hws: a hierarchical word spotting method for farsi printed words through word shape coding

Word shape coding (wsc) is a method of document image retrieval (dir) based on keyword spotting. byusing this method, a word can be recognized in the document image, only by identifying some of the features of theword. in this paper, a hierarchical word spotting method, namely hws, is presented for farsi document imageretrieval through wsc. in hws method, document images are retrieved by using a new indexing method. in hws, atfirst the words in the document images are shape coded based on topological properties. these features includenumber of sub-words, ascenders, descenders, and holes.a new feature that has been used for this paper is dot'sposition in word. six features are obtained which are one top dot, two top dots, three top dots and one bottom dot, twobottom dots, and three bottom dots. precision of retrieval increases by using these features. then, all of the shapecodes are indexed by building a tree. retrieval is done based on keyword query in the tree. the results show that theproposed technique is very fast for large volumes of documents. time complexity for successful and non-successfulsearching is ) (lognko .this value is better than values in ordinal method. also, time complexity for indexing is) (lognko . the hws method is tested on bijankhan database. 87867 common words from this database are used forbuilding the dictionary. test results show that average of precision is 0.83 and average recall is 0.94.