WPF实现头像裁剪

<Grid>         <Border x:Name="containerPanel">             <Canvas x:Name="DrawCanvas"                     VerticalAlignment="Center"                      Background="Transparent"                      Width="{Binding ElementName=containerPanel,Path=ActualWidth}"                     Height="{Binding ElementName=containerPanel,Path=ActualHeight}">                 <Rectangle x:Name="rectImage" VerticalAlignment="Center" HorizontalAlignment="Center"                            Width="{Binding ElementName=containerPanel,Path=ActualWidth}"                            Height="{Binding ElementName=containerPanel,Path=ActualHeight}">                     <Rectangle.Fill>                         <ImageBrush ImageSource="{Binding ImageSource,RelativeSource={ RelativeSource AncestorType={x:Type local:ImageCutCustoms}}}"/>                     </Rectangle.Fill>                 </Rectangle>                 <Rectangle VerticalAlignment="Center" HorizontalAlignment="Center"                            Width="{Binding ElementName=rectImage,Path=ActualWidth}"                            Height="{Binding ElementName=rectImage,Path=ActualHeight}"                            Fill="#99000000"/>                 <Rectangle VerticalAlignment="Center" HorizontalAlignment="Center"                            Width="{Binding ElementName=containerPanel,Path=ActualWidth}"                            Height="{Binding ElementName=containerPanel,Path=ActualHeight}">                     <Rectangle.Fill>                         <ImageBrush ImageSource="{Binding ImageSource,RelativeSource={ RelativeSource AncestorType={x:Type local:ImageCutCustoms}}}"/>                     </Rectangle.Fill>                     <Rectangle.Clip>                         <RectangleGeometry x:Name="rectRectangle" Rect="{Binding CutRect,RelativeSource={RelativeSource AncestorType={x:Type local:ImageCutCustoms}}}"/>                     </Rectangle.Clip>                 </Rectangle>                  <local:DragDropView x:Name="dragDropItem"                              Width="{Binding ElementName=rectRectangle, Path= Rect.Width}"                            Height="{Binding ElementName=rectRectangle, Path= Rect.Height}"                            Canvas.Left="{Binding ElementName=rectRectangle, Path= Rect.X}"                            Canvas.Top="{Binding ElementName=rectRectangle, Path= Rect.Y}"                            ParentMaxHeight="{Binding ElementName=DrawCanvas,Path=ActualHeight}"                            ParentMaxWidth="{Binding ElementName=DrawCanvas,Path=ActualWidth}"/>                              </Canvas>         </Border>     </Grid>

public partial class ImageCutCustoms : UserControl     {           public ImageSource ImageSource         {             get { return (ImageSource)GetValue(ImageSourceProperty); }             set { SetValue(ImageSourceProperty, value); }         }          // Using a DependencyProperty as the backing store for ImageSource.  This enables animation, styling, binding, etc...         public static readonly DependencyProperty ImageSourceProperty =             DependencyProperty.Register("ImageSource", typeof(ImageSource), typeof(ImageCutCustoms), new PropertyMetadata(ImageSourcePropertyChangedCallback));             public ImageSource SaveImageSource         {             get { return (ImageSource)GetValue(SaveImageSourceProperty); }             set { SetValue(SaveImageSourceProperty, value); }         }          // Using a DependencyProperty as the backing store for SaveImageSource.  This enables animation, styling, binding, etc...         public static readonly DependencyProperty SaveImageSourceProperty =             DependencyProperty.Register("SaveImageSource", typeof(ImageSource), typeof(ImageCutCustoms), new PropertyMetadata());            public Rect CutRect         {             get { return (Rect)GetValue(CutRectProperty); }             set { SetValue(CutRectProperty, value); }         }          // Using a DependencyProperty as the backing store for CutRect.  This enables animation, styling, binding, etc...         public static readonly DependencyProperty CutRectProperty =             DependencyProperty.Register("CutRect", typeof(Rect), typeof(ImageCutCustoms), new PropertyMetadata());          private Point startPoint, endPoint;          public ImageCutCustoms()         {             InitializeComponent();             this.dragDropItem.UpdateImageEvent += DragDropItem_UpdateImageEvent;         }         private void DragDropItem_UpdateImageEvent()         {             var x = Canvas.GetLeft(dragDropItem);             var y = Canvas.GetTop(dragDropItem);             var w = dragDropItem.Width;             var h = dragDropItem.Height;             RenderTargetBitmap rtb = new RenderTargetBitmap((int)rectImage.RenderSize.Width,     (int)rectImage.RenderSize.Height, 96d, 96d, System.Windows.Media.PixelFormats.Default);             rtb.Render(rectImage);              var crop = new CroppedBitmap(rtb, new Int32Rect((int)x, (int)y, (int)w, (int)h));             SaveImageSource = crop;             startPoint = new Point(x, y);             endPoint = new Point(x+w, y+h);             CutRect = new Rect(startPoint, endPoint);         }         private static void ImageSourcePropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)         {             var cutCustoms = d as ImageCutCustoms;             var x = cutCustoms.ActualWidth / 3;             var y = cutCustoms.ActualHeight / 3;             cutCustoms.startPoint = new Point(x, y);             cutCustoms.endPoint = new Point(x + 120, y + 120);             cutCustoms.CutRect = new Rect(cutCustoms.startPoint,cutCustoms.endPoint);         }             }