Computer Graphics: 十字繡曲線

以正方為基礎的十字繡，其1次與2次曲線如下所示：


以下為四個十字繡曲線所圍成的小方巾圖案程式：

• StachCurve.java

package onlyfun.caterpillar.graphics.recursive;

import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JApplet;
import onlyfun.caterpillar.graphics.Turtle;

public class StechCurve extends JApplet {
    private Turtle t;
    
    public void init() {    
        t = new Turtle(); 
        
        setBackground(Color.black); 
    }
    
    public void stech(int n, double leng, Turtle t) { 
        if(n == 0) { 
            t.move(leng); 
        } 
        else { 
            stech(n-1, leng, t); t.turn(-90); 
            stech(n-1, leng, t); t.turn(90); 
            stech(n-1, leng, t); t.turn(90); 
            stech(n-1, leng, t); t.turn(-90); 
            stech(n-1, leng, t); 
        } 
    }
 
    public void paint(Graphics g) {
        g.setColor(Color.yellow);
        
        t.setGraphics(g);
        t.window(0, 0, getSize().width, getSize().height); 
        t.view(0, 0, getSize().width, getSize().height); 
        t.setpoint(100, 150); 
        t.setangle(0); 
        
        for(int i = 1; i <= 4; i++) { 
            stech(4, 2, t); 
            t.turn(90); 
        }
    }     
}