作业2: 利用所学的图像滤波方法实现信号的去噪，分别在图像域（直接操作图像像素）和频率域（对傅立叶变换后的系数进行操作）给出实现的过程, 并提交具体算法和实验结果分析。

%1d signal
%generate a 1d signal
name = 'piece-regular';
n = 1024;
x0 = load_signal(name,n);
x0 = rescale(x0);

%We add some noise to it.

sigma = .04; % noise level
x = x0 + sigma*randn(size(x0));
clf;
subplot(2,1,1);
plot(x0); axis([1 n -.05 1.05]);
subplot(2,1,2);
plot(x); axis([1 n -.05 1.05]);





%2d signal
I = imread('rice.png');
I_n = imnoise(I,'gaussian');