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BlackmanWindow.cs
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BlackmanWindow.cs
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// Accord Audio Library
// The Accord.NET Framework
// http://accord-framework.net
//
// Copyright © César Souza, 2009-2017
// cesarsouza at gmail.com
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
//
namespace Accord.Audio.Windows
{
using System;
/// <summary>
/// Blackman window.
/// </summary>
///
/// <remarks>
/// By common convention, the unqualified term Blackman window refers to α=0.16.
/// </remarks>
///
public class BlackmanWindow : WindowBase
{
/// <summary>
/// Constructs a new Blackman window.
/// </summary>
///
/// <param name="length">The length for the window.</param>
///
public BlackmanWindow(int length)
: this(0.16, length)
{
}
/// <summary>
/// Constructs a new Blackman window.
/// </summary>
///
/// <param name="alpha">Blackman's alpha</param>
/// <param name="length">The length for the window.</param>
///
public BlackmanWindow(double alpha, int length)
: base(length)
{
double a0 = (1.0 - alpha) / 2.0;
double a1 = 0.5;
double a2 = alpha / 2.0;
for (int i = 0; i < length; i++)
this[i] = (float)(a0 - a1 * Math.Cos((2.0 * System.Math.PI * i) / (length - 1))
+ a2 * Math.Cos((4.0 * System.Math.PI * i) / (length - 1)));
}
}
}