/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2001-2006 Vivid Solutions
* (C) 2001-2008, Open Source Geospatial Foundation (OSGeo)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package org.geotools.geometry.iso.index.quadtree;
import org.geotools.geometry.iso.topograph2D.Coordinate;
import org.geotools.geometry.iso.topograph2D.Envelope;
/**
* A Key is a unique identifier for a node in a quadtree. It contains a
* lower-left point and a level number. The level number is the power of two for
* the size of the node envelope
*
*
*
*
*
* @source $URL$
* @version 1.7.2
*/
public class Key {
public static int computeQuadLevel(Envelope env) {
double dx = env.getWidth();
double dy = env.getHeight();
double dMax = dx > dy ? dx : dy;
int level = DoubleBits.exponent(dMax) + 1;
return level;
}
// the fields which make up the key
private Coordinate pt = new Coordinate();
private int level = 0;
// auxiliary data which is derived from the key for use in computation
private Envelope env = null;
public Key(Envelope itemEnv) {
computeKey(itemEnv);
}
public Coordinate getPoint() {
return pt;
}
public int getLevel() {
return level;
}
public Envelope getEnvelope() {
return env;
}
public Coordinate getCentre() {
return new Coordinate((env.getMinX() + env.getMaxX()) / 2, (env
.getMinY() + env.getMaxY()) / 2);
}
/**
* return a square envelope containing the argument envelope, whose extent
* is a power of two and which is based at a power of 2
*/
public void computeKey(Envelope itemEnv) {
level = computeQuadLevel(itemEnv);
env = new Envelope();
computeKey(level, itemEnv);
// MD - would be nice to have a non-iterative form of this algorithm
while (!env.contains(itemEnv)) {
level += 1;
computeKey(level, itemEnv);
}
}
private void computeKey(int level, Envelope itemEnv) {
double quadSize = DoubleBits.powerOf2(level);
pt.x = Math.floor(itemEnv.getMinX() / quadSize) * quadSize;
pt.y = Math.floor(itemEnv.getMinY() / quadSize) * quadSize;
env.init(pt.x, pt.x + quadSize, pt.y, pt.y + quadSize);
}
}