silverlight图片局部放大效果

 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Input;
 
 namespace PartMagnifier
 {
 public partial class MainPage : UserControl
     {
 bool trackingMouseMove = false;
         Point mousePosition;
 
 
 public MainPage()
         {
 // 为初始化变量所必需
             InitializeComponent();
 
 
         }
 
 private void LayoutRoot_Loaded(object sender, System.Windows.RoutedEventArgs e)
         {
             Adjust();
         }
 
 private void Rectangle_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
         {
             FrameworkElement element = sender as FrameworkElement;
             mousePosition = e.GetPosition(element);
             trackingMouseMove = true;
 if (null != element)
             {
                 element.CaptureMouse();
                 element.Cursor = Cursors.Hand;
             }
             Adjust();
             Debug();
             sb.Begin();//标题动画，可去掉
         }
 
 private void Rectangle_MouseMove(object sender, MouseEventArgs e)
         {
             FrameworkElement element = sender as FrameworkElement;
 if (trackingMouseMove)
             {
 double deltaV = e.GetPosition(element).Y - mousePosition.Y;
 double deltaH = e.GetPosition(element).X - mousePosition.X;
 double newTop = deltaV + (double)element.GetValue(Canvas.TopProperty);
 double newLeft = deltaH + (double)element.GetValue(Canvas.LeftProperty);
 if (newLeft <= 10)
                 {
                     newLeft = 10;
                 }
 if (newLeft >= 130)
                 {
                     newLeft = 130;
                 }
 if (newTop <= 10) { newTop = 10; }
 if (newTop >= 85) { newTop = 85; }
                 element.SetValue(Canvas.TopProperty, newTop);
                 element.SetValue(Canvas.LeftProperty, newLeft);
                 mousePosition = e.GetPosition(element);
                 Adjust();
 if (mousePosition.X <= 0 || mousePosition.Y <= 0) { return; }
                 Debug();
             }
         }
 
 private void Rectangle_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
         {
             FrameworkElement element = sender as FrameworkElement;
             trackingMouseMove = false;
             element.ReleaseMouseCapture();
             mousePosition.X = mousePosition.Y = 0;
             element.Cursor = null;
         }
 
 /// <summary>
 /// 调试信息
 /// </summary>
  void Debug()
         {
             txtResult.Text = "鼠标相对坐标：" + mousePosition.ToString() + "\n小框left：" + rect.GetValue(Canvas.LeftProperty) + ",小框top：" + rect.GetValue(Canvas.TopProperty) + "\n大图left：" + ((double)img.GetValue(Canvas.LeftProperty)).ToString("F0") + ",大图right：" + ((double)img.GetValue(Canvas.TopProperty)).ToString("F0");
         }
 
 
 /// <summary>
 /// 调整右侧大图的位置
 /// </summary>
  void Adjust()
         {
 
 double n = cBig.Width / rect.Width;
 double left = (double)rect.GetValue(Canvas.LeftProperty) - 10;
 double top = (double)rect.GetValue(Canvas.TopProperty) - 10;
 double newLeft = -left * n;
 double newTop = -top * n;
             img.SetValue(Canvas.LeftProperty, newLeft);
             img.SetValue(Canvas.TopProperty, newTop);
         }
 
     }
 }