private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
  {
   if (e.Button == MouseButtons.Left)
   {
    mouseDownPoint.X = Cursor.Position.X; //記錄鼠標(biāo)左鍵按下時(shí)位置
    mouseDownPoint.Y = Cursor.Position.Y;    
    isMove = true;
    pictureBox1.Focus(); //鼠標(biāo)滾輪事件(縮放時(shí))需要picturebox有焦點(diǎn)
   }
  }

  private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
  {
   if (e.Button == MouseButtons.Left)
   {
    isMove = false;    
   }
  }

  private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
  {
   pictureBox1.Focus(); //鼠標(biāo)在picturebox上時(shí)才有焦點(diǎn)，此時(shí)可以縮放
   if (isMove)
   {
    int x, y;   //新的pictureBox1.Location(x,y)
    int moveX, moveY; //X方向，Y方向移動(dòng)大小。
    moveX = Cursor.Position.X - mouseDownPoint.X;
    moveY = Cursor.Position.Y - mouseDownPoint.Y;
    x = pictureBox1.Location.X + moveX;
    y = pictureBox1.Location.Y + moveY;    
    pictureBox1.Location = new Point(x, y);
    mouseDownPoint.X = Cursor.Position.X;
    mouseDownPoint.Y = Cursor.Position.Y;    
   }
  }
  
  private void panel2_MouseDown(object sender, MouseEventArgs e)
  {
   if (e.Button == MouseButtons.Left)
   {
    mouseDownPoint.X = Cursor.Position.X; //記錄鼠標(biāo)左鍵按下時(shí)位置
    mouseDownPoint.Y = Cursor.Position.Y;
    isMove = true;
   }
  }

  private void panel2_MouseUp(object sender, MouseEventArgs e)
  {
   if (e.Button == MouseButtons.Left)
   {
    isMove = false;
   }
  }

  private void panel2_MouseMove(object sender, MouseEventArgs e)
  {
   panel2.Focus(); //鼠標(biāo)不在picturebox上時(shí)焦點(diǎn)給別的控件，此時(shí)無法縮放   
   if (isMove)
   {
    int x, y;   //新的pictureBox1.Location(x,y)
    int moveX, moveY; //X方向，Y方向移動(dòng)大小。
    moveX = Cursor.Position.X - mouseDownPoint.X;
    moveY = Cursor.Position.Y - mouseDownPoint.Y;
    x = pictureBox1.Location.X + moveX;
    y = pictureBox1.Location.Y + moveY;
    pictureBox1.Location = new Point(x, y);
    mouseDownPoint.X = Cursor.Position.X;
    mouseDownPoint.Y = Cursor.Position.Y;
   }
  }

//實(shí)現(xiàn)錨點(diǎn)縮放(以鼠標(biāo)所指位置為中心縮放)；
  //步驟：
  //①先改picturebox長寬，長寬改變量一樣；
  //②獲取縮放后picturebox中實(shí)際顯示圖像的長寬，這里長寬是不一樣的；
  //③將picturebox的長寬設(shè)置為顯示圖像的長寬；
  //④補(bǔ)償picturebox因縮放產(chǎn)生的位移，實(shí)現(xiàn)錨點(diǎn)縮放。
  // 注釋：為啥要②③步？由于zoom模式的機(jī)制，把picturebox背景設(shè)為黑就知道為啥了。
  //這里需要獲取zoom模式下picturebox所顯示圖像的大小信息，添加 using System.Reflection；
  //pictureBox1_MouseWheel事件沒找到。。。手動(dòng)添加，別忘在Form1.Designer.cs的“Windows 窗體設(shè)計(jì)器生成的代碼”里加入：  
  //this.pictureBox1.MouseWheel += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseWheel)。
  private void pictureBox1_MouseWheel(object sender, MouseEventArgs e)
  {
   int x = e.Location.X;
   int y = e.Location.Y;
   int ow = pictureBox1.Width;
   int oh = pictureBox1.Height;   
   int VX, VY;  //因縮放產(chǎn)生的位移矢量
   if (e.Delta > 0) //放大
   {
    //第①步
    pictureBox1.Width += zoomStep;
    pictureBox1.Height += zoomStep;
    //第②步
    PropertyInfo pInfo = pictureBox1.GetType().GetProperty("ImageRectangle", BindingFlags.Instance |
     BindingFlags.NonPublic);
    Rectangle rect = (Rectangle)pInfo.GetValue(pictureBox1, null);
    //第③步
    pictureBox1.Width = rect.Width;
    pictureBox1.Height = rect.Height;
   }
   if (e.Delta < 0) //縮小
   {
    //防止一直縮成負(fù)值
    if (pictureBox1.Width < myBmp.Width / 10)
     return;
    
    pictureBox1.Width -= zoomStep;
    pictureBox1.Height -= zoomStep;
    PropertyInfo pInfo = pictureBox1.GetType().GetProperty("ImageRectangle", BindingFlags.Instance |
     BindingFlags.NonPublic);
    Rectangle rect = (Rectangle)pInfo.GetValue(pictureBox1, null);
    pictureBox1.Width = rect.Width;
    pictureBox1.Height = rect.Height;
   }
   //第④步，求因縮放產(chǎn)生的位移，進(jìn)行補(bǔ)償，實(shí)現(xiàn)錨點(diǎn)縮放的效果
   VX = (int)((double)x * (ow - pictureBox1.Width) / ow);
   VY = (int)((double)y * (oh - pictureBox1.Height) / oh);
   pictureBox1.Location = new Point(pictureBox1.Location.X + VX, pictureBox1.Location.Y + VY);
}