chrome/browser/thumbnails/simple_thumbnail_crop.h

   1 // Copyright (c) 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_SIMPLE_THUMBNAIL_CROP_H_
   6 #define CHROME_BROWSER_THUMBNAILS_SIMPLE_THUMBNAIL_CROP_H_
   7
   8 #include "chrome/browser/thumbnails/thumbnailing_algorithm.h"
   9
  10 namespace thumbnails {
  11
  12 // The implementation of the 'classic' thumbnail cropping algorithm. It is not
  13 // content-driven in any meaningful way (save for score calculation). Rather,
  14 // the choice of a cropping region is based on relation between source and
  15 // target sizes. The selected source region is then rescaled into the target
  16 // thumbnail image.
  17 class SimpleThumbnailCrop : public ThumbnailingAlgorithm {
  18  public:
  19   explicit SimpleThumbnailCrop(const gfx::Size& target_size);
  20
  21   virtual ClipResult GetCanvasCopyInfo(const gfx::Size& source_size,
  22                                        ui::ScaleFactor scale_factor,
  23                                        gfx::Rect* clipping_rect,
  24                                        gfx::Size* target_size) const OVERRIDE;
  25
  26   virtual void ProcessBitmap(scoped_refptr<ThumbnailingContext> context,
  27                              const ConsumerCallback& callback,
  28                              const SkBitmap& bitmap) OVERRIDE;
  29
  30   // Calculates how "boring" a thumbnail is. The boring score is the
  31   // 0,1 ranged percentage of pixels that are the most common
  32   // luma. Higher boring scores indicate that a higher percentage of a
  33   // bitmap are all the same brightness.
  34   // Statically exposed for use by tests only.
  35   static double CalculateBoringScore(const SkBitmap& bitmap);
  36
  37   // Gets the clipped bitmap from |bitmap| per the aspect ratio of the
  38   // desired width and the desired height. For instance, if the input
  39   // bitmap is vertically long (ex. 400x900) and the desired size is
  40   // square (ex. 100x100), the clipped bitmap will be the top half of the
  41   // input bitmap (400x400).
  42   // Statically exposed for use by tests only.
  43   static SkBitmap GetClippedBitmap(const SkBitmap& bitmap,
  44                                    int desired_width,
  45                                    int desired_height,
  46                                    thumbnails::ClipResult* clip_result);
  47   static gfx::Size GetCopySizeForThumbnail(ui::ScaleFactor scale_factor,
  48                                            const gfx::Size& thumbnail_size);
  49   static gfx::Rect GetClippingRect(const gfx::Size& source_size,
  50                                    const gfx::Size& desired_size,
  51                                    ClipResult* clip_result);
  52
  53   // Computes the size of a thumbnail that should be stored in the database from
  54   // |given_size| (expected to be the thumbnail size we would normally want to
  55   // see). The returned size is expressed in pixels and is determined by
  56   // bumping the resolution up to the maximum scale factor.
  57   static gfx::Size ComputeTargetSizeAtMaximumScale(const gfx::Size& given_size);
  58
  59  protected:
  60   virtual ~SimpleThumbnailCrop();
  61
  62  private:
  63   static SkBitmap CreateThumbnail(const SkBitmap& bitmap,
  64                                   const gfx::Size& desired_size,
  65                                   ClipResult* clip_result);
  66
  67   const gfx::Size target_size_;
  68
  69   DISALLOW_COPY_AND_ASSIGN(SimpleThumbnailCrop);
  70 };
  71
  72 }
  73
  74 #endif  // CHROME_BROWSER_THUMBNAILS_SIMPLE_THUMBNAIL_CROP_H_