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 ij.process.FloatProcessor;
013
014import static imagingbook.common.math.Arithmetic.sqr;
015
016/**
017 * <p>
018 * Represents a hierarchical Gaussian scale space. See Secs. 25.1.2 and 25.1.4 of [1] for more details.
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 GaussianScaleSpace extends HierarchicalScaleSpace<GaussianOctave> {
029
030        /**
031         * Constructor, builds a {@link GaussianScaleSpace} from a {@link FloatProcessor}.
032         * 
033         * @param fp a {@link FloatProcessor}
034         * @param P the number of scale space octaves
035         * @param Q the number of scale steps (levels) per octave
036         * @param sigma_s the assumed sampling scale (typ. 0.5)
037         * @param sigma_0 the base scale of level 0 
038         * @param botLevel the index of the bottom level in each octave
039         * @param topLevel the index of the to level in each octave
040         */
041        public GaussianScaleSpace(FloatProcessor fp, int P, int Q, double sigma_s, double sigma_0, int botLevel, int topLevel) {
042                super(P, Q, sigma_s, sigma_0, botLevel, topLevel);      
043                build(fp);
044        }
045        
046        // -------------------------------------------------------------
047        
048        private final void build(FloatProcessor fp) {
049                double scaleA = getAbsoluteScale(0, botLevel) ;                 // absolute scale of level(0,-1) = bottom
050                double scaleR = Math.sqrt(sqr(scaleA) - sqr(sigma_s));  // relative scale from sampling scale
051                
052                float[] data = ((float[])fp.getPixels()).clone();
053                ScaleLevel Ginit = new ScaleLevel(fp.getWidth(), fp.getHeight(), data, scaleR);
054                Ginit.filterGaussian(scaleR);
055                
056                // create the bottom octave
057                setOctave(0, new GaussianOctave(0, Q, Ginit, botLevel, topLevel, sigma_0));
058                // build the remaining Q-1 octaves:
059                for (int p = 1; p < P; p++) {
060                        // get the top level of the previous octave and decimate it:
061                        ScaleLevel Gbase = getOctave(p-1).getLevel(Q-1).decimate();
062                        setOctave(p, new GaussianOctave(p, Q, Gbase, botLevel, topLevel, sigma_0));
063                }
064        }
065        
066}