steerable_gauss.m

加州大学伯克利分校的一个车俩识别程序, 用matlab实现

function [basis] = steerable_gauss(I,scale); 


% defines a set of seperable quadrature pair 
% basis filters as per freeman & adelson, pami, sept 1991
%
% returns the response to convolution with the
% basis functions.  use function steer.m to 
% generate actual orientation
%
% charless fowlkes, 2000
% [e-mail]

%% generate a gaussian to upsample the filters
%% if we need larger filters.
if (scale > 1)
 k = gen_gaussian(scale-2);
else
 k = [1];
end;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% even %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% x-y basis set for second derivative of gaussian 

f1 = [ 0.0094, 0.1148, 0.3964,-0.0601,-0.9213,-0.0601, 0.3964, 0.1148, 0.0094]; 
f2 = [ 0.0008, 0.0176, 0.1660, 0.6383, 1.0000, 0.6383, 0.1660, 0.0176, 0.0008];
f3 = [-0.0028,-0.0480,-0.3020,-0.5806, 0.0000, 0.5806, 0.3020, 0.0480, 0.0028];

f1 = conv(f1,k);
f2 = conv(f2,k);
f3 = conv(f3,k);

% compute response for gaussian 2nd derivative basis filters

basis.Ga = conv2(conv2(I,f1,'same'),f2','same');
basis.Gb = conv2(conv2(I,f3,'same'),f3','same');
basis.Gc = conv2(conv2(I,f2,'same'),f1','same');


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% odd %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% x-y basis set for hilbert transform of second derivative of gaussian

f1 = [-0.0098,-0.0618, 0.0998, 0.7551, 0.0000,-0.7551,-0.0998, 0.0618, 0.0098];
f2 = [ 0.0008, 0.0176, 0.1660, 0.6383, 1.0000, 0.6383, 0.1660, 0.0176, 0.0008];
f3 = [-0.0020,-0.0354,-0.2225,-0.4277, 0.0000, 0.4277, 0.2225, 0.0354, 0.0020];
f4 = [ 0.0048, 0.0566, 0.1695,-0.1889,-0.7349,-0.1889, 0.1695, 0.0566, 0.0048];

f1 = conv(f1,k);
f2 = conv(f2,k);
f3 = conv(f3,k);
f4 = conv(f4,k);

% compute response for hilbert trans. of gaussian 2nd derivative basis filters

basis.Ha = conv2(conv2(I,f1,'same'),f2','same');
basis.Hb = conv2(conv2(I,f4,'same'),f3','same');
basis.Hc = conv2(conv2(I,f3,'same'),f4','same');
basis.Hd = conv2(conv2(I,f2,'same'),f1','same');