/*
* The JTS Topology Suite is a collection of Java classes that
* implement the fundamental operations required to validate a given
* geo-spatial data set to a known topological specification.
*
* Copyright (C) 2001 Vivid Solutions
*
* 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; either
* version 2.1 of the License, or (at your option) any later version.
*
* 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.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* For more information, contact:
*
* Vivid Solutions
* Suite #1A
* 2328 Government Street
* Victoria BC V8T 5G5
* Canada
*
* (250)385-6040
* www.vividsolutions.com
*/
package com.revolsys.geometry.geomgraph;
import com.revolsys.geometry.model.LineString;
import com.revolsys.geometry.model.Point;
/**
* Utility functions for working with quadrants, which are numbered as follows:
* <pre>
* 1 | 0
* --+--
* 2 | 3
* <pre>
*
* @version 1.7
*/
public class Quadrant {
public static final int NE = 0;
public static final int NW = 1;
public static final int SE = 3;
public static final int SW = 2;
/**
* Returns the right-hand quadrant of the halfplane defined by the two quadrants,
* or -1 if the quadrants are opposite, or the quadrant if they are identical.
*/
public static int commonHalfPlane(final int quad1, final int quad2) {
// if quadrants are the same they do not determine a unique common
// halfplane.
// Simply return one of the two possibilities
if (quad1 == quad2) {
return quad1;
}
final int diff = (quad1 - quad2 + 4) % 4;
// if quadrants are not adjacent, they do not share a common halfplane
if (diff == 2) {
return -1;
}
//
final int min = quad1 < quad2 ? quad1 : quad2;
final int max = quad1 > quad2 ? quad1 : quad2;
// for this one case, the righthand plane is NOT the minimum index;
if (min == 0 && max == 3) {
return 3;
}
// in general, the halfplane index is the minimum of the two adjacent
// quadrants
return min;
}
/**
* Returns whether the given quadrant lies within the given halfplane (specified
* by its right-hand quadrant).
*/
public static boolean isInHalfPlane(final int quad, final int halfPlane) {
if (halfPlane == SE) {
return quad == SE || quad == SW;
}
return quad == halfPlane || quad == halfPlane + 1;
}
/**
* Returns true if the given quadrant is 0 or 1.
*/
public static boolean isNorthern(final int quad) {
return quad == NE || quad == NW;
}
/**
* Returns true if the quadrants are 1 and 3, or 2 and 4
*/
public static boolean isOpposite(final int quad1, final int quad2) {
if (quad1 == quad2) {
return false;
}
final int diff = (quad1 - quad2 + 4) % 4;
// if quadrants are not adjacent, they are opposite
if (diff == 2) {
return true;
}
return false;
}
/**
* Returns the quadrant of a directed line segment (specified as x and y
* displacements, which cannot both be 0).
*
* @throws IllegalArgumentException if the displacements are both 0
*/
public static int quadrant(final double dx, final double dy) {
if (dx == 0.0 && dy == 0.0) {
throw new IllegalArgumentException(
"Cannot compute the quadrant for point ( " + dx + ", " + dy + " )");
}
if (dx >= 0.0) {
if (dy >= 0.0) {
return NE;
} else {
return SE;
}
} else {
if (dy >= 0.0) {
return NW;
} else {
return SW;
}
}
}
public static int quadrant(final double x1, final double y1, final double x2, final double y2) {
if (x2 == x1 && y2 == y1) {
throw new IllegalArgumentException(
"Cannot compute the quadrant for two identical points POINT(" + x1 + " " + x2 + ")");
} else if (x2 >= x1) {
if (y2 >= y1) {
return NE;
} else {
return SE;
}
} else {
if (y2 >= y1) {
return NW;
} else {
return SW;
}
}
}
public static int quadrant(final LineString line, final int vertexIndex1,
final int vertexIndex2) {
final double x1 = line.getX(vertexIndex1);
final double y1 = line.getY(vertexIndex1);
final double x2 = line.getX(vertexIndex2);
final double y2 = line.getY(vertexIndex2);
return quadrant(x1, y1, x2, y2);
}
/**
* Returns the quadrant of a directed line segment from p0 to p1.
*
* @throws IllegalArgumentException if the points are equal
*/
public static int quadrant(final Point p0, final Point p1) {
final double x1 = p0.getX();
final double y1 = p0.getY();
final double x2 = p1.getX();
final double y2 = p1.getY();
return quadrant(x1, y1, x2, y2);
}
}