In the previous article, I explained that hinting is “an instruction to fit the shape of the character to the pixel grid.” From here, I will explore the specific mechanisms of PostScript hinting.

One of the fundamental concepts of PostScript hinting is the “stem hint.” In the context of typeface design, “stem” is often used to refer to the major vertical line, but the “stem” in stem hint is a broader concept.

Stem hints are categorized into two types depending on their direction: “horizontal hints” and “vertical hints.” A horizontal hint specifies the “stem in the horizontal direction range from here to there” using coordinates, while a vertical hint specifies a stem in the vertical direction. Not only the straight line parts, but also the width of the expanding parts on the right side of “D” are defined as vertical hints. If this definition exists within the font data, the rasterizer (program that draws characters) will prioritize processing the specified range.

In this manner, by defining the width forming the skeleton of characters as the “stem” and controlling it to fit nicely within the pixel grid, characters can be displayed without distortion even on low-resolution screens.

(mm)