Informations about digital font formats

TrueType

Type 1

OpenType CFF

OpenType TTF

Ikarus

Software developed by URW, a German company, in the 80's for converting existing typefaces and logos into digital format for use on computer driven printing, plotting and sign cutting devices.

Ikarus uses a cubic spline mathematical model of the outline shape of each character within a typeface to give a fully scalable representation. This means that any rendering resolution can be attained (by rasterisation) with equal accuracy from one relatively small set of data. The Ikarus coordinates for a shape all fall on the outline of that shape (as opposed to Bezier curves where there are 'guide' points which can be inside or outside the outline).

History

Originally invented by Peter Karrow, Ikarus (German spelling of the mythical figure Icarus) got its name from the frequency with which it crashed in the early days of its development. It was designed to run on Mini computers such as DEC Vax and later adapted to Micro computers as they became increasingly powerful.

By the nineteen eighties there was a huge library of typefaces and logos which existed as photographic film and which needed to be input into computers for the latest generation of printing and sign-making devices. Unfortunately, normal scanning gives a rasterized shape at the resolution of the scanning device which leads to degradation of quality when scaling up and down. This is a particular concern in the sign making industry where individual letters may be metres across, many times the size of the original artwork. Ikarus enables a human operator to input the features of a complex shape with curves, corners and straight lines (e.g. a letter of the alphabet) to a computer which stores it as a mathematical function which is for all intents and purposes independent of the size of the original artwork and of the final output.

The advent of desktop publishing in the eighties using Apple Macintosh computers coupled with laser printers led to a shift away from a small number of specialized print bureaux acquiring relatively expensive fonts to a growing market for cheap mass produced fonts. The drawback of Ikarus for catering for this new market was that, while extremely accurate, it was very labour intensive.

Digitizing

The first stage of digitization of a typeface is prepare the artwork by marking up. This involves putting tick marks around any curves at approximately 30 degree intervals along with extra tangent points where a curve blends onto a straight line. Some form of accurate graphics tablet is then used to input three types of points: curve points, corner points and tangent points. Any irregularities (e.g. lumps and flat spots) are then edited out by adjusting the position of the points on the computer. The human eye is extremely sensitive to spotting irregularities on smooth outlines and typical adjustments are of the order of tenths of millimetres on a character one hundred millimetres high. As the computer screen displays a rasterized image at relatively low resolution, high quality print outs (traditionally bromides) or cuts in film (Ulano) are used to proof the digitized shapes.