NAME

       pbmclean - despeckle a PBM image

SYNOPSIS

       pbmclean [-minneighbors=N] [-black|-white] [-extended] [pbmfile]

OPTION USAGE

       You can use the minimum unique abbreviation of the options.  You can use two hyphens instead of one.  You
       can separate an option name from its value with white space instead of an equals sign.

DESCRIPTION

       This program is part of Netpbm(1).

       pbmclean cleans up a PBM image of random specks.  It reads a PBM image as input and outputs a PBM that is
       the same as the input except with isolated pixels inverted.

       You can use pbmclean  to clean up "snow" on bitmap images.

       There  are  two  ways  pbmclean  can  define  "isolated"  pixels:  simple and extended.  When you specify
       -extended, pbmclean uses extended; otherwise it uses basic.

   Basic Mode
       In basic mode, pbmclean looks at each pixel individually, and any pixel that  doesn't  have  at  least  a
       minimum number of pixels of the same color touching it is considered isolated and pbmclean erases it.

       The -minneighbors option specifies the minimum number of neighboring pixels of the same color for a pixel
       not to be considered isolated.

       For  example,  if  -minneighbors  is  two and there are two contiguous black pixels in an otherwise white
       field, each of those pixels is isolated, so pbmclean erases them - turns both white.

       The default minimum 1 pixel - pbmclean flips only completely isolated pixels.

       (A -minneighbors value greater than 8 generates a completely inverted image  (but  use  pnminvert  to  do
       that) -- or a completely white or completely black image with the -black or -white option).

       pbmclean  considers  the area beyond the edges of the image to be white.  (This matters when you consider
       pixels right on the edge of the image).

       pbmclean does not distinguish between foreground and background; by default, it flips isolated pixels  of
       either color.  But you can specify -black or -white to have it flip only pixels of one color.

   Extended Mode
       In  extended  mode, pbmclean erases all blobs which don't have the specified minimum number of pixels.  A
       blob is a set of contiguous pixels of the foreground color.  The minimum number of pixels is one plus the
       -minneighbors value.  You specify the foreground color with -black and -white (default is black).

       For example, if -minneighbors is 2 and the foreground color is black, and the image contains  a  straight
       line  4  pixels long, pbmclean erases that -- turns all four pixels white.  pbmclean also erases 4 pixels
       in a square or L-shape.

       The default -minneighbors is 4, so a blob must have at least 5 pixels to escape pbmclean's purge.

       Extended mode was new in Netpbm 10.56 (September 2011).

OPTIONS

       In addition to the options common to all programs based on libnetpbm (most notably  -quiet,  see   Common
       Options ), pbmclean recognizes the following command line options:

       -black

       -white Flip  pixels  of  the  specified  color.   By  default,  if you specify neither -black nor -white,
              pbmclean flips both black and white pixels which do not have sufficient identical  neighbors.   If
              you  specify -black, pbmclean leaves the white pixels alone and just erases isolated black pixels.
              Vice versa for -white.  You may specify both -black and -white to get  the  same  as  the  default
              behavior.

       -minneighbors=N
              This  determines  how  many  pixels  must  be  in a cluster in order for pbmclean to consider them
              legitimate and not clean them out of the image.  See Description .

              Before December 2001, pbmclean accepted -N instead of -minneighbors.  Before Netpbm  10.27  (March
              2005), -minneighbors was -minneighbor.

       -extended
              pbmclean uses extended, as opposed to basic, isolated pixel detection.

              This option was new in Netpbm 10.56 (September 2011).

SEE ALSO

       pbm(1)

AUTHOR

       Copyright  (C)  1990  by Angus Duggan Copyright (C) 1989 by Jef Poskanzer.  Copyright (C) 2001 by Michael
       Sternberg.

       Permission to use, copy, modify, and distribute this software and its documentation for any  purpose  and
       without  fee  is  hereby  granted, provided that the above copyright notice appear in all copies and that
       both that copyright notice and this permission notice appear in supporting documentation.  This  software
       is provided "as is" without express or implied warranty.

DOCUMENT SOURCE

       This  manual  page was generated by the Netpbm tool 'makeman' from HTML source.  The master documentation
       is at

              http://netpbm.sourceforge.net/doc/pbmclean.html

netpbm documentation                            19 November 2011                         Pbmclean User Manual(1)