pnmnorm

Normalize the contrast in a PNM image. See also: pnmhisteq. More information: https://netpbm.sourceforge.net/doc/pnmnorm.html.

pnmnorm path/to/image.pnm > path/to/output.pnm

pnmnorm -midvalue n path/to/image.pnm > path/to/output.pnm

pnmnorm -keephues path/to/image.pnm > path/to/output.pnm

pnmnorm -luminosity|colorvalue|saturation path/to/image.pnm > path/to/output.pnm