float [] px = new float[0]; // hold the mouse pressed marks
  float [] py = new float[0];
  float [] distance = new float[0]; //holds the pixel’s distance to the marked point
  int [] idx = new int[0]; //used for sorting the pixels
  PImage MyImage;
  void setup(){
    size (400,400);
    MyImage = createImage (width, height, RGB); //create an image
    image(MyImage,0,0);
  }
  void draw(){
    stroke(0);
    for(int i=0; i<px.length; i++)
      rect(px[i],py[i],3,3); //draw the mark as a tiny rectangle
  }
  void mousePressed(){ //if the use presses the mouse
    px = append(px,mouseX); //add that clicked point
    py = append(py,mouseY);
    distance = append(distance,0); //allocate memory for the distance
    idx = append(idx,0); // and the id
    for(int x=0; x<width; x++) //for all pixels
      for(int y=0; y<height; y++){
        for(int i=0; i<px.length; i++) //for all already defined marks
          distance[i] = dist(x,y,px[i],py[i]); //find the distance from all points
        for(int i=0; i<idx.length; i++)
          idx[i]=i;
        for(int i=1; i<distance.length; i++) //sort all distances together with ids
          for(int j=0; j<distance.length-1; j++)
            if(distance[i]>distance[j]){
              float t = distance[i]; //swap in ascending order
              distance[i] = distance[j];
              distance[j] = t;
              int tr = idx[i];
              idx[i]=idx[j];
              idx[j] = tr;
            } 
        for(int i=0; i<idx.length; i++) //color the area with random colors
          set(x,y,color((idx[i]*126)%255,(idx[i]*133)%255,(idx[i]*144)%255));
      }
  
    //added code to detect the edges of color areas
    for(int x=1; x<width-1; x++)
      for(int y=1; y<height-1; y++) //check the difference between adjacent pixels
        if(abs(red(get(x,y))-red(get(x+1,y)))>0 ||
          abs(red(get(x,y))-red(get(x,y+1)))>0   )
          set(x,y,color(0));  //black
        else
          set(x,y,color(255)); //white
  
  }