image processing sinusoidal periodic noise

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Mohammad abu aqoulah 2020-6-1

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https://ww2.mathworks.cn/matlabcentral/answers/539335-image-processing-sinusoidal-periodic-noise

评论： Image Analyst 2021-9-21

how i add a sinusoidal periodic noise to image with a radius 50% from its maximum spectrum frequency (not located on the u nor v axes).and Show the original and resulting images and how to estimate the noise type (assume you do not know the noise and you do not have the original clean image) and how i can remove the added noise with filter

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Answer 1

Image Analyst 2020-6-1

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https://ww2.mathworks.cn/matlabcentral/answers/539335-image-processing-sinusoidal-periodic-noise#answer_443883

fft_filter.m

See attached demo.

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Shahrizan Jamaludin 2021-9-21

编辑：Image Analyst 2021-9-21

在 MATLAB Online 中打开

Hi. How do I create periodic noise in the vertical direction?

I can see other people used below equation to simulate horizontal noise.

cosVector = amplitude * (1 + cos(2 * pi * rowVector / period))/2 + offset

Image Analyst 2021-9-21

在 MATLAB Online 中打开

Try this:

rows = 1080;
columns = 1920;
amplitude = 150; % Brightness difference from peak to valley.
offset = 50; % Darkest it will be.
period = 500;
% Create column vector.
y = (1 : rows)';
cosVector = uint8(amplitude * (1 + cos(2 * pi * y / period)) / 2 + offset);
% Replicate it to turn it into a 2-D image.
horizontalBandsImage = repmat(cosVector, [1, columns]);
subplot(2, 2, 1);
imshow(horizontalBandsImage);
axis('on', 'image');
impixelinfo;
% Create column vector.
x = 1 : columns;
cosVector = uint8(amplitude * (1 + cos(2 * pi * x / period)) / 2 + offset);
% Replicate it to turn it into a 2-D image.
verticalBandsImage = repmat(cosVector, [rows, 1]);
subplot(2, 2, 2);
imshow(verticalBandsImage);
axis('on', 'image');
impixelinfo;
subplot(2, 2, 3:4);
histogram(verticalBandsImage, 0:255);
grid on;
title('Histogram', 'FontSize', 15);