FFT.class.php
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<?php
/**
* @author Michele Andreoli <michi.andreoli[at]gmail.com>
* @name FFT.class.php
* @version 0.5 updated 06-07-2010
* @license http://opensource.org/licenses/gpl-license-php GNU Public License
* @package FFT
*/
require_once 'Complex.class.php';
/**
* Class that calculate the FFT and the inverse FFT of a 1D signal
*/
class FFT {
private $dim;
private $p;
private $ind;
private $func;
private $w1;
private $w1i;
private $w2;
/**
* Constructor for FFT class
* @param int $dim dimension of the signal
*/
public function __construct($dim) {
$this->dim = $dim;
$this->p = log($this->dim, 2);
}
/**
* Calculate the FFT of a signal
* @param array<double> $func input signal
* @return array<complex> return the DFT for the signal in input
*/
public function fft($func) {
$this->func = $func;
for ($i = 0; $i < $this->dim; $i++)
$this->w1[$i] = new Complex($func[$i], 0);
$w[0] = new Complex(1, 0);
$w[1] = new Complex(cos((-2 * M_PI) / $this->dim), sin((-2 * M_PI) / $this->dim));
for ($i = 2; $i < $this->dim; $i++)
$w[$i] = Complex::Cmul($w[$i-1], $w[1]);
return $this->calculate($w);
}
/**
* Calculate the inverse FFT of a signal
* @param array<complex> $func input signal
* @return array<complex> result of inverse FFT for the signal in input
*/
public function ifft($func) {
$this->func = $func;
$norm = 1 / $this->dim;
for ($i = 0; $i < $this->dim; $i++)
$this->w1[$i] = new Complex($func[$i]->getReal(), $func[$i]->getImag());
$w[0] = new Complex(1, 0);
$w[1] = new Complex(cos((2 * M_PI) / $this->dim), sin((2 * M_PI) / $this->dim));
for ($i = 2; $i < $this->dim; $i++)
$w[$i] = Complex::Cmul($w[$i-1], $w[1]);
$this->w1i = $this->calculate($w);
for ($i = 0; $i < $this->dim; $i++)
$this->w1i[$i] = Complex::RCmul($norm, $this->w1i[$i]);
return $this->w1i;
}
private function calculate($w) {
$k = 1;
$ind[0] = 0;
for ($j = 0; $j < $this->p; $j++) {
for ($i = 0; $i < $k; $i++) {
$ind[$i] *= 2;
$ind[$i+$k] = $ind[$i] + 1;
}
$k *= 2;
}
for ($i = 0; $i < $this->p; $i++) {
$indw = 0;
for ($j = 0; $j < pow(2, $i); $j++) {
$inf = ($this->dim / pow(2, $i)) * $j;
$sup = (($this->dim / pow(2, $i)) * ($j+1)) - 1;
$comp = ($this->dim / pow(2, $i)) / 2;
for ($k = $inf; $k <= floor($inf+(($sup-$inf)/2)); $k++)
$this->w2[$k] = Complex::Cadd(Complex::Cmul($this->w1[$k], $w[0]), Complex::Cmul($this->w1[$k+$comp], $w[$ind[$indw]]));
$indw++;
for ($k = floor($inf+(($sup-$inf)/2)+1); $k <= $sup; $k++)
$this->w2[$k] = Complex::Cadd(Complex::Cmul($this->w1[$k], $w[$ind[$indw]]), Complex::Cmul($this->w1[$k-$comp], $w[0]));
$indw++;
}
for($j = 0; $j < $this->dim; $j++)
$this->w1[$j] = $this->w2[$j];
}
for ($i = 0; $i < $this->dim; $i++)
$this->w1[$i] = $this->w2[$ind[$i]];
return $this->w1;
}
/**
* Getter for the FFT
* @return array<complex> get the FFT of the signal
*/
public function getFFT() {
return $this->w1;
}
/**
* Getter for the inverse FFT
* @return array<complex> get the inverse FFT of the signal
*/
public function getIFFT() {
return $this->w1i;
}
/**
* Get the absolute value of the signal
* @param array<complex> $fft
* @return array<complex> get the absolute value of FFT
*/
public function getAbsFFT($w) {
for ($i = 0; $i < $this->dim; $i++)
$temp[$i] = Complex::Cabs($w[$i]);
return $temp;
}
/**
* Getter for the dimension of the signal
* @return int return the dimension of the signal
*/
public function getDim() {
return $this->dim;
}
/**
* Convert an array of double into an array of complex
* @param array<double> $func
* @return array<complex> return an array of complex
*/
public function doubleToComplex($func) {
for ($i = 0; $i < count($func); $i++)
$aux[$i] = new Complex($func[$i], 0);
return $aux;
}
/**
* Convert an array of complex into an array of double
* @param array<complex> $func
* @return array<double> return an array of double
*/
public function complexToDouble($func) {
for ($i = 0; $i < count($func); $i++)
$aux[$i] = $func[$i]->getReal();
return $aux;
}
}
?>