Visible to Intel only — GUID: GUID-B6C3A70D-47E0-4DEE-9A6C-1AD51A0C01AA
Visible to Intel only — GUID: GUID-B6C3A70D-47E0-4DEE-9A6C-1AD51A0C01AA
GradientVectorScharr
Computes gradient vectors of an image using the Scharr operator.
Syntax
IppStatus ippiGradientVectorScharr_<mod> (const Ipp<srcDatatype>* pSrc, int srcStep, Ipp<dstDatatype>* pGx, int gxStep, Ipp<dstDatatype>* pGy, int gyStep, Ipp<dstDatatype>* pMag, int magStep, Ipp32f* pAngle, int angleStep, IppiSize dstRoiSize, IppiMaskSize maskSize, IppNormType normType, IppiBorderType borderType, Ipp<srcDatatype> borderValue, Ipp8u* pBuffer);
Supported values for mod:
8u16s_C1R | 16s32f_C1R | 16u32f_C1R | 32f_C1R |
IppStatus ippiGradientVectorScharr_<mod> (const Ipp<srcDatatype>* pSrc, int srcStep, Ipp<dstDatatype>* pGx, int gxStep, Ipp<dstDatatype>* pGy, int gyStep, Ipp<dstDatatype>* pMag, int magStep, Ipp32f* pAngle, int angleStep, IppiSize dstRoiSize, IppiMaskSize maskSize, IppNormType normType, IppiBorderType borderType, const Ipp<srcDatatype> borderValue[3], Ipp8u* pBuffer);
Supported values for mod:
8u16s_C3C1R | 16s32f_C3C1R | 16u32f_C3C1R | 32f_C3C1R |
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 ROI. |
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srcStep |
Distance, in bytes, between the starting points of consecutive lines in the source image. |
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pGx |
Pointer to the destination image ROI for the X component of the gradient vector (in Cartesian form). |
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gxStep |
Distance, in bytes, between the starting points of consecutive lines in the X-component destination image. |
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pGy |
Pointer to the destination image ROI for the Y component of the gradient vector (in Cartesian form). |
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gyStep |
Distance, in bytes, between the starting points of consecutive lines in the Y-component destination image. |
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pMag |
Pointer to the magnitude of the gradient destination image ROI (in polar gradient form). |
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magStep |
Distance, in bytes, between the starting points of consecutive lines in the magnitude of the gradient destination image. |
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pAngle |
Pointer to the destination image ROI for the angle (in polar gradient form). |
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angleStep |
Distance, in bytes, between the starting points of consecutive lines in the angle destination image. |
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dstRoiSize |
Size of the source and destination image ROI in pixels. |
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maskSize |
Predefined mask of IppiMaskSize type. |
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normType |
Normalization mode of IppNormType type. |
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borderType |
Type of border. Possible values are:
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borderValue |
Constant value to assign to pixels in the constant border (not applicable for other border types). |
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pBuffer |
Pointer to the work buffer. |
Description
This function operates with ROI (see Regions of Interest in Intel IPP).
Before using this function, compute the size of the work buffer using the ippiGradientVectorGetBufferSize function.
Any of the pGx, pGy, pMag, and pAngle output parameters can be NULL. This means that the parameter(s) is not requested.
This function operates on "gray" single-channel (C1 flavors) and color (C3 flavors) images.
Single-channel image (C1) input :
If input is a single-channel image, the ippiGradientVectorScharr function computes the gradient vector at each pixel of the source image ROI and stores the result either in Cartesian (pGx and pGy) and/or polar (pMag and pAngle) form, or any combination of these possible outputs.
Cartesian projections Gx and Gy are stored in the pGx and pGy buffers, respectively. The formulas below describe the algorithm for the 3x3 Scharr operator:
where
A is the source image
* means two-dimensional convolution
Gx and Gy are X and Y components of the gradient
The magnitude of the gradient is computed according to the normType value by the following formulas:
L1 normalization:
L2 normalization:
The value of angle between Gx and Gy is computed by the formula:
Color image (C3) input :
If input is a color image, the ippiGradientVectorScharr function computes the spatial image derivatives Gx and Gy for each channel of the image using the specified differential operator. For each pixel (x, y) this function chooses the derivatives for which L2(Gx, Gy) is the maximal value and stores them in the pGx and pGy output arrays. In other words, for each pixel of a color image the function returns the derivatives composing the largest gradient across all channels.
The examples of using this function are similar to the examples provided with the GradientVectorSobel function description.
Return Values
ippStsNoErr |
Indicates no error. |
ippStsNullPtrErr |
Indicates an error when pSrc or pBuffer is NULL. |
ippStsSizeErr |
Indicates an error when one of the fields of dstRoiSize has a zero or negative value. |
ippStsMaskSizeErr |
Indicates an error when maskSize has an illegal value. |
ippStsStepErr |
Indicates an error when:
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ippStsBadArgErr |
Indicates an error when normType has an illegal value. |
ippStsBorderErr |
Indicates an error when borderType has an incorrect value. |