Developer Reference

  • 2020
  • 07/15/2020
  • Public Content
Contents

FilterSobel

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
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
.
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.
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.
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.
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
  • G
    x
    and G
    y
    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 G
x
and G
y
.
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

Product and Performance Information

1

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Notice revision #20110804