DFTInv

Applies an inverse DFT to complex source data and stores results in a destination image.

Syntax

Case 1: Not-in-place operation on integer data

IppStatus ippiDFTInv_PackToR_<mod>(const Ipp32s* pSrc, int srcStep, Ipp8u* pDst, int dstStep, const IppiDFTSpec_R_32s* pDFTSpec, int scaleFactor, Ipp8u* pBuffer);

Supported values for mod:

32s8u_C1RSfs

32s8u_C3RSfs

32s8u_C4RSfs

32s8u_AC4RSfs

Case 2: Not-in-place operation on floating-point data

IppStatus ippiDFTInv_PackToR_<mod>(const Ipp32f* pSrc, int srcStep, Ipp32f* pDst, int dstStep, const IppiDFTSpec_R_32f* pDFTSpec, Ipp8u* pBuffer);

Supported values for mod:

32f_C1R

32f_C3R

32f_C4R

32f_AC4R

Case 3: Not-in-place operation on complex data

IppStatus ippiDFTInv_CToC_32fc_C1R(const Ipp32fc* pSrc, int srcStep, Ipp32fc* pDst, int dstStep, const IppiDFTSpec_C_32fc* pDFTSpec, Ipp8u* pBuffer);

Case 4: In-place operation on floating-point data

IppStatus ippiDFTInv_PackToR_<mod>(Ipp32f* pSrcDst, int srcDstStep, const IppiDFTSpec_R_32f* pDFTSpec, Ipp8u* pBuffer);

Supported values for mod:

32f_C1IR

32f_C3IR

32f_C4IR

32f_AC4IR

Case 5: In-place operation on complex data

IppStatus ippiDFTInv_CToC_32fc_C1IR(Ipp32fc* pSrcDst, int srcDstStep, const IppiDFTSpec_C_32fc* pDFTSpec, Ipp8u* pBuffer);

Parameters

pSrc	Pointer to the source image ROI.
srcStep	Distance in bytes between starts of consecutive lines in the source image.
pDst	Pointer to the destination image ROI.
dstStep	Distance in bytes between starts of consecutive lines in the destination image.
pSrcDst	Pointer to the source and destination image ROI for the in-place operation.
srcDstStep	Distance in bytes between starts of consecutive lines in the source and destination image for the in-place operation.
pDFTSpec	Pointer to the previously initialized DFT context structure.
scaleFactor	Scale factor (see Integer Result Scaling).
pBuffer	Pointer to the external work buffer, can be NULL.

Description

The function ippiDFTInv is declared in the ippi.h file. It operates with ROI (see Regions of Interest in Intel IPP) of the size specified by the function ippiDFTInitAlloc.

This function performs an inverse DFT on each channel of the input buffer pSrc (pSrcDst for in-place flavors) and writes the restored image data into the corresponding channel of the output image buffer pDst (pSrcDst for in-place flavors).

For function flavor ippiDFTInv_PackToR, the input buffer must contain data in RCPack2D format.

The inverse DFT functions use the previously initialized pDFTSpec context structure to set the mode of calculations and retrieve support data.

The function may be used with the external work buffer pBuffer to avoid memory allocation within the functions. Once the work buffer is allocated, it can be used for all following calls to the functions computing DFT. As internal allocation of memory is too expensive operation and depends on operating system and/or runtime libraries used - the use of an external buffer improves performance significantly, especially for the small size transforms.

The size of the external buffer must be previously computed by the function ippiDFTGetBufSize. If the external buffer is not specified (pBuffer is set to NULL), the function itself allocates the memory needed for operation.

Return Values

ippStsNoErr	Indicates no error. Any other value indicates an error or a warning.
ippStsNullPtrErr	Indicates an error condition if pSrc, pDst, or pDFTSpec pointer is `NULL`.
ippStsStepErr	Indicates an error condition if srcStep or dstStep value is zero or negative.
ippStsContextMatchErr	Indicates an error condition if a pointer to an invalid pDFTSpec structure is passed.
ippStsMemAllocErr	Indicates an error condition if memory allocation fails.