说明：  分别设计理想低通滤波器、巴特沃思滤波器、指数滤波器、梯形低通滤波器,并对含高斯噪声的图像进行低通滤波，截止频率自选，观察不同的截止频率,不同的滤波器的滤波效果。
(Were designed for the ideal low pass filter, Butterworth filter, exponential filter, ladder low-pass filter, and Gaussian noise images with low-pass filter cutoff frequency chosen to observe the different cut-off frequency, different filter filtering device.)