Synthesis of Parametrisable Fonts by Shape Components

C. HU

Ph.D. dissertation by Changyuan HU, under the supervision of Prof. Roger D. Hersch, Thesis No 1905 presented at the School of Computer & Communication Sciences, Ecole Polytechnique Fédérale de Lausanne, 1998

Abstract 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 thesis a new highly flexible font description method, which explicitly describes characters as structure elements, i.e. as assemblies of parametrisable shape components. 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 highquality 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.

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