Place the GMT graphics logo on a map.
By default, the GMT logo is 2 inches wide and 1 inch high and will be positioned relative to the current plot origin. Use various options to change this and to place a transparent or opaque rectangular map panel behind the GMT logo.
Full option list at https://docs.generic-mapping-tools.org/latest/logo.html
J = projection
R = region
J (str) – Required if this is the first plot command. Select map projection.
D (str) –
'[g|j|J|n|x]refpoint+wwidth[+jjustify][+odx[/dy]]'. Sets reference point on the map for the image.