pnmnoise

Generate random noise PNM images (often an alias for pgmnoise)

TLDR

Create grayscale noise image (via pgmnoise)

$ pgmnoise [width] [height] > [noise.pgm]

Build color noise by combining three grayscale noise channels

$ rgb3toppm <(pgmnoise 256 256) <(pgmnoise 256 256) <(pgmnoise 256 256) > noise.ppm

Add noise to an existing image

$ pamaddnoise -type=gaussian -lsigma=0.1 [image.pnm] > [noisy.pnm]

SYNOPSIS

pgmnoise [-randomseed n] width height

There is no standalone pnmnoise program in modern Netpbm. The name is sometimes used loosely to refer to Netpbm's family of noise generators.Use pgmnoise to generate a grayscale PGM of white noise, pbmnoise for a PBM (bitmap) of random black/white pixels, and combine three pgmnoise outputs with rgb3toppm to create a color PPM noise image. pamaddnoise adds several noise distributions (gaussian, impulse, multiplicative-gaussian, etc.) to an existing image.

PARAMETERS

width

Image width in pixels.

height

Image height in pixels.

-randomseed n

Seed the pseudo-random number generator for reproducible output.

EXAMPLES

$ # Grayscale noise 512x512
pgmnoise 512 512 > noise.pgm

# Reproducible grayscale noise
pgmnoise -randomseed 12345 100 100 > noise.pgm

# Color noise by merging three channels
rgb3toppm <(pgmnoise 256 256) <(pgmnoise 256 256) <(pgmnoise 256 256) > noise.ppm

# Convert to PNG
pgmnoise 200 200 | pnmtopng > noise.png

CAVEATS

pnmnoise is not a distinct binary; pgmnoise/pbmnoise produce single-channel noise only. Random distribution is uniform; for other distributions use pamaddnoise on a base image.

HISTORY

The Netpbm noise generators are part of the Netpbm package (originally pbmplus by Jef Poskanzer, 1988). The older pnmaddnoise was renamed to pamaddnoise in Netpbm 10.30.