[37] | 1 | % SELECTSEG - Interactive selection of linesegments with mouse. |
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| 2 | % |
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| 3 | % Usage: segs = selectseg(seglist); |
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| 4 | % |
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| 5 | % seglist - an Nx4 array storing line segments in the form |
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| 6 | % [x1 y1 x2 y2 |
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| 7 | % x1 y1 x2 y2 |
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| 8 | % . . ] etc |
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| 9 | % |
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| 10 | % |
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| 11 | % See also: EDGELINK, LINESEG, MAXLINEDEV, MERGESEG |
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| 12 | % |
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| 13 | |
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| 14 | % Copyright (c) 2000-2005 Peter Kovesi |
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| 15 | % School of Computer Science & Software Engineering |
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| 16 | % The University of Western Australia |
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| 17 | % http://www.csse.uwa.edu.au/ |
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| 18 | % |
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| 19 | % Permission is hereby granted, free of charge, to any person obtaining a copy |
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| 20 | % of this software and associated documentation files (the "Software"), to deal |
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| 21 | % in the Software without restriction, subject to the following conditions: |
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| 22 | % |
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| 23 | % The above copyright notice and this permission notice shall be included in |
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| 24 | % all copies or substantial portions of the Software. |
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| 25 | % |
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| 26 | % The Software is provided "as is", without warranty of any kind. |
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| 27 | |
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| 28 | % December 2000 |
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| 29 | |
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| 30 | function segs = selectseg(seglist); |
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| 31 | |
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| 32 | segs = []; |
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| 33 | selectedSegs = [NaN]; |
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| 34 | |
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| 35 | figure(1), clf, drawseg(seglist,1); |
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| 36 | |
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| 37 | |
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| 38 | Nseg = size(seglist,1); |
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| 39 | |
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| 40 | fprintf('Select segments by clicking with the left mouse button\n'); |
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| 41 | fprintf('Last segment is indicated by clicking with any other mouse button\n'); |
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| 42 | |
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| 43 | count = 0; |
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| 44 | but = 1; |
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| 45 | while but==1 & count < Nseg |
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| 46 | [xp,yp,but] = ginput(1); % Get digitised point |
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| 47 | count = count + 1; |
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| 48 | rmin = Inf; |
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| 49 | for s = 1:Nseg |
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| 50 | r = segdist(xp,yp,seglist(s,:)); |
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| 51 | % if distance is closest so far and segment is not already |
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| 52 | % selected... |
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| 53 | if r < rmin & ~any(selectedSegs==s) |
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| 54 | rmin = r; |
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| 55 | closestseg = seglist(s,:); |
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| 56 | smin = s; |
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| 57 | end |
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| 58 | end |
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| 59 | |
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| 60 | segs = [segs; closestseg]; % Build up list of segments |
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| 61 | selectedSegs = [selectedSegs smin]; % Remeber selected seg Nos |
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| 62 | |
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| 63 | line([closestseg(1) closestseg(3)], [closestseg(2) closestseg(4)], ... |
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| 64 | 'Color',[1 0 0]); |
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| 65 | text((closestseg(1)+closestseg(3))/2, ... |
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| 66 | (closestseg(2)+closestseg(4))/2, sprintf('%d',count)); |
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| 67 | |
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| 68 | end |
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| 69 | |
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| 70 | function r = segdist(xp,yp,seg) |
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| 71 | |
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| 72 | % Function returns distance from point (xp,yp) to line defined by end |
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| 73 | % points (x1,y1) (x2,y2) |
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| 74 | % |
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| 75 | % |
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| 76 | % Eqn of line joining end pts (x1 y1) and (x2 y2) can be parameterised by |
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| 77 | % |
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| 78 | % x*(y1-y2) + y*(x2-x1) + y2*x1 - y1*x2 = 0 |
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| 79 | % |
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| 80 | % (See Jain, Rangachar and Schunck, "Machine Vision", McGraw-Hill |
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| 81 | % 1996. pp 194-196) |
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| 82 | |
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| 83 | x1=seg(1);y1=seg(2); |
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| 84 | x2=seg(3);y2=seg(4); |
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| 85 | |
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| 86 | y1my2 = y1-y2; % Pre-compute parameters |
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| 87 | x2mx1 = x2-x1; |
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| 88 | C = y2*x1 - y1*x2; |
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| 89 | D = norm([x1 y1] - [x2 y2]); % Distance between end points |
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| 90 | |
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| 91 | r = abs(xp*y1my2 + yp*x2mx1 + C)/D; % Perp. distance from line to (xp,yp) |
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| 92 | |
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| 93 | % Correct the distance if (xp,yp) is `outside' the ends of the segment |
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| 94 | d1 = [xp yp]-[x1 y1]; |
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| 95 | d2 = [xp yp]-[x2 y2]; |
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| 96 | if dot(d1,d2) > 0 % (xp,yp) is not `between' the end points of the |
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| 97 | % segment |
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| 98 | |
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| 99 | r = min(norm(d1),norm(d2)); % return distance to closest end |
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| 100 | % point |
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| 101 | end |
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| 102 | |
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