Class MortonCurveBuilder

1	/*
2	* Copyright (c) 2019 Martin Davis.
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.shape.fractal;
14
15	import org.locationtech.jts.geom.Coordinate;
16	import org.locationtech.jts.geom.Geometry;
17	import org.locationtech.jts.geom.GeometryFactory;
18	import org.locationtech.jts.geom.LineSegment;
19	import org.locationtech.jts.geom.LineString;
20	import org.locationtech.jts.shape.GeometricShapeBuilder;
21	import static org.locationtech.jts.shape.fractal.MortonCode.*;
22
23	/**
24	* Generates a {@link LineString} representing the Morton Curve
25	* at a given level.
26	*
27	* @author Martin Davis
28	* @see MortonCode
29	*/
30	public class MortonCurveBuilder
31	extends GeometricShapeBuilder
32	{
33
34	/**
35	* Creates a new instance using the provided {@link GeometryFactory}.
36	*
37	* @param geomFactory the geometry factory to use
38	*/
39	public MortonCurveBuilder(GeometryFactory geomFactory)
40	{
41	super(geomFactory);
42	// use a null extent to indicate no transformation
43	// (may be set by client)
44	extent = null;
45	}
46
47	/**
48	* Sets the level of curve to generate.
49	* The level must be in the range [0 - 16].
50	* This determines the
51	* number of points in the generated curve.
52	*
53	* @param level the level of the curve
54	*/
55	public void setLevel(int level) {
56	this.numPts = size(level);
57	}
58
59	@Override
60	public Geometry getGeometry() {
61	int level = level(numPts);
62	int nPts = size(level);
63
64	double scale = 1;
65	double baseX = 0;
66	double baseY = 0;
67	if (extent != null) {
68	LineSegment baseLine = getSquareBaseLine();
69	baseX = baseLine.minX();
70	baseY = baseLine.minY();
71	double width = baseLine.getLength();
72	int maxOrdinate = maxOrdinate(level);
73	scale = width / maxOrdinate;
74	}
75
76	Coordinate[] pts = new Coordinate[nPts];
77	for (int i = 0; i < nPts; i++) {
78	Coordinate pt = decode(i);
79	double x = transform(pt.getX(), scale, baseX);
80	double y = transform(pt.getY(), scale, baseY);
81	pts[i] = new Coordinate(x, y);
82	}
83	return geomFactory.createLineString(pts);
84	}
85
86	private static double transform(double val, double scale, double offset) {
87	return val * scale + offset;
88	}
89
90	}
91