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 ⟨index.html#commonoptions⟩ ), 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
              ⟨#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