Geometry/BsplineMitchellNetravali.cs

using System;

namespace FastPrint.Geometry
{
    public static class BsplineMitchellNetravali
    {
        // Cubic B-spline basis function
        public static double BSpline(double t)
        {
            t = Math.Abs(t);
            if (t < 1)
                return (3 * t * t * t - 6 * t * t + 4) / 6.0;
            else if (t < 2)
                return (-t * t * t + 6 * t * t - 12 * t + 8) / 6.0;
            return 0.0;
        }

        // Mitchell-Netravali filter
        public static double MitchellNetravali(double x, double B = 1.0 / 3.0, double C = 1.0 / 3.0)
        {
            x = Math.Abs(x);
            if (x < 1)
                return ((12 - 9 * B - 6 * C) * Math.Pow(x, 3) +
                        (-18 + 12 * B + 6 * C) * Math.Pow(x, 2) +
                        (6 - 2 * B)) / 6.0;
            else if (x < 2)
                return ((-B - 6 * C) * Math.Pow(x, 3) +
                        (6 * B + 30 * C) * Math.Pow(x, 2) +
                        (-12 * B - 48 * C) * x +
                        (8 * B + 24 * C)) / 6.0;
            return 0.0;
        }
    }
}