中文说明：
傅里叶谱与频域低通滤波 (a)从图书网站下载图4.41(a)并计算其(居中)傅里叶谱。(b)显示频谱。(c)在等式(4.8-7)中实现高斯低通滤波器。您必须能够指定结果2D函数的大小，M x N。此外，您必须能够指定高斯函数的中心位置。(d)从图书网站下载图4.41(a)，并对其进行低通滤波，以复制图4.48中的结果。
English Description：
Fourier spectrum and frequency domain low pass filter (a) Download figure 4.41 (a) from the book website and calculate its (Center) Fourier spectrum. (b) Display spectrum. (c) Implement the Gaussian low pass filter in equation (4.8-7). You must be able to specify the size of the resulting 2D function, m x n. In addition, you must be able to specify the center position of the Gaussian function. (d) Download figure 4.41 (a) from the book website and perform low-pass filtering to copy the results in Figure 4.48.