Robust reconstruction of damaged character images on the form documents

It is very common that the filled-in character images in the form documents touch, cross, or overlap the formatted-line images. In that case, it is not easy to extract characters correctly because the shapes of characters are transformed by line images. In this paper, we propose a new method to reconstruct the character images damaged by the preprinted lines of documents. The method consists of two stages - the character decomposition stage and the character reconstruction stage. In the character decomposition stage, an input character is decomposed into some line-elements which are units of reconstruction, through the hierarchical steps. In the character reconstruction stage, the various reconstruction methods are used to restore the characters according to the 4 types of line-elements. To evaluate the performance of the proposed method objectively, we used simple recognition modules on CENPARMI handwritten digits and NIST handwritten alphabets. Experimental results showed that the difference of the recognition rates between the original characters without any damages by lines and the characters reconstructed by the proposed method is within about 1%, and the shapes of reconstructed character images are almost the same as those of the original ones.