pnmconvol — Convolute a PNM image. More information: <https://netpbm.sourceforge.net/doc/pnmconvol.html>.

Convolve a PNM image with the specified convolution matrix

pnmconvol -matrix=-1,3,-1 {{path/to/image.pnm}} > {{path/to/output.pnm}}

Convolve a PNM image with the convolution matrix in the specified files, one for each layer in the input image

pnmconvol -matrixfile {{path/to/matrix1,path/to/matrix2,...}} {{path/to/image.pnm}} > {{path/to/output.pnm}}

Convolve a PNM image with the convolution matrix in the specified PNM file

pnmconvol {{path/to/matrix.pnm}} {{path/to/image.pnm}} > {{path/to/output.pnm}}

Normalize the weights in the convolution matrix such that they add up to one

pnmconvol -matrix=-1,3,-1 -normalize {{path/to/image.pnm}} > {{path/to/output.pnm}}