DCTInv
Applies an inverse discrete cosine transform to an image.
Syntax
IppStatus ippiDCTInv_<mod> (const Ipp32f*
pSrc
, int
srcStep
, Ipp32f*
pDst
, int
dstStep
, const IppiDCTInvSpec_32f*
pDCTSpec
, Ipp8u*
pBuffer
);
Supported values for
mod
:32f_C1R |
32f_C3R |
32f_C4R |
32f_AC4R |
Include Files
ippi.h
Domain Dependencies
Headers:
ippcore.h
,
ippvm.h
,
ipps.h
Libraries:
ippcore.lib
,
ippvm.lib
,
ipps.lib
Parameters
- pSrc
- Pointer to the source image ROI.
- srcStep
- Distance, in bytes, between the starting points of consecutive lines in the source image.
- pDst
- Pointer to the destination image ROI.
- dstStep
- Distance, in bytes, between the starting points of consecutive lines in the destination image.
- pDCTSpec
- Pointer to the previously initialized inverse DCT context structure.
- pBuffer
- Pointer to the external work buffer.
Description
This function operates with ROI (see Regions of Interest in Intel IPP) of the size that is specified by the
ippiDCTInvInit
function.This function performs an inverse DCT on each channel of the input image
pSrc
and writes the result into the corresponding channel of the output image buffer pDst
. Note that the function flavor with AC4
descriptor does not process alpha channel. This function uses the previously initialized pDCTSpec
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 DCT. 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.Before using the inverse DCT functions, you need to compute the size of the required buffers and the external work buffer using the
ippiDCTInvGetSize
function. Return Values
- ippStsNoErr
- Indicates no error. Any other value indicates an error or a warning.
- ippStsNullPtrErr
- Indicates an error condition ifpSrc, pDst,orpDCTSpecpointer isNULL.
- ippStsStepErr
- Indicates an error condition ifsrcStepordstStepvalue is zero or negative.
- ippStsContextMatchErr
- Indicates an error condition if a pointer to an invalidpDCTSpecstructure is passed.
- ippStsMemAllocErr
- Indicates an error condition if memory allocation fails.