Threshold

Performs thresholding of pixel values in an image buffer.

Syntax

Case 1: Not-in-place operation on one-channel data

IppStatus ippiThreshold_<mod>(const Ipp<datatype>* pSrc, int srcStep, Ipp<datatype>* pDst, int dstStep, IppiSize roiSize, Ipp<datatype> threshold, IppCmpOp ippCmpOp);

Supported values for mod:

8u_C1R

16u_C1R

16s_C1R

32f_C1R

Case 2: Not-in-place operation on multi-channel data

IppStatus ippiThreshold_<mod>(const Ipp<datatype>* pSrc, int srcStep, Ipp<datatype>* pDst, int dstStep, IppiSize roiSize, const Ipp<datatype> threshold[3], IppCmpOp ippCmpOp);

Supported values for mod:

8u_C3R	16u_C3R	16s_C3R	32f_C3R
8u_AC4R	16u_AC4R	16s_AC4R	32f_AC4R

Case 3: In-place operation on one-channel data

IppStatus ippiThreshold_<mod>(Ipp<datatype>* pSrcDst, int srcDstStep, IppiSize roiSize, Ipp<datatype> threshold, IppCmpOp ippCmpOp);

Supported values for mod:

8u_C1IR

16u_C1IR

16s_C1IR

32f_C1IR

Case 4: In-place operation on multi-channel data

IppStatus ippiThreshold_<mod>(Ipp<datatype>* pSrcDst, int srcDstStep, IppiSize roiSize, const Ipp<datatype> threshold[3], IppCmpOp ippCmpOp);

Supported values for mod:

8u_C3IR	16u_C3IR	16s_C3IR	32f_C3IR
8u_AC4IR	16u_AC4IR	16s_AC4IR	32f_AC4IR

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.
pSrcDst	Pointer to the source and destination image ROI (for the in-place operation).
srcDstStep	Distance in bytes between starts of consecutive lines in the source and destination image buffer (for the in-place operation).
roiSize	Size of the source and destination ROI in pixels.
threshold	The threshold level value to use for each pixel. In case of multi-channel data, an array of threshold values for each color channel is used.
ippCmpOp	The operation specified for comparing pixel values and the threshold. Comparison for either “less than” or “greater than” can be used.

Description

The function ippiThreshold is declared in the ippi.h file. It operates with ROI (see Regions of Interest in Intel IPP).

This function thresholds pixels in the source image pSrc using the specified level threshold. Pixel values in the source image are compared to the threshold value using the ippCmpOp comparison operation.

If the result of the compare is true, the corresponding output pixel is set to the threshold value. Otherwise, it is set to the source pixel value.

Example “Using the ippiThreshold Function” shows how to use the ippiThreshold_8u_C1R function.

Return Values

ippStsNoErr	Indicates no error. Any other value indicates an error or a warning.
ippStsNullPtrErr	Indicates an error condition if one of the specified pointer is NULL.
ippStsSizeErr	Indicates an error condition if roiSize has a field with zero or negative value.
ippStsStepErr	Indicates an error condition if srcStep, dstStep, or srcDstStep has a zero or negative value
ippStsNotSupportedModeErr	Indicates an error if the comparison mode is not supported.

Using the function ippiThreshold

void func_threshold()
{
    IppiSize ROI = {5,4};
    Ipp8u src[9*4] = {1, 2, 4, 8, 16, 8, 4, 2, 1,
                      1, 2, 4, 8, 16, 8, 4, 2, 1,                     
                      1, 2, 4, 8, 16, 8, 4, 2, 1,                     
                      1, 2, 4, 8, 16, 8, 4, 2, 1};
    Ipp8u dst[9*4];
    Ipp8u threshold = 6;
    ippiThreshold_8u_C1R(src, 9, dst, 9, ROI, threshold, ippCmpGreater);

}

Result:
dst 1 2 4 6 6 8 4 2 1 1 2 4 6 6 8 4 2 1 1 2 4 6 6 8 4 2 1 1 2 4 6 6 8 4 2 1