Intel® Integrated Performance Primitives Developer Reference

Developer Reference

  • 2021
  • 03/26/2021
  • Public Content
Contents

HarrisCorner

Implements Harris corner detection algorithm.

Syntax

IppStatus ippiHarrisCorner_8u32f_C1R(const Ipp8u*
pSrc
, int
srcStep
, Ipp32f*
pDst
, int
dstStep
, IppiSize
roiSize
, IppiDifferentialKernel
filterType
, IppiMaskSize
filterMask
, Ipp32u
avgWndSize
, float
k
, float
scale
, IppiBorderType
borderType
, Ipp8u
borderValue
, Ipp8u*
pBuffer
);
IppStatus ippiHarrisCorner_32f_C1R(const Ipp32f*
pSrc
, int
srcStep
, Ipp32f*
pDst
, int
dstStep
, IppiSize
roiSize
, IppiDifferentialKernel
filterType
, IppiMaskSize
filterMask
, Ipp32u
avgWndSize
, float
k
, float
scale
, IppiBorderType
borderType
, Ipp32f
borderValue
, 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.
srcStep
Distance, in bytes, between the starting points of consecutive lines in the source image.
pDst
Pointer to the destination image.
dstStep
Distance, in bytes, between the starting points of consecutive lines in the destination image.
roiSize
Size of the source and destination image ROI in pixels.
filterType
Type of the derivative operator. Possible values are:
ippKernelSobel
Sobel filter
ippKernelScharr
Scharr filter
ippKernelCentralDiff
Central differences operator
filterMask
Size of the derivative filter aperture. The list of possible values depends on the
filterType
 value:
Filter Type
Filter Mask
ippKernelSobel
ippMskSize3x3
,
ippMskSize5x5
ippKernelScharr
ippMskSize3x3
ippKernelCentralDiff
ippMskSize3x3
avgWndSize
Linear size of a neighborhood block for averaging.
k
Harris detector free coefficient.
scale
Destination image scale factor.
borderType
Type of border. Possible values are:
ippBorderConst
Values of all border pixels are set to constant.
ippBorderRepl
Border is replicated from the edge pixels.
ippBorderInMem
Border is obtained from the source image pixels in memory.
ippBorderMirror
Border pixels are mirrored from the source image boundary pixels.
Mixed borders are also supported. They can be obtained by the bitwise operation OR between
ippBorderRepl
 or
ippBorderConst
 and the following flags:
  • ippBorderInMemTop
  • ippBorderInMemBottom
  • ippBorderInMemLeft
  • ippBorderInMemRight
Each of these flags means that for the corresponding border the outside pixels of the source image are in memory.
borderValue
Constant value(s) to assign to pixels of the constant border. This parameter is applicable only to the
ippBorderConst
 border type. The
ippiHarrisCorner
 function uses the specified constant value only at the first stage of the algorithm. At the third stage, the function uses zero constant border.
pBuffer
Pointer to the pre-allocated temporary buffer. To calculate the size of the temporary buffer, use the HarrisCornerGetBufferSize function.
Description
This function goes through the following stages to implement the Harris corner detection algorithm:
  1. Computes
    I
    (
    x
    ,
    y
    )
    x
     and
    I
    (
    x
    ,
    y
    )
    y
     gradients for each (
    x
    ,
    y
    ) pixel of the image. The function computes gradients using the derivative operator specified by the
    filterType
     and
    filterMask
     parameters.
  2. Computes products of the gradients at each (
    x
    ,
    y
    ) pixel of the image:
  3. Performs averaging of the products of gradients over a rectangular neighborhood block at each pixel of the image. The block size is specified by the
    avgWndSize
     value.
  4. Defines 2x2 gradient covariance matrix
    H
    (
    x
    ,
    y
    )
     over a rectangular neighborhood block for each (
    x
    ,
    y
    ) pixel of the image.
  5. Computes the corner response at each pixel of the image:
    where
    k
     is the Harris detector free parameter
The first and third stages of the function algorithm are filtering operations; they use border processing approach that is specified by the
borderType
 parameter.
The
scale
 parameter is applied to the output image.
Before using this function, compute the size of the temporary work buffer using the HarrisCornerGetBufferSize function.
Return Values
ippStsNoErr
Indicates no error. Any other value indicates an error or a warning.
ippStsNullPtrErr
Indicates an error when
pSrc
,
pDst
, or
pBufferSize
 is
NULL
.
ippStsSizeErr
Indicates an error in the following cases:
  • when
    roiSize
     is less than, or equal to zero
  • when
    avgWndSize
     is equal to zero
ippStsNotEvenStepErr
Indicates an error when one of the step values is not divisible by 4 for floating point images.
ippStsFilterTypeErr
Indicates an error when
filterType
 has an illegal value.
ippStsMaskSizeErr
Indicates an error when
filterMask
 has an illegal value.
ippStsBorderErr
Indicates an error when
borderType
 has an illegal value.
ippStsStepErr
Indicates an error when
srcStep
 or
dstStep
 has a negative value.
ippStsInplaceModeNotSupportedErr
Indicates an error when
pSrc
 and
pDst
 point to the same image.

Example

The code example below demonstrates how to use the
ippiHarrisCorner_8u32f_C1R
 and
ippiHarrisCornerGetBufferSize
 functions.
    ...
    int    bufSize = 0;
    Ipp8u* pBuffer  = 0;
    Ipp32u numChannels = 1;
    IppStatus status = ippStsNoErr;
    IppiBorderType borderType = ippBorderRepl;
    IppiDifferentialKernel filterType = ippFilterSobel;
    IppiMaskSize filterMask = ippMskSize5x5;
    Ipp32u avgWndSize = 3;
    Ipp32f scale = 1.0f;

    /* Computes the temporary work buffer size */
    status = ippiHarrisCornerGetBufferSize(roiSize, filterMask, avgWndSize, ipp8u, numChannels, &bufSize);

    /* Memory allocation */
    if (status != ippStsNoErr) pBuffer = ippsMalloc_8u(bufSize);

    if (pBuffer != NULL)
    {
        /* Harris Corner processing */
        status = ippiHarrisCorner_8u32f_C1R(pSrc, srcStep, pDst, dstStep, roiSize, filterType, filterMask, avgWndSize, 0.04f,
            scale, borderType, 0, pBuffer);

        ippsFree(pBuffer);
    }
    ...

Product and Performance Information

1

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