pgmramp — Generate a greyscale map. More information: <https://netpbm.sourceforge.net/doc/pgmramp.html>.

Generate a left-to-right greyscale map

pgmramp -lr > {{path/to/output.pgm}}

Generate a top-to-bottom greyscale map

pgmramp -tb > {{path/to/output.pgm}}

Generate a rectangular greyscale map

pgmramp -rectangle > {{path/to/output.pgm}}

Generate an elliptical greyscale map

pgmramp -ellipse {{path/to/image.pgm}} > {{path/to/output.pgm}}

Generate a greyscale map from the top-left corner to the bottom-right corner

pgmramp -diagonal {{path/to/image.pgm}} > {{path/to/output.pgm}}