// Julia set dynamics,  Evgeny Demidov,  12 January 2006
  
  import java.awt.*;
  import java.awt.image.*;
  import java.awt.event.*;
  import java.util.StringTokenizer;
  
  public class applet-math-fractal-juliadyn1 extends java.applet.Applet implements KeyListener,
     MouseMotionListener{
  double maxIZI2=10., Ymid=.0, Xmid=-.5, DelX=3.,  Cr,Ci, Xm=1, Ym=0, Rm=.1, Step;
  int maxIt = 256, maxColor = 96, w, h, w2,h2,  ix,iy, ixo,iyo, ir,ir2,
    lbSize,   px[],py[], pxo[],pyo[],  pixArr[];
  Image img;             IndexColorModel RainbowColor;
  boolean   bXOR=false;
  Label  lbZ, lbCr, lbCi, lbR, lbD;    TextField tfZ, tfCr, tfCi, tfR, tfD;
  
  public void init() {
    String s=getParameter("XYmidDelCD"); if (s != null) {
      StringTokenizer st = new StringTokenizer(s);
      Xmid = Double.valueOf(st.nextToken()).doubleValue();
      Ymid = Double.valueOf(st.nextToken()).doubleValue();
      DelX = Double.valueOf(st.nextToken()).doubleValue();
      Cr = Double.valueOf(st.nextToken()).doubleValue();
      Ci = Double.valueOf(st.nextToken()).doubleValue();}
    s=getParameter("MaxIt"); if (s != null) maxIt=Integer.parseInt(s);
    s=getParameter("MaxIZI2");
    if (s != null) maxIZI2 = Double.valueOf(s).doubleValue();
    s=getParameter("MaxColor"); if (s != null) maxColor=Integer.parseInt(s);
    int M=maxColor/3,  M2=2*M;  maxColor = 3*M;     // maxColor is 3*int
    long M4 = (long)M*M*M*M;
    byte rColor[] = new byte[maxColor+2], bColor[] = new byte[maxColor+2],
         gColor[] = new byte[maxColor+2];
    for (int i = 1; i < M2; i++){                   // set Color Map
      long dum = M - i;  dum *=dum;  dum *=dum;
      gColor[i] =  bColor[(i+M) % maxColor] = rColor[(i+M2) % maxColor] =
          (byte)(255 - (255*dum)/M4);}
    rColor[maxColor+1] = gColor[maxColor+1] = bColor[maxColor+1] = (byte)200;
    RainbowColor = new IndexColorModel( 8, maxColor+2, rColor,gColor,bColor);
    s=getParameter("XYR"); if (s != null) {
      StringTokenizer st = new StringTokenizer(s);
      Xm = Double.valueOf(st.nextToken()).doubleValue();
      Ym = Double.valueOf(st.nextToken()).doubleValue();
      Rm = Double.valueOf(st.nextToken()).doubleValue();}
    this.setLayout( new FlowLayout(FlowLayout.LEFT, 0, 0) );
    lbZ = new Label("Z", Label.RIGHT);  add(lbZ);
    if (Ym < 0.) s = ""+Xm+" "+Ym+" i";  else s = ""+Xm+" +"+Ym+" i";
    tfZ = new TextField(s, 20);    add(tfZ);
    lbCr = new Label("Cr", Label.RIGHT);  add(lbCr);
    tfCr = new TextField(""+Cr, 8);    add(tfCr);
    lbCi = new Label("Ci", Label.RIGHT);  add(lbCi);
    tfCi = new TextField(""+Ci, 8);    add(tfCi);
    lbR = new Label("R", Label.RIGHT);  add(lbR);
    tfR = new TextField(""+Rm, 3);    add(tfR);
    lbD = new Label("dz", Label.RIGHT);  add(lbD);
    tfD = new TextField(""+DelX, 3);    add(tfD);
    tfCr.addKeyListener(this);  tfCi.addKeyListener(this);
    tfD.addKeyListener(this);   tfR.addKeyListener(this);
    w = getSize().width;   h = getSize().height;
    lbSize = tfZ.getPreferredSize().height;
    h -= lbSize;
    w2 = w/2;  h2 = h/2;
    Step=DelX/w;
    pixArr = new int[w*(h+2)];
    px = new int[9];  pxo = new int[9];  py = new int[9];  pyo = new int[9];
    addMouseMotionListener(this);
    Draw();
  }
  
  public void Draw(){
    Step=DelX/w;
    ix = ixo = w2 + (int)((Xm - Xmid)*w/DelX);
    iy = iyo = h2 - (int)((Ym - Ymid)*w/DelX);
    ir = (int)(Rm*w/DelX);   ir2 = 2*ir;
    Polygon();
    System.arraycopy(px,0,pxo,0,9);
    System.arraycopy(py,0,pyo,0,9);
    double X,Y;
    int pix=w, ix,iy;
    for (iy=0, Y=Ymid+Step*h2; iy < h; iy++, Y-=Step) {
     for (ix=0, X=Xmid-Step*(w2-1); ix < w; ix++, X+=Step, pix++) {
        pixArr[pix] =iterateDE(X,Y);
     }
    }
    img = createImage(new MemoryImageSource(w, h, RainbowColor, pixArr, w, w));
  }
  
