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.sift.scalespace;
011
012import static java.lang.Math.pow;
013import static java.lang.Math.sqrt;
014
015/**
016 * <p>
017 * Represents a single "octave" in a hierarchical Gaussian scale space. See Secs. 25.1.2 and 25.1.4 of [1] for more
018 * details. This class defines no public constructor.
019 * </p>
020 * <p>
021 * [1] W. Burger, M.J. Burge, <em>Digital Image Processing &ndash; An Algorithmic Introduction</em>, 3rd ed, Springer
022 * (2022).
023 * </p>
024 *
025 * @author WB
026 * @version 2022/11/20
027 */
028public class GaussianOctave extends ScaleOctave<ScaleLevel> {
029        
030        /**
031         * Constructor (non-public).
032         * @param p the index of the new octave
033         * @param Q the number of scale levels inside the new octave
034         * @param Gbot the bottom scale elevel to start with
035         * @param botIndex the bottom scale level index
036         * @param topIndex the top scale level index
037         * @param sigma_0 the scale at scale level with index 0
038         */
039        GaussianOctave(int p, int Q, ScaleLevel Gbot, int botIndex, int topIndex, double sigma_0) {
040                // initialize generic octave structures (no scale levels yet):
041                super(p, Q, Gbot.getWidth(), Gbot.getHeight(), botIndex, topIndex, sigma_0);
042                
043                // assign the bottom octave level:
044                double sigmaA_bot = getAbsoluteScale(p, botIndex);
045                this.setLevel(botIndex, Gbot);
046                Gbot.setAbsoluteScale(sigmaA_bot);
047                
048                // create octave levels q = botIndex + 1,...,topIndex
049                for (int q = botIndex + 1; q <= topIndex; q++) {
050                        double sigmaA = getAbsoluteScale(p, q); // absolute scale of level q
051                        // relative scale from bottom level (q = -1):
052                        double sigmaR = sigma_0 * sqrt(pow(2, 2.0 * q/Q) - pow(2, -2.0/Q)); 
053                        
054                        // duplicate the botton scale level with the new absolute scale:
055                        ScaleLevel G_pq = new ScaleLevel(Gbot, sigmaA);
056                        // filter the new scale level (destructively):
057                        G_pq.filterGaussian(sigmaR);
058                        // insert the new scale level into this scale octave
059                        this.setLevel(q, G_pq);
060                }
061        }
062        
063}