problem in executing,wiener program

Question

reem 2011-4-23

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链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/6073-problem-in-executing-wiener-program

Hi,

I have been working on the wiener filter for images, and have a question regarding the executing when I want to execute my program,this problem appear and I do not know how to solve it.

My Program

 clc;
 x = imread('lena.jpg');
 [m n]=size(x);
     figure(1),
     imshow(x);
     %%adding noise to image .

afterNoise = imnoise(x,'gaussian',0,0.025);

figure,

imshow(afterNoise);

%Implementing Wiener filter

N = size(x,1);

Yf = fft2(x);

Hf = fft2(afterNoise,m,n);

Pyf = abs(Yf).^2/N^2;

gamma=1;

alpha=1;

sigma=1;

% direct implementation of the regularized inverse filter,

% when alpha = 1, it is the Wiener filter

% Gf = conj(Hf).*Pxf./(abs(Hf.^2).*Pxf+alpha*sigma^2);

% Since we don't know Pxf, the following

% handle singular case (zero case)

sHf = Hf.*(abs(Hf)>0)+1/gamma*(abs(Hf)==0);

iHf = 1./sHf;

iHf = iHf.*(abs(Hf)*gamma>1)+gamma*abs(sHf).*iHf.*(abs (sHf)*gamma<=1);

Pyf = Pyf.*(Pyf>sigma^2)+sigma^2*(Pyf<=sigma^2);

Gf = iHf.*(Pyf-sigma^2)./(Pyf-(1-alpha)*sigma^2);

% max(max(abs(Gf).^2)) % should be equal to gamma^2

% Restorated image without denoising

eXf = Gf.*Yf;

ex = real(ifft2(eXf));

figure(3),

imshow(ex,gray(256));

Please help me, not ignore my question.

Thanks in advance

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bym 2011-4-23

what does whos('x') return?

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Answer 1

Andrew Newell 2011-4-23

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/6073-problem-in-executing-wiener-program#answer_8446

在 MATLAB Online 中打开

Your problem occurs in this line:

y = real(ifft2(Hf.*Xf))+sigma*randn(N,N); % circular convolution

Your noise term does not have the same dimensions as your image data. Try these two commands instead:

y = real(ifft2(Hf.*Xf)); % circular convolution
y = y + sigma*randn(size(y)); % add noise

I don't know if it will do what you are trying to do, but at least it doesn't produce an error.

A note on debugging scripts: You can locate the error more easily if you sprinkle the code with the occasional cell marker, e.g.,

N = 256;
x = imread('lena.jpg');
figure(1)
imshow(x)

This allows you to run small blocks of code at a time, and you can narrow down the source of the error to a single block. See Evaluating Subsections of Files Using Code Cells.

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reem 2011-4-23

Thank you so much Andrew

I am rewrote my program again in details but there is no error here but when executed my program,the last picture appear black, I mean there is no any picture in third figure,why???

Andrew Newell 2011-4-27