class Node {  
  public int x,y,size;  
  public Node[] child = new Node[4];
}

public Node createTree() {  
  return _createTree(0, 0, 0);
}

private Node _createTree(int x, int y, int level) {
  int size = img.width >> level;

  Node node = new Node();
  node.x = x;
  node.y = y;
  node.size = size;
    
  if (size > 1) {
    size = img.width >> ++level;
    node.child[0] = _createTree(x, y, level);
    node.child[1] = _createTree(x+size, y, level);
    node.child[2] = _createTree(x, y+size, level);
    node.child[3] = _createTree(x+size, y+size, level);
  }
  
  return node;
}