说明：  首先通过频域处理得到图像在频域中的图像，然后根据频域图像判断需要消除的特征频率个数，然后通过画矩形去除要去掉的频域信号，然后频域再转化回空域，就可以得到很好的处理效果。文件不仅仅可以去除周期信号，只要对空域特征在频域上有很深的理解，什么噪声都可以去除。
(Firstly, the image in frequency domain is obtained by processing in frequency domain. Then the number of characteristic frequencies to be eliminated is judged according to the frequency domain image. Then, the frequency domain signal to be removed is removed by drawing a rectangle, and then the frequency domain is transformed back into the spatial domain, which can get a good processing effect. Documents can not only remove periodic signals, but also remove any noise as long as they have a deep understanding of spatial features in frequency domain.)