Difference of Gaussian (Dog) Filter. 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 EXAMPLE G = filterDog2d( 40, 40, 1, 1 ); %order=1 (LoG) G = filterDog2d( 40, 40, 2, 3 ); %order=2 See also FILTERDOOG, FILTERGAUSS