1## Copyright (C) 2021 David Legland
2## All rights reserved.
3##
4## Redistribution and use in source and binary forms, with or without
5## modification, are permitted provided that the following conditions are met:
6##
7##     1 Redistributions of source code must retain the above copyright notice,
8##       this list of conditions and the following disclaimer.
9##     2 Redistributions in binary form must reproduce the above copyright
10##       notice, this list of conditions and the following disclaimer in the
11##       documentation and/or other materials provided with the distribution.
12##
13## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ''AS IS''
14## AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15## IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16## ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
17## ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18## DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
19## SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
20## CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
21## OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
22## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23##
24## The views and conclusions contained in the software and documentation are
25## those of the authors and should not be interpreted as representing official
26## policies, either expressed or implied, of the copyright holders.
27
28function line = medianLine(varargin)
29%MEDIANLINE Create a median line between two points.
30%
31%   L = medianLine(P1, P2);
32%   Create the median line of points P1 and P2, that is the line containing
33%   all points located at equal distance of P1 and P2.
34%
35%   L = medianLine(PTS);
36%   Creates the median line of 2 points, given as a 2*2 array. Array has
37%   the form:
38%   [ [ x1 y1 ] ; [ x2 y2 ] ]
39%
40%   L = medianLine(EDGE);
41%   Creates the median of the edge. Edge is a 1*4 array, containing [X1 Y1]
42%   coordinates of first point, and [X2 Y2], the coordinates of the second
43%   point.
44%
45%   Example
46%   % Draw the median line of two points
47%     P1 = [10 20];
48%     P2 = [30 50];
49%     med = medianLine(P1, P2);
50%     figure; axis square; axis([0 100 0 100]);
51%     drawEdge([P1 P2], 'linewidth', 2, 'color', 'k');
52%     drawLine(med)
53%
54%   % Draw the median line of an edge
55%     P1 = [50 60];
56%     P2 = [80 30];
57%     edge = createEdge(P1, P2);
58%     figure; axis square; axis([0 100 0 100]);
59%     drawEdge(edge, 'linewidth', 2)
60%     med = medianLine(edge);
61%     drawLine(med)
62%
63%
64%   See also:
65%   lines2d, createLine, orthogonalLine
66%
67%   ---------
68%   author : David Legland
69%   INRA - TPV URPOI - BIA IMASTE
70%   created the 31/10/2003.
71%
72
73% history
74% 2010-08-06 vectorize and change behaviour for N-by-4 inputs
75
76nargs = length(varargin);
77
78if nargs == 1
79    tab = varargin{1};
80    if size(tab, 2)==2
81        % input is an array of two points
82        x0 = tab(1,1);
83        y0 = tab(1,2);
84        dx = tab(2,1)-x0;
85        dy = tab(2,2)-y0;
86    else
87        % input is an edge
88        x0 = tab(:, 1);
89        y0 = tab(:, 2);
90        dx = tab(:, 3) - tab(:, 1);
91        dy = tab(:, 4) - tab(:, 2);
92    end
93
94elseif nargs==2
95    % input is given as two points, or two point arrays
96    p1 = varargin{1};
97    p2 = varargin{2};
98    x0 = p1(:, 1);
99    y0 = p1(:, 2);
100    dx = bsxfun(@minus, p2(:, 1), x0);
101    dy = bsxfun(@minus, p2(:, 2), y0);
102
103else
104    error('Too many input arguments');
105end
106
107% compute median using middle point of the edge, and the direction vector
108% rotated by 90 degrees counter-clockwise
109line = [bsxfun(@plus, x0, dx/2), bsxfun(@plus, y0, dy/2), -dy, dx];
110