Fix for Issue 331895: Make gesturenav screenshot greyscale

content/browser/frame_host/navigation_entry_screenshot_manager.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 "content/browser/frame_host/navigation_entry_screenshot_manager.h"
 
 #include "base/command_line.h"
 #include "base/threading/worker_pool.h"
 #include "content/browser/frame_host/navigation_controller_impl.h"
 #include "content/browser/frame_host/navigation_entry_impl.h"
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/common/content_switches.h"
+#include "third_party/skia/include/core/SkCanvas.h"
+#include "third_party/skia/include/core/SkPaint.h"
+#include "third_party/skia/include/effects/SkLumaColorFilter.h"
 #include "ui/gfx/codec/png_codec.h"
 
 namespace {
 
 // Minimum delay between taking screenshots.
 const int kMinScreenshotIntervalMS = 1000;
 
 }
 
 namespace content {
 
-// Encodes an SkBitmap to PNG data in a worker thread.
+// Converts SkBitmap to grayscale and encodes to PNG data in a worker thread.
 class ScreenshotData : public base::RefCountedThreadSafe<ScreenshotData> {
  public:
   ScreenshotData() {
   }
 
   void EncodeScreenshot(const SkBitmap& bitmap, base::Closure callback) {
     if (!base::WorkerPool::PostTaskAndReply(FROM_HERE,
             base::Bind(&ScreenshotData::EncodeOnWorker,
                        this,
                        bitmap),
             callback,
             true)) {
       callback.Run();
     }
   }
 
   scoped_refptr<base::RefCountedBytes> data() const { return data_; }
 
  private:
   friend class base::RefCountedThreadSafe<ScreenshotData>;
   virtual ~ScreenshotData() {
   }
 
   void EncodeOnWorker(const SkBitmap& bitmap) {
     std::vector<unsigned char> data;
-    if (gfx::PNGCodec::EncodeBGRASkBitmap(bitmap, true, &data))
+    // Paint |bitmap| to a kA8_Config SkBitmap
+    SkBitmap a8Bitmap;
+    a8Bitmap.setConfig(SkBitmap::kA8_Config,
+                       bitmap.width(),
+                       bitmap.height(),
+                       0);
+    a8Bitmap.allocPixels();
+    SkCanvas canvas(a8Bitmap);
+    SkPaint paint;
+    SkColorFilter* filter = SkLumaColorFilter::Create();
+    paint.setColorFilter(filter);
+    filter->unref();
+    canvas.drawBitmap(bitmap, SK_Scalar1, SK_Scalar1, &paint);
+    // Encode the a8Bitmap to grayscale PNG treating alpha as color intensity
+    if (gfx::PNGCodec::EncodeA8SkBitmap(a8Bitmap, &data))
       data_ = new base::RefCountedBytes(data);
   }
 
   scoped_refptr<base::RefCountedBytes> data_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenshotData);
 };
 
 NavigationEntryScreenshotManager::NavigationEntryScreenshotManager(
     NavigationControllerImpl* owner)
@@ skipping 204 matching lines @@
         owner_->GetEntryAtIndex(forward));
     if (ClearScreenshot(entry))
       --screenshot_count;
     ++forward;
   }
   CHECK_GE(screenshot_count, 0);
   CHECK_LE(screenshot_count, kMaxScreenshots);
 }
 
 }  // namespace content