pgmmedian(1)pgmmedian(1)NAMEpgmmedian - apply a median filter to a PGM file
SYNOPSISpgmmedian [-cutoff int] [-size width height] [-type
median_type] [pnmfile]
DESCRIPTION
Applies a median filter to a PGM image. The program auto-
matically selects whether to use a histogram sort or
select k'th value method to determine median. This auto-
matic selection is configurable via the -cutoff option and
which method to use can be forced with the -type option.
OPTIONS-cutoff int
The cutoff value to decide between using the his-
togram sort or select k'th value to find the
median. It is compared to (maxval / ((width *
height) - 1)). The default value is 250. If
expression is less than the cutoff the histogram
sort is used, otherwise select k'th value method is
used.
-size width height
Width and height of median mask to apply.
-type median_type
Selects which method to use to find median irre-
gardless of cutoff value. Choices currently are
histogram_sort and select. Only enough letters to
be unique are required for the type option.
BUGS
None.
REFERENCES
"Collected Algorithms from ACM" Volume II, Algorithm 489
by Robert W. Floyd
"A Fast Two-Dimensional Median Filtering Algorithm" in
"IEEE Transactions
on Acoustics, Speech, and Signal Processing" Vol.
ASSP-27, No. 1, February 1979
"Digital Image Processing Algorithms" by Ioannis Pitas,
Prentice Hall, 1993 ISBN 0-13-145814-0
SEE ALSOpgm(5), pgmnoise(1), pnmaddnoise(1), pnmsmooth(1)AUTHOR
Copyright (C) 1996 by Mike Burns <burns@cac.psu.edu>
28 September 1996 1