The retrieval of document images: a brief survey

The economic feasibility of creating large databases of document images has left a tremendous need for robust ways to access the information these images contain. Printed documents are often scanned for archiving or an an attempt to move toward a paper-less office and stored as images, but without adequate index information. In order to make full use of the capabilities of traditional database indexing and retrieval techniques, a full conversion of the document may be required. There are many factors, however, which may prohibit complete conversion including its high cost, insufficient document quality, or the fact that parts of the document can simply not be adequately represented in a converted form. In this paper, we provide a survey of methods developed by researchers to access document images without relying on complete and accurate conversion. We briefly discuss traditional text indexing techniques on imperfect data and the retrieval of partially converted documents, followed by a more complete review of techniques for the direct retrieval and characterization of document images including text, drawings and graphics.