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.adaptive;
011
012import ij.IJ;
013import ij.plugin.filter.RankFilters;
014import ij.process.ByteProcessor;
015import ij.process.FloatProcessor;
016import imagingbook.common.ij.DialogUtils.DialogLabel;
017import imagingbook.common.util.ParameterBundle;
018
019
020/**
021 * <p>
022 * This is an implementation of the adaptive thresholder proposed by Bernsen in [1]. It uses a circular support region
023 * implemented with ImageJ's built-in rank-filter methods. See Sec. 9.2.1 of [2] for a detailed description.
024 * </p>
025 * <p>
026 * [1] J. Bernsen. Dynamic thresholding of grey-level images. In "Proceedings of the International Conference on Pattern
027 * Recognition (ICPR)", pp. 1251–1255, Paris (October 1986). IEEE Computer Society. <br> [2] W. Burger, M.J. Burge,
028 * <em>Digital Image Processing &ndash; An Algorithmic Introduction</em>, 3rd ed, Springer (2022).
029 * </p>
030 *
031 * @author WB
032 * @version 2022/04/02
033 */
034public class BernsenThresholder implements AdaptiveThresholder {
035        
036        /**
037         * Parameters for class {@link BernsenThresholder}.
038         */
039        public static class Parameters implements ParameterBundle<BernsenThresholder> {
040                /** Radius of circular support region */ 
041                @DialogLabel("Radius")
042                public int radius = 15;
043                /** Minimum contrast */ 
044                @DialogLabel("Min. contrast")
045                public double cmin = 15;
046                /** Background type (see {@link BackgroundMode}) */
047                @DialogLabel("Background mode")
048                public BackgroundMode bgMode = BackgroundMode.DARK;
049        }
050        
051        // --------------------------------------------
052        
053        private final Parameters params;
054        
055        /**
056         * Constructor using default parameters.
057         */
058        public BernsenThresholder() {
059                this(new Parameters());
060        }
061        
062        /**
063         * Constructor using specified parameters.
064         * @param params an instance of {@link Parameters}
065         */
066        public BernsenThresholder(Parameters params) {
067                this.params = params;
068        }
069
070        @Override
071        public FloatProcessor getThreshold(ByteProcessor I) {
072                final int W = I.getWidth();
073                final int H = I.getHeight();
074                ByteProcessor Imin = (ByteProcessor) I.duplicate();
075                ByteProcessor Imax = (ByteProcessor) I.duplicate();
076
077                RankFilters rf = new RankFilters();
078                rf.rank(Imin, params.radius, RankFilters.MIN);  // minimum filter
079                rf.rank(Imax, params.radius, RankFilters.MAX);  // maximum filter
080
081                // new ImagePlus("Imin", Imin).show();
082                // new ImagePlus("Imax", Imax).show();
083
084                // ByteProcessor Contrast = (ByteProcessor) Imax.duplicate();
085                // for (int v = 0; v < H; v++) {
086                //      for (int u = 0; u < W; u++) {
087                //              Contrast.set(u, v, Contrast.get(u, v) - Imin.get(u, v));
088                //      }
089                // }
090                // new ImagePlus("Contrast", Contrast).show();
091
092                // threshold surface
093                FloatProcessor Q = new FloatProcessor(W, H);
094                // default threshold for regions with insufficient contrast
095                float qq = (params.bgMode == BackgroundMode.DARK) ? 256 : -1;
096
097
098                for (int v = 0; v < H; v++) {
099                        for (int u = 0; u < W; u++) {
100                                int gMin = Imin.get(u, v);
101                                int gMax = Imax.get(u, v);
102                                int c = gMax - gMin;                    // local contrast
103                                if (c >= params.cmin)
104                                        Q.setf(u, v, 0.5f * (gMin + gMax));
105                                else
106                                        Q.setf(u, v, qq);
107                        }
108                }
109                return Q;
110        }
111
112}