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.algorithm;
031
032import java.util.Set;
033
034import org.openimaj.image.FImage;
035import org.openimaj.image.pixel.Pixel;
036import org.openimaj.image.processor.SinglebandImageProcessor;
037
038/**
039 * Local contrast filter; replaces each pixel with the difference between the
040 * maximum and minimum of its neighbours.
041 * 
042 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
043 * 
044 */
045public class LocalContrastFilter implements SinglebandImageProcessor<Float, FImage> {
046        private Set<Pixel> support;
047
048        /**
049         * Construct with the given support region for selecting pixels to take the
050         * median from. The support mask is a set of <code>n</code> relative x, y
051         * offsets from the pixel currently being processed, and can be created
052         * using the methods or constants in the {@link FilterSupport} class.
053         * 
054         * @param support
055         *            the support coordinates
056         */
057        public LocalContrastFilter(Set<Pixel> support) {
058                this.support = support;
059        }
060
061        @Override
062        public void processImage(FImage image) {
063                final FImage tmpImage = new FImage(image.width, image.height);
064                float min;
065                float max;
066
067                for (int y = 0; y < image.height; y++) {
068                        for (int x = 0; x < image.width; x++) {
069                                min = Float.MAX_VALUE;
070                                max = -Float.MAX_VALUE;
071                                for (final Pixel sp : support) {
072                                        final int xx = x + sp.x;
073                                        final int yy = y + sp.y;
074
075                                        if (xx >= 0 && xx < image.width - 1 && yy >= 0 && yy < image.height - 1) {
076                                                min = Math.min(min, image.pixels[yy][xx]);
077                                                max = Math.max(max, image.pixels[yy][xx]);
078                                        }
079                                }
080
081                                tmpImage.pixels[y][x] = max - min;
082                        }
083                }
084                image.internalAssign(tmpImage);
085        }
086}