chrome/browser/thumbnails/content_based_thumbnailing_algorithm.h

   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   ClipResult GetCanvasCopyInfo(const gfx::Size& source_size,
  21                                ui::ScaleFactor scale_factor,
  22                                gfx::Rect* clipping_rect,
  23                                gfx::Size* copy_size) const override;
  24
  25   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   ~ContentBasedThumbnailingAlgorithm() override;
  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_