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 "SkDevice.h"
#include "SkColorPriv.h"
#include "SkReadBuffer.h"
#include "SkWriteBuffer.h"
#include "SkXfermode.h"
#if SK_SUPPORT_GPU
#include "GrContext.h"
#include "effects/GrSimpleTextureEffect.h"
#include "SkGr.h"
#include "SkImageFilterUtils.h"
#endif

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

SkXfermodeImageFilter::SkXfermodeImageFilter(SkXfermode* mode,
                                             SkImageFilter* background,
                                             SkImageFilter* foreground,
                                             const CropRect* cropRect)
  : INHERITED(background, foreground, cropRect), fMode(mode) {
    SkSafeRef(fMode);
}

SkXfermodeImageFilter::~SkXfermodeImageFilter() {
    SkSafeUnref(fMode);
}

SkXfermodeImageFilter::SkXfermodeImageFilter(SkReadBuffer& buffer)
  : INHERITED(2, buffer) {
    fMode = buffer.readXfermode();
}

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

bool SkXfermodeImageFilter::onFilterImage(Proxy* proxy,
                                            const SkBitmap& src,
                                            const SkMatrix& ctm,
                                            SkBitmap* dst,
                                            SkIPoint* offset) const {
    SkBitmap background = src, foreground = src;
    SkImageFilter* backgroundInput = getInput(0);
    SkImageFilter* foregroundInput = getInput(1);
    SkIPoint backgroundOffset = SkIPoint::Make(0, 0);
    if (backgroundInput &&
        !backgroundInput->filterImage(proxy, src, ctm, &background, &backgroundOffset)) {
        return false;
    }
    SkIPoint foregroundOffset = SkIPoint::Make(0, 0);
    if (foregroundInput &&
        !foregroundInput->filterImage(proxy, src, ctm, &foreground, &foregroundOffset)) {
        return false;
    }

    SkIRect bounds, foregroundBounds;
    background.getBounds(&bounds);
    bounds.offset(backgroundOffset);
    foreground.getBounds(&foregroundBounds);
    foregroundBounds.offset(foregroundOffset);
    bounds.join(foregroundBounds);
    if (!applyCropRect(&bounds, ctm)) {
        return false;
    }

    SkAutoTUnref<SkBaseDevice> device(proxy->createDevice(bounds.width(), bounds.height()));
    if (NULL == device.get()) {
        return false;
    }
    SkCanvas canvas(device);
    canvas.translate(SkIntToScalar(-bounds.left()), SkIntToScalar(-bounds.top()));
    SkPaint paint;
    paint.setXfermodeMode(SkXfermode::kSrc_Mode);
    canvas.drawBitmap(background, SkIntToScalar(backgroundOffset.fX),
                      SkIntToScalar(backgroundOffset.fY), &paint);
    paint.setXfermode(fMode);
    canvas.drawBitmap(foreground, SkIntToScalar(foregroundOffset.fX),
                      SkIntToScalar(foregroundOffset.fY), &paint);
    canvas.clipRect(SkRect::Make(foregroundBounds), SkRegion::kDifference_Op);
    paint.setColor(SK_ColorTRANSPARENT);
    canvas.drawPaint(paint);
    *dst = device->accessBitmap(false);
    offset->fX = bounds.left();
    offset->fY = bounds.top();
    return true;
}

#if SK_SUPPORT_GPU

bool SkXfermodeImageFilter::filterImageGPU(Proxy* proxy,
                                           const SkBitmap& src,
                                           const SkMatrix& ctm,
                                           SkBitmap* result,
                                           SkIPoint* offset) const {
    SkBitmap background;
    SkIPoint backgroundOffset = SkIPoint::Make(0, 0);
    if (!SkImageFilterUtils::GetInputResultGPU(getInput(0), proxy, src, ctm, &background,
                                               &backgroundOffset)) {
        return false;
    }
    GrTexture* backgroundTex = background.getTexture();
    SkBitmap foreground;
    SkIPoint foregroundOffset = SkIPoint::Make(0, 0);
    if (!SkImageFilterUtils::GetInputResultGPU(getInput(1), proxy, src, ctm, &foreground,
                                               &foregroundOffset)) {
        return false;
    }
    GrTexture* foregroundTex = foreground.getTexture();
    GrContext* context = foregroundTex->getContext();

    GrEffectRef* xferEffect = NULL;

    GrTextureDesc desc;
    desc.fFlags = kRenderTarget_GrTextureFlagBit | kNoStencil_GrTextureFlagBit;
    desc.fWidth = src.width();
    desc.fHeight = src.height();
    desc.fConfig = kSkia8888_GrPixelConfig;

    GrAutoScratchTexture ast(context, desc);
    SkAutoTUnref<GrTexture> dst(ast.detach());

    GrContext::AutoRenderTarget art(context, dst->asRenderTarget());

    SkXfermode::Coeff sm, dm;
    if (!SkXfermode::AsNewEffectOrCoeff(fMode, &xferEffect, &sm, &dm, backgroundTex)) {
        return false;
    }

    SkMatrix foregroundMatrix = GrEffect::MakeDivByTextureWHMatrix(foregroundTex);
    foregroundMatrix.preTranslate(SkIntToScalar(backgroundOffset.fX-foregroundOffset.fX),
                                  SkIntToScalar(backgroundOffset.fY-foregroundOffset.fY));


    SkRect srcRect;
    src.getBounds(&srcRect);
    if (NULL != xferEffect) {
        GrPaint paint;
        paint.addColorTextureEffect(foregroundTex, foregroundMatrix);
        paint.addColorEffect(xferEffect)->unref();
        context->drawRect(paint, srcRect);
    } else {
        GrPaint backgroundPaint;
        SkMatrix backgroundMatrix = GrEffect::MakeDivByTextureWHMatrix(backgroundTex);
        backgroundPaint.addColorTextureEffect(backgroundTex, backgroundMatrix);
        context->drawRect(backgroundPaint, srcRect);

        GrPaint foregroundPaint;
        foregroundPaint.setBlendFunc(sk_blend_to_grblend(sm), sk_blend_to_grblend(dm));
        foregroundPaint.addColorTextureEffect(foregroundTex, foregroundMatrix);
        context->drawRect(foregroundPaint, srcRect);
    }
    offset->fX = backgroundOffset.fX;
    offset->fY = backgroundOffset.fY;
    return SkImageFilterUtils::WrapTexture(dst, src.width(), src.height(), result);
}

#endif