How can I reduce periodic noises from my image? Please help

Question

Ayberk Ay 2020-2-18

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/506184-how-can-i-reduce-periodic-noises-from-my-image-please-help

评论： aseel malkawi 2022-5-26

woman-1_3.bmp

I've tried to reduce the periodic noises with frequency domain filtering.However, the result of the filter is not that good.Actually, even when I get fftshift of the image, I cannot see clearly noises (maybe there are four point that seems like noises, so I chose them in the code below).Please help me about this filtering.I don't have so much time.I am new at image processing btw.I thought that I can use Notch filter but I couldn't find any special function for it unlike median or average filters.

(The image is attached)

I = imread('woman-1_3.bmp');

I2=fft2(I);

imshow(log(1+abs(fftshift(I2))),[]);

m=ones(200,200);

m(84:1:92,85:1:93)=0;

m(109:1:117,85:1:93)=0;

m(84:1:92,109:1:117)=0;

m(109:1:117,109:1:117)=0;

imshow(m);

imshow(log(1+abs( fftshift(I2).*m)),[]);

imshow(log(1+abs(ifft2( fftshift(I2).*m))),[]);

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Answer 1

Akira Agata 2020-2-19

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在 MATLAB Online 中打开

Looking at your image, periodic noise pattern appears around every 20~30 pixel. So I think the first step is to use FFT or DCT and suppress these frequency components.

The following is my initial try:

% Read the image
I = imread('woman-1_3.bmp');
% Apply DCT
Iw = dct2(I);
% Reduce peaky high-frequency components
idx = abs(Iw) > 50;
idx(1:19,:) = false;
idx(:,1:19) = false;
Iw(idx) = Iw(idx)/100;
% Convert to image
I2 = idct2(Iw);
I2 = mat2gray(I2);
% Show the result
figure
imshowpair(I,I2,'montage')
title('Before / After','FontSize',14)