Christoph Ruegg
13 years ago
4 changed files with 328 additions and 1 deletions
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// <copyright file="Window.cs" company="Math.NET">
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// Math.NET Numerics, part of the Math.NET Project
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// http://numerics.mathdotnet.com
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// http://github.com/mathnet/mathnet-numerics
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// http://mathnetnumerics.codeplex.com
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//
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// Copyright (c) 2009-2013 Math.NET
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//
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// Permission is hereby granted, free of charge, to any person
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// obtaining a copy of this software and associated documentation
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// files (the "Software"), to deal in the Software without
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// restriction, including without limitation the rights to use,
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// copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the
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// Software is furnished to do so, subject to the following
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// conditions:
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//
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// The above copyright notice and this permission notice shall be
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// included in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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// OTHER DEALINGS IN THE SOFTWARE.
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// </copyright>
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using System; |
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namespace MathNet.Numerics |
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{ |
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public static class Window |
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{ |
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/// <summary>
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/// Hamming window. Named after Richard Hamming.
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/// </summary>
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public static double[] Hamming(int width) |
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{ |
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const double a = 0.53836; |
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const double b = -0.46164; |
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double phaseStep = (2.0*Math.PI)/(width - 1.0); |
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var w = new double[width]; |
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for (int i = 0; i < w.Length; i++) |
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{ |
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w[i] = a + b*Math.Cos(i*phaseStep); |
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} |
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return w; |
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} |
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/// <summary>
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/// Hann window. Named after Julius von Hann.
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/// </summary>
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public static double[] Hann(int width) |
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{ |
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double phaseStep = (2.0*Math.PI)/(width - 1.0); |
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var w = new double[width]; |
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for (int i = 0; i < w.Length; i++) |
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{ |
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w[i] = 0.5 - 0.5*Math.Cos(i*phaseStep); |
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} |
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return w; |
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} |
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/// <summary>
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/// Cosine window.
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/// </summary>
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public static double[] Cosine(int width) |
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{ |
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double phaseStep = Math.PI/(width - 1.0); |
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var w = new double[width]; |
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for (int i = 0; i < w.Length; i++) |
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{ |
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w[i] = Math.Sin(i*phaseStep); |
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} |
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return w; |
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} |
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/// <summary>
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/// Lanczos window.
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/// </summary>
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public static double[] Lanczos(int width) |
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{ |
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double phaseStep = 2.0/(width - 1.0); |
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var w = new double[width]; |
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for (int i = 0; i < w.Length; i++) |
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{ |
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w[i] = Trig.Sinc(i*phaseStep - 1.0); |
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} |
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return w; |
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} |
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/// <summary>
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/// Gauss window.
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/// </summary>
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public static double[] Gauss(int width, double sigma) |
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{ |
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double a = (width - 1)/2.0; |
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var w = new double[width]; |
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for (int i = 0; i < w.Length; i++) |
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{ |
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double exponent = (i - a)/(sigma*a); |
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w[i] = Math.Exp(-0.5*exponent*exponent); |
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} |
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return w; |
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} |
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/// <summary>
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/// Blackman window.
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/// </summary>
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public static double[] Blackman(int width) |
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{ |
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const double alpha = 0.16; |
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const double a = 0.5 - 0.5*alpha; |
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const double b = 0.5*alpha; |
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int last = width - 1; |
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double c = 2.0*Math.PI/last; |
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double d = 2.0*c; |
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var w = new double[width]; |
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for (int i = 0; i < w.Length; i++) |
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{ |
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w[i] = a |
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- 0.5*Math.Cos(i*c) |
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+ b*Math.Cos(i*d); |
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} |
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return w; |
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} |
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/// <summary>
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/// Blackman-Harris window.
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/// </summary>
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public static double[] BlackmanHarris(int width) |
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{ |
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const double a = 0.35875; |
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const double b = -0.48829; |
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const double c = 0.14128; |
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const double d = -0.01168; |
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int last = width - 1; |
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double e = 2.0*Math.PI/last; |
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double f = 2.0*e; |
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double g = 3.0*e; |
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var w = new double[width]; |
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for (int i = 0; i < w.Length; i++) |
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{ |
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w[i] = a |
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+ b*Math.Cos(e*i) |
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+ c*Math.Cos(f*i) |
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+ d*Math.Cos(g*i); |
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} |
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return w; |
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} |
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/// <summary>
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/// Blackman-Nuttall window.
