这是一个分辨图形对称度的参数。返回值为1，则对应图形为圆；其它图形都大于0，小于一。越接近1，则对称度越高。-This is a symmetry to distinguish graphics parameters. The return value is 1, then the corresponding graph for a round other graphics are greater than 0, less than one. The closer one, then the