silverlight实现图片局部放大效果的方法

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);
    }
  }
}