What is phase congruency principle?

[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...

 

[jedishrfu]

Did you see this paper?

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

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

 

[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...

 

[dlgoff]

... can anyone explain what is phase congruency ?

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

A recent development in edge detection techniques takes a frequency domain approach to finding edge locations. Phase congruency (also known as phase coherence) methods attempt to find locations in an image where all sinusoids in the frequency domain are in phase.

 

[ramdas]

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

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.

 

[jim hardy]

means as per your saying "edges and corners are in phase".

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
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

 

[ramdas]

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
see section 2 fig1 on page 3, it shows that square wave exercise

View attachment 82189

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

 

[ramdas]

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

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

 

[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

Full Definition of COHERENT

3
a : relating to or composed of waves having a constant difference in http://www.merriam-webster.com/dictionary/phase[1 <coherent light>

Definition of CONGRUOUS
1
a : being in agreement, harmony, or correspondence

b : conforming to the circumstances or requirements of a situation : appropriate <a congruous room to work in — G. B. Shaw>