Finding a Face Independent of Its Rotation in Image by Hexagonal Sampling

Abstract

If a circular mask is put on a human face to cover its main parts (an eye, a nose and a mouth). the content is invariant with the rotation in image planes. This invariance can be computed by the magnitude spectrum of Fourier transformation with polar coordinate systems. The correlation and rotation angle compared with a trained face model can further be computed based upon phase correlation method. However, the computation is necessary to carry out polar coordinate transformation at every position of an image for every face-finding processing when we use a normal rectangular input, lattice. In this paper, we take advantage of the characteristics of hexagonal lattice, sample an input image of rectangular lattice by hexagonal lattice, approximate the circular mask with a hexagonal one, and find a face independent of its rotation in an image plane.