Mac Font Formats


Digital fonts come in different formats; these are also known as font types. Font formats incorporate different technologies for producing fonts on a computer and, as a result, all formats are not supported by all computer platforms or operating systems. The following formats are supported by Mac OS X:

  • PostScript Type

  • Multiple Master

  • Mac and Windows TrueType

  • Mac and Windows OpenType

  • Mac OS X System dfont

Bitmap fonts

Bitmap fonts (sometimes referred to as bitmapped or fixed-size fonts) are the original fonts used on the very first Macs in 1984. Mac OS X does not use bitmap fonts. But Mac OS 9 and, therefore, the Classic environment, still work with them, although hopefully most users have switched to more-advanced font types. The fonts you use today are almost certainly not bitmap fonts.

Although bitmap fonts are fast becoming a historical curiosity, knowing something about them is helpful in understanding font technology.

In a bitmap font, every character is represented by an arrangement of dots. Figure 12-1 shows the dots in an enlarged view of two characters of a bitmapped font.

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Figure 12-1: Bitmap fonts contain dot-for-dot pictures of characters. (Times capital A and G at 12-, 14-, and 18-point sizes enlarged to show detail.)

The name bitmap refers to each dot’s value (filled in or not) being stored in one or more bits of data. For monochrome fonts (and images), one bit is sufficient to record each dot’s value. For shades of gray or colors, each dot requires more than one bit of data.

The computer translates the bitmap into pixels (picture elements) to display it on a monitor, or into ink dots to print it. The way each font looks on the screen, or after printing, depends on how its point size relates to the resolution, that is, the density of dots displayed on the monitor or produced by the printer.

Each bitmap font is designed for display in one size only, so bitmap fonts usually are installed in sets. A typical set includes 9-, 10-, 12-, 14-, 18-, and 24-point font sizes. If you need text in a size for which no bitmap font is installed, the Mac OS must scale a bitmap font’s character bitmaps up or down to the size you want. The results are misshapen or blocky, as shown in Figure 12-2.

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Figure 12-2: Bitmap fonts look best at installed sizes; in this scaling of the Times 24 font, note the blockiness of the 20- and 30-point font sizes. (Enlarged to show detail.)

PostScript fonts

PostScript fonts were the innovation that started the professional desktop publishing industry. Invented by Adobe Systems in 1984, they were the first fonts to look great at any size and any resolution. For this reason they are known as scaleable or variable-size fonts.

Instead of fixed-size bit maps, PostScript fonts use curves and straight lines to outline each character’s shape, as shown in Figure 12-3. PostScript fonts were the first of the many types of outline fonts.

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Figure 12-3: PostScript fonts are based on outlines. (Times capital G shown.)

This outline is a special kind of vector graphic, defined by mathematical instructions known as Bezier curves in the PostScript computer language. You may be familiar with vector graphics if you use an application such as Adobe Illustrator. In fact, Illustrator can be used to create or alter PostScript fonts.

Unlike other types of fonts, in which each font resides within a single file, the original Type 1 PostScript fonts have two files that must be properly installed for the font to function properly. Each PostScript font has a screen font file, and its associated printer font file. The screen font file contains a bitmap representation of the font in at least one point size; the printer font file contains the scalable outline font.

Although a PostScript screen font appears in font menus and onscreen correctly without its associated printer font installed, the screen font does not print correctly. In addition, a font does not appear in a font menu, nor does text previously formatted with that font appear correctly onscreen, without its associated screen font installed, because the screen font file contains the font metrics data. This is true whether Adobe Type Manager (described in a moment) is being used or not.

PostScript fonts are divided into two main categories: Type 1 and Type 3. (Type 2 was the font format used to embed fonts in Acrobat 3 PDF files, and so is no longer widely used.) Most PostScript fonts that you see are Type 1, because they yield better results at small font sizes and low resolutions. Although Type 1 fonts generally look better, Type 3 fonts are more elaborate. The characters in Type 3 fonts have variable stroke weights and are filled with something other than a solid color, such as shades of gray or blends that go from white to black. Type 3 fonts were popular in the late 1980s, and are still used for custom fonts and special effects. Mac OS X does not provide support for Type 3 fonts.

