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      1 // Copyright 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef CHROME_BROWSER_THUMBNAILS_CONTENT_BASED_THUMBNAILING_ALGORITHM_H_
      6 #define CHROME_BROWSER_THUMBNAILS_CONTENT_BASED_THUMBNAILING_ALGORITHM_H_
      7 
      8 #include "chrome/browser/thumbnails/thumbnailing_algorithm.h"
      9 
     10 namespace thumbnails {
     11 
     12 // Encapsulates a method of creating a thumbnail from a captured tab shot which
     13 // attempts to preserve only relevant fragments of the original image.
     14 // The algorithm detects areas of high activity at low resolution and discards
     15 // rows and columns which do not intersect with these areas.
     16 class ContentBasedThumbnailingAlgorithm : public ThumbnailingAlgorithm {
     17  public:
     18   explicit ContentBasedThumbnailingAlgorithm(const gfx::Size& target_size);
     19 
     20   virtual ClipResult GetCanvasCopyInfo(const gfx::Size& source_size,
     21                                        ui::ScaleFactor scale_factor,
     22                                        gfx::Rect* clipping_rect,
     23                                        gfx::Size* target_size) const OVERRIDE;
     24 
     25   virtual void ProcessBitmap(scoped_refptr<ThumbnailingContext> context,
     26                              const ConsumerCallback& callback,
     27                              const SkBitmap& bitmap) OVERRIDE;
     28 
     29   // Prepares (clips to size, copies etc.) the bitmap passed to ProcessBitmap.
     30   // Always returns a bitmap that can be properly refcounted.
     31   // Extracted and exposed as a test seam.
     32   static SkBitmap PrepareSourceBitmap(const SkBitmap& received_bitmap,
     33                                       const gfx::Size& thumbnail_size,
     34                                       ThumbnailingContext* context);
     35 
     36   // The function processes |source_bitmap| into a thumbnail of |thumbnail_size|
     37   // and passes the result into |callback| (on UI thread). |context| describes
     38   // how the thumbnail is being created.
     39   static void CreateRetargetedThumbnail(
     40       const SkBitmap& source_bitmap,
     41       const gfx::Size& thumbnail_size,
     42       scoped_refptr<ThumbnailingContext> context,
     43       const ConsumerCallback& callback);
     44 
     45  protected:
     46   virtual ~ContentBasedThumbnailingAlgorithm();
     47 
     48  private:
     49   static gfx::Rect GetClippingRect(const gfx::Size& source_size,
     50                                    const gfx::Size& thumbnail_size,
     51                                    gfx::Size* target_size,
     52                                    ClipResult* clip_result);
     53 
     54   const gfx::Size target_size_;
     55 
     56   DISALLOW_COPY_AND_ASSIGN(ContentBasedThumbnailingAlgorithm);
     57 };
     58 
     59 }  // namespace thumbnails
     60 
     61 #endif  // CHROME_BROWSER_THUMBNAILS_CONTENT_BASED_THUMBNAILING_ALGORITHM_H_
     62