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 ⟨index.html#commonoptions⟩ ), 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