Difference of Gaussian (Dog) Filter

Description

Adapted from code by Serge Belongie. Takes a “Difference of Gaussian” all centered on the same point but with different values for sigma. Also serves as an approximation to an Laplacian of Gaussian (LoG) filter (if order==1).

USAGE
G = filterDog2d( r, var, order, [show] )

INPUTS
r – Final filter will be 2*r+1 on each side
var – variance of central Gaussian
order – should be either 1-LoG or 2-difference of 3 Gaussians
show – [0] figure to use for optional display

OUTPUTS
G – filter

Steerable 2D Gaussian derivative filter

N-dimensional Gaussian filter