polygon Center Of Mass - Java 2D Graphics

Java examples for 2D Graphics:Polygon

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Description

polygon Center Of Mass

Demo Code

/*/*from w w w  . j  a  v  a  2  s  . c  o  m*/
 * This file is part of the LIRE project: http://www.semanticmetadata.net/lire
 * LIRE is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
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 * (at your option) any later version.
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 * LIRE 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 LIRE; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * We kindly ask you to refer the any or one of the following publications in
 * any publication mentioning or employing Lire:
 *
 * Lux Mathias, Savvas A. Chatzichristofis. Lire: Lucene Image Retrieval ?
 * An Extensible Java CBIR Library. In proceedings of the 16th ACM International
 * Conference on Multimedia, pp. 1085-1088, Vancouver, Canada, 2008
 * URL: http://doi.acm.org/10.1145/1459359.1459577
 *
 * Lux Mathias. Content Based Image Retrieval with LIRE. In proceedings of the
 * 19th ACM International Conference on Multimedia, pp. 735-738, Scottsdale,
 * Arizona, USA, 2011
 * URL: http://dl.acm.org/citation.cfm?id=2072432
 *
 * Mathias Lux, Oge Marques. Visual Information Retrieval using Java and LIRE
 * Morgan & Claypool, 2013
 * URL: http://www.morganclaypool.com/doi/abs/10.2200/S00468ED1V01Y201301ICR025
 *
 * Copyright statement:
 * --------------------
 * (c) 2002-2013 by Mathias Lux (mathias@juggle.at)
 *     http://www.semanticmetadata.net/lire, http://www.lire-project.net
 */
//package com.java2s;

import java.awt.geom.Point2D;

public class Main {
    public static Point2D.Double polygonCenterOfMass(
            Point2D.Double[] polygon) {
        int N = polygon.length - 1;

        double cx = 0, cy = 0;
        //        double A = signedPolygonArea(polygon);
        Point2D.Double res = new Point2D.Double();
        int i, j;
        double sumDet = 0;

        double factor = 0;
        for (i = 0; i < N; i++) {
            j = i + 1;
            factor = (polygon[i].x * polygon[j].y - polygon[j].x
                    * polygon[i].y);
            cx += (polygon[i].x + polygon[j].x) * factor;
            cy += (polygon[i].y + polygon[j].y) * factor;

            sumDet += factor;
        }
        factor = 1 / (3 * sumDet);

        //        A*=6.0;
        //        factor=1/A;
        cx *= factor;
        cy *= factor;
        res.x = cx;
        res.y = cy;
        return res;
    }
}

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