Perceptually Tuned Generation of Grayscale Fonts

Previous attempts to generate grayscale fonts by filtering and resampling high-resolution masters produced fuzzy looking characters lacking sharp contrast profiles and uniform character structure elements (horizontal and vertical bars, curved stems, serifs). Contrast sharpness in vertical bars and repetitive contrast profiles of similar character structure elements must be preserved in order to avoid characters having fuzzy appearance. Furthermore, thin character parts must be enhanced so as to preserve their visual structure. A new grayscale character generation method is proposed which uses outline weight- and phase-control techniques for generating characters with bars and curved stems of predictable intensity profiles. The grayscale design knowledge of type designers has been made explicit and incorporated into the grayscale character synthesizing system. Knowledge about character structure elements is added to the character's outline description in the form of hints. Visual knowledge about the rendering of quality of the produced weight- and phase-controlled grayscale characters comes close to that of manually tuned grayscale designs. Accurate spacing of grayscale characters is obtained by using a model providing the area equivalent to the perceived intercharacter space. Such perceptually tuned and optically spaced grayscale characters may find applications in high-quality CRT and LCD displays.