/*FreeMind - A Program for creating and viewing Mindmaps
*Copyright (C) 2000-2001 Joerg Mueller <joergmueller@bigfoot.com>
*See COPYING for Details
*
*This program is free software; you can redistribute it and/or
*modify it under the terms of the GNU General Public License
*as published by the Free Software Foundation; either version 2
*of the License, or (at your option) any later version.
*
*This program 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 General Public License for more details.
*
*You should have received a copy of the GNU General Public License
*along with this program; if not, write to the Free Software
*Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
// ConvexHull.java (c) fc
//
// Adapted from Sedgewick, Algorithms
//
package freemind.view.mindmapview;
import java.awt.Point;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedList;
import java.util.ListIterator;
import java.util.Vector;
public class ConvexHull {
protected int ccw(Point p0, Point p1, Point p2) {
int dx1, dx2, dy1, dy2;
dx1 = p1.x - p0.x;
dy1 = p1.y - p0.y;
dx2 = p2.x - p0.x;
dy2 = p2.y - p0.y;
int comp = dx1 * dy2 - dy1 * dx2;
if (comp > 0)
return 1;
if (comp < 0)
return -1;
if ((dx1 * dx2 < 0) || (dy1 * dy2 < 0))
return -1;
if (dx1 * dx1 + dy1 * dy1 >= dx2 * dx2 + dy2 * dy2)
return 0;
return 1;
}
protected class thetaComparator implements Comparator {
Point p0;
public thetaComparator(Point p0) {
this.p0 = new Point(p0);
}
/* the < relation. */
public int compare(Object p1, Object p2) {
double comp = theta(p0, (Point) p1) - theta(p0, (Point) p2);
if (((Point) p1).equals(p2))
return 0;
if (comp > 0)
return 1;
if (comp < 0)
return -1;
// here, the points are collinear with p0 (i.e. p0,p1,p2 are on one
// line). So we reverse the compare relation to get that nearer
// points are greater.
// we take the point that is nearer to p0:
int dx1, dx2, dy1, dy2;
dx1 = ((Point) p1).x - ((Point) p0).x;
dy1 = ((Point) p1).y - ((Point) p0).y;
dx2 = ((Point) p2).x - ((Point) p0).x;
dy2 = ((Point) p2).y - ((Point) p0).y;
int comp2 = (dx1 * dx1 + dy1 * dy1) - (dx2 * dx2 + dy2 * dy2);
if (comp2 > 0)
return -1;
if (comp2 < 0)
return 1;
return 0;
}
double theta(Point p1, Point p2) {
int dx, dy, ax, ay;
double t;
dx = p2.x - p1.x;
ax = Math.abs(dx);
dy = p2.y - p1.y;
ay = Math.abs(dy);
if ((dx == 0) && (dy == 0))
t = 0;
else
t = ((double) dy) / ((double) (ax + ay));
if (dx < 0)
t = 2f - t;
else {
if (dy < 0)
t = 4f + t;
}
return t * 90f;
}
}
Vector doGraham(Vector p) {
int i, j, min, M;
Point t;
min = 0;
// search for minimum:
for (i = 1; i < p.size(); ++i) {
if (((Point) p.get(i)).y < ((Point) p.get(min)).y)
min = i;
}
// continue along the values with same y component
for (i = 0; i < p.size(); ++i) {
if ((((Point) p.get(i)).y == ((Point) p.get(min)).y)
&& (((Point) p.get(i)).x > ((Point) p.get(min)).x)) {
min = i;
}
}
// swap:
t = (Point) p.get(0);
p.set(0, p.get(min));
p.set(min, t);
thetaComparator comp = new thetaComparator((Point) p.get(0));
Collections.sort(p, comp);
p.add(0, new Point((Point) p.get(p.size() - 1))); // the first is the
// last.
M = 3;
for (i = 4; i < p.size(); ++i) {
while (ccw((Point) p.get(M), (Point) p.get(M - 1), (Point) p.get(i)) >= 0) {
M--;
}
M++;
// swap:
t = (Point) p.get(M);
p.set(M, p.get(i));
p.set(i, t);
}
p.remove(0);
p.setSize(M);
return p;
}
public Vector/* <newPoint> */calculateHull(LinkedList coordinates) {
Vector q = new Vector();
int i = 0;
ListIterator coordinates_it = coordinates.listIterator();
while (coordinates_it.hasNext()) {
q.add(coordinates_it.next());
}
Vector res = doGraham(q);
return res;
}
}