One-to-many line matching across keyframes using minimum weight edge cover problem

Inbetweening, interpolating between two keyframes, is an essential step in traditional handdrawn animation production. Many interpolation methods used to assist in animation production require correspondences between lines in two consecutive keyframes. This paper proposes a method for finding line correspondences that can apply to two keyframes, even those with occlusions. Our method determines one-to-many line correspondences resulting from occlusions and other factors by iteratively finding line correspondences using minimum weight edge cover problems on a bipartite graph using a set of lines on two keyframes. In advance to finding these line correspondences, we decompose lines on keyframes into evenly spaced points and determine which lines in the other keyframe these points correspond to. Using the result, we calculate the weights for the minimum weight edge cover problem. Experiments show that our proposed method achieves higher accuracy in line correspondences, including one-to-many correspondences than five previous methods.