Compare phase and magnitude spectrum results of 2 Images I have read that from Fourier transform we obtain magnitude and phase spectrum. The magnitude spectrum tells you how strong are the harmonics in a image and the phase spectrum tells where this harmonic lies in space.

I have used Matlab to compute the magnitude and phase spectrum of the 2 grayscale images of babies using fftn function, but the all spectrum are difficult to understand.





Can anyone please explain the features given in 1st paragraph by comparing the spectrums of both images of babies? 

1.phase spectrum 

and 

2.magnitude spectrum 

(If you have results other than in Matlab, explaining with your method is also okay)

image1=imread('D:\baby1.jpg');%Read colour image
image1=rgb2gray(image1);%covert colour image into Gray scale

image2=imread('D:\baby2.jpg');%Read colour image
image2=rgb2gray(image2);%covert colour image into Gray scale

figure,
subplot(1,3,1);
imshow(image1);
title('Gray scale Image of Baby1');

%Apply Fourier transform on Gray scale image
fft1=fftn(image1);
fft1=log(1+fftshift(fft1));%Use log function for scaling

%Find the magnitude spectrum
magnitude1=abs(fft1);
subplot(1,3,2);
imshow(magnitude1,[]);
title('Amplitude Spectrum 1');

%Find the phase spectrum
phase1=angle(fft1);
subplot(1,3,3);
imshow(phase1,[]);
title('Phase Spectrum 1');



figure,
subplot(1,3,1);
imshow(image2);
title('Gray scale Image of Baby2');

%Apply Fourier transform on Gray scale image
fft2=fftn(image2);
fft2=log(1+fftshift(fft2));%Use log function for scaling

%Find the magnitude spectrum
magnitude2=abs(fft2);
subplot(1,3,2);
imshow(magnitude2,[]);
title('Amplitude Spectrum 2');

%Find the phase spectrum
phase2=angle(fft2);
subplot(1,3,3);
imshow(phase2,[]);
title('Phase Spectrum 2');
The images are mostly noise with a recognizable cross in the middle, that means that there is nothing in the image that repeats. The first image however shows some patterns (circles), not just the cross, those are probable the wall on the top-left which has some repeating pattern on it.