This paper introduces a new operator for the calculation of the bright
ness gradient (derived from the Compass gradient) and a new methodolog
y based on a fuzzy algorithm for extraction of the contour points of o
bjects in a real image. A bidimensional geometrical representation of
the contours thus extracted is then given in the form of arcs and segm
ents 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.