FilterLowpass

Filters an image using a lowpass filter.

Syntax

IppStatus ippiFilterLowpass_<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_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 ippiFilterLowpass is declared in the ippi.h file. It operates with ROI (see Regions of Interest in Intel IPP). This function applies a lowpass filter to an image ROI. The corresponding kernel is the matrix of either 3x3 or 5x5 size.

The 3x3 filter uses the following kernel:

1/9 1/9 1/9
1/9 1/9 1/9
1/9 1/9 1/9

The 5x5 filter uses the following kernel:

1/25 1/25 1/25 1/25 1/25
1/25 1/25 1/25 1/25 1/25
1/25 1/25 1/25 1/25 1/25
1/25 1/25 1/25 1/25 1/25
1/25 1/25 1/25 1/25 1/25

The anchor cell is the center cell of the kernel (red). The size of the source image ROI is equal to dstRoiSize, the size of the destination image ROI.

This filter blurs an image by averaging the pixel values over some neighborhood.

To ensure valid operation when image boundary pixels are processed, the application should correctly define additional border pixels (see Borders).

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.