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