WP8 writeablebitmap内存泄漏

Question

WP8 writeablebitmap内存泄漏

我正在c＃/ xaml中为wp8开发一个杂志阅读器应用程序。我正在使用MuPDF库来呈现PDF页面。我正在以PDF格式下载每个页面。我使用MuPDF库将PDF渲染为图像。但是无法成功实现缩放功能。我在flipview中一次加载3页以获得分页效果.MuPDF返回Writeablebitmap作为PDF文件的输出，但是一旦创建了图像，它就会保留在内存中。即使我重新使用Writeablebitmap对象，ApplicationPeakmemory也总是很高。如何管理这个writeablebitmap以避免这种类型的记忆泄漏？请帮忙......

以下是我的代码：

  public async void CreatePDFDocument()
       {

               string imagePath = MagazineModel.Instance.BASEPATH + "\\" + MagazineModel.Instance.MAGAZINE_ID + "\\" + issue_id + "\\pdf" + "\\page" + pagenumber + ".pdf";
               IStorageFolder applicationFolder = ApplicationData.Current.LocalFolder;
               IStorageFile storageFile = await applicationFolder.GetFileAsync(imagePath);

               using (var stream = await storageFile.OpenReadAsync())
               {

                   IBuffer readBuffer;
                   using (IInputStream inputStreamAt = stream.GetInputStreamAt(0))
                   using (var dataReader = new DataReader(inputStreamAt))
                   {
                       uint bufferSize = await dataReader.LoadAsync((uint)stream.Size);
                       readBuffer = dataReader.ReadBuffer(bufferSize);
                   }
                   document = await Task.Factory.StartNew(() => Document.Create(readBuffer, DocumentType.PDF, (int)Windows.Graphics.Display.DisplayProperties.LogicalDpi));
                   if (document.NeedsPassword)
                   {
                       document.AuthenticatePassword("Mag#*%12");
                   }
               }

                PrepareBitmap(0);
                image = await StartDraw(0, _bitmap,new Point());
}

  private async Task<WriteableBitmap> StartDraw(int pageNumber, WriteableBitmap writeableBitmap,Point position)
       {        
           await Task.Factory.StartNew(() =>
                                     document.DrawPage(
                                         pageNumber,
                                         writeableBitmap.Pixels,
                                         position.X,
                                         position.Y,
                                         writeableBitmap.PixelWidth,
                                         writeableBitmap.PixelHeight,
                                       false));

           return writeableBitmap;
       }

// Xaml code which binds WriteableBitmap to Flipview
  <toolkit:FlipView ItemsSource="{Binding PageList}"  x:Name="flipview"  IsHitTestVisible="{Binding IsHit}"  
                                  SelectionChanged="flipview_SelectionChanged" ScrollViewer.HorizontalScrollBarVisibility="Disabled"
                              >
                <toolkit:FlipView.ItemTemplate>
                        <DataTemplate>

                        <Image   Source="{Binding image}"
                                RenderTransformOrigin="0,0" CacheMode="BitmapCache" HorizontalAlignment="Stretch"
                                SizeChanged="MapImage_SizeChanged">
                            <toolkit:GestureService.GestureListener>
                                <toolkit:GestureListener   PinchStarted="GestureListener_PinchStarted"
                                                            PinchDelta="GestureListener_PinchDelta"
                                                            PinchCompleted="GestureListener_PinchCompleted"
                                                            DragStarted="GestureListener_DragStarted"
                                                            DragDelta="GestureListener_DragDelta"
                                                            DoubleTap="GestureListener_DoubleTap"
                                                            />
                            </toolkit:GestureService.GestureListener>
                            <Image.RenderTransform>
                                        <CompositeTransform
                                        ScaleX="1" ScaleY="1"
                                        TranslateX="0" TranslateY="0"/>
                                    </Image.RenderTransform>
                                </Image>             
                    </DataTemplate>
                </toolkit:FlipView.ItemTemplate>
            </toolkit:FlipView>