NAME

       pbmnoise - create a PBM image made up of white noise

SYNOPSIS

       pbmnoise width height

       [-ratio=M/N] [-pack] [-randomseed=integer] [-endian=]{big|little|native|swap}]

       Minimum  unique  abbreviations  of  option  are acceptable.  You may use double hyphens instead of single
       hyphen to denote options.  You may use white space in place of the equals sign to separate an option name
       from its value.

DESCRIPTION

       This program is part of Netpbm(1).

       pbmnoise creates a PBM image with random pixels.  You specify the probability each pixel will be black or
       white (essentially, the proportion of black to white pixels in the image).

       You specify the dimensions of the image with the width and height arguments.

OPTIONS

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

       -ratio=M/N
              The proportion of black pixels in the generated image.

              To  be  precise,  this is the probability that any given pixel will be black.  By the law of large
              numbers, we can expect the proportion of black pixels in a reasonably large image to be  close  to
              this fraction.

              The  option  value is a fraction.  The denominator must be 1 or an integer power of 2 up to 65536.
              the numerator must be 0 or a positive integer not exceeding denominator.

              The default is 1/2, meaning the output image has essentially the same number of  black  and  white
              pixels.

              If the ratio is 0 the output image is entirely white.  If 1, the output is entirely black.

       -pack  The  program  generates  pixels  in  32-bit  units discarding any fractional pixels at row ends by
              default.  When this option is specified, the unused pixels are  carried  over  to  the  next  row,
              eliminating waste in exchange for some overhead cost.

              Using this option improves performance when the image width is small.

       -randomseed=integer
              This is the seed for the random number generator that generates the pixels.

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

              By  default,  pbmnoise  uses  a  seed derived from the time of day and process ID, which gives you
              fairly uncorrelated results in multiple invocations.

       -endian=mode
              pbmnoise internally generates random 32-bit integers and uses the  machine's  binary  encoding  of
              those  integers as strings of pixels.  Because the integers are random, it doesn't normally matter
              what binaary encoding is used for them, but if you need consistent results between machines  using
              the  same  random number generator, it matters.  For that reason (mainly for testing the program),
              this option lets you control that encoding, between big-endian and little-endian.

              mode is one of the following:

       big    Force big-endian output by rearranging bytes on little-endian machines.  No effect  on  big-endian
              machines.

       little Likewise, force little-endian output.

       native Do not rearrange anything.  This is the default.

       swap   Always swap regardless of system endianness.

EXAMPLES

       This generates a random PBM image with roughly one-third of pixels colored black:
         pbmnoise -ratio=11/32 1200 1200 > random.pbm

       The  following  is an alternate method for generating a random PBM image which uses pgmnoise and pgmtopbm
       instead of pbmnoise.  It is less efficient.
         pgmnoise -maxval=100 1200 1200 | \
           pgmtopbm -threshold -value=0.333 > random.pbm

       This generates a random PPM image, maxval 1:
         pbmnoise 600 400 > red.pbm
         pbmnoise 600 400 > green.pbm
         pbmnoise 600 400 > blue.pbm
         rgb3topbm red.pbm green.pbm blue.pbm > random.ppm

SEE ALSO

       pbm(1) pgmnoise(1) pgmtopbm(1)

HISTORY

       pbmnoise was new in Netpbm 10.97 (December 2021).

       In Netpbm before that, you can use pgmnoise.

AUTHOR

       Akira F Urushibata wrote this program and contributed it to the public domain in December 2021.

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/pbmnoise.html

netpbm documentation                            18 December 2021                         Pbmnoise User Manual(1)