Outline font representations with structured description of characters

Abstract

A character is composed of strokes, and the shape of each stroke is determined by a brush movement. The outline representation of characters with simple geometry is not sufficient to accommodate such a character structure, and not efficient for digital font processing. The efficiency of font representation is analyzed in terms of storage, design, output, and flexibility. We propose several representation schemes for the outline font, and develop design systens implementing those schemes. First, we introduce the outline module composition appeoach by using module library for the commonly used character shapes. Next, we develop a mathematical apperach to represent the character outline by computing an approximation to the general sweep boundary of a brush trajectory. The characters are defined by a two dimensionally moving ellipse whose shape can be changed parametrically while traversing a trajectory. Last, we propose an approach called structured composition of stroke elements. Each character is considered to be a set of strokes and each stroke is represented by its primitive features called stroke elements. The outline of each stroke is generated from the stroke elements, and the character boundary is obtained by merging these stroke outlines. For the computation of stroke boundaries we develop a non-constant radius offsetting algorithm and a filleting algorithm of parametric curves. Compared to the sequential representation, the outline module composition reduces the amount of font data storage and easily renders consistency to the characters by reducing the design work. The general sweep boundary approximation makes it possible to represent the outline font by the brush movement. The apperoach of structured stroke elements conforms to the natural structure of characters, and reflects both the characteristics of trajectory-based description and outline module composition. This scheme alleviates design complexity, reduces font storage space, and increases flex...