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

/*
 * Copyright (C) 2011 Apple Inc. All rights reserved.
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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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 from 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