//threshold tartanaters
//fixed code 26/04/05
torch [] t;
BImage swap;
boolean drawit = false;
int w,h;
int saveCount = 0;
void setup(){
  swap = loadImage ("test.gif");
  w = swap.width;
  h = swap.height;
  println("canvas size:"+w+" by "+h);
  size (350,200);//change to w,h for image export
  t = new torch[1000];
  for (int i = 0; i < t.length/2; i++){
    t[i] = new torch(int(random(width)),int(random(height)),int(random(4)),false);
  }
  for (int i = t.length/2; i < t.length; i++){
    t[i] = new torch(int(random(width)),int(random(height)),int(random(4)),true);
  }
}

void loop(){
  background(swap);
  for (int i = 0; i < t.length; i++){
    t[i].trace();
    if (drawit){
      t[i].draw();
    }
  }
}
void keyPressed(){
  switch(key){
    case 's':
    case 'S':
    swap.save("tartan"+(saveCount)+".tif");
    println("saved tartan"+(++saveCount)+".tif");
    break;
    case 'd':
    case 'D':
    drawit = !drawit;
    break;
  }
}
class torch{
  int x,y,d;
  boolean light;
  torch(int x, int y, int d, boolean light){
    this.x = x;
    this.y = y;
    this.d = d;
    this.light = light;
  }
  void draw(){
    color c = swap.pixels[x + y * w];
    int r=c>>16&0xff;
    int g=c>>8&0xff;
    int b=c&0xff;
    noStroke();
    if (light){
      fill(r-30,g-30,b-30,130);
    } else {
      fill(r+30,g+30,b+30,130);
    }
    rect(x-3,y-3,6,6);
  }
  void trace(){
    int c = swap.pixels[x + y * width];
    if (light){
      switch(d){
        case 0:
        if (grey(swap.pixels[((x+1)%w) + y * width]) > 10){
          x = (x+1)%w;
        }else{
          d = (d+1)%4;
        }
        break;
        case 1:
        if (grey(swap.pixels[x + ((y+1)%h) * width]) > 10){
          y = (y+1)%h;
        }else{
          d = (d+1)%4;
        }
        break;
        case 2:
        if (grey(swap.pixels[wr(x-1,w-1) + y * width]) > 10){
          x = wr(x-1,w-1);
        }else{
          d = (d+1)%4;
        }
        break;
        case 3:
        if (grey(swap.pixels[x + wr(y-1,h-1) * width]) > 10){
          y = wr(y-1,h-1);
        }else{
          d = (d+1)%4;
        }
        break;
      }
      if (grey(swap.pixels[x + y * width])- 10 > 0){
        c = tone(swap.pixels[x + y * width],-10);
      }
    }else{
      switch(d){
        case 0:
        if (grey(swap.pixels[((x+1)%w) + y * width]) <= 245){
          x = (x+1)%w;
        }else{
          d = (d+1)%4;
        }
        break;
        case 1:
        if (grey(swap.pixels[x + ((y+1)%h) * width]) <= 245){
          y = (y+1)%h;
        }else{
          d = (d+1)%4;
        }
        break;
        case 2:
        if (grey(swap.pixels[wr(x-1,w-1) + y * width]) <= 245){
          x = wr(x-1,w-1);
        }else{
          d = (d+1)%4;
        }
        break;
        case 3:
        if (grey(swap.pixels[x + wr(y-1,h-1) * width]) <= 245){
          y = wr(y-1,h-1);
        }else{
          d = (d+1)%4;
        }
        break;
      }
      if (grey(swap.pixels[x + y * width])+ 10 < 255){
        c = tone(swap.pixels[x + y * width],10);
      }
    }
    swap.pixels[x + y * width] = c;
  }
}
int grey(color p) {
  return max((p >> 16) & 0xff, (p >> 8 ) & 0xff, p & 0xff);
}
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 wr(int v, int lim){
  if (v < 0){
    v = lim;
  }
  return v;
}