FilterColumn

Filters an image using a spatial kernel that consists of a single column.

Syntax

Case 1: Operation on integer data

IppStatus ippiFilterColumn_<mod>(const Ipp<datatype>* pSrc, int srcStep, Ipp<datatype>* pDst, int dstStep, IppiSize dstRoiSize, const Ipp32s* pKernel, int kernelSize, int yAnchor, int divisor);

Supported values for mod:

8u_C1R 16u_C1R 16s_C1R
8u_C3R 16u_C3R 16s_C3R
8u_C4R 16u_C4R 16s_C4R
8u_AC4R 16u_AC4R 16s_AC4R

Case 2: Operation on floating-point data

IppStatus ippiFilterColumn_<mod>(const Ipp<datatype>* pSrc, int srcStep, Ipp<datatype>* pDst, int dstStep, IppiSize dstRoiSize, const Ipp32f* pKernel, int kernelSize, int yAnchor);

Supported values for mod:

32f_C1R 64f_C1R
32f_C3R
32f_C4R
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.

pKernel

Pointer to the kernel values.

kernelSize

Size of the kernel in pixels.

yAnchor

Anchor cell specifying the kernel vertical alignment with respect to the position of the input pixel.

divisor

The integer value by which the computed result is divided (for operations on integer data only).

Description

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

This function uses the vertical column kernel of size kernelSize to filter an image ROI. This function sums the products between the kernel coefficients pKernel and pixel values taken over the source pixel neighborhood defined by kernelSize and yAnchor. Note that kernel coefficients are used in inverse order. The sum is written to the destination pixel. In case of integer data, the result is divided by the fixed scaling factor divisor. To ensure valid operation when image boundary pixels are processed, the application must correctly define additional border pixels (see Borders).

For function flavors that operate on integer data, the result value Yi,j for pixel Xi,j inside image's ROI is computed according to the following formula:



where:

Km are the kernel values;

H = kernelSize is the size of the vertical column kernel;

P = H - yAnchor - 1.

Function flavors that accept input data of the Ipp32f type use the same summation formula, but no scaling of the result is done.

Example “Using the Function ippiFilterColumn” show how to use the function ippiFilterColumn_8u_C1R.

Return Values

ippStsNoErr

Indicates no error. Any other value indicates an error.

ippStsNullPtrErr

Indicates an error condition if one of the specified pointers is NULL.

ippStsSizeErr

Indicates an error condition if dstRoiSize has a field with a zero or negative value.

ippStsDivisorErr

Indicates an error condition if the divisor value is zero.

Using the Function ippiFilterColumn

Ipp8u src[4*5] = {
       1, 2, 3, 4,
       1, 2, 3, 4,
       1, 2, 3, 4,
       1, 2, 3, 4,
       1, 2, 3, 4
    };
Ipp8u dst[4*3];
IppiSize srcRoi = { 4, 3 };
Ipp32s kern[] = { 1, -2, 1 };    // using "Sobel" kernel
int kernelSize = 3;
int yAnchor = 2;
int divisor = 2;

ippiFilterColumn_8u_C1R ( src, 4, dst, 4, srcRoi, kern, kernelSize, yAnchor, divisor);

Result:

1 2 3 4
1 2 3 4       src
1 2 3 4

1 -2 1    kern

0   0   0   0
0   0   0   0      dst
0   0   0   0


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