NOI~'IIt.I-IOU.AND Applications A New Method for Extracting and Representing Object Contours in Real Images G. IANNIZZOTTO A. PULIAFITO lstituto di Informatica e Telecornunicazioni, Facolth di Ingegneria, Universith di Catania, Catania, Italy and L. VITA Facohh di Ingegneria, Universith di Messina, Contrada Papardo, Messina, Italy ABSTRACT This paper introduces a new operator for the calculation of the brightness gradient (derived from the Compass gradient) and a new methodology based on a fuzzy algorithm for extraction of the contour points of objects in a real image. A bidimen- sional geometrical representation of the contours thus extracted is then given in the form of arcs and segments in order to exploit this simplified description as an index for a search in a database of 3-D primitives. The procedure described gives good results, even in the presence of juxtaposed surfaces of the same nature and color, or with contours which do not contrast very well. 1. INTRODUCTION In the last few years, research into artificial vision has seen the birth of useful instruments for the interpretation of real scenes, thanks to the creation of new, more efficient models of reality. These models try to solve the problems connected with the fragmentary nature of the information that can be obtained from real images (occlu- sions being a case in point), and to keep the computational load of the recognition and interpretation process relatively low so as to avoid heavy limitations on the size of the database of recognizable objects. INFORMATION SCIENCES 93, 159-185 (1996) © Elsevier Science Inc. 1996 0020-0255/96/$15.00 655 Avenue of the Americas, New York, NY 10010 PII S0020-0255(96)00073-4