Class SplitSegment

1	/*
2	* Copyright (c) 2016 Vivid Solutions.
3	*
4	* All rights reserved. This program and the accompanying materials
5	* are made available under the terms of the Eclipse Public License 2.0
6	* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
7	* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
8	* and the Eclipse Distribution License is available at
9	*
10	* http://www.eclipse.org/org/documents/edl-v10.php.
11	*/
12
13	package org.locationtech.jts.triangulate;
14
15	import org.locationtech.jts.geom.Coordinate;
16	import org.locationtech.jts.geom.LineSegment;
17
18	/**
19	* Models a constraint segment which can be split in two in various ways,
20	* according to certain geometric constraints.
21	*
22	* @author Martin Davis
23	*/
24	public class SplitSegment {
25	/**
26	* Computes the {@link Coordinate} that lies a given fraction along the line defined by the
27	* reverse of the given segment. A fraction of <code>0.0</code> returns the end point of the
28	* segment; a fraction of <code>1.0</code> returns the start point of the segment.
29	*
30	* @param seg the LineSegment
31	* @param segmentLengthFraction the fraction of the segment length along the line
32	* @return the point at that distance
33	*/
34	private static Coordinate pointAlongReverse(LineSegment seg, double segmentLengthFraction) {
35	Coordinate coord = new Coordinate();
36	coord.x = seg.p1.x - segmentLengthFraction * (seg.p1.x - seg.p0.x);
37	coord.y = seg.p1.y - segmentLengthFraction * (seg.p1.y - seg.p0.y);
38	return coord;
39	}
40
41	private LineSegment seg;
42	private double segLen;
43	private Coordinate splitPt;
44	private double minimumLen = 0.0;
45
46	public SplitSegment(LineSegment seg) {
47	this.seg = seg;
48	segLen = seg.getLength();
49	}
50
51	public void setMinimumLength(double minLen) {
52	minimumLen = minLen;
53	}
54
55	public Coordinate getSplitPoint() {
56	return splitPt;
57	}
58
59	public void splitAt(double length, Coordinate endPt) {
60	double actualLen = getConstrainedLength(length);
61	double frac = actualLen / segLen;
62	if (endPt.equals2D(seg.p0))
63	splitPt = seg.pointAlong(frac);
64	else
65	splitPt = pointAlongReverse(seg, frac);
66	}
67
68	public void splitAt(Coordinate pt) {
69	// check that given pt doesn't violate min length
70	double minFrac = minimumLen / segLen;
71	if (pt.distance(seg.p0) < minimumLen) {
72	splitPt = seg.pointAlong(minFrac);
73	return;
74	}
75	if (pt.distance(seg.p1) < minimumLen) {
76	splitPt = pointAlongReverse(seg, minFrac);
77	return;
78	}
79	// passes minimum distance check - use provided point as split pt
80	splitPt = pt;
81	}
82
83	private double getConstrainedLength(double len) {
84	if (len < minimumLen)
85	return minimumLen;
86	return len;
87	}
88
89	}
90