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comparison scripts/geometry/rectint.m @ 7551:5ed0cb9e9584

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rectint.m: added
author bill@denney.ws
date Tue, 04 Mar 2008 15:07:44 -0500
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children ea2344c4140b
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7550:bffb1e2ab732 7551:5ed0cb9e9584
1 ## Copyright (C) 2008 Bill Denney
2 ##
3 ## This file is part of Octave.
4 ##
5 ## Octave is free software; you can redistribute it and/or modify it
6 ## under the terms of the GNU General Public License as published by
7 ## the Free Software Foundation; either version 3 of the License, or (at
8 ## your option) any later version.
9 ##
10 ## Octave is distributed in the hope that it will be useful, but
11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ## General Public License for more details.
14 ##
15 ## You should have received a copy of the GNU General Public License
16 ## along with Octave; see the file COPYING. If not, see
17 ## <http://www.gnu.org/licenses/>.
18
19 ## -*- texinfo -*-
20 ## @deftypefn {Function File} {@var{area} =} rectint (@var{a}, @var{b})
21 ##
22 ## Compute the area of intersection of rectangles in @var{a} and
23 ## rectangles in @var{b}. Rectangles are defined as [x y width height]
24 ## where x and y are the minimum values of the two orthogonal
25 ## dimensions.
26 ##
27 ## If @var{a} or @var{b} are matrices, then the output, @var{area}, is a
28 ## matrix where the ith row corresponds to the ith row of a and the jth
29 ## column corresponds to the jth row of b.
30 ##
31 ## @seealso{polyarea}
32 ## @end deftypefn
33
34 ## Author: Bill Denney <bill@denney.ws>
35
36 function area = rectint (a, b)
37
38 if (nargin != 2)
39 print_usage ();
40 elseif (ndims (a) != 2 || ndims (b) != 2)
41 error ("rectint: expecting arguments to be 2-d arrays");
42 elseif (columns (a) != 4)
43 error ("rectint: a must have 4 columns");
44 elseif (columns (b) != 4)
45 error ("rectint: b must have 4 columns");
46 endif
47
48 area = zeros (rows (a), rows (b));
49 for i = 1:rows (area)
50 r1 = a(i,:);
51 for j = 1:columns (area)
52 r2 = b(j,:);
53 area(i,j) = (overlap (r1([1, 3]), r2([1, 3]))
54 * overlap (r1([2, 4]), r2([2, 4])));
55 endfor
56 endfor
57
58 endfunction
59
60 function amt = overlap (r1, r2)
61
62 ## Determine whether two ranges overlap. Ranges are given as [value
63 ## offset]
64 amt = 0;
65
66 ## Make sure that the values are in order.
67 r1 = sort ([r1(1), r1(1)+r1(2)]);
68 r2 = sort ([r2(1), r2(1)+r2(2)]);
69
70 ## Is the first point in range 1 in the middle of range 2?
71 p1 = sum (r1(1) <= r2) == 1;
72 ## is the second?
73 p2 = sum (r1(2) <= r2) == 1;
74 if (p1)
75 if (p2)
76 amt = r1(2) - r1(1);
77 else
78 amt = r2(2) - r1(1);
79 endif
80 elseif (sum (r1(2) < r2) == 1)
81 amt = r1(2) - r2(1);
82 endif
83
84 endfunction
85
86 ## Tests
87 %!assert(rectint([0 0 1 1], [1 1 2 2]), 0)
88 %!assert(rectint([0 0 1 1], [0.5 0.5 2 2]), 0.25)
89 %!assert(rectint([0 0 1 1;0.5 0.5 1 1], [1 1 2 2]), [0;0.25])
90 %!assert(rectint([1 1 2 2], [0 0 1 1;0.5 0.5 1 1]), [0 0.25])
91