Filters an image using a Sobel filter.
Syntax
IppStatus ippiFilterSobel_<mod>(const Ipp<srcdatatype>* pSrc, int srcStep, Ipp<dstdatatype>* pDst, int dstStep, 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 ippiFilterSobel_<mod>_T(const Ipp8u* pSrc, int srcStep, Ipp16s* pDst, int dstStep, IppiBorderType border, const Ipp8u borderValue, IppiFilterSobelSpec_T* pSpec, Ipp8u* pBuffer);
Supported values for mod:
| 8u16s_C1R_T |
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. | ||||||
srcStep |
Distance, in bytes, between the starting points of consecutive lines in the source image. | ||||||
pDst |
Pointer to the destination image ROI. | ||||||
dstStep |
Distance, in bytes, between the starting points of consecutive lines in the destination image. | ||||||
dstRoiSize |
Size of the source and destination ROI in pixels. | ||||||
maskSize |
Size of the predefined mask. Possible values are ippMskSize3x3 or ippMskSize5x5. | ||||||
normType |
Normalization mode of IppNormType. |
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borderType |
Type of border. Possible values are:
Mixed borders are also supported. They can be obtained by the bitwise operation OR between any of the ippBorderRepl or ippBorderConst values and the ippBorderInMemTop, ippBorderInMemBottom, ippBorderInMemLeft, ippBorderInMemRight values. |
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borderValue |
Constant value to assign to pixels of the constant border. This parameter is applicable only to the ippBorderConst border type. | ||||||
pBuffer |
Pointer to the work buffer. |
Description
Before using this function, you need to compute the size of the work buffer pBuffer using the ippiFilterSobelBufferSize function.
Call the ippiFilterSobelInit_T function before using the ippiFilterSobel*_T function.
This function applies a Sobel filter to the source image with the specified kernel size and normalization type. The values of border pixels are assigned in accordance with the borderType and borderValue parameters. The kernel of the filter is a matrix of 3x3 or 5x5 size depending on the maskSize value. The formulas below describe the algorithm for the 3x3 and 5x5 Sobel operators.
3x3 Sobel operator:
5x5 Sobel operator:
where
A is the source image
* is the 2D convolution operator
Gx and Gy are horizontal and vertical magnitude of the source image, respectively
Sobel filter output G, as overall gradient magnitude, is generated through L1 and L2 normalization of Gx and Gy.
L1 normalization:
L2 normalization:
Return Values
ippStsNoErr |
Indicates no error. |
ippStsNullPtrErr |
Indicates an error when one of the specified pointers is NULL. |
ippStsSizeErr |
Indicates an error when dstRoiSize has a field with a zero or negative value. |
ippStsMaskSizeErr |
Indicates an error when maskSize has an illegal value. |
ippStsStepErr |
Indicates an error when srcStep or dstStep is less than, or equal to zero. |
ippStsNotEvenStepErr |
Indicates an error when one of the step values is not divisible by 4 for floating-point images, or by 2 for short-integer images. |
ippStsBorderErr |
Indicates an error when borderType has an illegal value. |
Example
The code example below demonstrates how to use the ippiFilterSobelGetBufferSize and ippiFilterSobel_8u16s_C1R functions.
IppStatus filter_sobel_8u16s_c1( void ) {
Ipp8u pSrc[9*8] =
{
0, 1, 2, 120, 121, 122, 50, 51, 52,
1, 2, 3, 121, 122, 123, 52, 52, 53,
3, 4, 5, 130, 131, 132, 63, 64, 65,
4, 5, 6, 131, 132, 133, 64, 65, 66,
5, 6, 7, 132, 133, 134, 65, 66, 67,
8, 7, 6, 134, 133, 132, 67, 66, 65,
7, 6, 5, 133, 132, 131, 66, 65, 64,
6, 5, 4, 132, 131, 130, 65, 64, 63
};
Ipp16s pDst[8*7];
IppiSize roiSize = {8, 7};
IppiMaskSize mask = ippMskSize3x3;
IppiBorderType borderType = ippBorderConst | ippBorderInMemTop | ippBorderInMemRight;
int srcStep = 9 * sizeof(Ipp8u);
int dstStep = 8 * sizeof(Ipp16s);
int bufferSize;
IppStatus status;
Ipp8u *pBuffer;
IppNormType normType = ippNormL1;
ippiFilterSobelGetBufferSize(roiSize, mask, normType, ipp8u, ipp16s, 1, &bufferSize);
pBuffer = ippsMalloc_8u(bufferSize);
status = ippiFilterSobel_8u16s_C1R(pSrc+srcStep, srcStep, pDst, dstStep, roiSize, mask, normType, borderType, 33, pBuffer);
ippsFree(pBuffer);
return status;
}
The result is as follows:
pDst -->
132 20 502 516 48 322 330 58
126 20 516 530 48 316 322 58
118 16 512 512 16 280 280 16
118 12 510 512 8 272 276 8
110 4 510 508 8 272 268 8
114 16 516 516 16 272 272 16
162 114 398 652 402 526 394 134