A hybrid approach to detect graphical symbols in documents

Abstract

We propose to combine a feature descriptor method with a structural representation of symbols. An adaptation of the Radon transform, keeping main geometric transformations usually required for the recognition of symbols, is provided. In order to improve the recognition step we directly process on the grey level document. In this perspective, a three-dimensional signature integrates into a same formalism both the shape of the object and its photometric variations. More precisely the signature is computed within the symbol following several grey levels. Additionally a structural representation of symbols allows to localize into the document candidate symbols