Movable type printing identification based on Tangut characters registration

Scientific identification of the movable type printing provides favorable evidence to research the invention and dissemination of movable printing technique. However, the methods used to identify movable type printing are either unscientific or time-consuming. To solve those problems, a new method based on registration is introduced in this paper. Firstly, the boundary points of each character image are extracted, and the affine iterative closest point (ICP) with bidirectional distance is used to measure the shape similarity between two character point sets. Secondly, a heuristic tree of Tangut characters based on shape similarity is constructed, which connects two point sets with small deformation. In this way, the large deformation between characters is divided into several small differences. After that, the coherent point drift (CPD) algorithm is used to achieve the registration between these character point sets along the heuristic tree. Finally, after comparing the registrations errors between the subject character point sets and model character point set carefully and observing their character images as well as the registration images between them, the judgment of whether these characters are printed with the same movable character model is to be made. Experimental results demonstrate that the identification method of movable printing proposed has the advantages of being automatic, fast and accurate.