pnmcrop — Crop PNM images. More information: <https://netpbm.sourceforge.net/doc/pnmcrop.html>.

Remove white borders on a PNM image

pnmcrop {{[-w|-white]}} {{path/to/image.pnm}} > {{path/to/output.pnm}}

Remove borders of the specified color that are on the top and left side of the image

pnmcrop -bg-color {{color}} {{[-t|-top]}} {{[-l|-left]}} {{path/to/image.pnm}} > {{path/to/output.pnm}}

Determine the color of the borders to be removed by the color of the pixel in the specified corner

pnmcrop -bg-corner {{topleft|topright|bottomleft|bottomright}} {{path/to/image.pnm}} > {{path/to/output.pnm}}

Leave a border with a width of `n` pixels. Additionally, specify the behavior if the image is entirely made out of background

pnmcrop {{[-m|-margin]}} {{n}} {{[-blan|-blank-image]}} {{pass|minimize|maxcrop}} {{path/to/image.pnm}} > {{path/to/output.pnm}}