Directional mathematical morphology approach for line thinning and extraction of character strings from maps and line drawings

The use of computer aided design requires line drawings and maps to be digitized and stored in databases. The input of line drawings and maps into databases requires vectorization of lines, and recognition of symbols and characters. The paper addresses two aspects related to the input process. The first aspect is an automatic algorithm for the separation of character strings from maps. The second aspect is an algorithm for line thinning. The proposed algorithms are based on directional morphology operations. The character string extraction algorithm is independent of font style, size, and language and is suitable for a variety of map styles with straight or curved lines. The presented experimental results demonstrate very good performance of the algorithms even in cases where the character strings touch or intersect lines in the map