Why isn't the inverse Fourier transform giving

问题:

I took the Fourier transform of an image in Matlab and now I want to take the inverse fourier but the result is a completely black picture instead of the original image. I think there is some step that I need to do before taking the inverse. Thank you for any help. The code:

nasa=imread('nasaNoise _1_','jpg');
N_Fourier=fft2(nasa);
N_Fourier=fftshift(N_Fourier);
N_Fourier=abs(N_Fourier);
N_Fourier=log(N_Fourier+1);
N_Fourier=mat2gray(N_Fourier);

%Now doing the inverse
N_inverse=ifft2(N_Fourier);
N_inverse=abs(N_inverse);
N_inverse=uint8(N_inverse);
imshow(N_inverse);