function y = perform_convolution(x,h, bound)

% perform_convolution - compute convolution with centered filter.
%
%   y = perform_convolution(x,h,bound);
%
%   The filter 'h' is centred at 0 for odd
%   length of the filter, and at 1/2 otherwise.
%
%   This works either for 1D or 2D convolution.
%   For 2D the matrix have to be square.
%
%   'bound' is either 'per' (periodic extension) 
%   or 'sym' (symmetric extension).
%
%   Copyright (c) 2004 Gabriel Peyr