The escape sequence
\X'ps: import file llx lly urx ury
places a rectangle of the specified width containing the PostScript drawing from file file bound by the box from llx lly to urx ury (in PostScript coordinates) at the insertion point. If height is not specified, the embedded drawing is scaled proportionally.
See Miscellaneous, for the
psbb request which automatically
generates the bounding box.
This escape sequence is used internally by the macro
(see the groff_tmac(5) manual page).