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

chrome/renderer/chrome_render_frame_observer.cc

Index: chrome/renderer/chrome_render_frame_observer.cc
diff --git a/chrome/renderer/chrome_render_frame_observer.cc b/chrome/renderer/chrome_render_frame_observer.cc
index 08ca11e128025445d355c026ae12b3265e4af132..2876c3fdaffffccd88d31f2b4efefa3b9720331f 100644
--- a/chrome/renderer/chrome_render_frame_observer.cc
+++ b/chrome/renderer/chrome_render_frame_observer.cc
@@ -43,6 +43,7 @@
 #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"
 
@@ -70,6 +71,10 @@ static const char kTranslateCaptureText[] = "Translate.CaptureText";
 // 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
@@ -190,6 +195,7 @@ void ChromeRenderFrameObserver::RequestReloadImageForContextNode() {
 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;
@@ -215,8 +221,16 @@ void ChromeRenderFrameObserver::RequestThumbnailForContextNode(
   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);