A group of projective invariants was derived based on the cross ratio of five coplanar points, and used to recognize planar polygons. Experimental results show that the invariants have projective invariance and can be used to recognize planar polygons effectively.
CHEN Yan Xin QI Fei Hu. A GROUP OF PROJECTIVE INVARIANTS FOR RECOGNITION OF PLANAR POLYGONS[J]. Journal of Infrared and Millimeter Waves,1998,17(2):99~106Copy