---
syntax: markdown
tags: [tldr, common]
source: https://github.com/tldr-pages/tldr.git
---
# pnmnlfilt

> Apply a non-linear filter onto a PNM image.
> More information: <https://netpbm.sourceforge.net/doc/pnmnlfilt.html>.

- Apply the "alpha trimmed mean" filter with the specified alpha and radius values onto the PNM image:

`pnmnlfilt {{0.0..0.5}} {{radius}} {{path/to/image.pnm}} > {{path/to/output.pnm}}`

- Apply the "optimal estimation smoothing" filter with the specified noise threshold and radius onto the PNM image:

`pnmnlfilt {{1.0..2.0}} {{radius}} {{path/to/image.pnm}} > {{path/to/output.pnm}}`

- Apply the "edge enhancement" filter with the specified alpha and radius onto the PNM image:

`pnmnlfilt {{-0.9..(-0.1)}} {{radius}} {{path/to/image.pnm}} > {{path/to/output.pnm}}`
