Automatic indexing for storage and retrieval of line drawings
Oliver Lorenz, Gladys Monagan · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1995
The usefulness of a collection of scanned graphical documents can be measured by the facilities available for their retrieval. We present an approach for indexing a collection of line drawings automatically. The indexing is based on the textual and graphical content of the drawings. This approach has been developed to facilitate `retrieval by example' in heterogeneous collections of graphical documents. No a priori knowledge about the application domain is assumed. Starting with a raster image, candidate character patterns and graphical primitives (i.e., line segments and arcs) are extracted. Candidate character patterns are classified by an OCR method and grouped into word hypotheses. Graphical features of various types are computed from groupings of graphical primitives (e.g., sequences of adjacent lines, pairs of parallel lines). Retrieval occurs with a weighted information retrieval system. Each document of the collection and each query are described with a set of indexing features with their corresponding weights. The weight of an indexing feature reflects the descriptive nature of the feature and is computed from the number of occurrences of the indexing feature in the document (feature frequency ff) and the number of documents containing the indexing feature (document frequency df).