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Denoising by Donoho algorithm

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Soum
Soum on 15 Jun 2013
Hello I'm trying to apply Donoho formula on my noisy image to get the threshold value and apply it on details coefficients which i get it by using wavedec function please someone help me to get a results if some one have another idea for make my code useful please just tell me I'm waiting
clear all
I=imread('cameraman.tif');
n = prod( size(I) );
I=double(I);
Ib=I+25*randn(size(I));% add noise
[C,S] = wavedec2(Ib,2,'bior3.7');
DH = detcoef2('all',C,S,1);% extract details coefficient from level 1
delta = median( abs(DH) ) / 0.6745;
thr = delta * sqrt(2*log(n));
NC = wthcoef2('bior3.7',C,S,DH,thr,s) % i use the soft threshold
X = waverec2(C, S, 'bior3.7'); % how can i get my image after threshold
figure(2)
imagesc(X);axis off;colormap(gray)

Accepted Answer

Wayne King
Wayne King on 15 Jun 2013
Edited: Wayne King on 15 Jun 2013
You want to use the thresholded coefficients in the reconstruction. You also made a couple other errors in your code.
I = imread('cameraman.tif');
n = prod( size(I) );
I = double(I);
Ib = I+25*randn(size(I));% add noise
[C,S] = wavedec2(Ib,2,'bior3.7');
DH = detcoef2('all',C,S,1);% extract details coefficient from level 1
DH = DH(:);
delta = median( abs(DH) ) / 0.6745;
thr = delta * sqrt(2*log(n));
NC = wthcoef2('t',C,S,1,thr,'s'); % i use the soft threshold
X = waverec2(NC, S, 'bior3.7');
figure;
imagesc(Ib); title('Noisy Image'); colormap gray;
figure;
imagesc(X); title('Denoised 1st level coeffs'); colormap gray;
  8 Comments
Soum
Soum on 25 Jun 2013
Thanks Mr.Walter Yes I've read this http://www.mathworks.com/help/wavelet/ref/wthcoef2.html but my Problem is why we put the t ???? t is a literal string but what does it mean ?

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