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.image.interpolation;
011import imagingbook.common.image.access.ScalarAccessor;
012
013/**
014 * <p>
015 * A {@link PixelInterpolator} implementing bilinear interpolation in 2D. See Sec. 22.5.2 of [1] for additional
016 * details.
017 * </p>
018 * <p>
019 * [1] W. Burger, M.J. Burge, <em>Digital Image Processing &ndash; An Algorithmic Introduction</em>, 3rd ed, Springer
020 * (2022).
021 * </p>
022 *
023 * @author WB
024 */
025public class BilinearInterpolator implements PixelInterpolator {
026        
027        /**
028         * Constructor.
029         */
030        public BilinearInterpolator() {
031        }
032
033        @Override
034        public float getInterpolatedValue(ScalarAccessor ia, double x, double y) {
035                final int u = (int) Math.floor(x);
036                final int v = (int) Math.floor(y);
037                
038                final double a = x - u; // a >= 0
039                final double b = y - v; // b >= 0
040                
041                final double A = ia.getVal(u, v);
042                final double B = ia.getVal(u + 1, v);
043                final double C = ia.getVal(u, v + 1);
044                final double D = ia.getVal(u + 1, v + 1);
045                
046                final double E = A + a * (B - A);
047                final double F = C + a * (D - C);
048                final double G = E + b * (F - E);
049                
050                return (float) G;
051        }
052
053        /**
054         * Corresponds to function w_lin(x), see Eqn. 22.11 in [1].
055         * TODO: test, not used currently.
056         */
057        @Override
058        public double getWeight(double x) {
059                x = Math.abs(x);
060                return (x < 1) ? (1.0 - x) : 0.0;
061        }
062        
063}