C#控件picturebox实现图像拖拽和缩放

private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
  {
   if (e.Button == MouseButtons.Left)
   {
    mouseDownPoint.X = Cursor.Position.X; //记录鼠标左键按下时位置
    mouseDownPoint.Y = Cursor.Position.Y;    
    isMove = true;
    pictureBox1.Focus(); //鼠标滚轮事件(缩放时)需要picturebox有焦点
   }
  }

  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(); //鼠标在picturebox上时才有焦点，此时可以缩放
   if (isMove)
   {
    int x, y;   //新的pictureBox1.Location(x,y)
    int moveX, moveY; //X方向，Y方向移动大小。
    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; //记录鼠标左键按下时位置
    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(); //鼠标不在picturebox上时焦点给别的控件，此时无法缩放   
   if (isMove)
   {
    int x, y;   //新的pictureBox1.Location(x,y)
    int moveX, moveY; //X方向，Y方向移动大小。
    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;
   }
  }

//实现锚点缩放(以鼠标所指位置为中心缩放)；
  //步骤：
  //①先改picturebox长宽，长宽改变量一样；
  //②获取缩放后picturebox中实际显示图像的长宽，这里长宽是不一样的；
  //③将picturebox的长宽设置为显示图像的长宽；
  //④补偿picturebox因缩放产生的位移，实现锚点缩放。
  // 注释：为啥要②③步？由于zoom模式的机制，把picturebox背景设为黑就知道为啥了。
  //这里需要获取zoom模式下picturebox所显示图像的大小信息，添加 using System.Reflection；
  //pictureBox1_MouseWheel事件没找到。。。手动添加，别忘在Form1.Designer.cs的“Windows 窗体设计器生成的代码”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;  //因缩放产生的位移矢量
   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) //缩小
   {
    //防止一直缩成负值
    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，求因缩放产生的位移，进行补偿，实现锚点缩放的效果
   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);
}