PostScript fonts were originally designed for printing on Apple LaserWriter printers and other PostScript output devices. In Mac OS 9, and hence in the Classic environment, Adobe Type Manager (ATM) software smoothly scales PostScript fonts to any size for non-PostScript printers and the display screen. With ATM and PostScript fonts, you didn’t need a set of bitmap or TrueType fonts for the screen display. Just one bitmap size would suffice. ATM was included on the Mac OS 9 CD that came with Mac OS X 10.2 for awhile, in the Adobe Software folder. ATM Light is also available for free from Adobe’s Web site.

Mac OS X, on the other hand, includes built-in support for Type 1 fonts in three variations:

  • Screen font files, optionally in a font suitcase, plus corresponding PostScript Type 1 outline fonts

  • QuickDraw GX–enabled font suitcases

  • QuickDraw GX–enabled MultiMaster font suitcases

TrueType fonts (described later) cannot entirely replace PostScript fonts for a number of reasons. For one, PostScript fonts include a lot of information in the font file — kerning information and hints that help the font look better at different sizes — that TrueType fonts do not. Additionally, PostScript offers more than just outline fonts. It’s a page description language that precisely specifies the location and other characteristics of every text and graphic item on the page.

PostScript fonts are still commonly used, especially in graphic production, and many organizations have large collections of them that will not be replaced with another format in the foreseeable future.

Multiple Master fonts

Multiple Master (or MM) fonts are special versions of certain PostScript Type 1 fonts that allow variation of one or more font parameters, most often weight (bold or light), style (italic or plain), or width (condensed or extended). This enables the creation of an unlimited number of different styles, known as instances, from the same font file, a unique advantage.

However, the MM technology was not entirely a success. Not all applications support it, and the MM fonts can be difficult to output correctly. There are only about 50 MM fonts, and most are from Adobe. In late 1999, Adobe announced it would no longer develop MM fonts. However, the technology behind MM fonts is still used in ATM and Adobe Acrobat.

Mac OS 10.2 and above can activate existing instances of this font type, but cannot create instances. (To activate a font means to make it available to applications for use.)

TrueType fonts

TrueType fonts are outline fonts that contain both screen and printer font information in a single font file — an advance over PostScript fonts.

TrueType fonts look good at all sizes. They work with all Mac OS applications and all types of printers, including PostScript printers. The Mac OS smoothly scales a TrueType font’s character outlines to any size on a display screen and on printers of any resolution, all with equally good results. Figure 12-4 is an example of TrueType font scaling.

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Figure 12-4: TrueType fonts scale smoothly to all sizes and resolutions. (Enlarged to show detail.)

TrueType differs from PostScript in how it mathematically specifies font outlines and adjusts the outlines for small font sizes and low resolutions.

TrueType was developed by Apple and Microsoft initially as a response to the closed nature of PostScript fonts and the exceedingly high license fees charged by Adobe to include a PostScript rendering engine in LaserWriters. TrueType was introduced in 1991 as an integral part of Mac System 7 and Microsoft Windows 3.1. Adobe responded to this assault on the turf it controlled by releasing Adobe Type Manager to improve the onscreen appearance of PostScript Type 1 fonts, and by disclosing the PostScript Type 1 definition, allowing competition in the marketplace for PostScript fonts. TrueType was only a limited success. Font foundries were reluctant to develop TrueType fonts, concentrating instead on PostScript Type 1.

Mac OS X can recognize traditional Mac TrueType files and font suitcases, which are folder-like containers of traditional Mac font files. Because traditional Mac font files have two forks (parts), called the data fork and the resource fork, these font files and font suitcases must be stored on disks or other volumes that have the Mac OS Extended format (also known as HFS Plus).

Mac OS X also recognizes Windows TrueType font files, which have the file name extension of .ttf or .ttc. Windows TrueType font files, like all other Windows files, don’t have two forks.

TrueType fonts are commonly used in home or office environments. They are infrequently used in graphic production; however, they are supported by most current RIPs. (A RIP is a raster image processor, hardware or software which prepares digital files for printing on a PostScript printer.) If you are a designer using TrueType fonts, be sure to embed them when making a PDF or PostScript file to avoid problems during the RIP process.

OpenType fonts

An extension of the TrueType format, the OpenType format supports PostScript font data in the same file with TrueType font data. You can think of OpenType as a wrapper around PostScript or TrueType font data.

Adobe and Microsoft worked jointly to create the OpenType font format, which was announced in 1996. The first OpenType fonts appeared on the market in 2000. It is too early to tell if OpenType will become popular, but it is a powerful and promising technology.

