Intel® Integrated Performance Primitives Developer Guide and Reference

ID 790148
Date 11/07/2023
Public

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ThresholdAdaptiveGauss

Performs adaptive thresholding with the Gaussian method.

Syntax

IppStatus ippiThresholdAdaptiveGauss_8u_C1R(const Ipp8u* pSrc, int srcStep, Ipp8u* pDst, int dstStep, IppiSize roiSize, Ipp32f delta, Ipp8u valGT, Ipp8u valLE, IppiBorderType borderType, Ipp8u borderValue, IppiThresholdAdaptiveSpec* pSpec, Ipp8u* pBuffer);

IppStatus ippiThresholdAdaptiveGauss_8u_C1IR(Ipp8u* pSrcDst, int srcDstStep, IppiSize roiSize, Ipp32f delta, Ipp8u valGT, Ipp8u valLE, IppiBorderType borderType, Ipp8u borderValue, IppiThresholdAdaptiveSpec* pSpec, Ipp8u* pBuffer);

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.
pSrcDst
Pointer to the source and destination image ROI (for the in-place function).
srcDstStep
Distance, in bytes, between the starting points of consecutive lines in the source and destination image (for the in-place function).
roiSize
Size of the destination image ROI, in pixels.
delta
Value for threshold calculation.
valGT
Output pixel if the source pixel value is more than threshold.
valLE
Output pixel if the source pixel value is less than, or equal to threshold.
borderType

Type of border. Possible values are:

ippBorderConst

Values of all border pixels are set to a 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 ippBorderRepl or ippBorderConst and the following flags:

  • ippBorderInMemTop
  • ippBorderInMemBottom
  • ippBorderInMemLeft
  • ippBorderInMemRight
Each of these flags means that for the corresponding border the outside pixels of the source image are in memory.

borderValue

Constant value(s) to assign to pixels of the constant border. This parameter is applicable only to the ippBorderConst border type.

pSpec

Pointer to the adaptive threshold specification structure.

pBuffer
Pointer to the work buffer. To calculate the size of the temporary buffer, use the ThresholdAdaptiveGaussGetBufferSize function.

Description

This function performs adaptive thresholding of the source image ROI using the Gaussian method. Output pixels are calculated according to the following formulas:

pDst(x,y) = valGT if pSrc(x,y) > T(x,y)

pDst(x,y) = valLE if pSrc(x,y) <= T(x,y)

where

T(x,y) is a weighted sum (cross-correlation with a Gaussian window) of the maskSize.width*maskSize.height neighborhood of a (x, y) pixel minus delta.

The function uses a separable Gaussian filter. Filter coefficients are computed according to the following formula:

Gi = A * exp( - (i-(maskSize.width-1)/2)2)/(0.5 * sigma2)

where

A is a scale factor for ∑iGi = 1 (i = 0, ..., maskSize.width-1)

Before using this function, compute the size of the external work buffer and specification structure using the ThresholdAdaptiveGaussGetBufferSize function, and initialize the structure using the ThresholdAdaptiveGaussInit function.

Return Values

ippStsNoErr

Indicates no error.

ippStsNullPtrErr

Indicates an error when pSrc, pDst, pSrcDst, pSpec, or pBuffer is NULL.

ippStsSizeErr

Indicates an error when roiSize has a field with a zero or negative value.

ippStsContextMatchErr

Indicates an error when pSpec does not match.

ippStsBorderErr

Indicates an error when borderType has an illegal value.

Example

The code example below demonstrates how to use the ippiThresholdAdaptiveGauss_8u_C1R, ThresholdAdaptiveGaussGetBufferSize, and ThresholdAdaptiveGaussInit functions.

IppStatus threshold_adaptive_gauss_8u_c1( void ) {
    Ipp8u pSrc[8*8] =
    {
          0, 255,   1, 254,   2, 253,   3, 252,
        251,   4, 250,   5, 249,   6, 248,   7,
          8, 247,   9, 246,  10, 245,  11, 244,
        243,  12 , 242, 13, 241,  14, 240,  15,
         16, 239,  17, 238,  18, 237,  19, 236,
        235,  20, 234,  21, 233,  22, 232,  23,
         24, 231,  25, 230,  26, 229,  26, 228,
        227,  27, 226,  28, 225,  29, 224,  30
    };
    Ipp8u    pDst[8*8];
    IppiSize roiSize = {8, 8};
    IppiSize maskSize = {3, 3};
    IppiBorderType borderType = ippBorderConst;
    int     srcStep = 8 * sizeof(Ipp8u);
    int     dstStep = 8 * sizeof(Ipp8u);
    int     bufferSize;
    int     specSize;
    IppStatus status;
    Ipp32f  sigma = 10.0f;
    Ipp32f  delta = 0.5f;
    Ipp8u   valGT = 254;
    Ipp8u   valLE = 1;
    IppiThresholdAdaptiveSpec *pSpec;
    Ipp8u   *pBuffer;

    ippiThresholdAdaptiveGaussGetBufferSize(roiSize, maskSize, ipp8u, 1, &specSize, &bufferSize);
    pSpec = (IppiThresholdAdaptiveSpec *)ippsMalloc_8u(specSize);
    pBuffer = ippsMalloc_8u(bufferSize);
    ippiThresholdAdaptiveGaussInit(roiSize, maskSize, ipp8u, 1, sigma, pSpec);
    ippiThresholdAdaptiveGauss_8u_C1R(pSrc, srcStep, pDst, dstStep, roiSize, delta, valGT, valLE, borderType, 33, pSpec, pBuffer);
    ippsFree(pBuffer);
    ippsFree(pSpec);

    return status;
}

pDst after function execution:

   1 254   1 254   1 254   1 254
 254   1 254   1 254   1 254   1
   1 254   1 254   1 254   1 254
 254   1 254   1 254   1 254   1
   1 254   1 254   1 254   1 254
 254   1 254   1 254   1 254   1
   1 254   1 254   1 254   1 254
 254   1 254   1 254   1 254   1

See Also