Plugs in the new thumbnailing algorithm to ThumbnailTabHelper.

chrome/browser/thumbnails/content_based_thumbnailing_algorithm.h

+// Copyright (c) 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.
+
+#ifndef CHROME_BROWSER_THUMBNAILS_CONTENT_BASED_THUMBNAILING_ALGORITHM_H_
+#define CHROME_BROWSER_THUMBNAILS_CONTENT_BASED_THUMBNAILING_ALGORITHM_H_
+
+#include "chrome/browser/thumbnails/thumbnailing_algorithm.h"
+
+namespace thumbnails {
+
+// Encapsulates a method of creating a thumbnail from a captured tab shot which
+// attempts to preserve only relevant fragments of the original image.
+// The algorithm detects areas of high activity at low resolution and discards
+// rows and columns which do not intersect with these areas.
+class ContentBasedThumbnailingAlgorithm : public ThumbnailingAlgorithm {
+ public:
+  explicit ContentBasedThumbnailingAlgorithm(const gfx::Size& target_size);
+
+  virtual ClipResult GetCanvasCopyInfo(const gfx::Size& source_size,
+                                       ui::ScaleFactor scale_factor,
+                                       gfx::Rect* clipping_rect,
+                                       gfx::Size* target_size) const OVERRIDE;
+
+  virtual void ProcessBitmap(scoped_refptr<ThumbnailingContext> context,
+                             const ConsumerCallback& callback,
+                             const SkBitmap& bitmap) OVERRIDE;
+
+  // Prepares (clips to size, copies etc.) the bitmap passed to ProcessBitmap.
+  // Always returns a bitmap that can be properly refcounted.
+  // Extracted and exposed as a test seam.
+  static SkBitmap PrepareSourceBitmap(const SkBitmap& received_bitmap,
+                                      const gfx::Size& thumbnail_size,
+                                      ThumbnailingContext* context);
+
+  // The function processes |source_bitmap| into a thumbnail of |thumbnail_size|
+  // and passes the result into |callback| (on UI thread). |context| describes
+  // how the thumbnail is being created.
+  static void CreateRetargetedThumbnail(
+      const SkBitmap& source_bitmap,
+      const gfx::Size& thumbnail_size,
+      scoped_refptr<ThumbnailingContext> context,
+      const ConsumerCallback& callback);
+
+ protected:
+  virtual ~ContentBasedThumbnailingAlgorithm();
+
+ private:
+  static gfx::Rect GetClippingRect(const gfx::Size& source_size,
+                                   const gfx::Size& thumbnail_size,
+                                   gfx::Size* target_size,
+                                   ClipResult* clip_result);
+
+  const gfx::Size target_size_;
+
+  DISALLOW_COPY_AND_ASSIGN(ContentBasedThumbnailingAlgorithm);
+};
+
+}  // namespace thumbnails
+
+#endif  // CHROME_BROWSER_THUMBNAILS_CONTENT_BASED_THUMBNAILING_ALGORITHM_H_