Edge perserving smoothing filter
#include "dip_filtering.h"
dip_Error dip_Kuwahara ( in, out, se, boundary, param, shape )
binary, integer, float
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. Instead, it compares the variance of every region specified by the filter shape and size centered within the filter window.
Only the rectangular, elliptic and diamond filter shapes are supported (DIP_FLT_SHAPE_RECTANGULAR, DIP_FLT_SHAPE_ELLIPTIC and DIP_FLT_SHAPE_DIAMOND). Other filter shapes can be implemented by setting shape to DIP_FLT_SHAPE_STRUCTURING_ELEMENT, and passing a binary image in se. The "on" pixels define the shape of the filter window. Other values of shape are illegal.
If shape is not equal to DIP_FLT_SHAPE_STRUCTURING_ELEMENT, se can be set to zero. When shape is set to DIP_FLT_SHAPE_STRUCTURING_ELEMENT, param is ignored, and can be set to zero.
| Data type | Name | Description |
| dip_Image | in | Input image |
| dip_Image | out | Output image |
| dip_Image | se | Custom filter window (binary) |
| dip_BoundaryArray | boundary | Boundary conditions |
| dip_FloatArray | param | Filter sizes |
| dip_FilterShape | shape | Filter shape |
The enumerator dip_FilterShape contains the following constants:
| Name | Description |
| DIP_FLT_SHAPE_DEFAULT | Default filter window, same as DIP_FLT_SHAPE_RECTANGULAR |
| DIP_FLT_SHAPE_RECTANGULAR | Rectangular filter window, can be even in size |
| DIP_FLT_SHAPE_ELLIPTIC | Elliptic filter window, always odd in size |
| DIP_FLT_SHAPE_DIAMOND | Diamond-shaped filter window, always odd in size |
| DIP_FLT_SHAPE_PARABOLIC | Parabolic filter window (morphology only) |
| DIP_FLT_SHAPE_DISCRETE_LINE | Rotated line structuring element (morphology only) |
| DIP_FLT_SHAPE_INTERPOLATED_LINE | Rotated line structuring element, through interpolation (morphology only) |
| DIP_FLT_SHAPE_PERIODIC_LINE | (not implemented) |
| DIP_FLT_SHAPE_STRUCTURING_ELEMENT | Use se as filter window, can be any size |
GeneralisedKuwahara, KuwaharaImproved, GeneralisedKuwaharaImproved, VarianceFilter, Uniform