Calculates eigen values and eigen vectors of image blocks for corner detection.
Syntax
IppStatus ippiEigenValsVecsBorder_8u32f_C1R(const Ipp8u* pSrc, int srcStep, Ipp32f* pEigenVV, int eigStep, IppiSize roiSize, IppiKernelType kernType, int apertureSize, int avgWindow, IppiBorderType borderType, Ipp8u borderValue, Ipp8u* pBuffer);
IppStatus ippiEigenValsVecsBorder_32f_C1R(const Ipp32f* pSrc, int srcStep, Ipp32f* pEigenVV, int eigStep, IppiSize roiSize, IppiKernelType kernType, int apertureSize, int avgWindow, 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 ROI.
- srcStep
- Distance, in bytes, between the starting points of consecutive lines in the source image.
- pEigenVV
- Image to store the results.
- eigStep
- Distance, in bytes, between the starting points 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.
- border
Type of image border. Possible values:
ippBorderConst
Values of all border pixels are set to a constant.
ippBorderRepl
Border is replicated from the edge pixels.
- borderValue
Constant value to assign to pixels of the constant border. This parameter is applicable only to the ippBorderConst border type.
- avgWindow
- Size of the blurring 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 Dx and D y. This operation is performed for every pixel of the image using either Sobel or Scharr kernel in accordance with the kernType parameter. The apertureSize parameter specifies the size of the Sobel kernel. 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.
CAUTION
If the parameter apertureSize is set to 5 for operation with the Scharr kernel, the function returns error status.
The function computes eigen values and vectors of the following matrix: 
The summation is performed over the full block with averaging over the blurring window with size avgWindow.
The image eigenVV has the following format. For every pixel of the source image it contains six floating-point values - λ1, λ2 , x1, y1, x2, y2. These values are defined as follows:
λ1, λ2 |
Eigen values of the above matrix (λ1 ≥λ2 ≥ 0). |
x1, y1 |
Coordinates of the normalized eigen vector corresponding to λ1. |
x2, y2 |
Coordinates of the normalized eigen vector corresponding to λ2. |
In case of a singular matrix or when one eigen value is much smaller than the second one, all these six values are set to 0.
The function requires a temporary work buffer. Before using this function, compute the size of the buffer using the ippiEigenValsVecsGetBufferSize function.
CAUTION
The parameters apertureSize and avgWindow must be the same for both functions ippiEigenValsVecsGetBufferSize and ippiEigenValsVecsBorder.
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 a wrong value. |
ippStsStepErr |
Indicates an error condition if srcStep is less than roiSize.width*<pixelSize>, or eigStep is less than roiSize.width*sizeof(Ipp32f)*6. |
ippStsNotEvenStepErr |
Indicates an error condition if steps for floating-point images are not divisible by 4. |
ippStsBorderErr |
Indicates an error if borderType has an illegal value. |