System.Drawing.GeomUtilities.GetCurveTangents C# (CSharp) Method

        internal static PointF[] GetCurveTangents(int terms, PointF [] points, int count, float tension, CurveType type)
        {
            float coefficient = tension / 3f;
            PointF [] tangents = new PointF [count];

            if (count <= 2)
                return tangents;

            for (int i = 0; i < count; i++) {
                int r = i + 1;
                int s = i - 1;

                if (r >= count)
                    r = count - 1;
                if (type == CurveType.Open) {
                    if (s < 0)
                        s = 0;
                }
                else
                {
                    if (s < 0)
                        s += count;
                }

                tangents [i].X += (coefficient * (points [r].X - points [s].X));
                tangents [i].Y += (coefficient * (points [r].Y - points [s].Y));
            }

            return tangents;
        }