Query by dialog: an interactive approach to pictorial querying

We describe a prototype system, SQD (sketch-based query by dialog), designed for retrieving images by content according to shape similarity. At present, only shapes corresponding to closed contours have been considered. We represent them using normalized polar coordinates contour functions, from which image key features are extracted. The query system interface is based on the integration of the query-by-visual-example and the progressive-query approaches. A sketch-based query allows users to submit a drawn example of the target object. Whenever the system response does not match the searched object, users can continue the query process refining their request. The query specification and refinement cycle is iterated until the target object or a set of objects are obtained. The interface keeps track of the user's requests and of the system answers, so that it is always possible to fully control the query process and to analyze the system similarity evaluation.