Reference NASA Tech 1987 Watson & Ahumada

Papers that reference this paper.

An orthogonal oriented quadrature hexagonal image pyramid

Andrew B. Watson & A. J. Ahumada Jr. (1987) NASA Technical Memorandum 100054.

Abstract

We have developed an image pyramid with basis functions that are orthogonal, self-similar, and localized in space, spatial frequency, orientation and phase. The pyramid operates on a hexagonal sample lattice. The set of seven basis functions consist of three even high-pass kernels, three odd high-pass kernels, and one low-pass kernel. The three even kernels are identical when rotated by 60 deg or 120 deg, and likewise for the odd. The seven basis functions occupy a point and a hexagon of six nearest neigbors on a hexagonal sample lattice. At each higher level, the input lattice is provided by the low-pass coefficients computed at the previous level. At each level, the output is subsampled in such a way as to yield a new hexagonal lattice with a spacing the square root of seven larger than the previous level, so that the number of coefficients is reduced by a factor of seven at each level. In the biological model, the input lattice is the retinal ganglion cell array. We discuss the relationship between this image code and the processing architecture of the primary visual cortex.