An efficient binarization method for ancient Mongolian document images

In order to recognize and retrieve the Mongolian Kanjur images, lots of preprocessing tasks should be done. In this paper, we concentrate on the binarization of the Mongolian Kanjur images and we have proposed an efficient binarization method for them. The proposed method is applied to each image as follows: First, some preprocessing tasks including grayscaling and smoothing are executed. Second, three well-known global thresholding methods are used for extracting regions of interest (ROIs) from every gray-level image. Then, each ROI is processed by a modified Sauvola´s algorithm with variant sizes of the small windows. Experimental results have proved that the proposed binarization method is better than the original Sauvola´s algorithm.