Minor code health improvements in ImageBitmap and ImageBuffer

This CL contains minor changes in ImageBitmap and ImageBuffer to:

- use blending in SkCanvas::drawImage() only if needed
- fix ImageBitmap->CopyImageData() behavior to match the signature
- use SkImageInfo::minRowBytes() in SkImage::readPixels() call sites

Bug: 785313,788879,788881
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I1473fc71ce1785f87c0f3e47441515f6cd3dd7a7
Reviewed-on: https://chromium-review.googlesource.com/793951
Commit-Queue: Mohammad Reza Zakerinasab <zakerinasab@chromium.org>
Reviewed-by: Justin Novosad <junov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#519755}

third_party/WebKit/Source/core/imagebitmap/ImageBitmap.cpp

@@ -171,17 +171,20 @@ SkImageInfo GetSkImageInfo(const scoped_refptr<StaticBitmapImage>& image) {
 }
 
 // This function results in a readback due to using SkImage::readPixels().
+// Returns transparent black pixels if the input SkImageInfo.bounds() does
+// not intersect with the input image boundaries.
 scoped_refptr<Uint8Array> CopyImageData(
     const scoped_refptr<StaticBitmapImage>& input,
-    const SkImageInfo& info) {
+    const SkImageInfo& info,
+    const unsigned x = 0,
+    const unsigned y = 0) {
   if (info.isEmpty())
     return nullptr;
   sk_sp<SkImage> sk_image = input->PaintImageForCurrentFrame().GetSkImage();
   if (sk_image->bounds().isEmpty())
     return nullptr;
-  unsigned width = static_cast<unsigned>(input->width());
   scoped_refptr<ArrayBuffer> dst_buffer =
-      ArrayBuffer::CreateOrNull(width * input->height(), info.bytesPerPixel());
+      ArrayBuffer::CreateOrNull(info.computeMinByteSize(), 1);
   if (!dst_buffer)
     return nullptr;
   unsigned byte_length = dst_buffer->ByteLength();
@@ -189,8 +192,8 @@ scoped_refptr<Uint8Array> CopyImageData(
       Uint8Array::Create(std::move(dst_buffer), 0, byte_length);
   if (!dst_pixels)
     return nullptr;
-  bool read_pixels_successful = sk_image->readPixels(
-      info, dst_pixels->Data(), width * info.bytesPerPixel(), 0, 0);
+  bool read_pixels_successful =
+      sk_image->readPixels(info, dst_pixels->Data(), info.minRowBytes(), x, y);
   DCHECK(read_pixels_successful);
   if (!read_pixels_successful)
     return nullptr;
@@ -260,7 +263,9 @@ scoped_refptr<StaticBitmapImage> FlipImageVertically(
   SkCanvas* canvas = surface->getCanvas();
   canvas->scale(1, -1);
   canvas->translate(0, -input->height());
-  canvas->drawImage(image.get(), 0, 0);
+  SkPaint paint;
+  paint.setBlendMode(SkBlendMode::kSrc);
+  canvas->drawImage(image.get(), 0, 0, &paint);
   return StaticBitmapImage::Create(surface->makeImageSnapshot(),
                                    input->ContextProviderWrapper());
 }
@@ -548,7 +553,9 @@ static scoped_refptr<StaticBitmapImage> CropImageAndApplyColorSpaceConversion(
       sk_sp<SkSurface> surface =
           SkSurface::MakeRaster(GetSkImageInfo(StaticBitmapImage::Create(
               skia_image, image->ContextProviderWrapper())));
-      surface->getCanvas()->drawImage(skia_image.get(), 0, 0);
+      SkPaint paint;
+      paint.setBlendMode(SkBlendMode::kSrc);
+      surface->getCanvas()->drawImage(skia_image.get(), 0, 0, &paint);
       skia_image = surface->makeImageSnapshot();
     }
   }

third_party/WebKit/Source/core/imagebitmap/ImageBitmapTest.cpp

@@ -399,9 +399,8 @@ TEST_F(ImageBitmapTest, MAYBE_ImageBitmapColorSpaceConversionImageBitmap) {
 
   std::unique_ptr<uint8_t[]> src_pixel(
       new uint8_t[raster_image_info.bytesPerPixel()]());
-  EXPECT_TRUE(image->readPixels(
-      raster_image_info.makeWH(1, 1), src_pixel.get(),
-      image->width() * raster_image_info.bytesPerPixel(), 5, 5));
+  EXPECT_TRUE(image->readPixels(raster_image_info.makeWH(1, 1), src_pixel.get(),
+                                raster_image_info.minRowBytes(), 5, 5));
 
   ImageResourceContent* source_image_resource =
       ImageResourceContent::CreateLoaded(

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

@@ -274,14 +274,13 @@ bool ImageBuffer::GetImageData(const IntRect& rect,
                                bool* is_gpu_readback_invoked) const {
   uint8_t bytes_per_pixel = surface_->ColorParams().BytesPerPixel();
   CheckedNumeric<int> data_size = bytes_per_pixel;
-  data_size *= rect.Width();
-  data_size *= rect.Height();
+  data_size *= rect.Size().Area();
   if (!data_size.IsValid() ||
       data_size.ValueOrDie() > v8::TypedArray::kMaxLength)
     return false;
 
   if (!IsSurfaceValid()) {
-    size_t alloc_size_in_bytes = rect.Width() * rect.Height() * bytes_per_pixel;
+    size_t alloc_size_in_bytes = rect.Size().Area() * bytes_per_pixel;
     auto data = WTF::ArrayBufferContents::CreateDataHandle(
         alloc_size_in_bytes, WTF::ArrayBufferContents::kZeroInitialize);
     if (!data)
@@ -304,7 +303,7 @@ bool ImageBuffer::GetImageData(const IntRect& rect,
       || rect.X() < 0 || rect.Y() < 0 ||
       rect.MaxX() > surface_->Size().Width() ||
       rect.MaxY() > surface_->Size().Height();
-  size_t alloc_size_in_bytes = rect.Width() * rect.Height() * bytes_per_pixel;
+  size_t alloc_size_in_bytes = rect.Size().Area() * bytes_per_pixel;
   WTF::ArrayBufferContents::InitializationPolicy initialization_policy =
       may_have_stray_area ? WTF::ArrayBufferContents::kZeroInitialize
                           : WTF::ArrayBufferContents::kDontInitialize;
@@ -323,7 +322,7 @@ bool ImageBuffer::GetImageData(const IntRect& rect,
                                        kUnpremul_SkAlphaType);
   sk_sp<SkImage> sk_image = snapshot->PaintImageForCurrentFrame().GetSkImage();
   bool read_pixels_successful = sk_image->readPixels(
-      info, result.Data(), bytes_per_pixel * rect.Width(), rect.X(), rect.Y());
+      info, result.Data(), info.minRowBytes(), rect.X(), rect.Y());
   DCHECK(read_pixels_successful ||
          !sk_image->bounds().intersect(SkIRect::MakeXYWH(
              rect.X(), rect.Y(), info.width(), info.height())));
@@ -410,6 +409,8 @@ void ImageBuffer::SetSurface(std::unique_ptr<ImageBufferSurface> surface) {
     image = nullptr;
     image = StaticBitmapImage::Create(texture_image->makeNonTextureImage());
   }
+  SkPaint paint;
+  paint.setBlendMode(SkBlendMode::kSrc);
   surface->Canvas()->drawImage(image->PaintImageForCurrentFrame(), 0, 0);
   surface->SetImageBuffer(this);
   surface_ = std::move(surface);