Reflection Symmetry of Shapes Based on Skeleton Primitive Chains.

In this paper the novel fast approach to identify the reflection symmetry axis of binary images is proposed. We propose to divide a skeleton of a shape into two parts - the "left" and the "right" sub-skeletons. The left part is traversed counterclockwise and the right one - in clockwise direction. As a result, the "left" and the "right" primitive sub-chains are achieved; they can be compared by the known shape matching procedure based on pair-wise alignment of primitive chains. So, the most similar parts of a skeleton among all possible ones correspond to the most similar parts of a figure which are considered as reflection symmetric parts. The start and the end points of skeleton division into "left" and "right" parts will be the points belonging to a symmetry axis of a figure. Also, the exact brute-force symmetry evaluation algorithm and two its optimizations are suggested for finding ground truth of symmetry axis. All proposed methods were experimentally tested on Flavia leaves dataset.