01: /*
02: * The Unified Mapping Platform (JUMP) is an extensible, interactive GUI
03: * for visualizing and manipulating spatial features with geometry and attributes.
04: *
05: * Copyright (C) 2003 Vivid Solutions
06: *
07: * This program is free software; you can redistribute it and/or
08: * modify it under the terms of the GNU General Public License
09: * as published by the Free Software Foundation; either version 2
10: * of the License, or (at your option) any later version.
11: *
12: * This program is distributed in the hope that it will be useful,
13: * but WITHOUT ANY WARRANTY; without even the implied warranty of
14: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15: * GNU General Public License for more details.
16: *
17: * You should have received a copy of the GNU General Public License
18: * along with this program; if not, write to the Free Software
19: * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
20: *
21: * For more information, contact:
22: *
23: * Vivid Solutions
24: * Suite #1A
25: * 2328 Government Street
26: * Victoria BC V8T 5G5
27: * Canada
28: *
29: * (250)385-6040
30: * www.vividsolutions.com
31: */
32:
33: package com.vividsolutions.jump.algorithm;
34:
35: import com.vividsolutions.jts.geom.*;
36:
37: /**
38: * Computes the Euclidean distance (L2 metric) from a Point to a Geometry.
39: * Also computes two points which are separated by the distance.
40: */
41: public class EuclideanDistanceToPoint {
42:
43: // used for point-line distance calculation
44: private static LineSegment tempSegment = new LineSegment();
45:
46: public EuclideanDistanceToPoint() {
47: }
48:
49: public static void computeDistance(Geometry geom, Coordinate pt,
50: PointPairDistance ptDist) {
51: if (geom instanceof LineString) {
52: computeDistance((LineString) geom, pt, ptDist);
53: } else if (geom instanceof Polygon) {
54: computeDistance((Polygon) geom, pt, ptDist);
55: } else if (geom instanceof GeometryCollection) {
56: GeometryCollection gc = (GeometryCollection) geom;
57: for (int i = 0; i < gc.getNumGeometries(); i++) {
58: Geometry g = gc.getGeometryN(i);
59: computeDistance(g, pt, ptDist);
60: }
61: } else { // assume geom is Point
62: ptDist.setMinimum(geom.getCoordinate(), pt);
63: }
64: }
65:
66: public static void computeDistance(LineString line, Coordinate pt,
67: PointPairDistance ptDist) {
68: Coordinate[] coords = line.getCoordinates();
69: for (int i = 0; i < coords.length - 1; i++) {
70: tempSegment.setCoordinates(coords[i], coords[i + 1]);
71: // this is somewhat inefficient - could do better
72: Coordinate closestPt = tempSegment.closestPoint(pt);
73: ptDist.setMinimum(closestPt, pt);
74: }
75: }
76:
77: public static void computeDistance(LineSegment segment,
78: Coordinate pt, PointPairDistance ptDist) {
79: Coordinate closestPt = segment.closestPoint(pt);
80: ptDist.setMinimum(closestPt, pt);
81: }
82:
83: public static void computeDistance(Polygon poly, Coordinate pt,
84: PointPairDistance ptDist) {
85: computeDistance(poly.getExteriorRing(), pt, ptDist);
86: for (int i = 0; i < poly.getNumInteriorRing(); i++) {
87: computeDistance(poly.getInteriorRingN(i), pt, ptDist);
88: }
89: }
90: }
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