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function Y = colfilter(X, h) 
% function Y = colfilter(X, h) 
% Filter the columns of image X using filter vector h, without decimation. 
% If length(h) is odd, each output sample is aligned with each input sample 
% and Y is the same size as X. 
% If length(h) is even, each output sample is aligned with the mid point 
% of each pair of input samples, and size(Y) = size(X) + [1 0];  
% 
% Cian Shaffrey, Nick Kingsbury 
% Cambridge University, August 2000 
 
[r,c] = size(X); 
m = length(h); 
m2 = fix(m/2); 
 
if any(X(:)) 
   % Symmetrically extend with repeat of end samples. 
   xe = reflect([(1-m2):(r+m2)], 0.5, r+0.5); % Use 'reflect' so r < m2 works OK. 
    
   % Perform filtering on the columns of the extended matrix X(xe,:), keeping 
   % only the 'valid' output samples, so Y is the same size as X if m is odd.  
   Y = conv2(X(xe,:),h(:),'valid');  
else 
   Y = zeros(r+1-rem(m,2),c); 
end 
return;