N.B. An asterisk before a word means it has its own entry in the glossary.
Deltas are special *instructions in a TrueType font which nudge the *control points of the *glyph *outline at particular *ppem sizes. Using deltas, you can usually define the exact *bitmap you require at crucial small sizes. (There are also delta instructions to adjust entries in the *CVT.)
Some people use the term "delta-hinted font" as shorthand for a TrueType font whose rendering has been tuned at a range of sizes, for example the core Microsoft and Apple fonts, or Monotype's *ESQ range. In such fonts, not all glyphs necessarily require deltas - it's more efficient (in terms of space and performance) to avoid deltas in favour of more general instructions. If you're considering getting a TrueType font hinted, it may be cheaper if you request only a few specific ppem sizes to be delta-hinted.
- design axis
The concept used in *multiple master and GX *variations technology, for a typographic parameter that can be varied - either by typing a value directly or by using a slider control. Common design axes are weight (from light to bold), width (from condensed to expanded) and optical size (from, say, 6pt to display).
- dropout control
A set of modes that the TrueType *rasterizer can switch to, such that delicate parts of a *glyph do not disappear, even if no pixel-centres pass through those parts. Using the SCANCTRL and SCANTYPE *instructions, dropout control can be set for a whole font, or on a per-glyph basis. Invoking dropout control slows down the rasterizer, but is useful for complex glyphs that are difficult to hint.
TrueType Typography |