Error in using waverec2

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kash
kash 2013-2-28
I have a code below,where i used 2 level decomposition and added noise to image ,wen reconstructing i am not getting original image ,please assist
X = imread('cameraman.tif');
[C,S] = wavedec2(X,2,'haar');
A1 = appcoef2(C,S,'haar',1);
A2 = appcoef2(C,S,'haar',2);
[H1,V1,D1] = detcoef2('all',C,S,1);
[H2,V2,D2] = detcoef2('all',C,S,2);
lev=[A1,H1;V1,D1];
figure('name','One_level_Decomposition','numbertitle','off'), imshow(uint8(lev))
q=[A2,H2;V2,D2];
q1=[q,H1;V1,D1];
figure('name','Two_level_Decomposition','numbertitle','off'), imshow(uint8(q1)),title('Two_level_Decomposition')
J = imnoise(q1,'salt & pepper',0.02);
G=J(:)';
p=waverec2(G,S,'haar')

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采纳的回答

Wayne King
Wayne King 2013-2-28
You add noise to the image, then denoise in the wavelet domain, then reconstruct.
Like this:
load sinsin;
Y = X + 18*randn(size(X));
[thr,sorh,keepapp] = ddencmp('den','wv',Y);
xd = wdencmp('gbl',Y,'sym4',2,thr,sorh,keepapp);
subplot(221)
imagesc(X); title('Original Image');
subplot(222);
imagesc(Y); title('Noisy Image');
subplot(223)
imagesc(xd); title('Denoised Image');

更多回答（2 个）

Wayne King
Wayne King 2013-2-28
Why do you expect that after you have added noise to the coefficients and then inverted the wavelet transform that you would obtain the original image?
That will never happen. The wavelet transform (like the Fourier transform) is an invertible transform. If you modify the coefficients (in the wavelet domain or in the Fourier domain) and then invert the transform, you will end up with a different signal (image).
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kash
kash 2013-2-28
ok wayne is it possible to reconstruct from this variable q1
q1=[q,H1;V1,D1];

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Wayne King
Wayne King 2013-2-28
Yes, but you don't need to use anything other than the C,S vectors
load woman;
[C,S] = wavedec2(X,2,'haar');
Xnew = waverec2(C,S,'haar');
max(max(abs(X-Xnew)))
You see perfect reconstruction
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kash
kash 2013-2-28
not perfect reconstruction,nearly 70% is enough

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