using System using System Collections Generic using System ComponentMo

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace BSpline
{


    public partial class Form1 : Form
    {

        public Form1()
        {

            InitializeComponent();
            generateKnot(pCount, degree, knotArr, out knotSize);
            tmax = knotArr[knotSize - 1];

        }
        int activeId = -1;


        public void generateKnot(int pointCount, int degree, float[] knot, out int knotSize)
        {
            int k = degree + 1;
            int n = pointCount - 1;
            for (int i = 1; i <= n + k + 1; ++i)
            {
                if (i <= k)
                {
                    knot[i - 1] = 0;
                }
                else
                    if (i <= n + 1)
                    {
                        knot[i - 1] = i - k;
                    }
                    else
                    {
                        knot[i - 1] = n - k + 2;
                    }
            }
            knotSize = n + k + 1;
        }

        float[] knotArr = new float[500];

        int degree = 2;
        int pCount = 8;
        float tmin = 0;
        float tmax = 0;
        int knotSize = 0;

        float getN(float t, int ind, int k)
        {
            if (k == 1)
            {
                if (knotArr[ind] <= t && knotArr[ind + 1] > t)
                    return 1;
                else return 0;
            }

            float retval = 0;
            float vl1 = ((t - knotArr[ind]) * getN(t, ind, k - 1));
            float vl2 = (knotArr[ind + k - 1] - knotArr[ind]);
            if (vl2 > 0.00000001)
                retval += vl1 / vl2;
            vl1 = (knotArr[ind + k] - t) * getN(t, ind + 1, k - 1);
            vl2 = (knotArr[ind + k] - knotArr[ind + 1]);
            if (vl2 > 0.00000001)
                retval += vl1 / vl2;

            return retval;        
        }

        float[] xpnt = new float[8] { 10, 90, 120, 180, 230, 260, 270, 340};
        float[] ypnt = new float[8] { 10, -20, 10, -10, 20, -40, 20, 0};
        float[] h = new float[8] { 1, 1, 1, 1, 1, 2, 1, 1 };


        private void Form1_Paint(object sender, PaintEventArgs e)
        {

           

            Graphics v = e.Graphics;
            v.TranslateTransform(250, 250);

            for (int i = 0; i < xpnt.Length; ++i)
            {
                v.DrawEllipse(new Pen(Color.Red), xpnt[i], ypnt[i], 3, 3);
            }

            for (float t = tmin; t <= tmax; t += 0.01f)
            {
                float x = 0, y = 0;
                float sm = 0;
                for (int i = 0; i < xpnt.Length; ++i)
                {
                    float basis = getN(t, i, degree + 1);   
                    x += xpnt[i] * basis * h[i];
                    y += ypnt[i] * basis * h[i];
                    sm += basis * h[i];
                }
                v.DrawEllipse(new Pen(Color.Black), x / sm, y / sm, 1, 1);

            }

        
        }

        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {
            Invalidate();
        }

        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            activeId = 1;
        }

        private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
            activeId = -1;
        }
    }
}