kochpanel.java

E:JAVA源码资源Java 程序设计教程（第五版）EXAMPLESchap11例题源码。

//********************************************************************
//  KochPanel.java       Author: Lewis/Loftus
//
//  Represents a drawing surface on which to paint a Koch Snowflake.
//********************************************************************

import java.awt.*;
import javax.swing.JPanel;

public class KochPanel extends JPanel
{
   private final int PANEL_WIDTH = 400;
   private final int PANEL_HEIGHT = 400;

   private final double SQ = Math.sqrt(3.0) / 6;

   private final int TOPX = 200, TOPY = 20;
   private final int LEFTX = 60, LEFTY = 300;
   private final int RIGHTX = 340, RIGHTY = 300;

   private int current;  // current order

   //-----------------------------------------------------------------
   //  Sets the initial fractal order to the value specified.
   //-----------------------------------------------------------------
   public KochPanel (int currentOrder)
   {
      current = currentOrder;
      setBackground (Color.black);
      setPreferredSize (new Dimension(PANEL_WIDTH, PANEL_HEIGHT));
   }

   //-----------------------------------------------------------------
   //  Draws the fractal recursively. The base case is order 1 for
   //  which a simple straight line is drawn. Otherwise three
   //  intermediate points are computed, and each line segment is
   //  drawn as a fractal.
   //-----------------------------------------------------------------
   public void drawFractal (int order, int x1, int y1, int x5, int y5,
                            Graphics page)
   {
      int deltaX, deltaY, x2, y2, x3, y3, x4, y4;

      if (order == 1)
         page.drawLine (x1, y1, x5, y5);
      else
      {
         deltaX = x5 - x1;  // distance between end points
         deltaY = y5 - y1;

         x2 = x1 + deltaX / 3;  // one third
         y2 = y1 + deltaY / 3;

         x3 = (int) ((x1+x5)/2 + SQ * (y1-y5));  // tip of projection
         y3 = (int) ((y1+y5)/2 + SQ * (x5-x1));

         x4 = x1 + deltaX * 2/3;  // two thirds
         y4 = y1 + deltaY * 2/3;

         drawFractal (order-1, x1, y1, x2, y2, page);
         drawFractal (order-1, x2, y2, x3, y3, page);
         drawFractal (order-1, x3, y3, x4, y4, page);
         drawFractal (order-1, x4, y4, x5, y5, page);
      }
   }

   //-----------------------------------------------------------------
   //  Performs the initial calls to the drawFractal method.
   //-----------------------------------------------------------------
   public void paintComponent (Graphics page)
   {
      super.paintComponent (page);

      page.setColor (Color.green);

      drawFractal (current, TOPX, TOPY, LEFTX, LEFTY, page);
      drawFractal (current, LEFTX, LEFTY, RIGHTX, RIGHTY, page);
      drawFractal (current, RIGHTX, RIGHTY, TOPX, TOPY, page);
   }

   //-----------------------------------------------------------------
   //  Sets the fractal order to the value specified.
   //-----------------------------------------------------------------
   public void setOrder (int order)
   {
      current = order;
   }

   //-----------------------------------------------------------------
   //  Returns the current order.
   //-----------------------------------------------------------------
   public int getOrder ()
   {
      return current;
   }
}