NAME

       pamaddnoise - add noise to a Netpbm image

SYNOPSIS

       pamaddnoise { [-type gaussian]

       [-sigma1 value]

       [-sigma2 value] | -type  multiplicative_gaussian

       [-mgsigma value] | -type impulse

       [-tolerance ratio] | -type  laplacian

       [-lsigma value] | -type  poisson

       [-lambda value] } [-seed int]

       [netpbmfile]

DESCRIPTION

       This program is part of Netpbm(1).

       pamaddnoise  adds  the  specified  noise type to a Netpbm image.  pamaddnoise treats a PPM
       image as 3 independent planes, not as a plane of colors in a color space.

OPTIONS

       In addition to the options common to all programs based on libnetpbm (most notably -quiet,
       see
        Common Options ⟨index.html#commonoptions⟩ ), pamaddnoise recognizes the following command
       line options:

       -type noise_type
              Select type of noise by name.  The following noise types are  available:  gaussian,
              multiplicative_gaussian,  impulse,  laplacian,  poisson.  Only enough letters to be
              unique are required for the noise type option.  The default noise type is gaussian.

       gaussian

              To each sample value is added the value of a two Gaussian random variables.
                  The variance of one is independent of the sample value, while the variance
                  of the other is proportional to the sample value.  You control these
                  variances with options -sigma1 and -sigma2 (and can eliminate
                  either by setting the variance to 0).  The mean of the Gaussian
                  distributions is 0.

       multiplicative_gaussian

       impulse

              This is 'salt and pepper' noise.  Samples are changed randomly
                  to zero or full brightness or left alone.  This is also know as salt and
                  pepper noise, as in a grayscale picture, it adds white pixels and black
                  pixels, which look like salt and pepper, respectively.  Control this with
                  options -tolerance and -salt.

       laplacian

       poisson

       -lambda value
              This is valid only with -type=poisson.  It is the expected  value  of  the  Poisson
              distribution for a sample value of maximum intensity.  The expected value for other
              intensities is proportional; e.g. for half intensity, it is half this value.

              The default value is 12.

       -lsigma value
              This is meaningful only for laplacian noise.

              The default value is 10.0.

       -mgsigma value
              This is valid only for multiplicative gaussian noise.

              The default value is 0.5.

       -seed int
              This is the random number generator seed value.  Use this to get
                repeatable results.

       -sigma1 value
              This is valid only for gaussian noise.  It is the standard deviation
                of the Gaussian random variable that is multiplied by the square root of
                each sample value and added to that sample value.

                  The default value is 4.0.

       -sigma2 value
              This is valid only for gaussian noise.
                It is the standard deviation of the Gaussian random variable that is
                added directly to each sample value.

              The default value is 20.0.

       -tolerance fraction
              This is valid only for impulse noise.
                fraction is the fraction of samples that are changed
                in the output.  Whether each is changed to salt or pepper is controlled by
                -salt.

              The default value is 0.10.

       -salt=fraction

              This is valid only for impulse noise.  fraction is the
                  fraction of the pixels that are changed that are changed to salt (maxval);
                  the rest are changed to pepper (0).

              The default is 0.5 (half salt, half pepper).

              This option was new in Netpbm 11.04 (September 2023).  Before that, the
                noise is always half salt and half pepper.

REFERENCES

       •      "Adaptive Image Restoration in Signal-Dependent Noise" by R. Kasturi Institute  for
              Electronic Science, Texas Tech University, 1982

       •      "Digital  Image  Processing  Algorithms" by Ioannis Pitas, Prentice Hall, 1993 ISBN
              0-13-145814-0

SEE ALSO

       pgmnoise(1), pgmmedian(1), pnm(1), pam(1),

HISTORY

       pamaddnoise was added to Netpbm in Version 10.29 (August 2005).  It had  been  distributed
       by Mike Burns via his own web site before that (and continued to be so).

       Burns' version, and the one in Netpbm 10.29, was called pnmaddnoise and worked only on PNM
       images.  In  Netpbm  10.30,  it  was  converted  to  handle  PAM  images  and  renamed  to
       pamaddnoise.

AUTHOR

       Copyright (C) 1995 by Mike Burns <burns@cac.psu.edu>

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/pamaddnoise.html