// Continuum percolation,  Evgeny Demidov, 17 Feb 2002
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
public class @file extends java.applet.Applet
 implements ItemListener, ActionListener, MouseMotionListener{
  int  Rc = 8, Lc, w, h, lbSize = 30, iV[], maxColor = 9,
   cWhite = maxColor, cBlack = maxColor+1, hBar, hCol, nb[], delNb[];
  double V[], f[][], G[][],  Vo, sV, Vp = -.95;
  Choice chRc;    Label lbRc;    Button btNew;
  Image img, imBar;      IndexColorModel iColor;
  long generTime;
  boolean bBurn = false;
  Checkbox  cbBurn;

public void init() {
  w = getSize().width - 30;
  h = getSize().height - lbSize;
  nb = new int[w*h];   delNb = new int[4];
  delNb[0] = 1; delNb[1] = -1; delNb[2] = w; delNb[3] = -w;
  String s=getParameter("Rc"); if (s != null) Rc = Integer.parseInt(s);
  s=getParameter("Vp"); if (s != null) Vp = Double.valueOf(s).doubleValue();
  V = new double[w*h];  iV = new int[w*(h+2)];
  f = new double[h+64][w+64];
  for (int i = 0; i < h+64; i++)
   for (int j = 0; j < w+64; j++) f[i][j] = 2*Math.random() - 1;
//  f[100][100] = 1;
  G = new double[32][32];
  Lc = 2*Rc;
  double Rc2 = Rc*Rc;
  G[0][0] = 1;
  for (int i = 1; i < Lc; i++){
   G[0][i] = Math.exp(-(i*i/Rc2));
   for (int j = 1; j <= i; j++) G[j][i] = G[0][i]*G[0][j];}
  byte rColor[] = new byte[maxColor+2], bColor[] = new byte[maxColor+2],
       gColor[] = new byte[maxColor+2];
  int M=maxColor/2;
  long M4 = (long)M*M*M*M;
  for (int i = 0; i < M; i++){
    long dum = i;  dum *=dum;  dum *=dum;
    bColor[i] = gColor[M+i] = gColor[M-i] = rColor[maxColor-1-i] =
     (byte)(255 - (255*dum)/M4);}
  gColor[M] = (byte)220;
  rColor[cWhite] = gColor[cWhite] = bColor[cWhite] = (byte)255;
  iColor = new IndexColorModel( 8, maxColor+2, rColor,gColor,bColor);
  hCol = h/maxColor;   hBar = maxColor*hCol;
  int cBar[] = new int[20*hBar], t = 0;
  for (int i = maxColor-1; i >=0; i--)
   for (int j = 0; j < hCol; j++)
    for (int k = 0; k < 20; k++) cBar[t++] = i;
  imBar = createImage(new MemoryImageSource(20, hBar, iColor, cBar, 0, 20));

  lbRc = new Label("Rc", Label.RIGHT);  add(lbRc);
  chRc = new Choice();
  for (int i = 0, r = 1; i < 5; i++){
    chRc.addItem(Integer.toString(r));  r *= 2;}
  chRc.select("" + Rc);  chRc.addItemListener(this);  add(chRc);
  btNew = new Button("New");   btNew.addActionListener(this);
  add(btNew);
  s=getParameter("Burn"); if (s != null) bBurn = true;
  cbBurn = new Checkbox("Burn", bBurn);
  add(cbBurn);
  cbBurn.addItemListener(this);
  addMouseMotionListener(this);
  averaging();
}
public void destroy(){
 removeMouseMotionListener(this);
}
public void averaging(){
  generTime = System.currentTimeMillis();
  double Vmin = 100, Vmax = -100;
  sV = 0;
  int t = 0, w32 = w+32;
  for (int i = 32; i < h+32; i++){
   for (int j = 32; j < w32; j++){
    double s = G[0][0]*f[i][j];
    for (int m = 1; m < Lc; m++){
     int im = i+m, i_m = i-m, jm = j+m, j_m = j-m;
     s += G[0][m]*(f[im][j]+f[i_m][j]+f[i][jm]+f[i][j_m]) +
          G[m][m]*(f[im][jm]+f[i_m][jm]+f[im][j_m]+f[i_m][j_m]);
     for (int n = 1; n < m; n++){
      int in = i+n, i_n = i-n, jn = j+n, j_n = j-n;
      s += G[n][m]*(f[im][jn]+f[i_m][jn]+f[im][j_n]+f[i_m][j_n] +
                    f[in][jm]+f[i_n][jm]+f[in][j_m]+f[i_n][j_m]);}}
    V[t++] = s;
    if (s > Vmax) Vmax = s;
    if (s < Vmin) Vmin = s;
    sV += s;}}
  sV /= w*h;
  Vo = Vmax;  if (Vmax < -Vmin) Vo = -Vmin;
  makeImg();
  generTime = System.currentTimeMillis() - generTime;
}

public void makeImg(){
  double a = .5*maxColor/Vo, tmp, VpVo = Vp*Vo;
  for (int i = 0; i < w*h; i++)
    if ((tmp = V[i]) < VpVo) iV[i+w] = cWhite;
    else iV[i+w] = (int)(a*(tmp+Vo));
  if ( bBurn ){
    int lastNb = -1;
    for (int i = w; i < 2*w; i++)
      if (iV[i] == cWhite) nb[++lastNb] = i;
    while ( lastNb >= 0){
      int n = nb[lastNb--];
      if (iV[n] == cWhite){
        iV[n] = cBlack;
        for (int i = 0; i < 4; i++){
         int t = n+delNb[i];
         if (iV[t] == cWhite) nb[++lastNb] = t;}}}}
  if ( img != null) img.flush();
  img = createImage(new MemoryImageSource(w, h, iColor, iV, w, w));
}
public void paint(Graphics g) {
  g.drawImage(img, 0, lbSize, this);
  g.drawImage(imBar, w+10, lbSize, this);
  g.setColor(Color.white);
  int y = lbSize + (int)(hBar*(1 - sV/Vo)/2); 
  g.drawLine(w+10, y, w+30, y);
  g.setColor(Color.black);
  y = lbSize + (int)(hBar*(1 - Vp)/2); 
  g.drawLine(w+10, y, w+30, y);
  showStatus( "T=" + generTime + "ms ");
}

public void mouseMoved(MouseEvent e){}
public void mouseDragged(MouseEvent e) {
  if( e.getX() > w){
    int y = e.getY() - lbSize;
    Vp = 1 - y*2.0/hBar;
    if (Vp < -1) Vp = -1;  if (Vp > 1) Vp = 1;
    makeImg();
    repaint();
  }
}
public void itemStateChanged(ItemEvent e){
  Object src = e.getSource();
  if (src == cbBurn){
   bBurn = cbBurn.getState();
   makeImg();}
  if (src == chRc){
   Rc = Integer.parseInt(chRc.getSelectedItem());
   Lc = 2*Rc;
   double Rc2 = Rc*Rc;
   G[0][0] = 1;
   for (int i = 1; i < Lc; i++){
    G[0][i] = Math.exp(-(i*i/Rc2));
    for (int j = 1; j <= i; j++) G[j][i] = G[0][i]*G[0][j];}
   averaging();}
  repaint();
}
public void actionPerformed(ActionEvent e){
  for (int i = 0; i < h+64; i++)
   for (int j = 0; j < w+64; j++) f[i][j] = 2*Math.random() - 1;
  averaging();
  repaint();
}
public void update(Graphics g){ paint(g); }
}