graphics/libspiro 20240903 OpenBSD

Spiro is the creation of Raph Levien. It simplifies the drawing of beautiful curves.

Using bezier splines an artist can easily draw curves with the same slope on either side of an on-curve point. Spiros, on the other hand, are based on clothoid splines which make it easy to maintain constant curvature as well as constant slope. Such curves will simply look nicer.

Spiro splines only use on-curve points and so are easier to use and more intuitive to the artist.

This library will take an array of spiro control points and convert them into a series of bezier splines which can then be used in the myriad of ways the world has come to use beziers.