Hexagonal sub-band coding for images

An image coding system is proposed in which hexagonally sampled images are decomposed into subbands that are selective in both frequency and orientation. Nine high-frequency bands each of one octave and 60 degrees of angular orientation are built on a pyramidal structure along with one low-frequency band. Bits are then allocated optimally to the subbands under a mean-squared-error distortion measure. Optimal quantizers are designed for each subband for entropy coding under a Laplacian distribution assumption. An adaptive version of the coding scheme is also implemented, and the results are compared at rates of 0.5 and 1.0 bits per pixel.<<ETX>>