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BIN_NI

Section: C Library Functions (3)
Updated: 16 Mar 1998
Index

NAME

bin_ni - binarize a gray-scale band usingNiblack`s method

SYNTAX

#include <xite/binarize.h>

int bin_ni( int region_size, double weight,
IBAND inband, IBAND outband );

DESCRIPTION

The input band inbandis binarized using the method ofNiblack. The result is returned in outband.

The idea of this method is to vary the threshold over theimage, based on the local mean and local standard deviation.The threshold at pixel (x,y) is calculated as

T(x,y) = weight* sigma(x,y) + mu(x,y)

where sigma(x,y) and mu(x,y) are the estimated standarddeviation and mean value in a local neighborhood of (x,y) ofsize (region_sizex region_size).The value of weightisused to adjust how much of the foreground object edges thatare taken as a part of the object. A recommended value forweightis -0.2 for images with black foreground objects, andweight= +0.2 for images with white foreground objects.

RESTRICTIONS

inbandand outbandmust have pixel type unsigned byte.

REFERENCES

.I Wayne Niblack

"An introduction to Digital image processing",pp 115-116, Prentice Hall, 1986.

RETURN VALUE

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

FILES

src/binarize/bin_ni.c

AUTHOR

Řivind Due Trier

ID

$Id: bin_ni.c,v 1.16 1997/01/14 15:46:54 svein Exp $

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