Extracting trajectories from arrow pictograms

Abstract

A method extracts a trajectory of an arrow in a binary image. The method extracts a skeleton of an arrow in the image and splits the skeleton into bones. For each of the bones, the method extends a bone to obtain an extended bone having both ends of the bone reaching a border of the arrow, and warps the extended bone into a straight line using a thin plate spline. For each bone, the method warps the binary image into a warped image using a thin plate spline with same parameters as the thin plate spline used to warp the extended bone into the straight line. For each bone, the method selects a component that includes a center point of the warped image, computes a symmetric error of the selected component, and selects, as the trajectory of the arrow, a bone where the selected component has the lowest symmetric error.