Simplified Steerable pyramid

A cell structured steerable pyramid

A simplified version of steerable pyramid, where the steerable pyramid
is organized into cell structure for easy access.
For example, we can access different subbands

highpass: coeff{1}
subbands: coeff{2}{1}
lowpass: coeff{ht}

Original code by Eero Simoncelli <http://www.cns.nyu.edu/~eero/>, 2/97.
Ported by Dzung Nguyen <[e-mail]>, 04/2012