Linux cli command pbmreduce

➡ A Linux man page (short for manual page) is a form of software documentation found on Linux and Unix-like operating systems. This man-page explains the command pbmreduce and provides detailed information about the command pbmreduce, system calls, library functions, and other aspects of the system, including usage, options, and examples of _. You can access this man page by typing man followed by the pbmreduce.

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NAME 🖥️ pbmreduce 🖥️

read a PBM image and reduce it N times

SYNOPSIS

pbmreduce [-floyd|-fs|-threshold] [-value val] [**-randomseed=**integer] N [pbmfile]

You can abbreviate any option to its shortest unique prefix.

DESCRIPTION

This program is part of Netpbm(1) .

pbmreduce reads a PBM image as input and reduces it by a factor of N, producing a PBM image as output.

pbmreduce duplicates a lot of the functionality of pamditherbw; you could do something like pamscale | pamditherbw, but pbmreduce is a lot faster.

You can use pbmreduce to “re-halftone” an image. Let’s say you have a scanner that only produces black&white, not grayscale, and it does a terrible job of halftoning (most b&w scanners fit this description). One way to fix the halftoning is to scan at the highest possible resolution, say 300 dpi, and then reduce by a factor of three or so using pbmreduce. You can even correct the brightness of an image, by using the -value option.

OPTIONS

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

-threshold
By default, pbmreduce does the halftoning after the reduction via boustrophedonic Floyd-Steinberg error diffusion; however, you can use this option to specify simple thresholding. This gives better results when reducing line drawings.

-floyd, -fs
Specify the Floyd-Steinberg error diffusion method. This is the default.

-value
This option alters the thresholding value for all quantizations. It should be a real number between 0 and 1. Above 0.5 means darker images; below 0.5 means lighter.

**-randomseed=**integer
This is the seed for the random number generator that controls the halftoning.

Use this to ensure you get the same image on separate invocations.

This option was new in Netpbm 10.75 (June 2016).

SEE ALSO

pamenlarge(1) , pamscale(1) , pamditherbw(1) , pbm(1)

AUTHOR

Copyright (C) 1988 by Jef Poskanzer.

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/pbmreduce.html

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