Directional morphological operations for separation of characters from maps/graphics have been proposed previously. In this paper we present an approach to improve the efficiency of this algorithm using run-length-encoded (RLE) image representation. Directional edge images are all represented as directional run-length linked lists. Moreover, we migrate all of the processes used to the RLE data structure. As a result, we reduce significantly both the memory space and the processing time. The improved separation algorithm has all the advantages of the original one. It is independent of font style, font size, and language and map style. It performs well even in cases where lines and characters are connected.
Keywords: directional morphological operations, charater separation, line extraction, run length coding, maps/graphics recognition, map processing, document understanding, engineering drawings.