001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package org.openimaj.image.processing.resize.filters;
031
032import org.openimaj.image.processing.resize.ResizeFilterFunction;
033
034/**
035 * Bell (quadratic) filter for the resample function.
036 * 
037 * @author David Dupplaw (dpd@ecs.soton.ac.uk)
038 * 
039 */
040public class BellFilter implements ResizeFilterFunction
041{
042        /**
043         * The singleton instance of the filter
044         */
045        public static ResizeFilterFunction INSTANCE = new BellFilter();
046
047        @Override
048        public double getSupport()
049        {
050                return 1.5;
051        }
052
053        /**
054         * @see ResizeFilterFunction#filter(double)
055         */
056        @Override
057        public double filter(double t)
058        {
059                if (t < 0)
060                        t = -t;
061                if (t < .5)
062                        return (.75 - (t * t));
063                if (t < 1.5)
064                {
065                        t = (t - 1.5);
066                        return (.5 * (t * t));
067                }
068                return (0.0);
069        }
070}