An Efficient and Robust Real-Time Contour Tracking System

Abstract

In this paper we present an efficient and robust real-time system for object contour tracking in image sequences. The developed application partly relies on an optimized implementation of a state-of-the-art curve fitting algorithm, and integrates important additional features in order to achieve robustness while keeping the speed of the main estimation algorithm. An application program has been developed, which requires only a few standard libraries available on most platforms, and runs at video frame rate on a common PC with standard hardware equipment. Motivation and Scope of the Present WorkThe general problem of object contour tracking in image sequences is an important and challenging topic in the computer vision community; as many researchers already pointed out, an advanced contour tracking technique can provide crucial information for many image understanding problems and, at the same time, allows the development of efficient and useful working applications in many fields of interest. We refer the reader to [1] for a survey of these applications and the related references.Among the currently available methodologies, a very appealing one is the Contracting Curve Density (CCD) algorithm: this method has been recently developed and presented in [3] as a state-of-the-art improvement over other advanced techniques such as the Condensation algorithm [6], and it has been shown to overperform them in many different estimation tasks. Nevertheless, its higher complexity has been initially considered as an obstacle to an effective real-time implementation, even in the simplified form named Real-Time CCD from the same authors [4], and a working online version still had to be investigated.Moreover, in order to realize an autonomous and robust tracking system, some important additional issues have to be taken into account; one of them is the possibility of automatic initialization and reinitialization of the system, both at the beginning of the tracking, and in case of tracking loss. Nevertheless, one also expects that a "well behaving" tracking system does not need a global estimation procedure during most of the tracking task, or, in the ideal case, only at the beginning. The global initialization module is computationally more demanding than the online tracker, and a frequent reinitialization would significantly slow down the performance of the system. Therefore, most of the efforts in realizing such a system have to be focused on a robust real-time performance of the contour tracker itself, in terms of speed, accuracy and convergence area for the parameter search.All of the above mentioned issues, and other relevant aspects, constitute the main motivation of the present work; it will be shown how it contributes to the state-of-the-art in contour tracking systems with the following achievements:• The real-time CCD algorithm [4] has been reimplemented with a significant number of critical speedups with respect to the originally proposed version.• A global initialization and reinitialization module has been developed ...

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