For example, a font can have continuous variation on a weight axis, but the designer may identify particular variation instances as “Light” or “Semibold”. For example, an axis could trigger substitution to different alternate glyphs for discrete sub-ranges of axis values.Ī font designer can pre-define certain instances to have particular names. ![]() In some cases, however, appearance can vary in discrete steps as the axis setting is changed. So, for instance, if a user or application requires small adjustments to width or slightly more pronounced serifs, fine control over such axes of variation is available.Įvery axis allows for a continuous range of instance-selection values, and typically there will be continuous variation in appearance for a given axis. ![]() Each instance would be designated by a coordinates array within the design-variation space - a specific value along each of the design axes. Conceptually, this provides a continuous gradient of variation, allowing for a large number of design-variation instances to be selected. Each axis is defined by a numeric range, using fractional values represented using the Fixed (16.16) data type. This table determines how a variable font and its variation parameters will be presented to users and applications. For example, a font could vary line height metrics or appearance of gradients in color glyphs rather than (or in addition to) glyph outlines.Ī variable font includes a table, the font variations ('fvar') table, that describes the axes of variation used by that font. In general, however, potentially any aspect of the visual appearance may vary. Typically, variable fonts will vary the design of glyph outlines. For example, the following illustrates a combination of weight and width variation: Continuous variation along multiple design axes ![]() Variable fonts can combine two or more different axes of variation. Weight is one possible axis of variation, but many different kinds of variation are possible. Variable fonts - fonts that use OpenType Font Variations mechanisms - provide great flexibility for content authors and designers while also allowing the font data to be represented in an efficient format.Ī variable font allows for continuous variation along some given design axis, such as weight: Continuous variation along a design axisĬonceptually, variable fonts define one or more axes over which design characteristics can vary. OpenType Font Variations allow a font designer to incorporate multiple font faces within a font family into a single font resource. This chapter of the OpenType Specification provides an overview of OpenType Font Variations, including an introduction to essential concepts, a glossary of terminology, and a specification of key algorithms: coordinate normalization, and interpolation of instance values.
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