Intel® Integrated Performance Primitives Developer Reference

Developer Reference

  • 2021
  • 06/28/2021
  • Public Content
Contents

WarpPerspectiveLinear

Performs warp perspective transformation of an image using the linear interpolation method.

Syntax

IppStatus ippiWarpPerspectiveLinear_<mod>(const Ipp<datatype>*
pSrc
, int
srcStep
, Ipp<datatype>
pDst
, int
dstStep
, IppiPoint
dstRoiOffset
, IppiSize
dstRoiSize
, const IppiWarpSpec*
pSpec
, Ipp8u*
pBuffer
);
Supported values for
mod
:
8u_C1R
16u_C1R
16s_C1R
32f_C1R
8u_C3R
16u_C3R
16s_C3R
32f_C3R
8u_C4R
16u_C4R
16s_C4R
32f_C4R
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.
srcStep
Distance, in bytes, between the starting points of consecutive lines in the source image buffer.
pDst
Pointer to the destination image ROI.
dstStep
Distance, in bytes, between the starting points of consecutive lines in the destination image buffer.
dstRoiOffset
Offset of the destination image ROI with respect to the destination image origin.
dstRoiSize
Size of the destination image ROI, in pixels.
pSpec
Pointer to the specification structure for the warp operation.
pBuffer
Pointer to the work buffer.
Description
This function transforms the source image pixel coordinates (
x
,
y
) according to the following formulas:
x
' = (
c
00
*
x
 +
c
01
*
y
 +
c
02
)/ (
c
20
*
x
 +
c
21
*
y
 +
c
22
)
y
' = (
c
10
*
x
 +
c
11
*
y
 +
c
12
)/(
c
20
*
x
 +
c
21
*
y
 +
c
22
)
where
  • x
    ' and
    y
    ' are the pixel coordinates in the transformed image
  • c
    ij
     are the affine transform coefficients passed to the
    coeffs
     array during initialization
The
ippiWarpPerspectiveLinear
 function operates with ROI (see Regions of Interest in Intel IPP). The transformed part of the source image is resampled with the linear interpolation method and stored in the destination image ROI. You need to define the destination image ROI origin by the following parameters: the offset of the destination ROI with respect to the destination image origin and the destination image ROI size. The parameter
pDst
 must point to the processed destination image ROI.
If you initialize the warp specification structure using the
ippiWarpPerspectiveLinearInit
 function, you can specify the source image ROI in the following ways:
  • Set the
    srcRoi
     value to
    ippRectInfinite
    , which means that the ROI is not specified. In this case,
    pSrc
     must point to the processed source image. Pixels that are outside the source image boundaries are computed according to the specified border type.
  • Set the
    srcRoi
     value to the part of the processed source image. In this case,
    pSrc
     must point to the processed source image ROI. The operations take place only inside the specified region of interest
    srcRoi
    . It means that the destination image pixels mapped to the outer pixels of the specified source image region are not changed.
If you initialize the warp specification structure using the
ippiWarpQuadLinearInit
 function, set the
pSrc
 value to the processed source image. The operations take place only inside the source quadrangle
srcQuad
 that is specified in the
ippiWarpQuadLinearInit
 function.
To specify the algorithm for borders processing, set the
borderType
 and
pBorderValue
 parameters when initializing the
IppiWarpSpec
 structure. The data type of
pBorderValue
 is automatically converted from
Ipp64f
 to the data type of the processed images. The function supports the following algorithms for borders processing:
  • If the border type is equal to
    ippBorderRepl
    , the source image outer pixels are replicated from the edge pixels.
  • If the border type is equal to
    ippBorderConst
    , the outer pixels are set to the constant value specified in
    pBorderValue
    .
  • If the border type is equal to
    ippBorderTransp
     or
    ippBorderInMem
    , destination image pixels mapped to the outer source image pixels are not changed.
Before using the
ippiWarpPerspectiveLinear
 function, you need to initialize the
IppiWarpSpec
 structure using the
ippiWarpPerspectiveLinearInit
 function and compute the size of the external buffer
pBuffer
 using the
ippiWarpGetBufferSize
 function.
To compute the perspective transform parameters, use the
ippiGetPerspectiveQuad
,
ippiGetPerspectiveBound
, and
ippiGetPerspectiveTransform
 functions.
For an example on how to use this functionality, refer to the example provided with the
ippiWarpPerspectiveNearest
 function description.
Return Values
ippStsNoErr
Indicates no error.
ippStsNullPtrErr
Indicates an error when one of the specified pointers is
NULL
.
ippStsNoOperation
Indicates a warning when width or height of the destination image is equal to zero.
ippStsContextMatchErr
Indicates an error when context data is invalid.
ippStsNotSupportedModeErr
Indicates an error when the requested mode is not supported.
ippStsSizeErr
Indicates an error when width or height of the source or destination image ROI is negative.
ippStsStepErr
Indicates an error when the step value is not a multiple of data type.
ippStsOutOfRangeErr
Indicates an error when the destination image offset point is outside the destination image origin.
ippStsSizeWrn
Indicates a warning when the destination image ROI size is more than the destination image origin size.
ippStsWrongIntersectQuad
Indicates a warning that no operation is performed if the transformed source image extended with borders has no intersection with the destination image.

Product and Performance Information

1

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