此文件一共包含3个m文件。第一个文件的功能是绘制一个二值图像，并显示其傅立叶幅度谱。文件2功能是设计频域理想低通滤波器，并加以验证：读入一个二值图像(cameraman.tif)加噪声后在频域进行低通滤波观察滤波后的图像效果。文件3的功能是对图像eight.tif加入椒盐噪声后，实现Butterworth低通滤波.-This file contains 3 m documents. Functions of first file is to draw a binary image, and displays its Fourier amplitude spectrum. Document 2 is designed to function a frequency domain ideal low-pass filter , and verified it: reading a binary image (cameraman.tif) plus noise on it and smoothing it in the frequency domain　using low-pass filtering.The filtered effect will be observed by displaying image.Document 3 is designed to read a binary image(eight.tif) and add salt and pepper noise on it, realized frequence domain Butterworth low-pass filter.