pnmsmooth
Smooth and blur PNM images
TLDR
Smooth/blur image
$ pnmsmooth [input.pnm] > [output.pnm]
Smooth with custom size$ pnmsmooth -size [5] [input.pnm] > [output.pnm]
Multiple passes$ pnmsmooth [input.pnm] | pnmsmooth > [output.pnm]
SYNOPSIS
pnmsmooth [options] [pnmfile]
DESCRIPTION
pnmsmooth applies a smoothing (blur) filter to a PNM image using convolution. It averages neighboring pixels to reduce noise and sharp edges.
Wrapper around pnmconvol with a smoothing kernel.
PARAMETERS
-size n
Convolution size (default 3).-dump file
Dump convolution matrix.
EXAMPLES
$ # Basic smoothing
pnmsmooth noisy.ppm > smooth.ppm
# Stronger smoothing with larger kernel
pnmsmooth -size 5 image.ppm > blurred.ppm
# Multiple smoothing passes
pnmsmooth image.ppm | pnmsmooth | pnmsmooth > very_smooth.ppm
# Reduce noise then enhance
pnmsmooth noisy.pgm | pgmenhance > cleaned.pgm
pnmsmooth noisy.ppm > smooth.ppm
# Stronger smoothing with larger kernel
pnmsmooth -size 5 image.ppm > blurred.ppm
# Multiple smoothing passes
pnmsmooth image.ppm | pnmsmooth | pnmsmooth > very_smooth.ppm
# Reduce noise then enhance
pnmsmooth noisy.pgm | pgmenhance > cleaned.pgm
CONVOLUTION
Default 3x3 averaging kernel:
$ 1 1 1
1 1 1
1 1 1
Larger sizes create stronger blur effect.1 1 1
1 1 1
CAVEATS
Reduces image sharpness. Use pnmconvol for custom kernels. Part of Netpbm.
HISTORY
pnmsmooth is part of Netpbm by Jef Poskanzer, providing simple image smoothing via convolution.
SEE ALSO
pnmconvol(1), pgmenhance(1), pnmsharpen(1), netpbm(1)