src/effects/SkXfermodeImageFilter.cpp

/*
 * Copyright 2013 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "SkXfermodeImageFilter.h"

#include "SkCanvas.h"
#include "SkColorPriv.h"
#include "SkReadBuffer.h"
#include "SkSpecialImage.h"
#include "SkSpecialSurface.h"
#include "SkWriteBuffer.h"
#include "SkXfermode.h"
#if SK_SUPPORT_GPU
#include "GrContext.h"
#include "GrDrawContext.h"
#include "effects/GrConstColorProcessor.h"
#include "effects/GrTextureDomain.h"
#include "effects/GrSimpleTextureEffect.h"
#include "SkGr.h"
#endif

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

sk_sp<SkImageFilter> SkXfermodeImageFilter::Make(sk_sp<SkXfermode> mode,
                                                 sk_sp<SkImageFilter> background,
                                                 sk_sp<SkImageFilter> foreground,
                                                 const CropRect* cropRect) {
    sk_sp<SkImageFilter> inputs[2] = { std::move(background), std::move(foreground) };
    return sk_sp<SkImageFilter>(new SkXfermodeImageFilter(mode, inputs, cropRect));
}

SkXfermodeImageFilter::SkXfermodeImageFilter(sk_sp<SkXfermode> mode,
                                             sk_sp<SkImageFilter> inputs[2],
                                             const CropRect* cropRect)
    : INHERITED(inputs, 2, cropRect)
    , fMode(std::move(mode)) {
}

sk_sp<SkFlattenable> SkXfermodeImageFilter::CreateProc(SkReadBuffer& buffer) {
    SK_IMAGEFILTER_UNFLATTEN_COMMON(common, 2);
    sk_sp<SkXfermode> mode(buffer.readXfermode());
    return Make(std::move(mode), common.getInput(0), common.getInput(1), &common.cropRect());
}

void SkXfermodeImageFilter::flatten(SkWriteBuffer& buffer) const {
    this->INHERITED::flatten(buffer);
    buffer.writeFlattenable(fMode.get());
}

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

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

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

    SkIRect srcBounds = SkIRect::EmptyIRect();
    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 (source->isTextureBacked()) {
        return this->filterImageGPU(source,
                                    background, backgroundOffset, 
                                    foreground, foregroundOffset,
                                    bounds);
    }
#endif

    const SkImageInfo info = SkImageInfo::MakeN32(bounds.width(), bounds.height(),
                                                  kPremul_SkAlphaType);
    sk_sp<SkSpecialSurface> surf(source->makeSurface(info));
    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()));

    SkPaint paint;
    paint.setXfermodeMode(SkXfermode::kSrc_Mode);

    if (background) {
        background->draw(canvas,
                         SkIntToScalar(backgroundOffset.fX), SkIntToScalar(backgroundOffset.fY),
                         &paint);
    }

    paint.setXfermode(fMode);

    if (foreground) {
        foreground->draw(canvas,
                         SkIntToScalar(foregroundOffset.fX), SkIntToScalar(foregroundOffset.fY),
                         &paint);
    }

    canvas->clipRect(SkRect::Make(foregroundBounds), SkRegion::kDifference_Op);
    paint.setColor(SK_ColorTRANSPARENT);
    canvas->drawPaint(paint);

    return surf->makeImageSnapshot();
}

#ifndef SK_IGNORE_TO_STRING
void SkXfermodeImageFilter::toString(SkString* str) const {
    str->appendf("SkXfermodeImageFilter: (");
    str->appendf("xfermode: (");
    if (fMode) {
        fMode->toString(str);
    }
    str->append(")");
    if (this->getInput(0)) {
        str->appendf("foreground: (");
        this->getInput(0)->toString(str);
        str->appendf(")");
    }
    if (this->getInput(1)) {
        str->appendf("background: (");
        this->getInput(1)->toString(str);
        str->appendf(")");
    }
    str->append(")");
}
#endif

#if SK_SUPPORT_GPU

#include "SkXfermode_proccoeff.h"

sk_sp<SkSpecialImage> SkXfermodeImageFilter::filterImageGPU(SkSpecialImage* source,
                                                            sk_sp<SkSpecialImage> background,
                                                            const SkIPoint& backgroundOffset,
                                                            sk_sp<SkSpecialImage> foreground,
                                                            const SkIPoint& foregroundOffset,
                                                            const SkIRect& bounds) const {
    SkASSERT(source->isTextureBacked());

