N.B. An asterisk before a word means it has its own entry in the glossary.
Short for "scaler bitmaps", i.e. bitmaps used instead of scaling (and *hinting) an *outline. A set of sbits at a particular size is called a *strike.
TrueType fonts can contain sbits in the *'EBDT' and *'EBLC' tables (in Windows) or the *'bdat' and 'bloc' tables (in Apple GX).
- scalable image
An image represented by mathematical curves and straight lines. Scalable images can be used at all resolutions and at all sizes, unlike *bitmap images. TrueType *glyphs are scalable, using *quadratic *Bézier curve descriptions.
Scalable images suffer degradations at low resolutions, where the placement of a single pixel during *rasterization can badly affect aesthetics and, in type, legibility. These undesirable features are an inevitable consequence of representing continuous elements on a discontinuous device. (The so-called *"aliasing" problem rears its head in all areas of analogue-to-digital signal processing.) *Hinting (an integral part of TrueType) and *anti-aliasing (part of the Windows 95 TrueType system) are two very different, but complementary, techniques that alleviate the problem for text.
A program which fills *outlines to make *bitmaps, at the heart of any *rasterizer. In fonts, scan conversion is something that happens after *hints have been applied (under most paradigms of hinting).
The TrueType scan-converter uses the non-zero winding rule: when a scan-line is passed through the outline from negative infinity to positive infinity, a "winding count" is incremented when it intersects a white-to-black transition, and decremented when it intersects a black-to-white transition; pixels having a non-zero winding count are set to black, pixels with a winding count of zero are set to white. Microsoft has a page on TrueType Scan Conversion.
- 'sfnt' resource
TrueType font files are designated 'sfnt' resources on the Apple Macintosh. Exactly the same data is in a Windows *TTF file.
Font smoothing is Microsoft's term for *grey-scale or *anti-aliased type.
A common data structure in computing. Data items are "popped" and "pushed" (stored and retrieved) from the top of the stack. Stacks normally have a maximum size. It is an error to push items onto a full stack, or pop items off an empty stack.
In TrueType *hinting, all *instructions pop their arguments from the stack, although this aspect of the language is hidden in many TrueType hinting editors - and in *TypeMan Talk. For efficiency, hint assemblers and compilers typically push all the arguments for a glyph's instructions onto the stack at the beginning. The stack's maximum size is stored in the *'maxp' table of a TrueType font.
A TrueType *auto-hinting utility from Type Solutions. The hints it generates are in the *TypeMan Talk language, so they can be edited and added to by other compatible programs, e.g. *TypeMan and *Visual TrueType. StingRay is Mac only.
A *bitmap font of a particular *ppem.
Strikes can be embedded in TrueType (and *OpenType) fonts to avoid *hinting tricky *glyphs at certain ppem sizes. They use the *'EBDT' and *'EBLC' tables (in Windows) or the *'bdat' and 'bloc' tables (in Apple GX).
N.B. Since such bitmap embedding was not part of TrueType's original specification, the bitmaps will not work on older Macintosh systems or Windows 3.1 - the *outline and *hints will be used instead.
A bitmap font (i.e. *strike) editing program from TYPE*chimérique. There's a Striker information page. Windows version only.
- subsetted font
A font - TrueType, Type 1 or any other format - that for reasons of space efficiency has had unused characters removed, normally automatically. For example, a printer driver might check which characters will be used to print a document, then subset the fonts prior to downloading them to the printer. The *EOT font format uses font subsetting to serve compressed *OpenType font data efficiently to the web.
TrueType Typography |