1 /* Libart_LGPL - library of basic graphic primitives
2 * Copyright (C) 1999 Raph Levien
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Library General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
8 *
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Library General Public License for more details.
13 *
14 * You should have received a copy of the GNU Library General Public
15 * License along with this library; if not, write to the
16 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17 * Boston, MA 02111-1307, USA.
18 */
20 #include <math.h>
21 #include "art_misc.h"
23 #include "art_svp.h"
24 #include "art_svp_point.h"
26 /* Determine whether a point is inside, or near, an svp. */
28 /* return winding number of point wrt svp */
29 /**
30 * art_svp_point_wind: Determine winding number of a point with respect to svp.
31 * @svp: The svp.
32 * @x: The X coordinate of the point.
33 * @y: The Y coordinate of the point.
34 *
35 * Determine the winding number of the point @x, @y with respect to @svp.
36 *
37 * Return value: the winding number.
38 **/
39 int
40 art_svp_point_wind (ArtSVP *svp, double x, double y)
41 {
42 int i, j;
43 int wind = 0;
45 for (i = 0; i < svp->n_segs; i++)
46 {
47 ArtSVPSeg *seg = &svp->segs[i];
49 if (seg->bbox.y0 > y)
50 break;
52 if (seg->bbox.y1 > y)
53 {
54 if (seg->bbox.x1 < x)
55 wind += seg->dir ? 1 : -1;
56 else if (seg->bbox.x0 <= x)
57 {
58 double x0, y0, x1, y1, dx, dy;
60 for (j = 0; j < seg->n_points - 1; j++)
61 {
62 if (seg->points[j + 1].y > y)
63 break;
64 }
65 x0 = seg->points[j].x;
66 y0 = seg->points[j].y;
67 x1 = seg->points[j + 1].x;
68 y1 = seg->points[j + 1].y;
70 dx = x1 - x0;
71 dy = y1 - y0;
72 if ((x - x0) * dy > (y - y0) * dx)
73 wind += seg->dir ? 1 : -1;
74 }
75 }
76 }
78 return wind;
79 }
81 /**
82 * art_svp_point_dist: Determine distance between point and svp.
83 * @svp: The svp.
84 * @x: The X coordinate of the point.
85 * @y: The Y coordinate of the point.
86 *
87 * Determines the distance of the point @x, @y to the closest edge in
88 * @svp. A large number is returned if @svp is empty.
89 *
90 * Return value: the distance.
91 **/
92 double
93 art_svp_point_dist (ArtSVP *svp, double x, double y)
94 {
95 int i, j;
96 double dist_sq;
97 double best_sq = -1;
99 for (i = 0; i < svp->n_segs; i++)
100 {
101 ArtSVPSeg *seg = &svp->segs[i];
102 for (j = 0; j < seg->n_points - 1; j++)
103 {
104 double x0 = seg->points[j].x;
105 double y0 = seg->points[j].y;
106 double x1 = seg->points[j + 1].x;
107 double y1 = seg->points[j + 1].y;
109 double dx = x1 - x0;
110 double dy = y1 - y0;
112 double dxx0 = x - x0;
113 double dyy0 = y - y0;
115 double dot = dxx0 * dx + dyy0 * dy;
117 if (dot < 0)
118 dist_sq = dxx0 * dxx0 + dyy0 * dyy0;
119 else
120 {
121 double rr = dx * dx + dy * dy;
123 if (dot > rr)
124 dist_sq = (x - x1) * (x - x1) + (y - y1) * (y - y1);
125 else
126 {
127 double perp = (y - y0) * dx - (x - x0) * dy;
129 dist_sq = perp * perp / rr;
130 }
131 }
132 if (best_sq < 0 || dist_sq < best_sq)
133 best_sq = dist_sq;
134 }
135 }
137 if (best_sq >= 0)
138 return sqrt (best_sq);
139 else
140 return 1e12;
141 }