CAB@SU-AI.ARPA.UUCP (05/17/86)
In a previous response about the history of digital outline fonts, I did not mention two noteworthy contributions to the field -- Ikarus and Metafont -- because their outlines are part of systems for producing type rather than output device formats. Ikarus was developed by Peter Karow in 1974-75, with accretions and enhancements over the next decade, as a system for producing digital fonts. It is used by some two dozen type equipment manufacturers worldwide. Its font formats include both cubic spline outlines and arc & vector outlines. Metafont was developed by Donald Knuth in two stages, from 1978 - 1985 (Knuth himself could provide more accurate dates). The first version used cubic splines, but primarily for "inline" fonts described by skeletons rather than contours. The latest version uses cubic splines for outline fonts as well. Subsequent to the Adobe PostScript outline font format, which uses cubic splines, Imagen developed an outline font format using quadratic splines. Vaughan Pratt and Theo Pavlidis had earlier independently published articles on quadratic splines for font representations, and the Imagen format has much in common with these. Of course, each developer has arguments about why a particular form is superior. In general, ower order outline formats can be scan-converted faster on cheaper processors, but have less flexibility and less accuracy than the higher order outlines. There is considerable debate about which is the best compromise, and cubic is not even the highest order. Pijush Ghosh has published an article arguing the superiority of quartic splines over cubics, so the beat goes on!