import java.awt.*;
import java.applet.*;
import java.awt.event.*;

public class Juliazoom extends Applet implements MouseListener, MouseMotionListener {
	private final int MAX = 256;      
    private final double SX = -1.0; // 實部的最小值
    private final double SY = -1.5; // 虛部的最小值
    private final double EX = 2.0;    // 實部的最大值
    private final double EY = 1.5;  // 虛部的最大值
    private static int picX, picY, xs, ys, xe, ye;
    private static double x1, y1, x2, y2, p, q,xb,yb;
    private static boolean action, rechteck, fertig, stopit;
    private static float xy;
    private Image bild;
    private Graphics g1;
    private Cursor c1, c2;
     public void init() // 初始化所有實例
    {
            p = -0.46;
            q = 0.57;

            fertig = false;
            addMouseListener(this);
            addMouseMotionListener(this);
            c1 = new Cursor(Cursor.WAIT_CURSOR);
            c2 = new Cursor(Cursor.CROSSHAIR_CURSOR);
            picX = getSize().width;
            picY = getSize().height;
            xy = (float)picX / (float)picY;
            bild = createImage(picX, picY); 
            g1 = bild.getGraphics();
            fertig = true;
    }
     public void destroy() // 刪除所有實例 
    {
            if (fertig)
            {
                    removeMouseListener(this);
                    removeMouseMotionListener(this);
                    bild = null;
                    g1 = null;
                    c1 = null;
                    c2 = null;
                    System.gc(); 
            }
    }
     public void start()
    {
            action = false;
            rechteck = false;
    stopit = false;
            startwerte();
            xb = (x2 - x1) / (double)picX;
            yb = (y2 - y1) / (double)picY;


            julia();
    }
     public void stop()
    {
    }
    
    public void paint(Graphics g)
    {
            update(g); 
    }
    
    public void update(Graphics g)
    {
            g.drawImage(bild, 0, 0, this);
            if (rechteck)
            {
                    g.setColor(Color.white);
                    if (xs < xe)
                    {
                            if (ys < ye) g.drawRect(xs, ys, (xe - xs), (ye - ys));
                            else g.drawRect(xs, ye, (xe - xs), (ys - ye));
                    }
                    else
                    {
                            if (ys < ye) g.drawRect(xe, ys, (xs - xe), (ye - ys));
                            else g.drawRect(xe, ye, (xs - xe), (ys - ye));
                    }
            }
    }
    
    private void julia() // 計算所有的點
    {
            int x, y;
            float h, b, alt = 0.0f;
            
            action = false;
            setCursor(c1);
            showStatus("正在計算julia集，請等待...");
             p = -0.46;
             q = 0.57;
            for (x = 0; x < picX; x+=2) {
                    for (y = 0; y < picY; y++)
                    {
                            h = punktfarbe(x1 + xb * (double)x, y1 + yb * (double)y,p,q); // 顏色值
                            if (h != alt)
                            {
                                    b = 1.0f - h * h; 
                                    g1.setColor(Color.getHSBColor( h,1,b));
                                  
                                    alt = h;
                            }           
                            g1.drawLine(x, y, x + 1, y);
                    }
        showStatus( "At " + x + " of " + picX );
        if (stopit) x = picX;
    }

    if  (stopit) {
        showStatus("Aborted");
        stopit = false;
    }  else {
        showStatus("julia集已準備好，請用鼠標選擇放大區域.");
    }
            setCursor(c2);
            action = true;
    }
    // 由迭代產生的0.0到1.0的顏色值
    private float punktfarbe(double x0, double y0,double p,double q) 
    {
            double r = 0.0,  xk = 0, yk = 0;
            int j = 0;
            
            
            while ((j < MAX) && (r < 4.0))
            {
                    
                    xk = x0 * x0 - y0 * y0 + p;
                    yk = 2.0 * x0 * y0 + q;
                    j++;
                    r = yk * yk + xk * xk;
                    x0 = xk;
                    y0 = yk;

                

            }
            return (float)j / (float)MAX;
    }
    
    private void startwerte() // 重新開始值
    {
            x1 = SX;
            y1 = SY;
            x2 = EX;
            y2 = EY;
            if ((float)((x2 - x1) / (y2 - y1)) != xy ) 
                    x1 = x2 - (y2 - y1) * (double)xy;
    }
     public void mousePressed(MouseEvent e) 
    {
            e.consume();
            if (action)
            {
                    xs = e.getX();
                    ys = e.getY();
            }
    }
    
    public void mouseReleased(MouseEvent e)
    {
            int z, w;
            
            e.consume();
            if (action)
            {
                    xe = e.getX();
                    ye = e.getY();
                    if (xs > xe)
                    {
                            z = xs;
                            xs = xe;
                            xe = z;
                    }
                    if (ys > ye)
                    {
                            z = ys;
                            ys = ye;
                            ye = z;
                    }
                    w = (xe - xs);
                    z = (ye - ys);
                    if ((w < 2) && (z < 2)) startwerte();
                    else
                    {
                            if (((float)w > (float)z * xy)) ye = (int)((float)ys + (float)w / xy);
                            else xe = (int)((float)xs + (float)z * xy);
                            x2 = x1 + xb* (double)xe;
                            y2 = y1 + yb * (double)ye;
                            x1 += xb * (double)xs;
                            y1 += yb * (double)ys;
                    }
                    xb = (x2 - x1) / (double)picX;
                    yb = (y2 - y1) / (double)picY;
                    julia();
                    rechteck = false;
                    repaint();
            }  else {
        stopit = true;
    }
    }
     public void mouseEntered(MouseEvent e)
    {
    }
     public void mouseExited(MouseEvent e)
    {
    }
     public void mouseClicked(MouseEvent e) 
    {
    }
    
    public void mouseDragged(MouseEvent e)
    {
            e.consume();
            if (action)
            {
                    xe = e.getX();
                    ye = e.getY();
                    rechteck = true;
                    repaint();
            }
    }
    
    public void mouseMoved(MouseEvent e)
    {
    }
    


}