一般的高通、低通滤波器等功能，还有加窗算法。-General high-pass, low-pass filter, as well as windowing algorithm.

利用傅里叶变换，对图像进行低通滤波处理，利用sin函数窗-To avoid boundary artifacts and estimate really the frequency content of the image (and not of the artifacts!), one needs to multiply M by a smooth windowing function h and compute fft2(M.*h). Use a sine windowing functio