/*
*
      
_______
                       
_____
   
_____ _____
  

*
     
|__
   
__|
                     
|
  
__ \ / ____|__ \
 

*
        
| | __ _ _ __ ___
  
______| || | (___ | |__) |
*
        
| |/ _` | '__/ __|/ _ \/ __| |
  
| |\___ \|___/
 

*
        
| | (_| | |
  
\__ \ (_) \__ \ |__| |____) | |
     

*
        
|_|\__,_|_|
  
|___/\___/|___/_____/|_____/|_|
     

*
                                                         

* -------------------------------------------------------------
*
* TarsosDSP is developed by Joren Six at IPEM, University Ghent
*
  

* -------------------------------------------------------------
*
*
  
Info:
 
http://0110.be/tag/TarsosDSP
*
  
Github:
 
https://github.com/JorenSix/TarsosDSP
*
  
Releases:
 
http://0110.be/releases/TarsosDSP/
*
  

*
  
TarsosDSP includes modified source code by various authors,
*
  
for credits and info, see README.
*
 

*/

/*
*
  
Copyright (c) 2007 - 2008 by Damien Di Fede <ddf@compartmental.net>
*
*
   
This program is free software; you can redistribute it and/or modify
*
   
it under the terms of the GNU Library General Public License as published
*
   
by the Free Software Foundation; either version 2 of the License, or
*
   
(at your option) any later version.
*
*
   
This program 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 Library General Public License for more details.
*
*
   
You should have received a copy of the GNU Library General Public
*
   
License along with this program; if not, write to the Free Software
*
   
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/


package be.tarsos.dsp.util.fft;

/**
 
* A Blackman window function.
 
*
 
* @author Damien Di Fede
 
* @author Corban Brook
 
* @see
   
<a href="http://en.wikipedia.org/wiki/Window_function#Blackman_windows">The Blackman Window</a>
 
*/

public class BlackmanWindow extends WindowFunction {
	
protected float alpha;

	
/**
	 
* Constructs a Blackman window.
	 
*
 

	 
* @param alpha
	 
*/

	
public BlackmanWindow(float alpha) {
		
this.alpha = alpha;
	
}

	
/** Constructs a Blackman window with a default alpha value of 0.16 */
	
public BlackmanWindow() {
		
this(0.16f);
	
}

  
protected float value(int length, int index){
      
float a0 = (1 - this.alpha) / 2f;
      
float a1 = 0.5f;
      
float a2 = this.alpha / 2f;

      
return a0 - a1 * (float) Math.cos(TWO_PI * index / (length - 1)) + a2 * (float) Math.cos(4 * Math.PI * index / (length - 1));
  
}
}