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

// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "platform/graphics/ImagePattern.h"

#include "platform/graphics/Image.h"
#include "platform/graphics/skia/SkiaUtils.h"
#include "third_party/skia/include/core/SkCanvas.h"
#include "third_party/skia/include/core/SkImage.h"
#include "third_party/skia/include/core/SkShader.h"
#include "third_party/skia/include/core/SkSurface.h"

namespace blink {

PassRefPtr<ImagePattern> ImagePattern::create(PassRefPtr<Image> image,
                                              RepeatMode repeatMode) {
  return adoptRef(new ImagePattern(std::move(image), repeatMode));
}

ImagePattern::ImagePattern(PassRefPtr<Image> image, RepeatMode repeatMode)
    : Pattern(repeatMode), m_tileImage(image->imageForCurrentFrame()) {
  m_previousLocalMatrix.setIdentity();
  if (m_tileImage) {
    // TODO(fmalita): mechanism to extract the actual SkImageInfo from an
    // SkImage?
    const SkImageInfo info = SkImageInfo::MakeN32Premul(
        m_tileImage->width() + (isRepeatX() ? 0 : 2),
        m_tileImage->height() + (isRepeatY() ? 0 : 2));
    adjustExternalMemoryAllocated(info.getSafeSize(info.minRowBytes()));
  }
}

bool ImagePattern::isLocalMatrixChanged(const SkMatrix& localMatrix) const {
  if (isRepeatXY())
    return Pattern::isLocalMatrixChanged(localMatrix);
  return localMatrix != m_previousLocalMatrix;
}

sk_sp<SkShader> ImagePattern::createShader(const SkMatrix& localMatrix) {
  if (!m_tileImage)
    return SkShader::MakeColorShader(SK_ColorTRANSPARENT);

  if (isRepeatXY()) {
    // Fast path: for repeatXY we just return a shader from the original image.
    return m_tileImage->makeShader(SkShader::kRepeat_TileMode,
                                   SkShader::kRepeat_TileMode, &localMatrix);
  }

  // Skia does not have a "draw the tile only once" option. Clamp_TileMode
  // repeats the last line of the image after drawing one tile. To avoid
  // filling the space with arbitrary pixels, this workaround forces the
  // image to have a line of transparent pixels on the "repeated" edge(s),
  // thus causing extra space to be transparent filled.
  SkShader::TileMode tileModeX =
      isRepeatX() ? SkShader::kRepeat_TileMode : SkShader::kClamp_TileMode;
  SkShader::TileMode tileModeY =
      isRepeatY() ? SkShader::kRepeat_TileMode : SkShader::kClamp_TileMode;
  int borderPixelX = isRepeatX() ? 0 : 1;
  int borderPixelY = isRepeatY() ? 0 : 1;

  // Create a transparent image 2 pixels wider and/or taller than the
  // original, then copy the orignal into the middle of it.
  // FIXME: Is there a better way to pad (not scale) an image in skia?
  sk_sp<SkSurface> surface =
      SkSurface::MakeRasterN32Premul(m_tileImage->width() + 2 * borderPixelX,
                                     m_tileImage->height() + 2 * borderPixelY);
  if (!surface)
    return SkShader::MakeColorShader(SK_ColorTRANSPARENT);

  SkPaint paint;
  paint.setXfermodeMode(SkXfermode::kSrc_Mode);
  surface->getCanvas()->drawImage(m_tileImage, borderPixelX, borderPixelY,
                                  &paint);

  m_previousLocalMatrix = localMatrix;
  SkMatrix adjustedMatrix(localMatrix);
  adjustedMatrix.postTranslate(-borderPixelX, -borderPixelY);

  return surface->makeImageSnapshot()->makeShader(tileModeX, tileModeY,
                                                  &adjustedMatrix);
}

bool ImagePattern::isTextureBacked() const {
  return m_tileImage && m_tileImage->isTextureBacked();
}

}  // namespace blink