Synthesis of Parametrisable Fonts by Shape Components

Typographic characters implicitly incorporate structure elements such as stems, bars, round parts, arches and serifs, which are repeated throughout the characters of a font. Although this structure information is important when typographers design typefaces, it is however not explicitly described in today's outline font technology. As a consequence, coherently varying the style of an outline font has to be done by modifying contours of all characters in the font.

We propose in this research a new highly flexible font description method, which explicitly describes characters as structure elements, i.e., assemblies of parametrisable shape components (see the figure below). Structure elements are either predefined parametrisable components such as stems or bars of parametrisable width, or can be described by assemblies of parametrisable shape components such as sweeps and half-loops. Terminal elements are either predefined parametrisable serif shape components or are described by components such as sweeps and ellipse-like round parts and by boundary correcting paths. The component based character synthesis method is illustrated by the reconstruction of the basic characters of a few traditional text typefaces.

Using this method, we have developed a prototype of our component based parametrisable font synthesis system. Fonts are characterized by the font independent structure of individual characters, by typeface category information (serif types, junction types, squareness and obliqueness of round parts), by font-dependent global parameters and by further font-dependent parameters, referring either to a group of characters or to a single character. By varying global parameters, derived fonts can be created which vary in width, weight, contrast and shape. Such derived fonts are useful for producing high-quality condensed text, for varying the character weight and for optical scaling. Varying the typeface category information as well enables exploring parts of the traditional latin character design space.

We show the high quality of our synthesized fonts by synthesizing characters of some existing typefaces (Times, Helvetica and Bodoni). To demonstrate the application potential of this method, we have successfully accomplished typographical experiments, which are beyond the capability of traditional outline font technology, such as variation of weight, condensation, height proportion, contrast and oblique stress, and optical scaling for printing at different physical sizes.

Some results of our experiments

The following images have been created by our page generating software using the Component-based Parametrisable Font (CPF) synthesis system. Since character width and kerning table are not suitable for parametrization, our CPF synthesis system automatically generates the spaces between character pairs on the fly. High quality printed specimens are available at the LSP/EPFL).

• Synthesized characters of existing fonts (waterfall tests of some typical lowercase letters):
  • Times Roman (gif, 21k) and its component description (gif, 24k).
  • Helvetica (gif, 20k) and its component description (gif, 20k).
  • Bodoni (gif, 20k) and its component description (gif, 17k).
• Fonts derived by varying parameters, using our parametrisable Times font as the "mother":
  • Times Bold (gif, 21k) and continuous boldness variation (gif, 31k)
  • Times Condensed (gif. 20k) and continuous character width variation (gif, 30k)
  • Times Low Contrast (gif, 20k) and continuous contrast variation (gif, 30k)
  • Times Low Stress (gif, 20k) and continuous oblique stress variation (gif, 30k)
  • Times Low x-height (gif, 20k) and continuous x-height proportion variation (gif, 30k)
• Others:
  • Optically scaled characters (zoomed, gif, 9k) - traditional typographers knew that small letters must be bolder and fatter to retain their legibility.
  • A cube of the letter "e" (gif, 45k) - showing combination of boldness, obliqueness stress and contrast variations.