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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/base/layout.h"
     11 #include "ui/gfx/rect.h"
     12 #include "ui/gfx/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. Parameters of the required copy operation are assigned to
     29   // |clipping_rect| (cropping rectangle for the source canvas) and
     30   // |target_size| (the size of the target bitmap).
     31   // The return value indicates the type of clipping that will be done.
     32   virtual ClipResult GetCanvasCopyInfo(const gfx::Size& source_size,
     33                                        ui::ScaleFactor scale_factor,
     34                                        gfx::Rect* clipping_rect,
     35                                        gfx::Size* target_size) const = 0;
     36 
     37   // Invoked to produce a thumbnail image from a |bitmap| extracted by the
     38   // callee from source canvas according to instructions provided by a call
     39   // to GetCanvasCopyInfo.
     40   // Note that ProcessBitmap must be able to handle bitmaps which might have not
     41   // been processed (scalled/cropped) as requested. |context| gives additional
     42   // information on the source, including if and how it was clipped.
     43   // The function shall invoke |callback| once done, passing in fully populated
     44   // |context| along with resulting thumbnail bitmap.
     45   virtual void ProcessBitmap(scoped_refptr<ThumbnailingContext> context,
     46                              const ConsumerCallback& callback,
     47                              const SkBitmap& bitmap) = 0;
     48 
     49  protected:
     50   virtual ~ThumbnailingAlgorithm() {}
     51   friend class base::RefCountedThreadSafe<ThumbnailingAlgorithm>;
     52 };
     53 
     54 }
     55 
     56 #endif  // CHROME_BROWSER_THUMBNAILS_THUMBNAILING_ALGORITHM_H_
     57