public SplinePoint Eval(double x, bool debug = false)
        {
            double[] xx = { x };

            List <CubicSplinePoint> xs = xSpline.Eval(xx, debug);
            List <CubicSplinePoint> ys = ySpline.Eval(xx, debug);

            return(new SplinePoint(xs[0].Y, ys[0].Y, xs[0].ControlPointNum));
        }
        public System.Drawing.PointF Eval(float x, bool debug = false)
        {
            float[] xx = { x };

            float[] xs = xSpline.Eval(xx, debug);
            float[] ys = ySpline.Eval(xx, debug);

            return(new System.Drawing.PointF(xs[0], ys[0]));
        }