Model-Based Instantiation of Symbols from Structurally Related Image Primitives

Abstract

A generalized syntactic pattern recognition method is presented and applied to the interpretation of binary images containing arbitrary line structures, e.g. documents with graphics like technical drawings or road maps. The grammar is based on a set of robust image primitives as terminal elements. These primitive elements include their spatial relationship and are represented as a relational database. The primitive extraction uses (Euklidean) distance transforms, thinning and label propagation methods. The model description uses an attributed grammar with generalized production rules which are formulated by predicate calculus. This formulation allows straightforward implementation in PROLOG. Symbol recognition is thus reduced to an instantiation process using the built-in inference mechanism of PROLOG. The efficiency of primitive extraction, relational description and symbol recognition is demonstrated in technical drawings containing several line styles (e.g. dashed lines).