    GrContext* context = source->getContext();

    sk_sp<GrTexture> backgroundTex, foregroundTex;
    
    if (background) {
        backgroundTex = background->asTextureRef(context);
    }

    if (foreground) {
        foregroundTex = foreground->asTextureRef(context);
    }

    GrPaint paint;
    // SRGBTODO: AllowSRGBInputs?
    sk_sp<GrFragmentProcessor> bgFP;

    if (backgroundTex) {
        SkMatrix backgroundMatrix;
        backgroundMatrix.setIDiv(backgroundTex->width(), backgroundTex->height());
        backgroundMatrix.preTranslate(SkIntToScalar(-backgroundOffset.fX),
                                      SkIntToScalar(-backgroundOffset.fY));
        bgFP = GrTextureDomainEffect::Make(
                            backgroundTex.get(), backgroundMatrix,
                            GrTextureDomain::MakeTexelDomain(backgroundTex.get(),
                                                             background->subset()),
                            GrTextureDomain::kDecal_Mode,
                            GrTextureParams::kNone_FilterMode);
    } else {
        bgFP = GrConstColorProcessor::Make(GrColor_TRANSPARENT_BLACK,
                                             GrConstColorProcessor::kIgnore_InputMode);
    }

    if (foregroundTex) {
        SkMatrix foregroundMatrix;
        foregroundMatrix.setIDiv(foregroundTex->width(), foregroundTex->height());
        foregroundMatrix.preTranslate(SkIntToScalar(-foregroundOffset.fX),
                                      SkIntToScalar(-foregroundOffset.fY));

        sk_sp<GrFragmentProcessor> foregroundFP;

        foregroundFP = GrTextureDomainEffect::Make(
                            foregroundTex.get(), foregroundMatrix,
                            GrTextureDomain::MakeTexelDomain(foregroundTex.get(), 
                                                             foreground->subset()),
                            GrTextureDomain::kDecal_Mode,
                            GrTextureParams::kNone_FilterMode);

        paint.addColorFragmentProcessor(std::move(foregroundFP));

        // A null fMode is interpreted to mean kSrcOver_Mode (to match raster).
        SkAutoTUnref<SkXfermode> mode(SkSafeRef(fMode.get()));
        if (!mode) {
            // It would be awesome to use SkXfermode::Create here but it knows better
            // than us and won't return a kSrcOver_Mode SkXfermode. That means we
            // have to get one the hard way.
            struct ProcCoeff rec;
            rec.fProc = SkXfermode::GetProc(SkXfermode::kSrcOver_Mode);
            SkXfermode::ModeAsCoeff(SkXfermode::kSrcOver_Mode, &rec.fSC, &rec.fDC);

            mode.reset(new SkProcCoeffXfermode(rec, SkXfermode::kSrcOver_Mode));
        }

        sk_sp<GrFragmentProcessor> xferFP(
            mode->makeFragmentProcessorForImageFilter(std::move(bgFP)));

        // A null 'xferFP' here means kSrc_Mode was used in which case we can just proceed
        if (xferFP) {
            paint.addColorFragmentProcessor(std::move(xferFP));
        }
    } else {
        paint.addColorFragmentProcessor(std::move(bgFP));
    }

    paint.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);

    sk_sp<GrDrawContext> drawContext(context->newDrawContext(SkBackingFit::kApprox,
                                                             bounds.width(), bounds.height(),
                                                             kSkia8888_GrPixelConfig));
    if (!drawContext) {
        return nullptr;
    }

    SkMatrix matrix;
    matrix.setTranslate(SkIntToScalar(-bounds.left()), SkIntToScalar(-bounds.top()));
    drawContext->drawRect(GrNoClip(), paint, matrix, SkRect::Make(bounds));

    return SkSpecialImage::MakeFromGpu(SkIRect::MakeWH(bounds.width(), bounds.height()),
                                       kNeedNewImageUniqueID_SpecialImage,
                                       drawContext->asTexture());
}

#endif