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.ImagePlus;
013import ij.plugin.filter.RankFilters;
014import ij.process.ByteProcessor;
015import ij.process.FloatProcessor;
016import imagingbook.common.ij.DialogUtils;
017import imagingbook.common.util.ParameterBundle;
018
019/**
020 * <p>
021 * This is an implementation of the adaptive thresholder proposed in [1]. See also Sec. 9.2 (Eq. 9.74) of [2].
022 * </p>
023 * <p>
024 * [1] Adaptive thresholder as proposed in J. Sauvola and M. Pietikäinen, "Adaptive document image binarization",
025 * Pattern Recognition 33(2), 1135-1143 (2000). <br> [2] W. Burger, M.J. Burge, <em>Digital Image Processing &ndash; An
026 * Algorithmic Introduction</em> 3rd ed, Springer (2022).
027 * </p>
028 *
029 * @author WB
030 * @version 2022/08/01
031 */
032public class SauvolaThresholder implements AdaptiveThresholder {
033        
034        /**
035         * Parameters for class {@link SauvolaThresholder}.
036         */
037        public static class Parameters implements ParameterBundle<SauvolaThresholder> {
038                @DialogUtils.DialogLabel("Radius")
039                public int radius = 15;
040                @DialogUtils.DialogLabel("kappa")
041                public double kappa = 0.5;
042                @DialogUtils.DialogLabel("sigma_max")
043                public double sigmaMax = 128;
044                @DialogUtils.DialogLabel("Background mode")
045                public BackgroundMode bgMode = BackgroundMode.DARK;
046        }
047
048        private final Parameters params;
049        
050        public SauvolaThresholder() {
051                this(new Parameters());
052        }
053        
054        public SauvolaThresholder(Parameters params) {
055                this.params = params;
056        }
057        
058        @Override
059        public FloatProcessor getThreshold(ByteProcessor I) {
060                FloatProcessor Imean = I.convertToFloatProcessor();
061                FloatProcessor Isigma = (FloatProcessor) Imean.duplicate();
062                
063                RankFilters rf = new RankFilters();
064                rf.rank(Imean, params.radius, RankFilters.MEAN);
065                // new ImagePlus("Imean", Imean). show();
066                
067                rf.rank(Isigma, params.radius, RankFilters.VARIANCE);
068                Isigma.sqrt();
069                // new ImagePlus("Isigma", Isigma). show();
070                
071                final int W = I.getWidth();
072                final int H = I.getHeight();
073                final float kappa = (float) params.kappa;
074                final float sigmaMax = (float) params.sigmaMax;
075                final boolean darkBg = (params.bgMode == BackgroundMode.DARK);
076
077                FloatProcessor DIFF = new FloatProcessor(W, H);
078                FloatProcessor Q = new FloatProcessor(W, H);
079                for (int v = 0; v < H; v++) {
080                        for (int u = 0; u < W; u++) {
081                                final float sigmaR = Isigma.getf(u, v);
082                                final float meanR = Imean.getf(u, v);
083                                final float diff = kappa * (sigmaR / sigmaMax - 1);
084                                DIFF.setf(u, v, diff);
085                                float q = (darkBg) ? meanR * (1 - diff) : meanR * (1 + diff);
086                                // if (q < 0) q = 0;            // necessary?
087                                // if (q > 255) q = 255;
088                                Q.setf(u, v, q);
089                        }
090                }
091
092                // new ImagePlus("DIFF", DIFF). show();
093                return Q;
094        }
095        
096}