C#地图效果(PictureBox与Panel滚动条)

private Point pt = Point.Empty; //记录鼠标按下时的坐标
private Point def = Point.Empty; //记录鼠标按下panel横纵滚动条的值

private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
　if (MouseButtons.Left != e.Button) return;
　Cursor = Cursors.SizeAll;
　pt = panel1.PointToClient(pictureBox1.PointToScreen(e.Location)); //鼠标是按在picturebox上，需要转化成相对于panel的坐标
　def.X = panel1.HorizontalScroll.Value; //HScroll值
　def.Y = panel1.VerticalScroll.Value; //VScroll值
}

private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
　if (MouseButtons.Left != e.Button) return;
　Point cur = panel1.PointToClient(pictureBox1.PointToScreen(e.Location)); //当前鼠标坐标，同样需要转化成相对于panel的坐标
　cur = new Point(pt.X - cur.X, pt.Y - cur.Y); //计算差
　cur.X = def.X + cur.X; //计算和
　cur.Y = def.Y + cur.Y;
　if (0 > cur.X) cur.X = 0;  //如果超出范围，需要修正
　if (panel1.Width < cur.X) cur.X = panel1.Width;
　if (0 > cur.Y) cur.Y = 0;
　if (panel1.Height < cur.Y) cur.Y = panel1.Height;

　if (panel1.HorizontalScroll.Visible) panel1.HorizontalScroll.Value = cur.X;  //如果存在对应的滚动条，则赋值
　if (panel1.VerticalScroll.Visible) panel1.VerticalScroll.Value = cur.Y;
}

private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
{
　Cursor = Cursors.Default;
}