {
    SkIPoint backgroundOffset = SkIPoint::Make(0, 0);
    sk_sp<SkSpecialImage> background(this->filterInput(0, ctx, &backgroundOffset));

    SkIPoint foregroundOffset = SkIPoint::Make(0, 0);
    sk_sp<SkSpecialImage> foreground(this->filterInput(1, ctx, &foregroundOffset));

    SkIRect foregroundBounds = SkIRect::MakeEmpty();
    if (foreground) {
        foregroundBounds = SkIRect::MakeXYWH(foregroundOffset.x(), foregroundOffset.y(),
                                             foreground->width(), foreground->height());
    }

    SkIRect srcBounds = SkIRect::MakeEmpty();
    if (background) {
        srcBounds = SkIRect::MakeXYWH(backgroundOffset.x(), backgroundOffset.y(),
                                      background->width(), background->height());
    }

    srcBounds.join(foregroundBounds);
    if (srcBounds.isEmpty()) {
        return nullptr;
    }

    SkIRect bounds;
    if (!this->applyCropRect(ctx, srcBounds, &bounds)) {
        return nullptr;
    }

    offset->fX = bounds.left();
    offset->fY = bounds.top();

#if SK_SUPPORT_GPU
    if (ctx.gpuBacked()) {
        return this->filterImageGPU(ctx, background, backgroundOffset, foreground,
                                    foregroundOffset, bounds);
    }
#endif

    sk_sp<SkSpecialSurface> surf(ctx.makeSurface(bounds.size()));
    if (!surf) {
        return nullptr;
    }

    SkCanvas* canvas = surf->getCanvas();
    SkASSERT(canvas);

    canvas->clear(0x0);  // can't count on background to fully clear the background
    canvas->translate(SkIntToScalar(-bounds.left()), SkIntToScalar(-bounds.top()));

    if (background) {
        SkPaint paint;
        paint.setBlendMode(SkBlendMode::kSrc);
        background->draw(canvas, SkIntToScalar(backgroundOffset.fX),
                         SkIntToScalar(backgroundOffset.fY), &paint);
    }

    this->drawForeground(canvas, foreground.get(), foregroundBounds);

    return surf->makeImageSnapshot();
}

SkIRect ArithmeticImageFilterImpl::onFilterBounds(const SkIRect& src,
                                                  const SkMatrix& ctm,
                                                  MapDirection dir,
                                                  const SkIRect* inputRect) const {
    if (kReverse_MapDirection == dir) {
        return INHERITED::onFilterBounds(src, ctm, dir, inputRect);
    }

    SkASSERT(2 == this->countInputs());

    // result(i1,i2) = k1*i1*i2 + k2*i1 + k3*i2 + k4
    // Note that background (getInput(0)) is i2, and foreground (getInput(1)) is i1.
    auto i2 = this->getInput(0) ? this->getInput(0)->filterBounds(src, ctm, dir, nullptr) : src;
    auto i1 = this->getInput(1) ? this->getInput(1)->filterBounds(src, ctm, dir, nullptr) : src;

    // Arithmetic with non-zero k4 may influence the complete filter primitive
    // region. [k4 > 0 => result(0,0) = k4 => result(i1,i2) >= k4]
    if (!SkScalarNearlyZero(fInputs.fK[3])) {
        i1.join(i2);
        return i1;
    }

    // If both K2 or K3 are non-zero, both i1 and i2 appear.
    if (!SkScalarNearlyZero(fInputs.fK[1]) && !SkScalarNearlyZero(fInputs.fK[2])) {
        i1.join(i2);
        return i1;
    }

    // If k2 is non-zero, output can be produced whenever i1 is non-transparent.
    // [k3 = k4 = 0 => result(i1,i2) = k1*i1*i2 + k2*i1 = (k1*i2 + k2)*i1]
    if (!SkScalarNearlyZero(fInputs.fK[1])) {
        return i1;
    }

    // If k3 is non-zero, output can be produced whenever i2 is non-transparent.
    // [k2 = k4 = 0 => result(i1,i2) = k1*i1*i2 + k3*i2 = (k1*i1 + k3)*i2]
    if (!SkScalarNearlyZero(fInputs.fK[2])) {
        return i2;
    }

    // If just k1 is non-zero, output will only be produce where both inputs
    // are non-transparent. Use intersection.
    // [k1 > 0 and k2 = k3 = k4 = 0 => result(i1,i2) = k1*i1*i2]
    if (!SkScalarNearlyZero(fInputs.fK[0])) {
        if (!i1.intersect(i2)) {
            return SkIRect::MakeEmpty();
        }
        return i1;
    }

    // [k1 = k2 = k3 = k4 = 0 => result(i1,i2) = 0]
    return SkIRect::MakeEmpty();
}

#if SK_SUPPORT_GPU

sk_sp<SkSpecialImage> ArithmeticImageFilterImpl::filterImageGPU(
        const Context& ctx,
        sk_sp<SkSpecialImage> background,
        const SkIPoint& backgroundOffset,
        sk_sp<SkSpecialImage> foreground,
        const SkIPoint& foregroundOffset,
        const SkIRect& bounds) const {
    SkASSERT(ctx.gpuBacked());

    auto context = ctx.getContext();

    GrSurfaceProxyView backgroundView, foregroundView;

    GrProtected isProtected = GrProtected::kNo;
    if (background) {
        backgroundView = background->view(context);
        SkASSERT(backgroundView.proxy());
        isProtected = backgroundView.proxy()->isProtected();
    }

    if (foreground) {
        foregroundView = foreground->view(context);
        SkASSERT(foregroundView.proxy());
        isProtected = foregroundView.proxy()->isProtected();
    }

