Filters an image using a Gaussian kernel.
Syntax
IppStatus ippiFilterGauss_<mod>(const Ipp<datatype>* pSrc, int srcStep, Ipp<datatype>* pDst, int dstStep, IppiSize dstRoiSize, IppiMaskSize mask);
Supported values for mod:
| 8u_C1R | 16u_C1R | 16s_C1R | 32f_C1R |
| 8u_C3R | 16u_C3R | 16s_C3R | 32f_C3R |
| 8u_C4R | 16u_C4R | 16s_C4R | 32f_C4R |
| 8u_AC4R | 16u_AC4R | 16s_AC4R | 32f_AC4R |
Parameters
pSrc |
Pointer to the source image ROI. |
srcStep |
Distance in bytes between starts of consecutive lines in the source image. |
pDst |
Pointer to the destination image ROI. |
dstStep |
Distance in bytes between starts of consecutive lines in the destination image. |
dstRoiSize |
Size of the source and destination ROI in pixels. |
mask |
Predefined mask of IppiMaskSize type. |
Description
The function ippiFilterGauss is declared in the ippi.h file. It operates with ROI (see Regions of Interest in Intel IPP). This function applies a lowpass Gaussian filter to an image ROI. The corresponding kernel is the matrix of either 3x3 or 5x5 size.
The 3x3 filter uses the kernel:
1/16 2/16 1/16
2/16 4/16 2/16
1/16 2/16 1/16
These filter coefficients correspond to a 2-dimensional Gaussian distribution with standard deviation 0.85.
The 5x5 filter uses the kernel:
2/571 7/571 12/571 7/571 2/571
7/571 31/571 52/571 31/571 7/571
12/571 52/571 127/571 52/571 12/571
7/571 31/571 52/571 31/571 7/571
2/571 7/571 12/571 7/571 2/571
These filter coefficients correspond to a 2-dimensional Gaussian distribution with standard deviation 1.0.
The anchor cell is the center cell of the kernels (red). The size of the source image ROI is equal to dstRoiSize, the size of the destination image ROI.
To ensure valid operation when image boundary pixels are processed, the application should correctly define additional border pixels (see Borders).
Example “Using the Logarithm Function” shows how to use the function ippiFilterGauss_8u_C1R.
Return Values
ippStsNoErr |
Indicates no error. Any other value indicates an error or a warning. |
ippStsNullPtrErr |
Indicates an error condition if pSrc or pDst is NULL. |
ippStsSizeErr |
Indicates an error condition if dstRoiSize has a field with a zero or negative value. |
ippStsStepErr |
Indicates an error condition if srcStep or dstStep has a zero or negative value. |
ippStsMaskSizeErr |
Indicates an error condition if mask has an illegal value. |
Using the Gauss Filter
Ipp8u src[9*9] = {
0, 1, 2, 3, 4, 5, 6, 7, 0,
1, 2, 3, 4, 5, 6, 7, 0, 1,
2, 3, 4, 5, 6, 7, 0, 1, 2,
3, 4, 5, 6, 7, 0, 1, 2, 3,
4, 5, 6, 7, 0, 1, 2, 3, 4,
5, 6, 7, 0, 1, 2, 3, 4, 5,
6, 7, 0, 1, 2, 3, 4, 5, 6,
7, 0, 1, 2, 3, 4, 5, 6, 7,
0, 1, 2, 3, 4, 5, 6, 7, 0
};
Ipp8u dst[9*9];
IppiSize roiSize = { 9, 9 };
ippiFilterGauss_8u_C1R ( src, 9, dst, 9, roiSize, ippMskSize5x5 );
Result:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 src 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 80 62 58 59 60 60 60 57 44 26 15 14 15 15 16 15 12 09 05 04 04 05 05 04 03 02 02 03 04 05 05 04 03 02 02 03 04 05 05 04 03 02 02 03 04 dst 05 05 04 03 02 02 03 04 05 05 04 03 02 02 03 04 05 08 12 13 13 13 13 14 15 18 26 39 48 53 54 52 50 50 53 63
for example, on real picture it can look like this
size 128x128 size 124x124
roi 124x124 roi 124x124
ippMskSize5x5
+ ippiAddRandGauss_Direct_8u_C3IR (.., 2, 50, 57328065)
size 128x128 size 124x124
roi 124x124 roi 124x124
ippMskSize5x5
