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.color.cie;
011
012import imagingbook.common.math.Arithmetic;
013
014/**
015 * <p>
016 * Enumeration of selected standard illuminants. See Sec. 14.1.3 of [1] for 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 enum StandardIlluminant implements Illuminant {
026        /** Equal energy illuminant, neutral point (5400K). */
027        N       (1.0/3, 1.0/3),
028        /** D50 standard illuminant (5000K). */
029        D50 (0.3457, 0.3585),
030        /** D55 standard illuminant (5500K). */
031        D55 (0.33411, 0.34877), 
032        /** D65 standard illuminant used for television and sRGB color space (6500K). */
033        D65 (0.3127, 0.3290),
034        /** D75 standard illuminant (7500K). */
035        D75 (0.29968, 0.31740),
036        /** Incandescent tungsten (2856K). */
037        A       (0.45117, 0.40594),
038        /** Obsolete, direct sunlight at noon (4874K). */
039        B       (0.3498, 0.3527),
040        /** Obsolete, north sky daylight (6774K). */
041        C       (0.31039, 0.31905),
042        /** Cool White Fluorescent CWF (4200K). */
043        F2      (0.37928, 0.36723),
044        /** Broad-Band Daylight Fluorescent (6500K). */
045        F7      (0.31565, 0.32951),
046        /** Narrow Band White Fluorescent (4000K). */
047        F11     (0.38543, 0.37110);
048
049        private final double x, y;
050        private final double X, Y, Z;
051        
052        private StandardIlluminant(double x, double y) {
053                if (Arithmetic.isZero(y)) {
054                        throw new IllegalArgumentException("illuminant y cannot be zero");
055                }
056                this.x = x;
057                this.y = y;
058                double[] XYZ = CieUtils.xyYToXYZ(x, y, 1);
059                this.X = XYZ[0];
060                this.Y = XYZ[1];
061                this.Z = XYZ[2];
062                // this.Y = 1.0;
063                // this.X = x * this.Y / y;
064                // this.Z = (1.0 - x - y) * this.Y / y;
065        }
066        
067        @Override
068        public double[] getXYZ() {
069                return new double[] {X, Y, Z};
070        }
071
072        @Override
073        public double[] getXy() {
074                return new double[] {x, y};
075        }
076
077        
078}