pnmnlfilt
Apply a non-linear filter onto a PNM image.
TLDR
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]