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/// </summary>
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public static double[] BlackmanNuttall(int width) |
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{ |
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const double a = 0.3635819; |
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const double b = -0.4891775; |
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const double c = 0.1365995; |
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const double d = -0.0106411; |
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int last = width - 1; |
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double e = 2.0*Math.PI/last; |
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double f = 2.0*e; |
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double g = 3.0*e; |
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var w = new double[width]; |
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for (int i = 0; i < w.Length; i++) |
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{ |
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w[i] = a |
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+ b*Math.Cos(e*i) |
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+ c*Math.Cos(f*i) |
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+ d*Math.Cos(g*i); |
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} |
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return w; |
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} |
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/// <summary>
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/// Bartlett window.
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/// </summary>
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public static double[] Bartlett(int width) |
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{ |
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int last = width - 1; |
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double a = 2.0/last; |
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double b = last/2.0; |
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var w = new double[width]; |
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for (int i = 0; i < w.Length; i++) |
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{ |
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w[i] = a*(b - Math.Abs(i - b)); |
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} |
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return w; |
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} |
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/// <summary>
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/// Bartlett-Hann window.
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/// </summary>
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public static double[] BartlettHann(int width) |
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{ |
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const double a = 0.62; |
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const double b = -0.48; |
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const double c = -0.38; |
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int last = width - 1; |
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double d = 1.0/last; |
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double e = 2.0*Math.PI/last; |
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var w = new double[width]; |
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for (int i = 0; i < w.Length; i++) |
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{ |
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w[i] = a |
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+ b*Math.Abs(i*d - 0.5) |
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+ c*Math.Cos(i*e); |
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} |
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return w; |
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} |
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/// <summary>
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/// Nuttall window.
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/// </summary>
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public static double[] Nuttall(int width) |
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{ |
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const double a = 0.355768; |
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const double b = -0.487396; |
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const double c = 0.144232; |
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const double d = -0.012604; |
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int last = width - 1; |
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double e = 2.0*Math.PI/last; |
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double f = 2.0*e; |
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double g = 3.0*e; |
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var w = new double[width]; |
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for (int i = 0; i < w.Length; i++) |
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{ |
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w[i] = a |
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+ b*Math.Cos(e*i) |
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+ c*Math.Cos(f*i) |
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+ d*Math.Cos(g*i); |
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} |
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return w; |
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} |
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/// <summary>
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/// Flat top window.
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/// </summary>
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public static double[] FlatTop(int width) |
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{ |
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const double a = 1.0; |
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const double b = -1.93; |
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const double c = 1.29; |
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const double d = -0.388; |
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const double e = 0.032; |
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int last = width - 1; |
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double f = 2.0*Math.PI/last; |
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double g = 2.0*f; |
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double h = 3.0*f; |
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double k = 4.0*f; |
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double[] w = new double[width]; |
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for (int i = 0; i < w.Length; i++) |
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{ |
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w[i] = a |
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+ b*Math.Cos(f*i) |
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+ c*Math.Cos(g*i) |
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+ d*Math.Cos(h*i) |
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+ e*Math.Cos(k*i); |
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} |
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return w; |
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} |
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/// <summary>
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/// Uniform rectangular (dirichlet) window.
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/// </summary>
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public static double[] Dirichlet(int width) |
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{ |
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var w = new double[width]; |
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for (int i = 0; i < w.Length; i++) |
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{ |
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w[i] = 1.0; |
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} |
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return w; |
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} |
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/// <summary>
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/// Triangular window.
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/// </summary>
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public static double[] Triangular(int width) |
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{ |
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double a = 2.0/width; |
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double b = width/2.0; |
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double c = (width - 1)/2.0; |
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var w = new double[width]; |
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for (int i = 0; i < w.Length; i++) |
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{ |
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w[i] = a*(b - Math.Abs(i - c)); |
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} |
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return w; |
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} |
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} |
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} |
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