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.MedianFilter;
035
036/**
037 * Adaptive local thresholding using the median of the patch and an offset.
038 * 
039 * @see <a
040 *      href="http://homepages.inf.ed.ac.uk/rbf/HIPR2/adpthrsh.htm">http://homepages.inf.ed.ac.uk/rbf/HIPR2/adpthrsh.htm</a>
041 * 
042 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
043 * 
044 */
045public class AdaptiveLocalThresholdMedian extends AbstractLocalThreshold {
046        float offset = 0;
047
048        /**
049         * Construct the thresholding operator with the given patch size (assumed
050         * square)
051         * 
052         * @param size
053         *            size of the local image patch
054         */
055        public AdaptiveLocalThresholdMedian(int size) {
056                super(size);
057        }
058
059        /**
060         * Construct the thresholding operator with the given patch size
061         * 
062         * @param size_x
063         *            width of patch
064         * @param size_y
065         *            height of patch
066         */
067        public AdaptiveLocalThresholdMedian(int size_x, int size_y) {
068                super(size_x, size_y);
069        }
070
071        /**
072         * Construct the thresholding operator with the given patch size (assumed
073         * square) and offset
074         * 
075         * @param size
076         *            size of the local image patch
077         * @param offset
078         *            offset from the patch mean at which the threshold occurs
079         */
080        public AdaptiveLocalThresholdMedian(int size, float offset) {
081                this(size, size, offset);
082        }
083
084        /**
085         * Construct the thresholding operator with the given patch size and offset
086         * 
087         * @param size_x
088         *            width of patch
089         * @param size_y
090         *            height of patch
091         * @param offset
092         *            offset from the patch mean at which the threshold occurs
093         */
094        public AdaptiveLocalThresholdMedian(int size_x, int size_y, float offset) {
095                super(size_x, size_y);
096                this.offset = offset;
097        }
098
099        @Override
100        public void processImage(FImage image) {
101                final FImage tmp = image.process(new MedianFilter(FilterSupport.createBlockSupport(sizeX, sizeY)));
102
103                final float[][] tpix = tmp.pixels;
104                final float[][] ipix = image.pixels;
105                for (int y = 0; y < image.height; y++)
106                        for (int x = 0; x < image.width; x++)
107                                tpix[y][x] = ipix[y][x] < (tpix[y][x] - offset) ? 0f : 1f;
108
109                image.internalAssign(tmp);
110        }
111}