001/*******************************************************************************
002 * This software is provided as a supplement to the authors' textbooks on digital
003 * image processing published by Springer-Verlag in various languages and editions.
004 * Permission to use and distribute this software is granted under the BSD 2-Clause
005 * "Simplified" License (see http://opensource.org/licenses/BSD-2-Clause).
006 * Copyright (c) 2006-2023 Wilhelm Burger, Mark J. Burge. All rights reserved.
007 * Visit https://imagingbook.com for additional details.
008 ******************************************************************************/
009
010package imagingbook.common.threshold.global;
011
012/**
013 * <p>
014 * Simple global thresholder which sets the threshold centered between the image's minimum and maximum pixel value. See
015 * Sec. 9.1.2 of [1] for additional details (Eq. 9.12).
016 * </p>
017 * <p>
018 * [1] W. Burger, M.J. Burge, <em>Digital Image Processing &ndash; An Algorithmic Introduction</em>, 3rd ed, Springer
019 * (2022).
020 * </p>
021 *
022 * @author WB
023 * @version 2022/08/23
024 */
025public class MinMaxThresholder implements GlobalThresholder {
026        
027        public MinMaxThresholder() {
028                super();
029        }
030
031        @Override
032        public float getThreshold(int[] h) {
033                // calculate mean of entire image:
034                int K = h.length;
035                int minVal, maxVal;
036                
037                // find the min. pixel value
038                for (minVal = 0; minVal < K; minVal++) {
039                        if (h[minVal] > 0) {
040                                break;
041                        }
042                }
043                
044                // find the max. pixel value
045                for (maxVal = K - 1; maxVal >= 0; maxVal--) {
046                        if (h[maxVal] > 0) {
047                                break;
048                        }
049                }
050                
051                if (minVal < maxVal)
052                        return (float) Math.floor((minVal + maxVal) / 2.0);
053                else
054                        return NoThreshold;
055        }
056}