1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /** \file
3 * LPE "Circle through 3 points" implementation
4 */
5
6 /*
7 * Authors:
8 * Maximilian Albert
9 *
10 * Copyright (C) Johan Engelen 2007 <j.b.c.engelen@utwente.nl>
11 * Copyright (C) Maximilian Albert 2008 <maximilian.albert@gmail.com>
12 *
13 * Released under GNU GPL v2+, read the file 'COPYING' for more information.
14 */
15
16 #include "live_effects/lpe-circle_3pts.h"
17
18 // You might need to include other 2geom files. You can add them here:
19 #include <2geom/circle.h>
20 #include <2geom/path-sink.h>
21 // TODO due to internal breakage in glibmm headers, this must be last:
22 #include <glibmm/i18n.h>
23
24 namespace Inkscape {
25 namespace LivePathEffect {
26
LPECircle3Pts(LivePathEffectObject * lpeobject)27 LPECircle3Pts::LPECircle3Pts(LivePathEffectObject *lpeobject) :
28 Effect(lpeobject)
29 {
30 }
31
32 LPECircle3Pts::~LPECircle3Pts()
33 = default;
34
_circle3(Geom::Point const & A,Geom::Point const & B,Geom::Point const & C,Geom::PathVector & path_out)35 static void _circle3(Geom::Point const &A, Geom::Point const &B, Geom::Point const &C, Geom::PathVector &path_out) {
36 using namespace Geom;
37
38 Point D = (A + B)/2;
39 Point E = (B + C)/2;
40
41 Point v = (B - A).ccw();
42 Point w = (C - B).ccw();
43
44 double det = -v[0] * w[1] + v[1] * w[0];
45
46 Point M;
47 if (!v.isZero()) {
48 Point F = E - D;
49 double lambda = det == 0 ? 0 : (-w[1] * F[0] + w[0] * F[1]) / det;
50 M = D + v * lambda;
51 } else {
52 M = E;
53 }
54
55 double radius = L2(M - A);
56
57 Geom::Circle c(M, radius);
58 path_out = Geom::Path(c);
59 }
60
61 Geom::PathVector
doEffect_path(Geom::PathVector const & path_in)62 LPECircle3Pts::doEffect_path (Geom::PathVector const & path_in)
63 {
64 Geom::PathVector path_out = Geom::PathVector();
65
66 // we assume that the path has >= 3 nodes
67 Geom::Point A = path_in[0].initialPoint();
68 Geom::Point B = path_in[0].pointAt(1);
69 Geom::Point C = path_in[0].pointAt(2);
70
71 _circle3(A, B, C, path_out);
72
73 return path_out;
74 }
75
76 /* ######################## */
77
78 } //namespace LivePathEffect
79 } /* namespace Inkscape */
80
81 /*
82 Local Variables:
83 mode:c++
84 c-file-style:"stroustrup"
85 c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
86 indent-tabs-mode:nil
87 fill-column:99
88 End:
89 */
90 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4 :
91