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   ClipResult GetCanvasCopyInfo(const gfx::Size& source_size,
  22                                ui::ScaleFactor scale_factor,
  23                                gfx::Rect* clipping_rect,
  24                                gfx::Size* copy_size) const override;
  25
  26   void ProcessBitmap(scoped_refptr<ThumbnailingContext> context,
  27                      const ConsumerCallback& callback,
  28                      const SkBitmap& bitmap) override;
  29
  30   // Gets the clipped bitmap from |bitmap| per the aspect ratio of the
  31   // desired width and the desired height. For instance, if the input
  32   // bitmap is vertically long (ex. 400x900) and the desired size is
  33   // square (ex. 100x100), the clipped bitmap will be the top half of the
  34   // input bitmap (400x400).
  35   // Statically exposed for use by tests only.
  36   static SkBitmap GetClippedBitmap(const SkBitmap& bitmap,
  37                                    int desired_width,
  38                                    int desired_height,
  39                                    thumbnails::ClipResult* clip_result);
  40   // Returns the size copied from the backing store. |thumbnail_size| is in
  41   // DIP, returned size in pixels.
  42   static gfx::Size GetCopySizeForThumbnail(ui::ScaleFactor scale_factor,
  43                                            const gfx::Size& thumbnail_size);
  44   static gfx::Rect GetClippingRect(const gfx::Size& source_size,
  45                                    const gfx::Size& desired_size,
  46                                    ClipResult* clip_result);
  47
  48   // Computes the size of a thumbnail that should be stored in the database from
  49   // |given_size| (expected to be the thumbnail size we would normally want to
  50   // see). The returned size is expressed in pixels and is determined by
  51   // bumping the resolution up to the maximum scale factor.
  52   static gfx::Size ComputeTargetSizeAtMaximumScale(const gfx::Size& given_size);
  53
  54  protected:
  55   ~SimpleThumbnailCrop() override;
  56
  57  private:
  58   static SkBitmap CreateThumbnail(const SkBitmap& bitmap,
  59                                   const gfx::Size& desired_size,
  60                                   ClipResult* clip_result);
  61
  62   // The target size of the captured thumbnails, in DIPs.
  63   const gfx::Size target_size_;
  64
  65   DISALLOW_COPY_AND_ASSIGN(SimpleThumbnailCrop);
  66 };
  67
  68 }  // namespace thumbnails
  69
  70 #endif  // CHROME_BROWSER_THUMBNAILS_SIMPLE_THUMBNAIL_CROP_H_