third_party/WebKit/Source/platform/graphics/CrossfadeGeneratedImage.cpp

/*
 * Copyright (C) 2011 Apple Inc. All rights reserved.
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 *
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
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#include "platform/graphics/CrossfadeGeneratedImage.h"

#include "platform/geometry/FloatRect.h"
#include "platform/graphics/GraphicsContext.h"

namespace blink {

CrossfadeGeneratedImage::CrossfadeGeneratedImage(PassRefPtr<Image> fromImage, PassRefPtr<Image> toImage, float percentage, IntSize crossfadeSize, const IntSize& size)
    : GeneratedImage(size)
    , m_fromImage(fromImage)
    , m_toImage(toImage)
    , m_percentage(percentage)
    , m_crossfadeSize(crossfadeSize)
{
}

void CrossfadeGeneratedImage::drawCrossfade(SkCanvas* canvas, const SkPaint& paint, ImageClampingMode clampMode)
{
    FloatRect fromImageRect(FloatPoint(), FloatSize(m_fromImage->size()));
    FloatRect toImageRect(FloatPoint(), FloatSize(m_toImage->size()));
    FloatRect destRect((FloatPoint()), FloatSize(m_crossfadeSize));

    // TODO(junov): The various effects encoded into paint should probably be applied here
    // instead of inside the layer.  This probably faulty behavior was maintained in order
    // to preserve pre-existing behavior while refactoring this code.  This should be
    // investigated further. crbug.com/472634
    SkPaint layerPaint;
    layerPaint.setXfermode(sk_ref_sp(paint.getXfermode()));
    SkAutoCanvasRestore ar(canvas, false);
    canvas->saveLayer(nullptr, &layerPaint);

    SkPaint imagePaint(paint);
    imagePaint.setXfermodeMode(SkXfermode::kSrcOver_Mode);
    int imageAlpha = clampedAlphaForBlending(1 - m_percentage);
    imagePaint.setAlpha(imageAlpha > 255 ? 255 : imageAlpha);
    imagePaint.setAntiAlias(paint.isAntiAlias());
    // TODO(junov): This code should probably be propagating the RespectImageOrientationEnum
    // form CrossfadeGeneratedImage::draw. Code was written this way during refactoring to
    // avoid modifying existing behavior, but this warrants further investigation. crbug.com/472634
    m_fromImage->draw(canvas, imagePaint, destRect, fromImageRect, DoNotRespectImageOrientation, clampMode);
    imagePaint.setXfermodeMode(SkXfermode::kPlus_Mode);
    imageAlpha = clampedAlphaForBlending(m_percentage);
    imagePaint.setAlpha(imageAlpha > 255 ? 255 : imageAlpha);
    m_toImage->draw(canvas, imagePaint, destRect, toImageRect, DoNotRespectImageOrientation, clampMode);
}

void CrossfadeGeneratedImage::draw(SkCanvas* canvas, const SkPaint& paint, const FloatRect& dstRect, const FloatRect& srcRect, RespectImageOrientationEnum, ImageClampingMode clampMode)
{
    // Draw nothing if either of the images hasn't loaded yet.
    if (m_fromImage == Image::nullImage() || m_toImage == Image::nullImage())
        return;

    SkAutoCanvasRestore ar(canvas, true);
    canvas->clipRect(dstRect);
    canvas->translate(dstRect.x(), dstRect.y());
    if (dstRect.size() != srcRect.size())
        canvas->scale(dstRect.width() / srcRect.width(), dstRect.height() / srcRect.height());
    canvas->translate(-srcRect.x(), -srcRect.y());

    drawCrossfade(canvas, paint, clampMode);
}

void CrossfadeGeneratedImage::drawTile(GraphicsContext& context, const FloatRect& srcRect)
{
    // Draw nothing if either of the images hasn't loaded yet.
    if (m_fromImage == Image::nullImage() || m_toImage == Image::nullImage())
        return;

    SkPaint paint = context.fillPaint();
    paint.setXfermodeMode(SkXfermode::kSrcOver_Mode);
    paint.setAntiAlias(context.shouldAntialias());
    FloatRect destRect((FloatPoint()), FloatSize(m_crossfadeSize));
    paint.setFilterQuality(context.computeFilterQuality(this, destRect, srcRect));
    drawCrossfade(context.canvas(), paint, ClampImageToSourceRect);
}

} // namespace blink