% HIGHPASSFILTER  - Constructs a high-pass butterworth filter.%% usage: f = highpassfilter(sze, cutoff, n)% % where: sze    is a two element vector specifying the size of filter %               to construct [rows cols].%        cutoff is the cutoff frequency of the filter 0 - 0.5%        n      is the order of the filter, the higher n is the sharper%               the transition is. (n must be an integer >= 1).%% The frequency origin of the returned filter is at the corners.%% See also: LOWPASSFILTER, HIGHBOOSTFILTER, BANDPASSFILTER%% Copyright (c) 1999 Peter Kovesi% School of Computer Science & Software Engineering% The University of Western Australia% http://www.csse.uwa.edu.au/% % Permission is hereby granted, free of charge, to any person obtaining a copy% of this software and associated documentation files (the "Software"), to deal% in the Software without restriction, subject to the following conditions:% % The above copyright notice and this permission notice shall be included in % all copies or substantial portions of the Software.%% The Software is provided "as is", without warranty of any kind.% October 1999function f = highpassfilter(sze, cutoff, n)        if cutoff < 0 | cutoff > 0.5	error('cutoff frequency must be between 0 and 0.5');    end    if rem(n,1) ~= 0 | n < 1	error('n must be an integer >= 1');    end        f = 1.0 - lowpassfilter(sze, cutoff, n);