fractile

Name

fractile - noise reduction filtering

Syntax

 #include <xite/median.h>

 int fractile( IBAND input, IBAND output,
    int dx, int dy, double frac );

Description

Filters the input band into the output band using a fractile filter with window size dx x dy. The filter sorts the pixels inside the window and choses the (dx * dy * frac) pixel.

frac = 1.0/dx/dy gives the minfilter, frac = 0.5 gives the median filter and frac = 1.0-1/dx/dy gives the max filter.

Even values of dx and dy are increased by one. Uses histogram updating when moving horizontally from pixel to pixel.

Restrictions

Accepts only pixel type unsigned byte.

Reference

Huang, Yang and Tang: "A Fast Two-Dimensional Median Filtering Algorithm" IEEE Trans. Ac., Speech, and Signal Proc, Vol ASSP-27, No.1, Feb.1979.

Return value

 0 => ok
 1 => bad pixel value input band
 2 => bad pixel value output band
 3 => bad dx value (less than 1 or greater than xsize)
 4 => bad dy value (less than 1 or greater than ysize)

Author

Tor Lønnestad, BLAB, Ifi, UiO

Modified

Otto Milvang, BLAB, Ifi, UiO

Id

$Id: fractile.c,v 1.22 1997/03/07 12:52:08 svein Exp $