Kuwahara

Edge perserving smoothing filter

SYNOPSIS

#include "dip_filtering.h"

dip_Error dip_Kuwahara ( in, out, se, boundary, filterSize, shape )

DATA TYPES

binary, integer, float

FUNCTION

This function implements the kuwahara edge-preserving smoothing function. See section 9.4, "Smoothing operations", in "Fundamentals of Image Processing" for a description of the algorithm. However, this function does not implement the classical kuwahara filter, which only compares the variance of four regions in the filter window, but compares the variance of every region specified by the filter shape and size centered withing the filter window.

If shape is not equal to DIP_FLT_SHAPE_STRUCTURING_ELEMENT, se is allowed to be set to zero. When shape is set to DIP_FLT_SHAPE_STRUCTURING_ELEMENT, filterParam is ignored, (and can be set to zero).

ARGUMENTS

Data type	Name	Description
`dip_Image`	`in`	Input image
`dip_Image`	`out`	Output image
`dip_Image`	`se`	Structuring element
`dip_BoundaryArray`	`boundary`	Boundary conditions
`dip_FloatArray`	`filterSize`	Filter sizes
`dip_FilterShape`	`shape`	Filter shape

The enumerator dip_FilterShape contains the following constants:

Name	Description
`DIP_FLT_SHAPE_DEFAULT`	default structuring element, same as `DIP_FLT_SHAPE_RECTANGULAR`
`DIP_FLT_SHAPE_RECTANGULAR`	rectangular structuring element
`DIP_FLT_SHAPE_ELLIPTIC`	elliptic structuring element
`DIP_FLT_SHAPE_DIAMOND`	diamond shaped structuring element
`DIP_FLT_SHAPE_PARABOLIC`	parabolic structuring element
`DIP_FLT_SHAPE_STRUCTURING_ELEMENT`	use `se` as structuring element

NOTE

The filter shape DIP_FLT_SHAPE_PARABOLIC, as well as custom grey-value shapes, are not supported.