Convert a PostScript file to a PNM image.
Convert a PS file to PNM images, storing page N of the input to `path/to/fileN.ppm`
pstopnm path/to/file.ps
Explicitly specify the output format
pstopnm -pbm|pgm|ppm path/to/file.ps
Specify the resolution of the output in dots per inch
pstopnm -dpi n path/to/file.ps