Intel® Integrated Performance Primitives Developer Reference

Developer Reference

  • 2021
  • 01/15/2021
  • Public Content
Contents

FFTInit

Initializes the context structure for the image FFT functions.

Syntax

IppStatus ippiFFTInit_R_32f (int
orderX
, int
orderY
, int
flag
, IppHintAlgorithm
hint
, IppiFFTSpec_R_32f*
pFFTSpec
, Ipp8u* pMemInit
);
IppStatus ippiFFTInit_C_32fc (int
orderX
, int
orderY
, int
flag
, IppHintAlgorithm
hint
, IppiFFTSpec_C_32fc*
pFFTSpec
, Ipp8u*
pMemInit
);
Include Files
ippi.h
Domain Dependencies
Headers:
ippcore.h
,
ippvm.h
,
ipps.h
Libraries:
ippcore.lib
,
ippvm.lib
,
ipps.lib
Parameters
orderX, orderY
Order of the FFT in x- and y- directions, respectively.
flag
Flag to choose the option for results normalization.
hint
This parameter is deprecated. Set the value to
ippAlgHintNone
.
pFFTSpec
Pointer to the FFT context structure.
pMemInit
Pointer to the temporary work buffer.
Description
This function initializes the
pFFTSpec
 context structure needed to compute the forward and inverse FFT of a two-dimensional image data.
Before calling this function, you need to allocate memory for the FFT context structure and temporary work buffer (if it is required). To compute the size of the FFT context structure and temporary work buffer, use the
ippiFFTGetSize
 function.
The
pMemInit
 parameter can be
NULL
 only if the work buffer is not used. After initialization is done, you can free the temporary work buffer.
The
ippiFFTFwd
 and
ippiFFTInv
 functions called with the pointer to the initialized
pFFTSpec
 structure, compute the fast Fourier transform with the following characteristics:
The suffix after the function name indicates the type of the context structure to be initialized:
ippiFFTInit_C
 is for the complex FFT context structure and
ippiFFTInit_R
 is for the real FFT context structure.
Return Values
ippStsNoErr
Indicates no error.
ippStsNullPtrErr
Indicates an error when one of the specified pointers is
NULL
.
ippStsFftOrderErr
Indicates an error condition when the FFT order value is illegal.
ippStsFFTFlagErr
Indicates an error condition when the
flag
value is illegal.

Example

The code example below demonstrates how to use the
ippiFFTGetSize
 and
ippiFFTInit
 functions.
/// get sizes for required buffers
    ippiFFTGetSize_R_32f( orderX, orderY, IPP_FFT_DIV_INV_BY_N, ippAlgHintNone, &sizeSpec, &sizeInit, &sizeBuffer );

    /// allocate memory for required buffers
    pMemSpec = (IppiFFTSpec_R_32f*) ippMalloc ( sizeSpec );

    if ( sizeInit > 0 )
    {
        pMemInit = ippMalloc ( sizeInit );
    }

    if ( sizeBuffer > 0 )
    {
        pMemBuffer = ippMalloc ( sizeBuffer );
    }

    /// initialize FFT specification structure
    ippiFFTInit_R_32f( orderX, orderY, IPP_FFT_DIV_INV_BY_N, ippAlgHintNone, pMemSpec, pMemInit );

    /// free initialization buffer
    if ( sizeInit > 0 )
    {
        ippFree( pMemInit );
    }

    /// perform forward FFT to put source data to frequency domain
    ippiFFTFwd_RToPack_32f_C1R( pSrc, srcStep, pDst, dstStep, pMemSpec, pMemBuffer );

    /// ...

    /// free buffers
    if ( sizeBuffer > 0 )
    {
        ippFree( pMemBuffer );
    }

    ippFree( pMemSpec );

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.