fft2

Fast Fourier Transform. More...

Functions
AFAPI array	fft2Norm (const array &in, const double norm_factor, const dim_t odim0=0, const dim_t odim1=0)
	C++ Interface for fast fourier transform on two dimensional signals. More...
AFAPI void	fft2InPlace (array &in, const double norm_factor=1)
	C++ Interface for fast fourier transform on two dimensional signals. More...
AFAPI array	fft2 (const array &in, const dim_t odim0=0, const dim_t odim1=0)
	C++ Interface for fast fourier transform on two dimensional signals. More...
AFAPI af_err	af_fft2 (af_array *out, const af_array in, const double norm_factor, const dim_t odim0, const dim_t odim1)
	C Interface for fast fourier transform on two dimensional signals. More...
AFAPI af_err	af_fft2_inplace (af_array in, const double norm_factor)
	C Interface for fast fourier transform on two dimensional signals. More...

Detailed Description

Fast Fourier Transform.

The Fast Fourier Transform (FFT) is an efficient algorithm to compute the discrete Fourier transform (DFT) of a signal or array. This is most commonly used to convert data in the time (or space) domain to the frequency domain, Then, the inverse FFT (iFFT) is used to return the data to the original domain.

There are numerous algorithms to compute the FFT of an array, and the specifics of the algorithm depend on the target hardware. Most algorithms, however, use a Cooley-Tukey scheme in a divide-and-conquer approach.

Note

There are some convenience functions provided for fft where normalization factor is not required as input paramter. In such cases, the normalization factor is calculated internally based on the input data provided.

Function Documentation

AFAPI af_err af_fft2	(	af_array *	out,
		const af_array	in,
		const double	norm_factor,
		const dim_t	odim0,
		const dim_t	odim1
	)

C Interface for fast fourier transform on two dimensional signals.

Parameters

[out]	out	is the transformed array
[in]	in	is the input array
[in]	norm_factor	is the normalization factor with which the input is scaled before the transformation is applied
[in]	odim0	is the length of output signals along first dimension - used to either truncate/pad the input
[in]	odim1	is the length of output signals along second dimension - used to either truncate/pad the input

Returns

AF_SUCCESS if the fft transform is successful, otherwise an appropriate error code is returned.

AFAPI af_err af_fft2_inplace	(	af_array	in,
		const double	norm_factor
	)

C Interface for fast fourier transform on two dimensional signals.

Parameters

[in,out]	in	is the input array on entry and the output of 2D forward fourier transform on exit
[in]	norm_factor	is the normalization factor with which the input is scaled before the transformation is applied

Returns

AF_SUCCESS if the fft transform is successful, otherwise an appropriate error code is returned.

Note

The input in must be a complex array

AFAPI array af::fft2	(	const array &	in,
		const dim_t	odim0 = 0,
		const dim_t	odim1 = 0
	)

C++ Interface for fast fourier transform on two dimensional signals.

This version of fft function uses a default norm_factor parameter that is calculated internally based on the input signals.

Parameters

[in]	in	is the input array
[in]	odim0	is the length of output signals along first dimension - used to either truncate/pad the input
[in]	odim1	is the length of output signals along second dimension - used to either truncate/pad the input

Returns

the transformed array

Examples:

benchmarks/fft.cpp.

AFAPI void af::fft2InPlace	(	array &	in,
		const double	norm_factor = 1
	)

C++ Interface for fast fourier transform on two dimensional signals.

Parameters

[in,out]	in	is the input array on entry and the output of 2D forward fourier transform on exit
[in]	norm_factor	is the normalization factor with which the input is scaled before the transformation is applied

Returns

the transformed array

Note

The input in must be complex

AFAPI array af::fft2Norm	(	const array &	in,
		const double	norm_factor,
		const dim_t	odim0 = 0,
		const dim_t	odim1 = 0
	)

C++ Interface for fast fourier transform on two dimensional signals.

Parameters

[in]	in	is the input array
[in]	norm_factor	is the normalization factor with which the input is scaled before the transformation is applied
[in]	odim0	is the length of output signals along first dimension - used to either truncate/pad the input
[in]	odim1	is the length of output signals along second dimension - used to either truncate/pad the input

Returns

the transformed array