%  PSF - Generates point spread functions for use with deconvolution fns.%%  This function can generate a variety function shapes based around the%  Butterworth filter.  In plan view the filter can be elliptical and at%  any orientation.  The `squareness/roundness' of the shape can also be%  manipulated.%%  Usage:  h = psf(sze, order, ang, eccen, rc, sqrness)%%   sze   - two element array specifying size of filter [rows cols]%   order - an even integer specifying the order of the Butterworth filter.%           This controls the sharpness of the cutoff.%   ang   - angle of rotation of the filter in radians%   eccen - ratio of eccentricity of the filter shape (major/minor axis ratio)%   rc    - mean radius of the filter in pixels%   sqrness - even integer specifying `squareness' of the filter shape%             a value of 2 gives a circular filter (if eccen = 1), higher%             values make the shape squarer.       % 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.% June 1999function h = psf(sze, order, ang, eccen, rc, sqrness)    if mod(sqrness,2) ~=0	error('squareness parameter must be an even integer');    end        rows = sze(1);    cols = sze(2);        x = ones(rows,1) * [1:cols]  - (fix(cols/2)+1);    y = [1:rows]' * ones(1,cols) - (fix(rows/2)+1);        xp = x*cos(ang) - y*sin(ang);   % Rotate axes by specified angle.    yp = x*sin(ang) + y*cos(ang);        x = sqrt(eccen)*xp;             % Distort x and y according to eccentricity.    y = yp/sqrt(eccen);        radius = (x.^sqrness + y.^sqrness).^(1/sqrness);  % Distort distance metric						      % by squareness measure.    h = 1./(1+(radius./rc).^order);  % Butterworth filter     h = h./(sum(sum(h)));            % and normalise.