IFFT of a Hanning windowed FFT Image

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

[Luke Dineen-Woolnough]

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]

Thanks a lot

Answer 1

[Mona Mahboob Kanafi]

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

[Luke Dineen-Woolnough]

Thank You So much Mona, that helps a lot.

Take Care

Luke