libxmi originated with the vector graphics code in the X11 sample server,
which was written in the mid-to-late 1980's by Brian Kelleher, Joel
McCormack, Todd Newman, Keith Packard, Robert Scheifler and Ken Whaley, who
worked for Digital Equipment Corp., MIT, and/or the X Consortium.

In 1998-99, Robert S. Maier <rsm@math.arizona.edu> extracted the vector
graphics code and merged it into the GNU plotutils package.  He later broke
it out again, as libxmi.  The code needed to be ANSI-ized, rearranged, and
extensively commented.  Also, basic data structures were changed, so that a
two-stage graphics pipeline could be set up.  All painting of pixels was
changed to go through a miPaintedSet object, and a single method
(miAddSpansToPaintedSet).  That eliminated all double-painting of pixels.
Also, some rendering extensions were added (e.g., multicolored dashes).