pbmclean(1) - phpMan

Pbmclean User Manual(0) Pbmclean User Manual(0)

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 out-
puts 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.

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 oth-
erwise 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 iso-
lated pixels of either color. But you can specify -black or -white to have it flip only
pixels of one color.

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 fore-
ground 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 con-
tains 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
-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 con-
sider 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).