static L<Rect> floodFillGrid(BitSet grid, int gw, int gh, int g) {
  new L<Rect> clips;
  
  for (int y = 0; y < gh; y++)
    for (int x = 0; x < gw; x++)
      if (grid.get(y*gw+x)) {
        Rect r = floodFillGrid_step(grid, gw, gh, x, y);
        r = scaleRect(r, g);
        clips.add(r);
      }
      
  ret clips;
}