Class HilbertEncoder

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	package org.locationtech.jts.index.hprtree;
13
14	import org.locationtech.jts.geom.Envelope;
15	import org.locationtech.jts.shape.fractal.HilbertCode;
16
17	public class HilbertEncoder {
18	private int level;
19	private double minx;
20	private double miny;
21	private double strideX;
22	private double strideY;
23
24	public HilbertEncoder(int level, Envelope extent) {
25	this.level = level;
26	int hside = (int) Math.pow(2, level) - 1;
27
28	minx = extent.getMinX();
29	double extentX = extent.getWidth();
30	strideX = extentX / hside;
31
32	miny = extent.getMinX();
33	double extentY = extent.getHeight();
34	strideY = extentY / hside;
35	}
36
37	public int encode(Envelope env) {
38	double midx = env.getWidth()/2 + env.getMinX();
39	int x = (int) ((midx - minx) / strideX);
40
41	double midy = env.getHeight()/2 + env.getMinY();
42	int y = (int) ((midy - miny) / strideY);
43
44	return HilbertCode.encode(level, x, y);
45	}
46
47	}
48