ppmrainbow — Generate a rainbow. More information: <https://netpbm.sourceforge.net/doc/ppmrainbow.html>.

Generate a rainbow consisting of the specified colors

ppmrainbow {{color1 color2 ...}} > {{path/to/output_file.ppm}}

Specify the size of the output in pixels

ppmrainbow {{[-w|-width]}} {{width}} {{[-h|-height]}} {{height}} {{color1 color2 ...}} > {{path/to/output_file.ppm}}

End the rainbow with the last color specified, do not repeat the first color

ppmrainbow {{[-n|-norepeat]}} {{color1 color2 ...}} > {{path/to/output_file.ppm}}