pnmconvol
Apply convolution filters to PNM images
TLDR
Apply convolution matrix
$ pnmconvol [matrix.pgm] [input.pnm] > [output.pnm]
Create blur effect$ pnmconvol -matrix=[1,1,1;1,1,1;1,1,1] [input.pnm] > [output.pnm]
Edge detection$ pnmconvol -matrix=[-1,-1,-1;-1,8,-1;-1,-1,-1] [input.pnm] > [output.pnm]
SYNOPSIS
pnmconvol [options] convolution input
DESCRIPTION
pnmconvol applies convolution matrix filters to PNM images for effects like blurring, sharpening, and edge detection. The convolution kernel can be specified as a PGM file or inline with the -matrix option.Each output pixel is computed as the weighted sum of surrounding input pixels according to the kernel values. Part of the Netpbm toolkit for image processing.
PARAMETERS
CONVOLUTION
Convolution matrix as a PGM file.INPUT
Input PNM image file.-matrix SPEC
Specify convolution matrix inline (e.g., "1,1,1;1,1,1;1,1,1").-matrixfile FILE
Read convolution matrix from a file.-normalize
Scale weights to sum to one, preserving overall image brightness.-bias n
Amount to add to each convolved sample value, useful for handling negative results.-nooffset
Normalize matrix values by dividing by maxval instead of using offset calculations.
INSTALL
sudo apt install netpbm
sudo dnf install netpbm
sudo pacman -S netpbm
sudo apk add netpbm
sudo zypper install netpbm
brew install netpbm
nix profile install nixpkgs#netpbm
CAVEATS
Part of Netpbm. Matrix defines effect. Slow for large kernels.
HISTORY
pnmconvol is part of Netpbm for convolution operations.
