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   -> Volume 4, Issue 5


Preprint: Image Features From Phase Congruency
 
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Peter Kovesi
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PostPosted: Tue Dec 03, 2002 11:34 am    
Subject: Preprint: Image Features From Phase Congruency
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Preprint: Image Features From Phase Congruency

Technical Report Available by anonymous ftp from
cs.uwa.edu.au /pub/techreports/95/4.ps.gz

Title: Image Features From Phase Congruency

Author: Peter Kovesi
Department of Computer Science
The University of Western Australia
Nedlands, W.A. 6009
email: pk@cs.uwa.oz.au

Abstract: Image features such as step edges, lines and Mach bands all
give rise to points where the Fourier components of the image are
maximally in phase. The use of phase congruency for marking features
has significant advantages over gradient based methods. It is a
dimensionless quantity that is invariant to changes in image
brightness or contrast, hence it provides an absolute measure of the
significance of feature points. This allows the use of universal
threshold values that can be applied over wide classes of images.
This paper presents a new way of calculating phase congruency through
the use of wavelets. The existing theory that has been developed for
1D signals is extended to allow the calculation of phase congruency in
2D images. It is shown that for good localization it is important to
consider the spread of frequencies present at a point of phase
congruency. An effective method for identifying, and compensating
for, the level of noise in an image is presented. Finally, it is
argued that high-pass filtering should be used to obtain image
information at different scales. With this approach the choice of
scale only affects the relative significance of features without
degrading their localization.
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