private void DrawBezier(Point pt, int length)
        {
            // gorna linia
            Point pt1 = new Point { X = pt.X - 25, Y = pt.Y };
            Point pt2 = new Point { X = pt.X - 5, Y = pt.Y };
            dc.DrawLine(pen, pt1, pt2);

            //dolna linia
            Point pt3 = new Point { X = pt.X - 25, Y = pt.Y + length };
            Point pt4 = new Point { X = pt.X - 5, Y = pt.Y + length };
            dc.DrawLine(pen, pt3, pt4);

            //krzywa (brzuszek)
            Point pt5 = new Point { X = pt1.X - (length / 2), Y = (((pt1.Y + pt3.Y) / 2) + pt1.Y) / 2 };
            Point pt6 = new Point { X = pt3.X - (length / 2), Y = (((pt1.Y + pt3.Y) / 2) + pt3.Y) / 2 };
            Point start = pt1;
            foreach (Point p in GetBezierPoints(pt1, pt5, pt6, pt3))
            {
                dc.DrawLine(pen, start, p);
                start = p;
            }

            //przekreślenie
            dc.DrawLine(pen, new Point { X = pt2.X - 5, Y = pt2.Y - 5 }, new Point { X = pt3.X + 5, Y = pt3.Y + 5 });
        }