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 T = createHomothecy(point, ratio)
29%CREATEHOMOTHECY Create the the 3x3 matrix of an homothetic transform.
30%
31%   TRANS = createHomothecy(POINT, K);
32%   POINT is the center of the homothecy, K is its factor.
33%   TRANS is a 3-by-3 matrix representing the homothetic transform in
34%   homogeneous coordinates.
35%
36%   Example:
37%
38%      p  = [0 0; 1 0; 0 1];
39%      s  = [-0.5 0.4];
40%      T  = createHomothecy (s, 1.5);
41%      pT = transformPoint (p, T);
42%      drawPolygon (p,'-b')
43%      hold on;
44%      drawPolygon (pT, '-r');
45%
46%      drawEdge (p(:,1), p(:,2), pT(:,1), pT(:,2), ...
47%                'color', 'k','linestyle','--')
48%      hold off
49%      axis tight equal
50%
51
52% ---------
53% Author: David Legland
54% e-mail: david.legland@inra.fr
55% INRA - TPV URPOI - BIA IMASTE
56% created the 20/01/2005.
57
58
59%   HISTORY
60%   22/04/2009: rename as createHomothecy
61%   05/04/2017: improved code by JuanPi Carbajal <ajuanpi+dev@gmail.com>
62
63point = point(:);
64if length (point) > 2
65    error('Only one point accepted.');
66end
67if length (ratio) > 1
68    error('Only one ratio accepted.');
69end
70
71T        = diag ([ratio ratio 1]);
72T(1:2,3) = point .* (1 - ratio);
73