FilterMin

Applies the ‘min' filter to an image.

Syntax

IppStatus ippiFilterMin_<mod>(const Ipp<datatype>* pSrc, int srcStep, Ipp<datatype>* pDst, int dstStep, IppiSize dstRoiSize, IppiSize maskSize, IppiPoint anchor);

Supported values for mod:

8u_C1R	16u_C1R	16s_C1R	32f_C1R
8u_C3R	16u_C3R	16s_C3R	32f_C3R
8u_C4R	16u_C4R	16s_C4R	32f_C4R
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.
maskSize	Size of the mask in pixels.
anchor	Anchor cell specifying the mask alignment with respect to the position of the input pixel.

Description

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

This function sets each pixel in the destination image to the minimum value of all the source image pixel values in the neighborhood of size maskSize with the anchor cell at that pixel. This has the effect of decreasing the contrast in the image.

The anchor cell is specified by its coordinates anchor.x and anchor.y in the coordinate system associated with the top left corner of the kernel. To ensure valid operation when image boundary pixels are processed, the application should correctly define additional border pixels (see Borders).

The Example “Applying the Min Filter” illustrates the use of the ippiFilterMin function. Note that this function operates on the assumption that all neighborhood pixels needed from outside the ROI are available.

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 maskSize has a field with a zero or negative value.
ippStsAnchorErr	Indicates an error condition if anchor is outside the mask size.

Applying the Min Filter

IppStatus filterMin( void) {
   Ipp8u x[5*4], y[5*4]={0};
   IppiSize img={5,4}, roi={3,2}, mask={3,3};
   IppiPoint anchor = {1,1};
   ippiSet_8u_C1R( 3, x, 5, img );
   /// set a hole (1) at strow 1 and column 1.
   /// The value will be extended on filter
   /// mask area, depending on anchor
   x[5+1] = 1;
   /// ROI is inside the image.
   /// Offset pointers to jump at the ROI start
   return ippiFilterMin_8u_C1R( x+6, 5, y+6, 5, roi, mask, anchor );
}

The destination image y contains:

00 00 00 00 00
00 01 01 03 00
00 01 01 03 00
00 00 00 00 00