Большая нагрузка и тормоза при движении картинки по форме

        private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
            pictureBox1.Image = pictureBox2.Image;
            Bitmap btmp = new Bitmap(pictureBox1.Width, pictureBox1.Height);
            pictureBox1.DrawToBitmap(btmp, new Rectangle(0, 0, pictureBox1.Width, pictureBox1.Height));
            Image img = Image.FromHbitmap(btmp.GetHbitmap());
            Graphics gr = Graphics.FromImage(img);
            gr.FillRectangle(new SolidBrush(Color.Red), e.X, 0, 1, 600);
            gr.FillRectangle(new SolidBrush(Color.Red), 0, e.Y, 600, 1);
            pictureBox1.Image = img;
        }

public partial class Form1 : Form
{
    private readonly Pen Pen = new Pen(Brushes.Red);
    private Point lastMousePos;
 
    public Form1()
    {
        InitializeComponent();
        DoubleBuffered = true;
    }        
   
    protected override void OnMouseMove(MouseEventArgs e)
    {
        base.OnMouseMove(e);
        lastMousePos = e.Location;
        Invalidate();
    }
 
    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        e.Graphics.DrawLine(Pen, lastMousePos.X, 0, lastMousePos.X, 600);
        e.Graphics.DrawLine(Pen, 0, lastMousePos.Y, 600, lastMousePos.Y);
    }
}

e.Graphics.DrawImage(pictureBox1.Image, pictureBox1.Location.X, pictureBox1.Location.Y);