    GrPaint paint;
    std::unique_ptr<GrFragmentProcessor> bgFP;
    const auto& caps = *ctx.getContext()->priv().caps();
    GrSamplerState sampler(GrSamplerState::WrapMode::kClampToBorder,
                           GrSamplerState::Filter::kNearest);

    if (background) {
        SkRect bgSubset = SkRect::Make(background->subset());
        SkMatrix backgroundMatrix = SkMatrix::MakeTrans(
                SkIntToScalar(bgSubset.left() - backgroundOffset.fX),
                SkIntToScalar(bgSubset.top()  - backgroundOffset.fY));
        bgFP = GrTextureEffect::MakeSubset(std::move(backgroundView), background->alphaType(),
                                           backgroundMatrix, sampler, bgSubset, caps);
        bgFP = GrColorSpaceXformEffect::Make(std::move(bgFP), background->getColorSpace(),
                                             background->alphaType(),
                                             ctx.colorSpace());
    } else {
        bgFP = GrConstColorProcessor::Make(SK_PMColor4fTRANSPARENT,
                                           GrConstColorProcessor::InputMode::kIgnore);
    }

    if (foreground) {
        SkRect fgSubset = SkRect::Make(foreground->subset());
        SkMatrix foregroundMatrix = SkMatrix::MakeTrans(
                SkIntToScalar(fgSubset.left() - foregroundOffset.fX),
                SkIntToScalar(fgSubset.top()  - foregroundOffset.fY));
        auto fgFP = GrTextureEffect::MakeSubset(std::move(foregroundView), foreground->alphaType(),
                                                foregroundMatrix, sampler, fgSubset, caps);
        fgFP = GrColorSpaceXformEffect::Make(std::move(fgFP),
                                             foreground->getColorSpace(),
                                             foreground->alphaType(),
                                             ctx.colorSpace());
        paint.addColorFragmentProcessor(std::move(fgFP));

        static auto effect = std::get<0>(SkRuntimeEffect::Make(SkString(SKSL_ARITHMETIC_SRC)));
        SkASSERT(effect->inputSize() == sizeof(fInputs));
        std::unique_ptr<GrFragmentProcessor> xferFP = GrSkSLFP::Make(
                context, effect, "Arithmetic", SkData::MakeWithCopy(&fInputs, sizeof(fInputs)));
        if (xferFP) {
            ((GrSkSLFP&) *xferFP).addChild(std::move(bgFP));
            paint.addColorFragmentProcessor(std::move(xferFP));
        }
    } else {
        paint.addColorFragmentProcessor(std::move(bgFP));
    }

    paint.setPorterDuffXPFactory(SkBlendMode::kSrc);

    auto renderTargetContext = GrRenderTargetContext::Make(
            context, ctx.grColorType(), ctx.refColorSpace(), SkBackingFit::kApprox, bounds.size(),
            1, GrMipMapped::kNo, isProtected, kBottomLeft_GrSurfaceOrigin);
    if (!renderTargetContext) {
        return nullptr;
    }

    SkMatrix matrix;
    matrix.setTranslate(SkIntToScalar(-bounds.left()), SkIntToScalar(-bounds.top()));
    renderTargetContext->drawRect(GrNoClip(), std::move(paint), GrAA::kNo, matrix,
                                  SkRect::Make(bounds));

    return SkSpecialImage::MakeDeferredFromGpu(context,
                                               SkIRect::MakeWH(bounds.width(), bounds.height()),
                                               kNeedNewImageUniqueID_SpecialImage,
                                               renderTargetContext->readSurfaceView(),
                                               renderTargetContext->colorInfo().colorType(),
                                               renderTargetContext->colorInfo().refColorSpace());
}
#endif

void ArithmeticImageFilterImpl::drawForeground(SkCanvas* canvas, SkSpecialImage* img,
                                               const SkIRect& fgBounds) const {
    SkPixmap dst;
    if (!canvas->peekPixels(&dst)) {
        return;
    }

    const SkMatrix& ctm = canvas->getTotalMatrix();
    SkASSERT(ctm.getType() <= SkMatrix::kTranslate_Mask);
    const int dx = SkScalarRoundToInt(ctm.getTranslateX());
    const int dy = SkScalarRoundToInt(ctm.getTranslateY());
    // be sure to perform this offset using SkIRect, since it saturates to avoid overflows
    const SkIRect fgoffset = fgBounds.makeOffset(dx, dy);

    if (img) {
        SkBitmap srcBM;
        SkPixmap src;
        if (!img->getROPixels(&srcBM)) {
            return;
        }
        if (!srcBM.peekPixels(&src)) {
            return;
        }

        auto proc = fInputs.fEnforcePMColor ? arith_span<true> : arith_span<false>;
        SkPixmap tmpDst = dst;
        if (intersect(&tmpDst, &src, fgoffset.fLeft, fgoffset.fTop)) {
            for (int y = 0; y < tmpDst.height(); ++y) {
                proc(fInputs.fK, tmpDst.writable_addr32(0, y), src.addr32(0, y), tmpDst.width());
            }
        }
    }

    // Now apply the mode with transparent-color to the outside of the fg image
    SkRegion outside(SkIRect::MakeWH(dst.width(), dst.height()));
    outside.op(fgoffset, SkRegion::kDifference_Op);
    auto proc = fInputs.fEnforcePMColor ? arith_transparent<true> : arith_transparent<false>;
    for (SkRegion::Iterator iter(outside); !iter.done(); iter.next()) {
        const SkIRect r = iter.rect();
        for (int y = r.fTop; y < r.fBottom; ++y) {
            proc(fInputs.fK, dst.writable_addr32(r.fLeft, y), r.width());
        }
    }
}