What does phase spectrum of image signal mean?????
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Hello everyone....!!!
I take phase spectrum of an image using Fourier transform, but I don't understand what it represents. So I have some basic doubts:
1.What does phase spectrum of Image actually mean?
2.What information do we get about each pixel from phase spectrum?
3.suppose u are given two phase spectrum instead of actual images,So can u recognize rotation of one image occurred in the second image using phase spectrum only? i have added my code and figure for reference
clc;
clear all;
close all;
i=imread('C:\Users\Public\Pictures\Sample Pictures\index.jpg');
i1=rgb2gray(i);
figure,
subplot(1,2,1);imshow(i1);title('Test image 1');
f1=fftshift(fft2(i1));
phase1=angle(f1);
subplot(1,2,2);imshow(phase1,[]),title('phase spectrum 1');
i2=imrotate(i,45);
i2=rgb2gray(i2);
figure,
subplot(1,2,1);imshow(i2);title('Test image 2');
f2=fftshift(fft2(i2));
phase2=angle(f2);
subplot(1,2,2);imshow(phase2,[]);title('phase spectrum 2');
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/163213/image.jpeg)
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Accepted Answer
Image Analyst
on 3 Jun 2014
The magnitude of the FFT is like how much energy there is in the sine waves used to build up your image. The phase is like how those sine waves are positioned. For a real, unsymmetrical image, your FFT will be Hermitian. See table about a quarter of the way down this page: http://www.cv.nrao.edu/course/astr534/FourierTransforms.html
More Answers (1)
JB Braendel
on 8 Jun 2014
I'm currently taking a course on continuous time signals, and our prof provided a visual interpretation behind the magnitude and phase spectrum of images:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/175070/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/175071/image.png)
My confusion however comes from how 2d signal processing works for images. What portion of the image does the FFT represent? Is it an FFT for each row of the image? Each column? An overall mix?
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