srecord noeq G22Tiling<Img extends WidthAndHeight>(Img img) {
  new L<Tile> tiles;
  
  // for each pixel: tile index+1 (or 0 for empty)
  int[] tileMatrix;

  // index = dual log of tile size, value = tile index
  //new L<IntBuffer> tilesBySize;
  
  sclass Tile {
    Rect position;
    
    // Lists of neighbors in all 4 directions (index like NESWDirection)
    // (If only a corner is touching, it's not a neighbor.)
    Cl<Tile>[] neighbors = new Cl[4];
  }
  
  int w() { ret img.w(); }
  int h() { ret img.h(); }
  
  void initTileMatrix {
    tileMatrix = new int[w()*h()];
  }
}