Manual: pbmclean

Pbmclean User Manual(1) General Commands Manual Pbmclean User Manual(1)

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 sepa‐
rate 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), -min‐
neighbors was -minneighbor.

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

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

Manual: pbmclean

Related Commands: