stvar

Name

stvar - local variance

Syntax

 #include <xite/stdiff.h>

 int stvar( IBAND input, IBAND output,
    int deltax, int deltay, double kt, int t );

Description

Local variable threshold.

 t(x,y) = k*s(x,y) + u(x,y)
      r(x,y) = b(x,y) - t(x,y) + 128
 [-t] r(x,y) = if( b(x,y) >= t(x,y)) then 255 else 0

 r(x,y)  = output image
 u(x,y)  = mean component
 s(x,y)  = st. dev component
 b(b,y)  = pixel value in (x,y)

deltax is local area width, deltay is local area height.

Restrictions

input and output must have pixel type unsigned byte.

Return value

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

Reference

Wayne Niblack: An introduction to Digital Image Processing

Author

Otto Milvang