DLA [] w;
BImage swap;
int W,H;
boolean drawit = true;
int saveCount = 0;
void setup(){
  swap = loadImage("e.gif");
  size (600,450);
  background(swap);
  w = new DLA[20000];
  for(int i = 0; i < w.length; i++){
    w[i] = new DLA();
  }
}
void loop(){
  background(swap);
  for(int i = 0; i < w.length; i++){
    w[i].move();
    w[i].check();
    if(drawit){
      w[i].draw();
    }
  }
}
void keyPressed(){
  switch(key){
    case 'd':
    case 'D':
    drawit = !drawit;
    break;
    case 's':
    case 'S':
    println("saved DLA"+(++saveCount)+".tif");
    save("DLA"+saveCount+".tif");
    break;
  }
}
class vector{
  int x,y;
  vector(){
    reset();
  }
  void reset(){
    int option = int(random(3));
    switch(option){
      case 0:
      x = int(random(1,width-1));
      y = minOrMax(1,height-2);
      break;
      case 1:
      x = minOrMax(1,width-2);
      y = int(random(1,height-1));
      break;
      default:
      x = int(random(1,width-1));
      y = int(random(1,height-1));
    }
  }
}
class DLA{
  vector v;
  int thresh;
  DLA(){
    v = new vector();
    thresh = int(grey(swap.pixels[(v.x+1) + v.y * width]));
  }
  void move(){
    int d = int(random(4));
    switch(d){
      case 0:
      v.x++;
      break;
      case 1:
      v.y++;
      break;
      case 2:
      v.x--;
      break;
      case 3:
      v.y--;
      break;
    }
    if (v.y < 1 || v.x < 1 || v.y > height-2  || v.x > width-2){
    v.reset();
    }
  }
  void check(){
    if (int(grey(swap.pixels[(v.x+1) + v.y * width])) == thresh){
      int delta = thresh - int(grey(swap.pixels[v.x + v.y * width]));
      swap.pixels[v.x + v.y * width] = tone(swap.pixels[v.x + v.y * width],delta);
      v.reset();
    }
    if (int(grey(swap.pixels[v.x + (v.y+1) * width])) == thresh){
      int delta = thresh - int(grey(swap.pixels[v.x + v.y * width]));
      swap.pixels[v.x + v.y * width] = tone(swap.pixels[v.x + v.y * width],delta);
      v.reset();
    }
    if (int(grey(swap.pixels[(v.x-1) + v.y * width])) == thresh){
      int delta = thresh - int(grey(swap.pixels[v.x + v.y * width]));
      swap.pixels[v.x + v.y * width] = tone(swap.pixels[v.x + v.y * width],delta);
      v.reset();
    }
    if (int(grey(swap.pixels[v.x + (v.y-1) * width])) == thresh){
      int delta = thresh - int(grey(swap.pixels[v.x + v.y * width]));
      swap.pixels[v.x + v.y * width] = tone(swap.pixels[v.x + v.y * width],delta);
      v.reset();
    }
  }
  void draw(){
    stroke(thresh);
    point(v.x,v.y);
  }
}
int ini(){
  return int(random(height));
}
int minOrMax(int n1, int n2){
  return int(random(2)) > 0 ? n1 : n2;
}
color tone (color c, int val){
  int r=c>>16&0xff;
  int g=c>>8&0xff;
  int b=c&0xff;
  r += val;
  g += val;
  b += val;
  return color(r,g,b);
}
 int grey(color p) {
  return max((p >> 16) & 0xff, (p >> 8 ) & 0xff, p & 0xff);  
}