Developer Reference

  • 2020
  • 10/21/2020
  • Public Content
Contents

MinEigenVal

Calculates the minimal eigen value of image blocks for corner detection.

Syntax

IppStatus ippiMinEigenVal_8u32f_C1R(const Ipp8u*
pSrc
, int
srcStep
, Ipp32f*
pMinEigenVal
, int
minValStep
, IppiSize
roiSize
, IppiKernelType
kernType
, int
apertureSize
, int
avgWindow
, Ipp8u*
pBuffer
);
IppStatus ippiMinEigenVal_32f_C1R(const Ipp32f*
pSrc
, int
srcStep
, Ipp32f*
pMinEigenVal
, int
minValStep
, IppiSize
roiSize
, IppiKernelType
kernType
, int
apertureSize
, int
avgWindow
, Ipp8u*
pBuffer
);
Include Files
ippcv.h
Domain Dependencies
Headers:
ippcore.h
,
ippvm.h
,
ipps.h
,
ippi.h
Libraries:
ippcore.lib
,
ippvm.lib
,
ipps.lib
,
ippi.lib
Parameters
pSrc
Pointer to the source image ROI.
srcStep
Distance in bytes between starts of consecutive lines in the source image.
pMinEigenVal
Pointer to the image that is filled with the minimal eigen values.
minValStep
Distance in bytes between starts of consecutive lines in the output image.
roiSize
Size of the source image ROI in pixels.
kernType
Specifies the type of kernel used to compute derivatives, possible values are:
ippKernelSobel
Sobel kernel 3x3 or 5x5
ippKernelSobelNeg
Negative Sobel kernel 3x3 or 5x5
ippKernelScharr
Scharr kernel 3x3
apertureSize
Size of the derivative operator in pixels, possible values are 3 or 5.
avgWindow
Size of the averaging window in pixels, possible values are 3 or 5.
pBuffer
Pointer to the temporary buffer.
Description
This function operates with ROI (see Regions of Interest in Intel IPP). This function takes a block around the pixel and computes the first derivatives D
x
and D
y
. When using the
MinEigenVal
function, you need to verify that the processing pixels beyond the ROI are available in memory. This operation is performed for every pixel of the image using either Sobel or Scharr kernel in accordance with the
kernType
parameter. The size of the Sobel kernel may be specified the parameter
apertureSize
. If this parameter is set to 3, the function used 3x3 kernel, if it is set to 5, the function uses 5x5 kernel. Only 3x3 size is available for the Scharr kernel, therefore the parameter
apertureSize
must be set to 3 if the Scharr kernel is used.
If the parameter
apertureSize
is set to 5 for operation with the Scharr kernel, the function returns error status.
Then, the function computes the minimal eigen value
λ
(
λ
0) of the following matrix:
The summation is performed over the full block with averaging over the blurring window with size
avgWindow
.
The function requires a temporary working buffer; its size should be computed previously by calling the function
ippiMinEigenValGetBufferSize
.
The parameters
apertureSize
and
avgWindow
must be the same for both functions
ippiMinEigenValGetBufferSize
and
ippiMinEigenVal
.
Return Values
ippStsNoErr
Indicates no error. Any other value indicates an error or a warning.
ippStsNullPtrErr
Indicates an error condition if one of the specified pointers is
NULL
.
ippStsSizeErr
Indicates an error condition if
pRoiSize
has a field with zero or negative value, or if
apertureSize
or
avgWindow
has an illegal value; or if
kernType
has wrong value.
ippStsStepErr
Indicates an error condition if
srcStep
is less than
roiSize.width*<pixelSize>
, or
eigenvvStep
is less than
roiSize.width*sizeof(Ipp32f)
.
ippStsNotEvenStepErr
Indicates an error condition if steps for floating-point images are not divisible by 4.

Product and Performance Information

1

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804