Visible to Intel only — GUID: GUID-A0AD88AA-CDCB-47F1-81BE-AA16B800CBEF
Visible to Intel only — GUID: GUID-A0AD88AA-CDCB-47F1-81BE-AA16B800CBEF
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
- 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:
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.
Computes products of the gradients at each (x, y) pixel of the image:
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.
Defines 2x2 gradient covariance matrix H(x , y) over a rectangular neighborhood block for each (x, y) pixel of the image.
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:
|
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); } ...