Three-dimensional approach to thresholding seal impressions

Most of the conventional methods for automatic seal identification performed one-to-one matching between the reference impression and the input one which are measured as 2D images. However, those methods cannot absorb the various qualify by only the matching techniques. This paper proposes a new approach to deal with the various quality of impressions by measuring the seals for reference as 3D (three-dimensional) images, that is, range images. By storing the seal impressions as 3D images, it becomes possible to construct various 2D impressions from only one 3D reference image; according to the affixing conditions of an input impression such as the slant, the pressure, and the state of ink on the seal. Primarily, this paper considers how to construct 2D images from a 3D reference image by determining the affixing conditions. The performance is verified by experiment, and the result shows that plural 2D impressions according to the affixing conditions can be constructed from only one 3D reference image.