ppmdist

Map PPM colors to evenly distributed grayscale levels

TLDR

Sort by intensity and map to grayscale

$ ppmdist -intensity [input.ppm] > [output.pgm]

Sort by frequency and map to grayscale

$ ppmdist -frequency [input.ppm] > [output.pgm]

SYNOPSIS

ppmdist [-intensity | -frequency] [ppmfile]

ppmdist reads a PPM image and produces a PGM output with evenly distributed gray levels. An input of n colors produces n gray levels, maximizing contrast in the output. The mapping order is controlled by the -intensity or -frequency options. Most useful for images with a small number of colors. Part of the Netpbm toolkit.

PARAMETERS

-intensity

Sort input colors by grayscale intensity before mapping to evenly distributed gray levels.

-frequency

Sort input colors by number of occurrences before mapping to evenly distributed gray levels.

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

CAVEATS

Only helpful for images with a very small number of colors. Reads from stdin if no file is specified.