All options can be abbreviated to their shortest unique prefix. You may use two hyphens instead of one to designate an option. You may use either white space or an equals sign between an option name and its value.
Generates a graymap of the specified size containing a black-to-white ramp. These ramps are useful for multiplying with other images, using the pnmarith tool.
To generate a simple ramp of all the value from 0 to maxval, and not necessarily a graphic image, use pamseq.
This option did not exist before June 2002. Before, the maxval was always 255.