说明：  自己实现的一维、二维DFT。优点：变换后的低频分量在中间，弥补了matlab库函数的不足（高频分量在中间）
(Realize their own one-dimensional, two-dimensional DFT. Advantages: low-frequency components after the transformation in the middle, made up for the inadequacy of matlab library function (high-frequency component in the middle))