% SELECTSEG - Interactive selection of linesegments with mouse.%% Usage: segs = selectseg(seglist);%                            %         seglist - an Nx4 array storing line segments in the form%                    [x1 y1 x2 y2%                     x1 y1 x2 y2%                         . .     ] etc %%% See also:  EDGELINK, LINESEG, MAXLINEDEV, MERGESEG%% Copyright (c) 2000-2005 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.% December 2000function segs = selectseg(seglist);segs = [];selectedSegs = [NaN];figure(1), clf, drawseg(seglist,1);Nseg = size(seglist,1);    fprintf('Select segments by clicking with the left mouse button\n');    fprintf('Last segment is indicated by clicking with any other mouse button\n');    count = 0;    but = 1;    while but==1 & count < Nseg        [xp,yp,but] = ginput(1);       % Get digitised point	count = count + 1;		rmin = Inf;	for s = 1:Nseg	    r = segdist(xp,yp,seglist(s,:));	    % if distance is closest so far and segment is not already            % selected...	    if r < rmin & ~any(selectedSegs==s)		rmin = r;		closestseg = seglist(s,:);                smin = s;	    end	end		segs = [segs; closestseg];          % Build up list of segments	selectedSegs = [selectedSegs smin]; % Remeber selected seg Nos		line([closestseg(1) closestseg(3)], [closestseg(2) closestseg(4)], ...	     'Color',[1 0 0]);	text((closestseg(1)+closestseg(3))/2, ...	     (closestseg(2)+closestseg(4))/2, sprintf('%d',count));    end               function r = segdist(xp,yp,seg)    % Function returns distance from point (xp,yp) to line defined by end% points (x1,y1) (x2,y2)%	%    % Eqn of line joining end pts (x1 y1) and (x2 y2) can be parameterised by%%    x*(y1-y2) + y*(x2-x1) + y2*x1 - y1*x2 = 0%% (See Jain, Rangachar and Schunck, "Machine Vision", McGraw-Hill% 1996. pp 194-196)        x1=seg(1);y1=seg(2);    x2=seg(3);y2=seg(4);           y1my2 = y1-y2;                       % Pre-compute parameters    x2mx1 = x2-x1;    C = y2*x1 - y1*x2;    D = norm([x1 y1] - [x2 y2]);         % Distance between end points    r = abs(xp*y1my2 + yp*x2mx1 + C)/D;  % Perp. distance from line to (xp,yp)    % Correct the distance if (xp,yp) is `outside' the ends of the segment    d1 = [xp yp]-[x1 y1];    d2 = [xp yp]-[x2 y2];        if dot(d1,d2) > 0    % (xp,yp) is not `between' the end points of the                         % segment			 	r = min(norm(d1),norm(d2));  % return distance to closest end                                     % point    end