pgmnorm
Normalize the contrast in a Netpbm image
TLDR
Normalize image contrast
$ pgmnorm [input.pgm] > [output.pgm]
Normalize with custom percentile cutoffs$ pgmnorm -bpercent [2] -wpercent [1] [input.pgm] > [output.pgm]
Specify exact pixel values for black and white mapping$ pgmnorm -bvalue [30] -wvalue [220] [input.pgm] > [output.pgm]
Normalize while preserving hues in color images$ pgmnorm -keephues [input.ppm] > [output.ppm]
SYNOPSIS
pgmnorm [options] [file]
DESCRIPTION
pgmnorm reads a PNM image (PBM, PGM, or PPM), normalizes the contrast by forcing the darkest pixels to black and the lightest pixels to white, and linearly rescales the values in between. It outputs the same kind of image. This is an older name for pnmnorm.By default, the darkest 2 percent of pixels are mapped to black and the lightest 1 percent to white. These thresholds can be changed with -bpercent and -wpercent, or exact cutoff values can be specified with -bvalue and -wvalue. If both percentage and value options are given for the same end, the one producing the least change is used.Part of the Netpbm toolkit.
PARAMETERS
-bpercent n
Percentage of darkest pixels to map to black. Default: 2.-wpercent n
Percentage of lightest pixels to map to white. Default: 1.-bvalue n
Exact pixel value to map to black (overrides -bpercent if it produces less change).-wvalue n
Exact pixel value to map to white (overrides -wpercent if it produces less change).-keephues
Keep each pixel the same hue; only adjust brightness. Without this, components are normalized independently, which may shift hues.-brightmax
Use the most intense RGB component as the pixel's brightness instead of luminosity.
INSTALL
sudo apt install netpbm
sudo dnf install netpbm
sudo pacman -S netpbm
sudo apk add netpbm
sudo zypper install netpbm
brew install netpbm
nix profile install nixpkgs#netpbm
SEE ALSO
pnmnorm(1), pgmhist(1), pnmhisteq(1), pgmenhance(1)
