Artículos

 

Recognition–free Retrieval of Old Arabic Document Images

 

Recuperación de documentos árabes antiguos a partir de imágenes sin usar reconocimiento de caracteres

 

Toufik Sari and Abderrahmane Kefali

 

Laboratoire de Gestion Electronique de Documents (LabGED), University Badji Mokhtar, Annaba, Algeria. E–mail: sari@labged.net, kefali@labged.net

 

Article received on 11/15/2010.
Accepted 05/06/2011.

 

Abstract

Searching of old document images is a relevant issue today. In this paper, we tackle the problem of old Arabic document images retrieval which form a good part of our heritage and possess an inestimable scientific and cultural richness. We propose an approach for indexing and searching degraded document images without recognizing the textual patterns in order to avoid the high cost and the difficult effort of the optical character recognition (OCR). Our basic idea consists in casting the problem of document images retrieval from the field of document analysis to the field of information retrieval. Thus, we can combine symbolic notation and semic representation and exploit techniques from the two fields, in particular, the techniques of suffix trees and approximate string matching. Each document of the collection is assigned an ASCII file of word codes. Words are represented by their topological features, namely, ascenders, descenders, etc. So, instead of searching in the image, we look for word codes in the corresponding file code. The tests performed on two types of documents, Arabic historical documents and Algerian postal envelopes, have showed good performance of the proposed approach.

Keywords: Document retrieval, Arabic handwriting recognition, approximate string matching, document analysis.

 

Resumen

La búsqueda en imágenes de documentos antiguos es en la actualidad un tema relevante. En este artículo abordamos el problema de recuperación de documentos árabes antiguos a partir de imágenes sin usar el reconocimiento de caracteres (OCR). Dichos documentos forman una buena parte de nuestra herencia y poseen una riqueza científica y cultural invaluable. Nosotros proponemos un enfoque para indexar y buscar imágenes degradadas de documentos sin recurrir al reconocimiento de patrones textuales para así evitar el esfuerzo considerable y el alto costo que conlleva el OCR. La idea básica consiste en migrar el problema de la recuperación de estos documentos, desde el campo del análisis de documentos hacia el campo de la recuperación de información. Así, podemos combinar la notación simbólica y la representación sémica y explotar las técnicas que provienen de ambos campos de investigación, particularmente, las técnicas de árboles de sufijos y búsqueda aproximada de cadenas. A cada documento de la colección se le asigna un archivo en ASCII con códigos de palabras. Las palabras son representadas por sus características topológicas; ej. ascendientes, descendientes, etc. De esta forma, en vez de buscar en la imagen, nosotros buscamos en los códigos de palabra dentro del archivo de códigos correspondiente. Las pruebas se realizan en dos tipos de documentos: documentos históricos árabes y sobres postales argelinos. El enfoque propuesto muestra un buen rendimiento.

Palabras clave: Recuperación de documentos, reconocimiento de manuscrito árabe, búsqueda aproximada de cadenas, análisis de documento.

 

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