package graphics0;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.awt.image.*;
import java.awt.geom.*;

/**
 * <p>Title: computer graphics </p>
 * <p>Description: homeworks</p>
 * <p>Copyright: Copyright (c) 2004 </p>
 * <p>Company: shu</p>
 * @author dxf
 * @version 1.0
 */

public class CurvePanel
    extends JPanel {
  Point[] x=new Point[4];
  int i,j=0;

   public CurvePanel(){
     addMouseListener(new MouseAdapter() {
       public void mouseClicked(MouseEvent e) {
         Graphics g = getGraphics();
         if (j < 4) {
           x[j] = new Point(e.getX(), e.getY());
           g.fillOval(x[j].x - 3, x[j].y - 3, 6, 6);
           if (j >= 1) {
             g.drawLine(x[j - 1].x, x[j - 1].y, x[j].x, x[j].y);
           }
           j++;
         }
         if (j == 4) {
           draw_Bezier(g, x);
           j = 0;
           for (i = 0; i < 4; i++) {
             x[i].x = 0;
             x[i].y = 0;
           }
         }
       }
     });
   }

   void draw_Bezier(Graphics g, Point[] p) {
     Point[][] result = new Point[2][4];
     Point[] q = new Point[4];
     Point[] r = new Point[4];
     if (Math.max(distance(p[1], p[0], p[3]), distance(p[2], p[0], p[3])) <=
         1.0d)
       g.drawLine(p[0].x, p[0].y, p[3].x, p[3].y);
     else {
       result = curve_split(p);
       for (i = 0; i < 4; i++) {
         q[i] = new Point(result[0][i].x, result[0][i].y);
         r[i] = new Point(result[1][i].x, result[1][i].y);
       }
       draw_Bezier(g, q);
       draw_Bezier(g, r);
     }
   }

   Point[][] curve_split(Point[] p) {
     Point[][] result = new Point[2][4];
     Point[] q = new Point[4];
     Point[] r = new Point[4];
     System.arraycopy(p, 0, q, 0, p.length);
     for (i = 1; i < 4; i++) {
       r[4 - i] = new Point(q[3].x, q[3].y);
       for (j = 3; j >= i; j--) {
         q[j].x = (q[j].x + q[j - 1].x) >> 1;
         q[j].y = (q[j].y + q[j - 1].y) >> 1;
       }

     }
     r[0] = new Point(q[3].x, q[3].y);
     for (i = 0; i < 4; i++) {
       result[0][i] = new Point(q[i].x, q[i].y);
       result[1][i] = new Point(r[i].x, r[i].y);
     }
     return result;
   }

   double distance(Point p1, Point p2, Point p3) {
     double d;
     Line2D.Float line = new Line2D.Float(p2.x, p2.y, p3.x, p3.y);
     d = line.ptLineDist(p1);
     return d;
   }
 }