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.threshold;
031
032import org.openimaj.image.FImage;
033import org.openimaj.image.processing.algorithm.FilterSupport;
034import org.openimaj.image.processing.algorithm.LocalContrastFilter;
035import org.openimaj.image.processing.convolution.AverageBoxFilter;
036
037/**
038 * Bernsen's adaptive local thresholding.
039 * 
040 * @see <a
041 *      href="http://fiji.sc/wiki/index.php/Auto_Local_Threshold">http://fiji.sc/wiki/index.php/Auto_Local_Threshold</a>
042 * 
043 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
044 * 
045 */
046public class AdaptiveLocalThresholdBernsen extends AbstractLocalThreshold {
047        private float threshold;
048
049        /**
050         * Construct the thresholding operator with the given patch size (assumed
051         * square)
052         * 
053         * @param threshold
054         *            the contrast threshold
055         * @param size
056         *            size of the local image patch
057         */
058        public AdaptiveLocalThresholdBernsen(float threshold, int size) {
059                super(size);
060                this.threshold = threshold;
061        }
062
063        /**
064         * Construct the thresholding operator with the given patch size
065         * 
066         * @param threshold
067         *            the contrast threshold
068         * @param size_x
069         *            width of patch
070         * @param size_y
071         *            height of patch
072         */
073        public AdaptiveLocalThresholdBernsen(float threshold, int size_x, int size_y) {
074                super(size_x, size_y);
075                this.threshold = threshold;
076        }
077
078        @Override
079        public void processImage(FImage image) {
080                final FImage contrast = image.process(new LocalContrastFilter(FilterSupport.createBlockSupport(sizeX, sizeY)));
081                final FImage avg = image.process(new AverageBoxFilter(sizeX, sizeY));
082
083                final float[][] cpix = contrast.pixels;
084                final float[][] mpix = avg.pixels;
085                final float[][] ipix = image.pixels;
086
087                for (int y = 0; y < image.height; y++) {
088                        for (int x = 0; x < image.width; x++) {
089                                if (cpix[y][x] < threshold)
090                                        ipix[y][x] = (mpix[y][x] >= 128) ? 1 : 0;
091                                else
092                                        ipix[y][x] = (ipix[y][x] >= mpix[y][x]) ? 1 : 0;
093                        }
094                }
095        }
096}