Refactored-out the code of thumbnaling algorithm from thumbnail_tab_helper.

chrome/browser/thumbnails/simple_thumbnail_crop.h

Index: chrome/browser/thumbnails/simple_thumbnail_crop.h
diff --git a/chrome/browser/thumbnails/simple_thumbnail_crop.h b/chrome/browser/thumbnails/simple_thumbnail_crop.h
new file mode 100644
index 0000000000000000000000000000000000000000..a81112761d1c4a254f162d4421239957a557a0a0
--- /dev/null
+++ b/chrome/browser/thumbnails/simple_thumbnail_crop.h
@@ -0,0 +1,66 @@
+// 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_SIMPLE_THUMBNAIL_CROP_H_
+#define CHROME_BROWSER_THUMBNAILS_SIMPLE_THUMBNAIL_CROP_H_
+
+#include "chrome/browser/thumbnails/thumbnailing_algorithm.h"
+
+namespace thumbnails {
+
+// An interface abstracting thumbnailing algorithms. Instances are intended to

[mazda, 2013/01/17 18:08:43]

This is a concrete class. Could you change the comment accordingly?

[motek., 2013/01/17 18:39:42]

Done.

+// be created by ThumbnailService's implementations and used by
+// ThumbnailTabHelper as consumers of captured source images.
+class SimpleThumbnailCrop : public ThumbnailingAlgorithm {
+ public:
+  explicit SimpleThumbnailCrop(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(ThumbnailingContext* context,
+                             const SkBitmap& bitmap,
+                             const ConsumerCallback& callback) OVERRIDE;
+
+  // Calculates how "boring" a thumbnail is. The boring score is the
+  // 0,1 ranged percentage of pixels that are the most common
+  // luma. Higher boring scores indicate that a higher percentage of a
+  // bitmap are all the same brightness.
+  // Statically exposed for use by tests only.
+  static double CalculateBoringScore(const SkBitmap& bitmap);
+
+  // Gets the clipped bitmap from |bitmap| per the aspect ratio of the
+  // desired width and the desired height. For instance, if the input
+  // bitmap is vertically long (ex. 400x900) and the desired size is
+  // square (ex. 100x100), the clipped bitmap will be the top half of the
+  // input bitmap (400x400).
+  // Statically exposed for use by tests only.
+  static SkBitmap GetClippedBitmap(const SkBitmap& bitmap,
+                                   int desired_width,
+                                   int desired_height,
+                                   thumbnails::ClipResult* clip_result);
+  static gfx::Size GetCopySizeForThumbnail(ui::ScaleFactor scale_factor,
+                                           const gfx::Size& thumbnail_size);
+
+ protected:
+  virtual ~SimpleThumbnailCrop();
+
+ private:
+  gfx::Size GetThumbnailSizeInPixel() const;
+  static gfx::Rect GetClippingRect(const gfx::Size& source_size,
+                                   const gfx::Size& desired_size,
+                                   ClipResult* clip_result);
+  static SkBitmap CreateThumbnail(const SkBitmap& bitmap,
+                                  const gfx::Size& desired_size,
+                                  ClipResult* clip_result);
+
+
+  gfx::Size target_size_;
+};
+
+}
+
+#endif  // CHROME_BROWSER_THUMBNAILS_SIMPLE_THUMBNAIL_CROP_H_