  public void Polygon(){
    double R=Xm-Rm, I=Ym-Rm;  st(R, I, 0);
    R=Xm;     st(R,I,1);
    R=Xm+Rm;  st(R,I,2);
    I=Ym;     st(R,I,3);
    I=Ym+Rm;  st(R,I,4);
    R=Xm;     st(R,I,5);
    R=Xm-Rm;  st(R,I,6);
    I=Ym;     st(R,I,7);
    px[8]=px[0]; py[8]=py[0];
  }
  
  public void st(double R, double I, int k){
    px[k] = w2 + (int)((R*R-I*I+Cr - Xmid)*w/DelX);
    py[k] = h2 - (int)((2*R*I+Ci - Ymid)*w/DelX) + lbSize;
  }
  
  public void destroy(){ removeMouseMotionListener(this); }
  public void mouseMoved(MouseEvent e){}  //1.1 event handling
  
  public void mouseDragged(MouseEvent e) {
    ix = e.getX(); iy = e.getY() - lbSize;
    Xm = Xmid+(ix-w2)*Step;  Ym = Ymid-(iy-h2)*Step;
      if (Ym < 0.) tfZ.setText( ""+(float)Xm+" "+(float)Ym+" i");
         else  tfZ.setText( ""+(float)Xm+" +"+(float)Ym+" i");
    Polygon();
    bXOR = true;
    repaint();
  }
  
  public void keyTyped(KeyEvent e){}
  public void keyPressed(KeyEvent e){}
  public void keyReleased(KeyEvent e){
    final int keyEnter = 10;
    if (e.getKeyCode() == keyEnter){
      try{
        Cr = Double.valueOf(tfCr.getText()).doubleValue();
        Ci = Double.valueOf(tfCi.getText()).doubleValue();
        Rm = Double.valueOf(tfR.getText()).doubleValue();
        DelX = Double.valueOf(tfD.getText()).doubleValue();
      }catch(NumberFormatException ne){}
      Draw();
      repaint();
    }
  }
  
  public void update(Graphics g){ paint(g); }
  
  public void paint(Graphics g) {
    if(!bXOR){
     g.drawImage(img, 0, lbSize, this);
     drawLabel(g);
     int r = (int)(w/DelX);
     g.setColor(Color.white);
     g.drawOval(w2-r,h2-r+lbSize,r+r,r+r);
     g.drawLine(w2-5,h2+lbSize, w2+5,h2+lbSize);
     g.drawLine(w2,h2-5+lbSize, w2,h2+5+lbSize);
     g.setXORMode(Color.black);
     g.fillPolygon(px,py,9);
     g.drawRect(ix-ir,iy-ir+lbSize,ir2,ir2);
     g.setPaintMode();}
    else{
     g.setXORMode(Color.black);
     g.setColor(Color.white);
     g.fillPolygon(pxo,pyo,9);
     g.drawRect(ixo-ir,iyo-ir+lbSize,ir2,ir2);
     System.arraycopy(px,0,pxo,0,9);   System.arraycopy(py,0,pyo,0,9);
     ixo = ix; iyo = iy;
     g.fillPolygon(px,py,9);
     g.drawRect(ix-ir,iy-ir+lbSize,ir2,ir2);
     g.setPaintMode();
     bXOR=false;}
  //   showStatus( "Cr="+Cr+"  Ci="+Ci);
  }
  
  public void drawLabel(Graphics gra) {
   double  R=0.,I=0.;
   gra.setColor(Color.white);
   int x,y;
   gra.setFont(
     new Font( gra.getFont().getName(), Font.BOLD, 15 ) );
   int maxLabel=0;
   while (true) {
     String s=getParameter("lb"+maxLabel);
     if (s == null) break;
     StringTokenizer st = new StringTokenizer(s);
     x=w2+(int)((Double.valueOf(st.nextToken()).doubleValue()-Xmid)/Step);
     y=h2+(int)((Ymid-Double.valueOf(st.nextToken()).doubleValue())/Step);
     gra.drawString(st.nextToken(), x,y);
     maxLabel++; }
  }
  
  int iterateDE(double X, double Y){
      double I=Y, R=X,  I2=I*I, R2=R*R, Dr=.7,Di=.7,D, K=5;   int n=0;
      do  {
        D = (R*Dr - I*Di);  Di = (R*Di + I*Dr);  Dr = D;
        I=(R+R)*I+Ci;  R=R2-I2+Cr;  R2=R*R;  I2=I*I;  n++;
      } while ((R2+I2 < 100.) && (n < maxIt) );
      if (n == maxIt) return maxColor;
      else{
       R = -K*(Math.log(Math.log(R2+I2)*Math.sqrt((R2+I2)/(Dr*Dr+Di*Di)))-n*.693);
       if (R < 0) R=0;
       return (int)R % maxColor; };
  }
  
  }