Glossary about font
[ I ripped this right out of the manual I wrote for Sfware. If you have
comments, improvements, suggestions, please tell me... ]
anti-aliasing
[ed: this is an 'off-the-cuff' definition, feel free to clarify it
for me ;-) ]
On low-resolution bitmap devices (where ragged, ugly characters
are the norm) which support more than two colors, it is possible
to provide the appearance of higher resolution with anti-aliasing.
Anti-aliasing uses shaded pixels around the edges of the bitmap
to give the appearance of partial-pixels which improves the
apparent resolution.
baseline
The baseline is an imaginary line upon which each character rests.
Characters that appear next to each other are (usually) lined up so
that their baselines are on the same level. Some characters extend
below the baseline ("g" and "j", for example) but most rest on it.
bitmap
A bitmap is an array of dots. If you imagine a sheet of graph paper
with some squares colored in, a bitmap is a compact way of
representing to the computer which squares are colored and which
are not.
In a bitmapped font, every character is represented as a pattern of
dots in a bitmap. The dots are so small (300 or more dots-per-inch,
usually) that they are indistinguishable on the printed page.
character
(1) The smallest component of written language that has semantic
value. Character refers to the abstract idea, rather than a
specific shape (see also glyph), though in code tables some form
of visual representation is essential for the reader's
understanding. (2) The basic unit of encoding for the Unicode
character encoding, 16 bits of information. (3) Synonym for "code
element". (4) The English name for the ideographic written
elements of Chinese origin.
font
A particular collection of characters of a typeface with unique
parameters in the 'Variation vector', a particular instance of
values for orientation, size, posture, weight, etc., values. The
word font or fount is derived from the word foundry, where,
originally, type was cast. It has come to mean the vehicle which
holds the typeface character collection. A font can be metal,
photographic film, or electronic media (cartridge, tape, disk).
glyph
(1) The actual shape (bit pattern, outline) of a character image.
For example, an italic 'a' and a roman 'a' are two different glyphs
representing the same underlying character. In this strict sense,
any two images which differ in shape constitute different glyphs.
In this usage, "glyph" is a synonym for "character image", or
simply "image". (2) A kind of idealized surface form derived from
some combination of underlying characters in some specific
context, rather than an actual character image. In this broad
usage, two images would constitute the same glyph whenever they
have essentially the same topology (as in oblique 'a' and roman
'a'), but different glyphs when one is written with a hooked top
and the other without (the way one prints an 'a' by hand). In
this usage, "glyph" is a synonym for "glyph type," where glyph is
defined as in sense 1.
hints
When a character is described in outline format the outline has
unlimited resolution. If you make it ten times as big, it is just
as accurate as if it were ten times as small.
However, to be of use, we must transfer the character outline to a
sheet of paper through a device called a raster image processor
(RIP). The RIP builds the image of the character out of lots of
little squares called picture elements (pixels).
The problem is, a pixel has physical size and can be printed only
as either black or white. Look at a sheet of graph paper. Rows and
columns of little squares (think: pixels). Draw a large `O' in the
middle of the graph paper. Darken in all the squares touched by the
O. Do the darkened squares form a letter that looks like the O you
drew? This is the problem with low resolution (300 dpi). Which
pixels do you turn on and which do you leave off to most accurately
reproduce the character?
All methods of hinting strive to fit (map) the outline of a
character onto the pixel grid and produce the most
pleasing/recognizable character no matter how coarse the grid is.
kerning
(noun): That portion of a letter which extends beyond its width,
that is, the letter shapes that overhang - the projection of a
character beyond its sidebearings.
(verb): To adjust the intercharacter spacing in character groups
(words) to improve their appearance. Some letter combinations
("AV" and "To", for example) appear farther apart than others
because of the shapes of the individual letters.
Many sophisticated word processors move these letter combinations
closer together automatically.
outline font/format
See 'scalable font'
point
The (more or less) original point system (Didot) did have exactly
72 points to the inch. The catch is that it was the French
imperial inch, somewhat longer than the English inch, and it went
away in the French revolution. What most people now think of as
points were established by the United States Typefounders
Association in 1886. This measure was a matter of convenience for
the members of the Association, who didn't want to retool any more
than they had to, so it had no relationship to the inch. By that
date, people realized that the inch was an archaic measure anyway;
the point was set to be 1/12 of a pica, and an 83-pica distance
was made equal to 35 centimeters. (Talk about arbitrary!)
Thus the measure of 72.27/in. is just an approximation. Of course,
when PostScript was being written, it was necessary to fit into an
inch-measured world. For the sake of simplicity PostScript defined
a point as exactly 1/72". With the prevalance of DTP, the
simplified point has replaced the older American point in many
uses. Personally, I don't see that it matters one way or the
other; all that counts is that there's a commonly-understood unit
of measurement that allows you to get the size you think you want.
That is, after all, the point ;)
scalable font
A scalable font, unlike a bitmapped font, is defined mathematically
and can be rendered at any requested size (within reason).
softfont
A softfont is a bitmapped or scalable description of a typeface or
font. They can be downloaded to your printer and used just like
any other printer font. Unlike built-in and cartridge fonts,
softfonts use memory inside your printer. Downloading a lot of
softfonts may reduce the printers ability to construct complex
pages.
symbol set
The symbol set of a font describes the relative positions of
individual characters within the font. Since there can only be 256
characters in most fonts, and there are well over 256 different
characters used in professional document preparation, there needs
to be some way to map characters into positions within the font.
The symbol set serves this purpose. It identifies the "map" used
to position characters within the font.
typeface
The features by which a character's design is recognized, hence
the word face. Within the Latin language group of graphic shapes
are the following forms: Uncial, Blackletter, Serif, Sans Serif,
Scripts, and Decorative. Each form characterizes one or more
designs. Example: Serif form contains four designs called Old
Style, Transitional, Modern, and Slab Serif designs. The typeface
called Bodoni is a Modern design, while Times Roman is a
Transitional design.
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