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 ******************************************************************************/
009package imagingbook.spectral.dft;
010
011/**
012 * Scaling mode used for the DFT.
013 */
014public enum ScalingMode {
015        /**
016         * Same scaling factor (1/sqrt(M)) is applied in forward and inverse transform.
017         */
018        DEFAULT {
019                @Override
020                public double getScale(int M, boolean forward) {
021                        return 1.0 / Math.sqrt(M);
022                }
023        },
024        
025        /**
026         * Scaling by a factor 1/M is applied to the forward transformation only.
027         */
028        FORWARD_ONLY {
029                @Override
030                public double getScale(int M, boolean forward) {
031                        return forward ? 1.0 / M : 1.0;
032                }
033        },
034        
035        /**
036         * Scaling by a factor 1/M is applied to the inverse transformation only.
037         */
038        INVERSE_ONLY {
039                @Override
040                public double getScale(int M, boolean forward) {
041                        return forward ? 1.0 : 1.0 / M;
042                }
043        };
044        
045        /**
046         * Returns the DFT scale factor for the specified data size and transformation
047         * direction.
048         * @param M the data size
049         * @param forward {@code true} for a forward, {@code false} for a inverse transform
050         * @return the scale factor
051         */
052        public abstract double getScale(int M, boolean forward);
053}