Create a montage from multiple PNM images. More information: https://netpbm.sourceforge.net/doc/pnmmontage.html.
pnmmontage {{path/to/image1.pnm path/to/image2.pnm ...}} > {{path/to/output.pnm}}
pnmmontage -{{0..9}} {{path/to/image1.pnm path/to/image2.pnm ...}} > {{path/to/output.pnm}}
p percent of the optimal packing:pnmmontage {{[-qua|-quality]}} {{p}} {{path/to/image1.pnm path/to/image2.pnm ...}} > {{path/to/output.pnm}}
pnmmontage {{[-d|-data]}} {{path/to/datafile}} {{path/to/image1.pnm path/to/image2.pnm ...}} > {{path/to/output.pnm}}