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Section: Misc. Reference Manual Pages (16 Mar 1998)
Index

NAME

bin_etm - binarize a gray-scale band usingEikvil, Taxt and Moen`s method

SYNTAX

int bin_etm( int region_size, int step_size,
    double dist_limit, double weight,
    int glob_min, int glob_max, int bin_method,
    IBAND inband, IBAND outband );

DESCRIPTION

The input band inbandis binarized usingthe method of Eikvil, Taxt and Moen, the result returnedin outband.

The pixels inside a small window Sof size(small_window_sizex small_window_size)are thresholded onbasis of the clustering of the pixels inside a largerconcentric window Lof size (region_sizex region_size)Sand Lslide across the image in steps equal to the sideof S.For all pixels inside L,a threshold Tiscalculated to divide the pixels into two clusters. If the twoestimated cluster means mu1 and mu2 are further apart than alimit, mu2 - mu1 > mean_diff_limitthe pixels inside Sarebinarized using the threshold value T.When mu2 - mu1 <mean_diff_limit,the pixels inside Sare all assigned tothe class with the closest updated mean value, being it printor background.

bin_methodis used to select the global binarization methodwhich finds T.Use bin_method= OTSU or bin_method=KITTLER_ILLINGWORTH.

weightis used to calculate the updated mean values MU1 andMU2. For each small window S,the new values are caluculatedas

MU1 = 'weight' * MU1 + (1.0-'weight') * mu1
MU2 = 'weight' * MU2 + (1.0-'weight') * mu2

weight= 1.0 means that the initial estimates for MU1 andMU2 are kept forever, while weight= 0.0 means that the meanvalues mu1 and mu2 of the two clusters in Lare used in thenext step.

For extremely difficult images, a preprocessing step can beused on the image. Replace all pixel values higher than thevalue glob_maxby glob_maxitself, and similarly, replaceall pixel values lower than glob_minby glob_min.

FILES

src/binarize/bin_etm.c

REFERENCES

.I L. Eikvil, T. Taxt & K. Moen

"An Adaptive Method for Binarization of Grey Level Images",NOBIM National Conference on Image Processing and PatternRecognition,pp 123-131, June 1991

RETURN VALUE

0 : ok
1 : Bad input pixel type
2 : Bad output pixel type

RESTRICTIONS

inbandand outbandmust have pixel type unsigned byte.

AUTHOR

Řivind Due Trier

ID

$Id: bin_etm.c,v 1.16 1997/01/14 15:46:51 svein Exp $

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