001/**
002 *
003 * Copyright (c) 2014, the Railo Company Ltd. All rights reserved.
004 *
005 * This library is free software; you can redistribute it and/or
006 * modify it under the terms of the GNU Lesser General Public
007 * License as published by the Free Software Foundation; either 
008 * version 2.1 of the License, or (at your option) any later version.
009 * 
010 * This library is distributed in the hope that it will be useful,
011 * but WITHOUT ANY WARRANTY; without even the implied warranty of
012 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
013 * Lesser General Public License for more details.
014 * 
015 * You should have received a copy of the GNU Lesser General Public 
016 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
017 * 
018 **/
019package lucee.runtime.img.interpolation;
020
021public class Lanczos implements Interpolation
022{
023    public double f(double x) {
024        if (x < -3.0)
025            return 0.0;
026        if (x < 0.0)
027            return sinc(-x) * sinc(-x / 3.0);
028        if (x < 3.0)
029            return sinc(x) * sinc(x / 3.0);
030        return 0.0;
031    }
032    
033    public double sinc(double x) {
034        x *= 3.141592653589793;
035        if (x != 0.0)
036            return Math.sin(x) / x;
037        return 1.0;
038    }
039    
040    public double getSupport() {
041        return 3.0;
042    }
043}