tldr/pages/common/pnmnlfilt.md

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# 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}}`