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.convolution;
031
032import org.openimaj.image.FImage;
033import org.openimaj.math.util.FloatArrayStatsUtils;
034
035/**
036 * Disk - a circular averaging filter.
037 * 
038 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
039 *
040 */
041public class Disk extends FConvolution {
042        
043        /**
044         * Default constructor. Makes a disk averaging filter
045         * with the given radius.
046         * @param radius the radius.
047         */
048        public Disk(int radius) {
049                super(createKernelImage(radius));
050        }
051
052        /**
053         * Makes a disk averaging filter with the given radius.
054         * @param radius
055         * @return the filter image
056         */
057        public static FImage createKernelImage(int radius) {
058                int sze = 2*radius+1;
059                FImage f = new FImage(sze, sze);
060                int hsz = (sze-1)/2;
061                
062                for (int y=-hsz, j=0; y<hsz; y++, j++) {
063                        for (int x=-hsz, i=0; x<hsz; x++, i++) {
064                                double rad = Math.sqrt(x*x + y*y);
065                                f.pixels[j][i] = rad < radius ? 1 : 0;                          
066                        }
067                }
068                float sum = FloatArrayStatsUtils.sum(f.pixels);
069                return f.divideInplace(sum);            
070        }
071}