Noise estimation in an image

Question

scaramanga 2012-1-11

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/25869-noise-estimation-in-an-image

Hello,

When I want to estimate the noise variance of an image, I use to select an homogeneous region and compute the variance in that area. But I found another way to compute it in the web that I don't really understand and which yields the same results :

function [sigma,eps1]=estimateNoise(im)
h=zeros(3,3); h(2,2)=1;
h(2,1)=-1/4; h(2,3)=-1/4;
h(1,2)=-1/4; h(1,3)=-1/4;
f=sqrt(4/5);
eps1=f*imfilter(im,h,'replicate');
sigma=sqrt(1/numel(im)*sum(eps1(:).^2));