Sigma

Adaptive uniform smoothing filter

SYNOPSIS

#include "dip_filtering.h"

dip_Error dip_Sigma ( in, out, se, boundary, filterSize, shape, sigma, outputCount )

DATA TYPES

integer, float

FUNCTION

The Sigma filter is an adaptive Uniform smoothing filter. The value of the pixel underinvestigation is replaced by the average of the pixelvalues in the filter region (as specified by filterSize, shape and se) which lie in the interval +/- 2 sigma from the value of the pixel that is filtered. If outputCount is DIP_TRUE, the output values represent the number of pixel over which the average has been calculated. When threshold is DIP_TRUE, the pixel intensities are being thresholded at +/- 2 sigma, when it is set to DIP_FALSE, the intensities are weighted with the Gaussian difference with the intensity of the central pixel.

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
`dip_float`	`sigma`	Sigma
`dip_Boolean`	`outputCount`	Output the Count

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.

LITERATURE

John-Sen Lee, Digital Image Smoothing and the Sigma Filter, Computer Vision, Graphics and Image Processing, 24, 255-269, 1983