GaussWindow.java (2576B)
1 /* 2 * _______ _____ _____ _____ 3 * |__ __| | __ \ / ____| __ \ 4 * | | __ _ _ __ ___ ___ ___| | | | (___ | |__) | 5 * | |/ _` | '__/ __|/ _ \/ __| | | |\___ \| ___/ 6 * | | (_| | | \__ \ (_) \__ \ |__| |____) | | 7 * |_|\__,_|_| |___/\___/|___/_____/|_____/|_| 8 * 9 * ------------------------------------------------------------- 10 * 11 * TarsosDSP is developed by Joren Six at IPEM, University Ghent 12 * 13 * ------------------------------------------------------------- 14 * 15 * Info: http://0110.be/tag/TarsosDSP 16 * Github: https://github.com/JorenSix/TarsosDSP 17 * Releases: http://0110.be/releases/TarsosDSP/ 18 * 19 * TarsosDSP includes modified source code by various authors, 20 * for credits and info, see README. 21 * 22 */ 23 24 /* 25 * Copyright (c) 2007 - 2008 by Damien Di Fede <ddf@compartmental.net> 26 * 27 * This program is free software; you can redistribute it and/or modify 28 * it under the terms of the GNU Library General Public License as published 29 * by the Free Software Foundation; either version 2 of the License, or 30 * (at your option) any later version. 31 * 32 * This program is distributed in the hope that it will be useful, 33 * but WITHOUT ANY WARRANTY; without even the implied warranty of 34 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 35 * GNU Library General Public License for more details. 36 * 37 * You should have received a copy of the GNU Library General Public 38 * License along with this program; if not, write to the Free Software 39 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 40 */ 41 42 package be.tarsos.dsp.util.fft; 43 44 /** 45 * A Gauss window function. 46 * 47 * @author Damien Di Fede 48 * @author Corban Brook 49 * @see <a href="http://en.wikipedia.org/wiki/Window_function#Gauss_windows">The 50 * Gauss Window</a> 51 */ 52 public class GaussWindow extends WindowFunction { 53 double alpha; 54 55 /** 56 * Constructs a Gauss window function. 57 * 58 * @param alpha 59 */ 60 public GaussWindow(double alpha) { 61 if (alpha < 0.0 || alpha > 0.5) { 62 new IllegalArgumentException( 63 "Range for GaussWindow out of bounds. Value must be <= 0.5"); 64 } else { 65 this.alpha = alpha; 66 } 67 } 68 69 /** Constructs a Gauss window with a default alpha value of 0.25 */ 70 public GaussWindow() { 71 this(0.25); 72 } 73 74 protected float value(int length, int index) { 75 return (float) Math.pow(Math.E, -0.5 * Math.pow((index - (length - 1) / (double) 2) / (this.alpha * (length - 1) / (double) 2),(double) 2)); 76 } 77 }