Fixing transparent pixels appearing black when rendered for the context menu.

chrome/renderer/chrome_render_frame_observer.cc

 // Copyright 2013 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 "chrome/renderer/chrome_render_frame_observer.h"
 
 #include <stddef.h>
 #include <string.h>
 
 #include <limits>
@@ skipping 25 matching lines @@
 #include "third_party/WebKit/public/platform/WebURLRequest.h"
 #include "third_party/WebKit/public/web/WebDataSource.h"
 #include "third_party/WebKit/public/web/WebDocument.h"
 #include "third_party/WebKit/public/web/WebElement.h"
 #include "third_party/WebKit/public/web/WebFrameContentDumper.h"
 #include "third_party/WebKit/public/web/WebLocalFrame.h"
 #include "third_party/WebKit/public/web/WebNode.h"
 #include "third_party/WebKit/public/web/WebSecurityPolicy.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/gfx/codec/jpeg_codec.h"
+#include "ui/gfx/codec/png_codec.h"
 #include "ui/gfx/geometry/size_f.h"
 #include "url/gurl.h"
 
 #if BUILDFLAG(ENABLE_PRINTING)
 #include "components/printing/common/print_messages.h"
 #include "components/printing/renderer/print_web_view_helper.h"
 #endif
 
 using blink::WebDataSource;
 using blink::WebElement;
 using blink::WebFrameContentDumper;
 using blink::WebLocalFrame;
 using blink::WebNode;
 using blink::WebString;
 using content::RenderFrame;
 
 // Maximum number of characters in the document to index.
 // Any text beyond this point will be clipped.
 static const size_t kMaxIndexChars = 65535;
 
 // Constants for UMA statistic collection.
 static const char kTranslateCaptureText[] = "Translate.CaptureText";
 
 // For a page that auto-refreshes, we still show the bubble, if
 // the refresh delay is less than this value (in seconds).
 static const double kLocationChangeIntervalInSeconds = 10;
 
+// For the context menu, we want to keep transparency as is instead of
+// replacing transparent pixels with black ones
+static const bool kDiscardTransparencyForContextMenu = false;

[msarett1, 2017/06/21 04:18:15]

I'm glad this is false.

"true" is fairly awkward because the png encoder must (1) unpremultiply by alpha
then (2) discard the alpha channel.  I'd like to remove that capability if
possible.

[Daniel Park, 2017/06/22 01:11:35]

I'm a little unsure of how to proceed with regards to this comment.
I made this constant a local variable in order to prevent confusion.

+
 namespace {
 
 // If the source image is null or occupies less area than
 // |thumbnail_min_area_pixels|, we return the image unmodified.  Otherwise, we
 // scale down the image so that the width and height do not exceed
 // |thumbnail_max_size_pixels|, preserving the original aspect ratio.
 SkBitmap Downscale(const blink::WebImage& image,
                    int thumbnail_min_area_pixels,
                    const gfx::Size& thumbnail_max_size_pixels) {
   if (image.IsNull())
@@ skipping 100 matching lines @@
   // to investigate what it is doing and fix (http://crbug.com/606164).
   WebNode context_node = frame->ContextMenuNode();
   if (!context_node.IsNull() && context_node.IsElementNode()) {
     frame->ReloadImage(context_node);
   }
 }
 
 void ChromeRenderFrameObserver::RequestThumbnailForContextNode(
     int32_t thumbnail_min_area_pixels,
     const gfx::Size& thumbnail_max_size_pixels,
+    bool use_png_codec,
     const RequestThumbnailForContextNodeCallback& callback) {
   WebNode context_node = render_frame()->GetWebFrame()->ContextMenuNode();
   SkBitmap thumbnail;
   gfx::Size original_size;
   if (!context_node.IsNull() && context_node.IsElementNode()) {
     blink::WebImage image = context_node.To<WebElement>().ImageContents();
     original_size = image.Size();
     thumbnail = Downscale(image,
                           thumbnail_min_area_pixels,
                           thumbnail_max_size_pixels);
   }
 
   SkBitmap bitmap;
   if (thumbnail.colorType() == kN32_SkColorType) {
     bitmap = thumbnail;
   } else {
     SkImageInfo info = thumbnail.info().makeColorType(kN32_SkColorType);
     if (bitmap.tryAllocPixels(info)) {
       thumbnail.readPixels(info, bitmap.getPixels(), bitmap.rowBytes(), 0, 0);
     }
   }
 
   std::vector<uint8_t> thumbnail_data;
   constexpr int kDefaultQuality = 90;
   std::vector<unsigned char> data;
-  if (gfx::JPEGCodec::Encode(bitmap, kDefaultQuality, &data)) {
-    thumbnail_data.swap(data);
+
+  if (use_png_codec) {
+    if (gfx::PNGCodec::EncodeBGRASkBitmap(
+            bitmap, kDiscardTransparencyForContextMenu, &data)) {
+      thumbnail_data.swap(data);
+    }
+  } else {
+    if (gfx::JPEGCodec::Encode(bitmap, kDefaultQuality, &data)) {
+      thumbnail_data.swap(data);
+    }
   }
 
   callback.Run(thumbnail_data, original_size);
 }
 
 void ChromeRenderFrameObserver::OnPrintNodeUnderContextMenu() {
 #if BUILDFLAG(ENABLE_PRINTING)
   printing::PrintWebViewHelper* helper =
       printing::PrintWebViewHelper::Get(render_frame());
   if (helper)
@@ skipping 130 matching lines @@
     const service_manager::BindSourceInfo& source_info,
     chrome::mojom::ImageContextMenuRendererRequest request) {
   image_context_menu_renderer_bindings_.AddBinding(this, std::move(request));
 }
 
 void ChromeRenderFrameObserver::OnThumbnailCapturerRequest(
     const service_manager::BindSourceInfo& source_info,
     chrome::mojom::ThumbnailCapturerRequest request) {
   thumbnail_capturer_bindings_.AddBinding(this, std::move(request));
 }