segmSpannWilson

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Contents

Name

segmSpannWilson - segmentation by the Spann and Wilson method

Syntax

 segmSpannWilson [-m <m>] [-mean] [-median] [-eq] [-s <s>]
                 <inimage> <outimage>

Description

Performs segmentation of every band in the inimage image (separately) into the outimage image. The algorithm has three steps:

Quad-tree smoothing

A quad-tree is created, and pixels are averaged 4 by 4 up in the quad-tree. n quad-tree levels are created, including the bottom level, which is inband.

Local centriod clustering

The topmost quad-tree level is clustered by moving histogram mass to the centroid (mean or median) of a local window moved over the histogram. Applied iteratively, until stable. See thresMlCentroid.

Boundary estimation

The classification result is copied down the quad-tree, but at every level, all pixels close to a differently classified pixel are reclassified to determine the border more precisely.

Options

-n n
Quad-tree levels. Default = 4.

-m m
Use histogram window of size (2*m)+1. Default = 0, implying search for stable value.

-mean
Move histogram mass to local mean (default).

-median
Move histogram mass to local median.

Use either -mean or -median (or none), not both. If no -m option is given, a loop over the m-values 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50 is performed, exiting if two consecutive runs give the same thresholding result.

See also

segmSpannWilson(3), thresMlCentroid(1), segmRandom(1)

Diagnostics

 Warning: Bad pixel type in band ..
 Warning: Clustering never stable
 Error  : Bad m value: ..
 Error  : Bad number of arguments

Restrictions

inimage must have bands with pixel type unsigned byte. Bands are handled one at a time, not multi-dimensionally.

Reference

M. Spann and R. Wilson,
"A Quad-three Approach to Image Segmentation which Combines Statistical and Spatial Information" Pattern Recognition, Vol 18, Nos 3/4, pp 257-269, 1985

Author

Tor Lønnestad, BLAB, Ifi, UiO

Examples

 segmSpannWilson -median mona.img monaseg.img
 segmSpannWilson -mean -n 3 mona.img monaseg.img
 segmSpannWilson -m 25 -verbose mona.img monaseg.img

Id

$Id: segmSpannWilson.c,v 1.25 1997/01/16 16:08:53 svein Exp $