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THRESMLWAHA

Section: User Commands (1)
Updated: 16 Mar 1998
Index

 

NAME

thresMlWaHa - Finds multiple thresholds by Wang & Haralick method

 

SYNTAX

 thresMlWaHa [-n <n>] [-nt <nt>] [-p <p>] [-et <et>] \
       [-verbose] [-tri <trilevel-image>] \
       [-edge <edge-image>] <inimage> <outimage>

 

DESCRIPTION

The pixels in inimageare first classified as either edgepixels or nonedge pixels. Edge pixels are then classified, onthe basis of their neighborhoods, as being relatively dark,relatively bright or gray. A histogram of the graytoneintensities is obtained for those pixels which are edgepixels and relatively dark, and another histogram is obtainedfor those which are edge pixels and relatively bright. Twocandidate thresholds are found at the intensity valuescorresponding to peaks in the two histograms. The thresholdgiving the highest probability of getting pure dark or brightregions is selected. If the selected threshold corresponds tothe peak in the dark edge histogram, the process is repeatedfor the graytone range above the threshold, if the thresholdcorresponds to the peak in the bright edge histogram, theprocess is repeated for the graytone range below thethreshold.

You can specify the number of thresholds to be found, or aminimum population of the two histograms at which to stop.The population of the two histograms decreases rapidly, andmight reach zero before the specified number of thresholds isfound. There is no peak in a histogram with only zero entriesand the process stops.

 

OPTIONS

-n n

An integer nused to adjust the number of edge pixelsclassified as either dark or bright. The number of pixelsclassified as either dark or bright increases withincreasing n.Default n= 3.

-et et

Edge threshold et.The sobel magnitude operator is used to findthe edge strenght in every pixel. The edge threshold valueetis then used to classify pixels as edge pixels ornonedge pixels. Default et= 100.

-nt nt

Number ntof thresholds wanted.

-p p

The minimum population pin dark or bright edge histogramsallowed before stopping. Only one of ntand pmay bespecified. If none of them are specified, the default valuep= 100 is used as stop criteria.

-verbose

Verbose. Will cause certain messages to be written to"stdout". ie. the thresholds found, the poulation of thedark and bright histograms and the graytone range, and thetotal number of thresholds found.

-edge edge-image

Specifies that the thresholded sobel magnitude imageshould be written to edge-image.

-tri trilevel-image

Specifies that the classified edge image should bewritten to trilevel-image.Edge pixels classified as darkwill be dark, edgepixels classified as bright will be bright,and other pixels will be gray.

The result written to outimagewill be a multithresholdedversion of inimagewith either ntthresholds (ifpossible), or as many thresholds found with significantpopulations in both dark and bright histograms.

 

REFERENCE

S. Wang and R. M. Haralick

"Automatic Multithreshold Selection".Computer Vision, Graphics, and Image Processing,25, 46-67 (1984).

 

SEE ALSO

thresMl(1), thresMlAppScale(3), thresMlAppMean(3),thresMlAppMedian(3), thresMlApply(3), histoCentroid(3),thresMlCentroid(3), thresMlCentroid(3), mkComCur(3),thresMlComCur(3), thresMlComCur(1), thresMlReddi(3),thresMlReddi(3), thresMlWaHa(3), sobel(1)

 

RESTRICTIONS

inimagemust have bands with pixel type unsigned byte.

 

RETURN VALUE

0 => OK.1 => Bad number of arguments.2 => Cant open inimage.3 => Malloc error.4 => Error in thresMlWaHa function.

 

AUTHOR

Jřrn Tilley Jacobsen, BLAB, Ifi, UiO

 

EXAMPLES

 thresMlWaHa solflekk.img solSeg.img
 thresMlWaHa -nt 5 -n 2 -et 50 -verbose -edge solE.img \
     -tri solT.img solflekk.img solSeg.img

 

ID

$Id: thresMlWaHa.c,v 1.22 1997/01/14 13:09:28 svein Exp $

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Index

NAME

SYNTAX

DESCRIPTION

OPTIONS

REFERENCE

SEE ALSO

RESTRICTIONS

RETURN VALUE

AUTHOR

EXAMPLES

ID

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