code: def _whctrs(anchor):
          
          w = anchor[2] - anchor[0] + 1
          h = anchor[3] - anchor[1] + 1
          x_ctr = anchor[0] + 0.5 * (w - 1)
          y_ctr = anchor[1] + 0.5 * (h - 1)
          return w, h, x_ctr, y_ctr
docs: Return width, height, x center, and y center for an anchor (window).