chrome/browser/thumbnails/thumbnailing_algorithm.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_THUMBNAILING_ALGORITHM_H_
   6 #define CHROME_BROWSER_THUMBNAILS_THUMBNAILING_ALGORITHM_H_
   7
   8 #include "base/memory/ref_counted.h"
   9 #include "chrome/browser/thumbnails/thumbnailing_context.h"
  10 #include "ui/base/layout.h"
  11 #include "ui/gfx/geometry/rect.h"
  12 #include "ui/gfx/geometry/size.h"
  13
  14 class SkBitmap;
  15
  16 namespace thumbnails {
  17
  18 // An interface abstracting thumbnailing algorithms. Instances are intended to
  19 // be created by ThumbnailService's implementations and used by
  20 // ThumbnailTabHelper as consumers of captured source images.
  21 class ThumbnailingAlgorithm
  22     : public base::RefCountedThreadSafe<ThumbnailingAlgorithm> {
  23  public:
  24   typedef base::Callback<void(const ThumbnailingContext&, const SkBitmap&)>
  25       ConsumerCallback;
  26   // Provides information necessary to crop-and-resize image data from a source
  27   // canvas of |source_size|. Auxiliary |scale_factor| helps compute the target
  28   // thumbnail size to be copied from the backing store, in pixels. Parameters
  29   // of the required copy operation are assigned to |clipping_rect| (cropping
  30   // rectangle for the source canvas) and |copy_size| (the size of the copied
  31   // bitmap in pixels). The return value indicates the type of clipping that
  32   // will be done.
  33   virtual ClipResult GetCanvasCopyInfo(const gfx::Size& source_size,
  34                                        ui::ScaleFactor scale_factor,
  35                                        gfx::Rect* clipping_rect,
  36                                        gfx::Size* copy_size) const = 0;
  37
  38   // Invoked to produce a thumbnail image from a |bitmap| extracted by the
  39   // callee from source canvas according to instructions provided by a call
  40   // to GetCanvasCopyInfo.
  41   // Note that ProcessBitmap must be able to handle bitmaps which might have not
  42   // been processed (scalled/cropped) as requested. |context| gives additional
  43   // information on the source, including if and how it was clipped.
  44   // The function shall invoke |callback| once done, passing in fully populated
  45   // |context| along with resulting thumbnail bitmap.
  46   virtual void ProcessBitmap(scoped_refptr<ThumbnailingContext> context,
  47                              const ConsumerCallback& callback,
  48                              const SkBitmap& bitmap) = 0;
  49
  50  protected:
  51   virtual ~ThumbnailingAlgorithm() {}
  52   friend class base::RefCountedThreadSafe<ThumbnailingAlgorithm>;
  53 };
  54
  55 }  // namespace thumbnails
  56
  57 #endif  // CHROME_BROWSER_THUMBNAILS_THUMBNAILING_ALGORITHM_H_