IFFT of a Hanning windowed FFT Image

Question

Luke Dineen-Woolnough 2016-1-27

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https://ww2.mathworks.cn/matlabcentral/answers/265430-ifft-of-a-hanning-windowed-fft-image

评论： rashmi deshpande 2021-8-26

Hi, Im Trying to IFFT a Hanning Windowed FFT Image for the code below, to obtain the original image.

w = hanning(434)*hanning(362)'; fft = fftshift(fft2(Pixel_Reassign)); fft = abs(fft); [24 100000]; colormap gray; fftimage = log(fft+1).*w; figure, imshow(fftimage,[]);

Can anyone suggest how i go about this, i've tried to simply IFFT the fft output but i dont seem to get the original image back.

Thanks

Luke

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Luke Dineen-Woolnough 2016-1-28

The beggining of my ifft line looks like this

ifft = fftshift(ifft2(ifftshift(fft1))); ifft1 = log(abs(ifft));[24 100000]; colormap gray;

but there seems to be something inherently wrong with it.

any help would really be appreciated.

rashmi deshpande 2021-8-26

Thanks a lot

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Answer 1

Mona Mahboob Kanafi 2016-1-28

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https://ww2.mathworks.cn/matlabcentral/answers/265430-ifft-of-a-hanning-windowed-fft-image#answer_207747

编辑：Mona Mahboob Kanafi 2016-1-28

在 MATLAB Online 中打开

Hello,

You have used your absolute values to plot your image. Now, to reverse the operation you need the full fft results which is a complex matrix for regenerating your input image. Otherwise, you get something else!

Each fft component has value and phase. You shouldn't ignore the phase component which is ignored when you only use absolute values.

This is what you should do:

w = hanning(434)*hanning(362)';
FFT = fftshift(fft2(w)); % complex matrix
FFT_abs = abs(FFT); % absolut values of fft
imagesc(1+log10(FFT_abs)) % show fft results
w_new = ifft2(ifftshift(FFT)); % you need fft not fft_abs

Hope it helps,

Mona