Hexagonal QMF pyramids

It is widely recognized that effective image processing and machine vision must involve the use of information at multiple scales, and that models of human vision must be multi-scale as well. The most commonly used image representations are linear transforms, in which an image is decomposed into a sum of elementary basis functions. Besides being well understood, linear transformations in the form of convolutions provide a useful model of some of the early processing in the human visual system.