ltl::FourierTransform< T, N > Class Template Reference
[FFTW3 interface for MArrays]

List of all members.

Public Member Functions

• FourierTransform ()

  constructor
  

• virtual ~FourierTransform ()

  destructor
  

• void FFT_Real2Complex (MArray< T, N > &A, MArray< complex< T >, N > &FFT_A)

  Real to complex (forward) fourier transform. Plan and execute the transform. Output array is not normalized.
  

• void FFT_Complex2Real (MArray< complex< T >, N > &FFT_A, MArray< T, N > &A)

  Complex to real (inverse) fourier transform. Plan and execute the transform. Output array is not normalized.
  

• void reset ()

  dispose plan and call fftw_cleanup().
  

• void FFT (MArray< complex< T >, N > &A, MArray< complex< T >, N > &FFT_A)

  Forward and inverse fourier transform. Plan and execute the transform. Output array is not normalized.
  

• void iFFT (MArray< complex< T >, N > &FFT_A, MArray< complex< T >, N > &A)
• void normalize (MArray< complex< T >, N > &A)

  normalize the array by dividing by the number of elements.
  

• void normalize (MArray< T, N > &A)
• MArray< T, N > shiftDC (MArray< T, N > &A)

  shift DC component to center of MArray.
  

• MArray< complex< T >, N > shiftDC (MArray< complex< T >, N > &A)

Protected Member Functions

• void execute ()

Protected Attributes

• unsigned mode
• fftw_plan plan

---

Detailed Description

template<typename T, int N>
class ltl::FourierTransform< T, N >

FourierTransform class

Interface to fftw3 FFT library. Currently, each call to one of the FFT methods causes a new plan to be generated. This is highly inefficient, but safe. It guarantees that pointers to the data strorage of MArray do not escape by being stored in a plan that might survive the MArray object.

All transforms leave the output array un-normalized. To normalize (divide by number of elements) call normalize().

  #include <ltl/fftw.h>

  // example of 1-dimensional FFT using fftw3 library:
  MArray<double, 1> in(size);
  MArray<std::complex<double>, 1> out(size);
  FourierTransform<double,1> FFT;

  in = 10.0 +
       20.0 * sin(indexPosDbl(in,1) / double(size) * 2.0 * M_PI * 3.0) +
       30.0 * cos(indexPosDbl(in,1) / double(size) * 2.0 * M_PI * 4.0);
  FFT.FFT_Real2Complex(in,out);
  FFT.normalize(out);
  out = merge(real(out * conj(out)) > 1e-9, out, 0);
  std::cout << out << std::endl;

---

Constructor & Destructor Documentation

template<typename T , int N>

ltl::FourierTransform< T, N >::FourierTransform

(

)

constructor

template<typename T , int N>

virtual ltl::FourierTransform< T, N >::~FourierTransform

(

)

[virtual]

destructor

---

Member Function Documentation

template<typename T , int N>

void ltl::FourierTransform< T, N >::FFT	(	MArray< complex< T >, N > &	A,
		MArray< complex< T >, N > &	FFT_A
	)

Forward and inverse fourier transform. Plan and execute the transform. Output array is not normalized.

template<typename T , int N>

void ltl::FourierTransform< T, N >::iFFT	(	MArray< complex< T >, N > &	FFT_A,
		MArray< complex< T >, N > &	A
	)

template<typename T , int N>

void ltl::FourierTransform< T, N >::FFT_Real2Complex	(	MArray< T, N > &	A,
		MArray< complex< T >, N > &	FFT_A
	)

Real to complex (forward) fourier transform. Plan and execute the transform. Output array is not normalized.

template<typename T , int N>

void ltl::FourierTransform< T, N >::FFT_Complex2Real	(	MArray< complex< T >, N > &	FFT_A,
		MArray< T, N > &	A
	)

Complex to real (inverse) fourier transform. Plan and execute the transform. Output array is not normalized.

template<typename T , int N>

void ltl::FourierTransform< T, N >::normalize

(

MArray< complex< T >, N > &

A

)

normalize the array by dividing by the number of elements.

template<typename T , int N>

void ltl::FourierTransform< T, N >::normalize

(

MArray< T, N > &

A

)

template<typename T , int N>

MArray<T,N> ltl::FourierTransform< T, N >::shiftDC

(

MArray< T, N > &

A

)

shift DC component to center of MArray.

template<typename T , int N>

MArray<complex<T>,N> ltl::FourierTransform< T, N >::shiftDC

(

MArray< complex< T >, N > &

A

)

template<typename T , int N>

void ltl::FourierTransform< T, N >::reset

(

)

[inline]

dispose plan and call fftw_cleanup().

References ltl::FourierTransform< T, N >::mode.

template<typename T , int N>

void ltl::FourierTransform< T, N >::execute

(

)

[protected]

---

Member Data Documentation

template<typename T , int N>

unsigned ltl::FourierTransform< T, N >::mode [protected]

Referenced by ltl::FourierTransform< T, N >::reset().

template<typename T , int N>

fftw_plan ltl::FourierTransform< T, N >::plan [protected]