# What is phase congruency principle?

1. Jul 27, 2014

### ramdas

Hello everyone,can anyone help me to understand the phase congruency principle. I have read that,in image processing if we reconstruct an image using its phase only,we can get obtain edges and lines and this is because of phase congruency principle.
I am searching more about phase congruence on web but i not understanding it properly.so can anyone explain what is phase congruency and its importance in image processing and other domain..... thank u....

2. Jul 28, 2014

### Staff: Mentor

Did you see this paper?

http://www.csse.uwa.edu.au/~pk/Research/research.html [Broken]

there's some attached matlab code that might provide the answers you're looking for.

Last edited by a moderator: May 6, 2017
3. Apr 16, 2015

### ramdas

Hello everyone,can anyone help me to understand the phase congruency principle.
I am searching more about phase congruence on web but i not understanding it properly.so can anyone explain what is phase congruency ?Thank u...

4. Apr 16, 2015

### dlgoff

I thought jedishrfu's link was very informative on the subject. You do know what Edge detection is, right? From this link:

5. Apr 18, 2015

### ramdas

sir,sorry to disturb you.but as you said that "in phase congruency ,we find locations in an image where all sinusoids in the frequency domain are in phase." means as per your saying "edges and corners are in phase".Right!! but sir,there can be other locations other than edges and corners which can be in phase . here,why "phase congruency concept doen't detect these locations which are in phase". So my question is why only edges and corners?why not other locations? If possible can you reply me using any simple image .Thank you.

6. Apr 18, 2015

### jim hardy

edges and corners are where the Fourier components are maximally in phase
if you've ever manually (that is with pencil ruler and paper) plotted a square wave as sum of its first few Fourier terms it seems intuitive.
The steepest slopes occur where the Fourier terms come in phase, ie their individual steepest slopes (zero crossings) coincide.

Same author, more detailed presentation
http://www.csse.uwa.edu.au/~pk/research/pkpapers/phasecorners.pdf [Broken]
see section 2 fig1 on page 3, it shows that square wave exercise

were that part of an old fashioned black&white NTSC video signal, it'd change from very dark to very bright right there in the middle.
Note that's where all your components have briefly come into phase with one another. It's obvious from the picture but probably not from just the list of (nωt + Φ) terms

Last edited by a moderator: May 7, 2017
7. Apr 18, 2015

### ramdas

Last edited by a moderator: May 7, 2017
8. Apr 18, 2015

### ramdas

Thank u very much for your feedback.but whether phase congruency and phase coherence are same meaning?

9. Apr 18, 2015

### jim hardy

i don't think so.

Look up both definitions.

Coherence means constant phase relationship

congruence means they come together at some point, if only briefly.

from Webster's online

Last edited by a moderator: May 7, 2017