Steerable filter

This package implements the 1st and 2nd order Gaussian derivative steerable filter

This packages implements the steerable filter of the first derivative and the second of Gaussian function of the paper

W. T. Freeman and E. H. Adelson, "The Design and Use of Steerable Filters", IEEE PAMI, 1991.

Acknowledgment: this file is inspired by Douglas Lanman's "Steerable Gaussian Filters" at http://www.mathworks.com/matlabcentral/fileexchange/9645-steerable-gaussian-filters

However there are two major improvements over Douglas Lanman's implementation:

1. The filter template is normalized, so the magnitude of the response is more reasonable.
2. The second derivative of Gaussian (LOG) is added.