Recovering Drawing Order from Offline Handwritten Image Using Direction Context and Optimal Euler Path

This paper addresses the problem to recover drawing order from single-stroked offline handwritten image. The recovery problem is formulated as to find the smoothest path to cover all the edges in the graph representation of an input image. The two main contributions are: (1) we introduce direction context to calculate the smoothness between edges; (2) the smoothest path is found by solving a new graph problem: the optimal Euler path problem. An O(n+m+nlog(m/2)) time algorithm is developed to find the optimal Euler path in a graph with 4-degree nodes only. The double traced lines are identified using the maximum weighted matching of general graph. Experimental results on about 13,000 static images converted from the online data in the Unipen database demonstrated the utility of our methods