A Flexible content-based image retrieval model and a customizable system for the retrieval of Shapes

The authors describe a flexible model and a system for
content-based image retrieval of objects’ shapes. Flexibility
is intended as the possibility of customizing the
system behavior to the user’s needs and perceptions.
This is achieved by allowing users to modify the retrieval
function.The system implementing this model uses multiple
representations to characterize some macroscopic
characteristics of the objects shapes. Specifically, the
shape indexes describe the global features of the object’s
contour (represented by the Fourier coefficients), the
contour’s irregularities (represented by the multifractal
spectrum), and the presence of concavities and convexities
(represented by the contour scale space distribution).
During a query formulation, the user can specify
both the preference for the macroscopic shape aspects
that he or she considers meaningful for the retrieval,
and the desired level of accuracy of the matching, which
means that the visual query shape must be considered
with a given tolerance in representing the desired
shapes. The evaluation experiments showed that this
system can be suited to different retrieval behaviors, and
that, generally, the combination of the multiple shape
representations increases both recall and precision with
respect to the application of any single representation.