An efficient extraction of character string positions in a document is proposed by using a morphological operator. In regions of character strings, axial edge pixels and diagonal edge pixels are mingled together, but in other regions, they are distributed separately. Based on this difference in the directional edge pixel distribution between the character and the non-character regions, string positions are extracted directly from arbitrary blocks without any block analysis, in contrast to previous work which requires block analysis to extract string positions (F.M. Wahl et al., 1982; S. Imade et al., 1993). Experiments are conducted on the document images acquired through the scanner, and the proposed method can directly extract the character string positions from the plain text of character blocks, and even from the document containing tables and flow-charts, without any block analysis.
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