  Constructing stroke correspondences between keyframes is one of the most
important processes in the production pipeline of hand-drawn inbetweening
frames. This process requires time-consuming manual work imposing a tremendous
burden on the animators. We propose a method to estimate stroke correspondences
between raster character images (keyframes) without vectorization processes.
First, the proposed system separates the closed areas in each keyframe and
estimates the correspondences between closed areas by using the characteristics
of shape, depth, and closed area connection. Second, the proposed system
estimates stroke correspondences from the estimated closed area
correspondences. We demonstrate the effectiveness of our method by performing a
user study and comparing the proposed system with conventional approaches.
