Text document filters using morphological and geometrical features of characters

This paper aims at irregular noise removal in binary document images. A new filtering algorithm called the modified directional morphological filter (MDMF) is introduced with dual properties for eliminating document salt-and-pepper noises, and for remedying eroded character stroke distortion. For eliminating larger noise, an enhanced algorithm called the image geometric structure filter (IGSF) is proposed based on the geometric stroke information of the characters. The IGSF can especially be used for noise removal in alphanumeric documents. Experiments demonstrate that the performance of combining two filters is robust, which can feasibly filter out various isolated noises in the binary images.