// Henon attractor,  Evgeny Demidov,  21 June 2004
  
  import java.awt.*;
  import java.awt.image.*;
  import java.awt.event.*;
  import java.util.StringTokenizer;
  
  public class applet-math-fractal-ahenon extends java.applet.Applet implements MouseListener {
  double Ymid=0, Xmid=-.5, stX,stJ,  A=-1.4, B=.3, Xj=0,Yj=0;
  int MaxIt = 256,  maxColor = 96, w,w2,h,h2, pixArr[], pixJ[];
  Image img, imgJ;             IndexColorModel RainbowColor;
  boolean   drawM = true, drawJ = true;
  
  public void init() {
    w = getSize().width/2;  h = getSize().height;  w2 = w/2; h2 = h/2;
    stX = 3./w;  stJ = 5./w;
    String s=getParameter("XYmidDelCD"); if (s != null) {
      StringTokenizer st = new StringTokenizer(s);
      Xmid = Double.valueOf(st.nextToken()).doubleValue();
      Ymid = Double.valueOf(st.nextToken()).doubleValue();
      stX = Double.valueOf(st.nextToken()).doubleValue()/w;}
  //    paramC = Double.valueOf(st.nextToken()).doubleValue();
  //    paramD = Double.valueOf(st.nextToken()).doubleValue();}
    s=getParameter("MaxIt"); if (s != null) MaxIt=Integer.parseInt(s);
    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+3], bColor[] = new byte[maxColor+3],
         gColor[] = new byte[maxColor+3];
    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;
    rColor[maxColor+2] = gColor[maxColor+2] = bColor[maxColor+2] = (byte)255;
    RainbowColor = new IndexColorModel( 8, maxColor+3, rColor,gColor,bColor);
    pixArr = new int[w*h];  pixJ = new int[w*h];
    Draw(Xmid, Ymid, stX);
    DrawJ();
    addMouseListener(this);
  }
  
  public void destroy() {  removeMouseListener(this); }
  public void mouseClicked(MouseEvent e) {}      //1.1 event handling
  public void mousePressed(MouseEvent e) {}
  public void mouseEntered(MouseEvent e) {}
  public void mouseExited(MouseEvent  e) {}
  
  public void mouseReleased(MouseEvent e) {
    int ix = e.getX();
    double xt,yt;
    if (ix < w){
      xt = Xmid+(ix-w2)*stX;  yt = Ymid-(e.getY()-h2)*stX;
      if ( e.isControlDown() ){
        if ( e.isShiftDown() )  stX *=4.;  else  stX *=2.;
        Xmid = xt; Ymid = yt;   Draw(Xmid, Ymid, stX);}
      else if( e.isAltDown() ){
        if ( e.isShiftDown() )  stX /=4.;  else  stX /=2.;
        Xmid = xt; Ymid = yt;   Draw(Xmid, Ymid, stX);}
      else{
        A = xt; B = yt;
        DrawJ();
        showStatus( "a=" + A + " b=" + B);}}
    else{
      xt = Xj+(ix-w2-w)*stJ;  yt = Yj-(e.getY()-h2)*stJ;
      if ( e.isControlDown() ){
        if ( e.isShiftDown() )  stJ *=4.;  else  stJ *=2.;
        Xj = xt; Yj = yt;   DrawJ();}
      else if( e.isAltDown() ){
        if ( e.isShiftDown() )  stJ /=4.;  else  stJ /=2.;
        Xj = xt; Yj = yt;   DrawJ();}}
    repaint();
  }
  
  public void paint(Graphics g) {
    g.drawImage(img, 0, 0, this);
    g.drawImage(imgJ, w, 0, this);
    g.setColor(Color.white);
    int n=0, x,y;
    y = h2 + (int)(Ymid/stX);  g.drawLine(0,y, w,y);
    x = w2 + (int)((A - Xmid)/stX);  y = h2 - (int)((B - Ymid)/stX);
    if(x < w) g.drawLine(x-3,y, x+3,y); g.drawLine(x,y-3, x,y+3);
  }
  
  public void Draw( double Xm, double Ym, double Step){
    double X,Y;
    int pix=0, ix,iy;
    for (iy=0, Y=Ym+Step*h2; iy < h; iy++, Y-=Step) {
     for (ix=0, X=Xm-Step*(w2-1); ix < w; ix++, X+=Step, pix++){
        pixArr[pix] = iterate(X, Y);}}
    img = createImage(new MemoryImageSource(w, h, RainbowColor, pixArr, 0, w));
  }
  
  int iterate(double a, double b){
      double X, X2, X1, Y;   int n=0;
      double b1 = (1-b)*.5, d=b1*b1-a;
      if (d < 0) X = 0;
      else  X = b1 - Math.sqrt(d) + 1e-10;
      Y = X; X2 = X*X;
      do{ X1 = a + X2 + b*Y;  Y = X;  X = X1;  X2 = X*X;   n++;
      } while ((X2 < 1000.) && (n < MaxIt) );
      if (n < MaxIt) return maxColor+1;
      double Xo = X, Yo = Y;  n = -1;
      do{ X1 = a + X*X + b*Y;  Y = X;  X = X1;  n++;
      } while ((Math.abs(X - Xo) + Math.abs(Y - Yo) > 1e-8) && (n < 64) );
      if (n == 64) return maxColor;
      return n % maxColor;
  }
  
  public void DrawJ(){
    int ix,iy;
    for (int it=0; it < w*h; it++) pixJ[it] = maxColor+2;
    double X, X2, X1, Y,  b1 = (1-B)*.5, d=b1*b1-A;
    if (d < 0) X = 0;  else  X = b1 - Math.sqrt(d) + 1e-10;
    Y = X; X2 = X*X;
    for (int it=0; it <= 10000*MaxIt; it++){
      X1 = A + X2 + B*Y;  Y = X;  X = X1;  X2 = X*X;
      ix = (int)((X - Xj)/stJ) + w2;
      iy = -(int)((Y - Yj)/stJ) + h2;
  //System.out.println(""+X +"  "+Y+"  "+it);
      if ((ix >= 0)&&(ix < w)&&(iy >= 0)&&(iy < h)) pixJ[ix+iy*w] = maxColor;
    }
  //  for (int it=0; it < w*h; it++) pixJ[it] %= maxColor;
    imgJ = createImage(new MemoryImageSource(w, h, RainbowColor, pixJ, 0, w));
  }
  
  }