Elsevier

Pattern Recognition Letters

Volume 20, Issue 2, February 1999, Pages 199-206
Pattern Recognition Letters

Robust detection of significant points in multiframe images1

https://doi.org/10.1016/S0167-8655(98)00135-4Get rights and content

Abstract

Significant point (SP) detection is an important pre-processing step in image registration, data fusion, object recognition and in many other tasks. This paper deals with multiframe SP detection, i.e. detection in two or more images of the same scene which are supposed to be blurred, noisy, rotated and shifted with respect to each other. We present a new method invariant under rotation that can handle differently blurred images. Thanks to this, the point sets extracted from different frames have relatively high number of common elements. This property is highly desirable for further multiframe processing. The performance of the method is demonstrated experimentally on satellite images.

Introduction

Detection of significant points (SP) or landmarks is an important step in image processing and computer vision. It provides input information for further operations, such as image registration, image fusion, time-sequence analysis and object recognition. By significant points we understand the points that are easy to identify in the image, such as corners, line intersections, T-junctions, etc.

In this paper, we address a multiframe version of this problem: having two or more images of the same scene, the aim is to detect significant points in each of them. Multiframe SP detection methods must fulfill the condition of repeatability. This property means that the results should not be affected by imaging geometry, radiometric conditions and by additive noise and that the sets of points detected in all frames should be identical. Since the last requirement is not realistic in practice, “maximum overlap” is usually required instead of identity.

In this paper we assume that the individual frames may be rotated and shifted with respect one another, they may have different contrast, they may be degraded by a linear shift-invariant blur and corrupted by additive random noise. Our primary motivation comes from the area of remote sensing, where the registration of images with such kinds of distortions is a very frequent task. Having the SP detection method which works on differently distorted frames and which yields high repetition rate is a fundamental requirement.

Section snippets

Present state-of-the-art

Numerous methods for single-frame significant point detection in gray-level images have been published in last two decades. Most of them are known as corner detectors. A survey of basic methods along with a comparison of their localization properties can be found in (Rohr, 1994).

Kitchen and Rosenfeld (1982) proposed a corner detection scheme based on a differential operator that consists of first and second order partial derivatives of the image f(x,y):K(x,y)=fx2fyy−2fxfyfxy+fy2fxxfx2+fy2,where

Description of the proposed method

Our newly proposed method for the detection of significant points uses a parameter approach to handle differently distorted images. Points, which belong to two edges with an angle from the interval [π/2−da,π/2+da] (da is user defined parameter) in between regardless of its orientation are understood here as significant points. The described method is based on this definition.

Information about the number of edges passing through each pixel and about the angle between them is acquired from the

Numerical experiments

In this section, practical capabilities of the proposed SP detection method are demonstrated and a comparison with the classical techniques (Kitchen and Rosenfeld, 1982; Förstner, 1986) is shown. Since the intended major application area is the area of remote sensing, the experiments are performed on satellite images.

A subscene covering the landscape near Prague (Czech capital city) of the size 180×180 pixels was extracted from the SPOT image of the central part of the Czech Republic. This

Conclusion

In this paper we proposed a novel method for detection of significant points – corners with high local contrast. The method works in two stages: all possible candidates are found first and then the desirable number of resulting significant points is selected among them by maximizing the weight function.

Although the method can be applied to any image, it is particularly devoted to SP detection in blurred images because it provides high consistence. We compared the performance of the method with

Acknowledgements

This work has been supported by the grant No. 102/96/1694 of the Grant Agency of the Czech Republic. Most of this work was done when Gabriele Peters and Jaroslav Kautsky were visiting the Institute of Information Theory and Automation, Academy of Sciences of the Czech Republic.

References (12)

There are more references available in the full text version of this article.

Cited by (52)

View all citing articles on Scopus
1

Electronic Annexes available. See http://www.elsevier.nl/locate/patrec.

View full text