Apply a non defined noise to an image

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Ana Gabriela Guedes
Ana Gabriela Guedes on 30 Nov 2021
Answered: yanqi liu on 30 Nov 2021
I have a user defined function that lets us set some kinds of noise and I want to apply that noise to an image. How can I do this since the imfilter function only allows us to apply pre defined noises?
Thank you in advance
Ana Gabriela Guedes
Ana Gabriela Guedes on 30 Nov 2021
I have the following function (that also depends on other functions)
function [noise, PSD, kernel] = getExperimentNoise(noise_type, noise_var, realization, sz)
% Get pre-specified kernel
kernel = getExperimentKernel(noise_type, noise_var, sz);
% Create noisy image
half_kernel = ceil(size(kernel) ./ 2);
if(numel(sz) == 3 && numel(half_kernel) == 2)
half_kernel(3) = 0;
% Crop edges
noise = convn(randn(sz + 2 * half_kernel), kernel(end:-1:1,end:-1:1, :), 'same');
noise = noise(1+half_kernel(1):end-half_kernel(1), 1+half_kernel(2):end-half_kernel(2), :);
PSD = abs(fft2(kernel, sz(1), sz(2))).^2 * sz(1) * sz(2);
and I use it to create 3 different types of noises: additive Gaussian white noise gw with variance 0.04, circular repeating pattern noise g2 with variance 0.04 and diagonal line pattern noise g3 with variance 0.04:
I = im2double(imread('lighthouse.png'));
gausN = getExperimentNoise('gw',0.04,0,size(I));
cRepN = getExperimentNoise('g2',0.04,0,size(I));
dLineN = getExperimentNoise('g3',0.04,0,size(I));
And now I want to apply this noises to the original image. How can I do it? (I know I could use imnoise() for the gaussian but the exercise really needs us to use the given functions)

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Answers (1)

yanqi liu
yanqi liu on 30 Nov 2021
yes,sir,may be define the noise matrix and add to image ,such as
x = imread('carmeraman.tif');
nx = double(x) + 18*randn(size(x));

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