常用去噪之中值滤波

中值滤波即对于每一像素点取其邻域中值替代该像素点原值，对于椒盐噪声有极其显著的去噪效果，脱离邻域的像素点被拉回到邻域附近，图像细节，噪声都被平滑。
Matlab实现:

% 中值滤波 test
A = imread('C:\Users\gh\Desktop\photo\lena.pgm');
B = imnoise(A,'salt');

figure;subplot(221),imshow(A);title('原图')
subplot(222),imshow(B);title('椒盐噪声图')

C = m_median_filter(B,3);
subplot(223),imshow(C);title('中值滤波后')

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%
% Purpose:do median filter
% Author: pottor
% Date: 2017/5/9
% w is required to be odd

function out = m_median_filter(in,w)

out = in;
[m,n] = size(in);
hw = floor(w/2);

for i = 1+hw : m-hw
    for j = 1+hw : n-hw
        out(i,j) = median(reshape(in(i-hw:i+hw,j-hw:j+hw),[1,w*w]));
    end
end