OpenType fonts and the operating system services that support them provide users with a simple way to install and use fonts, whether the fonts contain TrueType outlines or PostScript outlines.

The OpenType font format addresses the following goals:

  • Broader multiplatform support

  • Better support for international character sets

  • Better protection for font data

  • Smaller file sizes to make font distribution more efficient

  • Broader support for advanced typographic control

An OpenType font is a single file and works across platforms, unlike PostScript and TrueType fonts that are made in separate Mac and PC versions. However, not all applications support OpenType fonts.

OpenType fonts also have the advantage of supporting extended character sets. OpenType fonts support the Unicode standard used in Mac OS X, which encodes characters for over 65,000 different glyphs in a single font. Compare this with PostScript and TrueType fonts, which can only handle the 256 glyphs of the ASCII standard, not enough for many languages.

OpenType fonts are also referred to as TrueType Open v.2.0 fonts because they use the TrueType font file format (which the Mac OS identifies internally with the file type code sfnt). PostScript data included in OpenType fonts may be directly rasterized, or converted, to the TrueType outline format for rendering, depending on which rasterizers have been installed in the host operating system. But the user experience is the same: OpenType fonts just work. Users do not need to be aware of the type of outline data in OpenType fonts. And font creators can use whichever outline format they feel provides the best set of features for their work, without worrying about limiting a font’s usability.

OpenType fonts enable font creators to design better international and high-end fonts by including OpenType Layout tables. These tables contain information on glyph (character) substitution, glyph positioning, justification, and baseline positioning, which enables text- processing applications to improve text layout by making minute adjustments to the kerning and tracking.

In Mac OS X, OpenType fonts typically have a file name extension of .otf.

Mac OS X System dfonts

Mac OS X introduced the dfont format, a special Apple version of TrueType fonts that contain their information in the data fork instead of a separate resource fork like previous Mac font files did. This way they are compatible with Unix file systems, such as the Unified File System (UFS) that can be installed optionally with Mac OS X.

The system software uses the dfonts internally, and they are located in the System/Library/Fonts folder.

Some of the dfonts are high-quality fonts with extensive glyph sets, so graphic designers may be interested in using them. If you are installing PostScript or TrueType fonts on your system, be aware that some of their names conflict with some of the dfont names. As described later in this Chapter, you should remove the conflicting fonts you don’t want.

Also, if you are a designer and use dfonts, make sure your service provider is also using Mac OS X to output your documents, as they will not work with earlier versions of the Mac OS. You can get around this problem by creating a PDF to send instead of the application file.

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Mac OS X Font Facts and Features

Mac OS X is full of font-related features and technologies. To introduce them, here are some facts you should know:

  • Mac OS X 10.3 provides support for more font types than any other operating system. (You will find the types listed and described previously.) As a result, cross-platform file exchange is simplified.

  • Unlike other operating systems, there is no limit to the number of fonts you can have open at one time in Mac OS X. If you wanted to, you could put an immense library of fonts in a single Fonts folder, and nothing would break; the operating system would automatically find the necessary memory. But as you see later in this Chapter, there are better alternatives for managing large numbers of fonts.

  • If you used Adobe Type Manager in Mac OS 9 to render your fonts, you will not need it in Mac OS X. In fact, Adobe does not provide a version of ATM for Mac OS X. Mac OS X contains a built-in rasterizer technology, Apple Type Services, to automatically render all font formats, including PostScript. But if you used ATM Deluxe, you may wonder how you can replace its font management features; read on, as your options are discussed later.

  • Mac OS X uses subpixel filtering to increase the perceived resolution of fonts rendered on screen; Apple calls this Font Smoothing. The readability of fonts displayed by Mac OS X 10.3 can be controlled in the Appearance pane of System Preferences. In the Font Smoothing style pop-up menu, you may choose Standard (best for CRT displays), Light, Medium (best for flat-panel displays), and Strong. At very small font sizes, the smoothed fonts can seem fuzzy, so you can set the font size below which the operating system turns off text smoothing in the pop-up menu at the bottom of the Appearance pane.

  • Mac OS X provides multiple font locations, with different access privileges for each location. This gives you better control and more options to organize fonts for different users and uses.

  • With every new version of Mac OS X, Apple seems to provide more professional-quality fonts, and support for more non-Roman languages. Mac OS 10.3 currently includes 100 font families, almost double the number included with 10.2. To see the new fonts, you have to allow them to be added when you install Mac OS 10.3.

  • Mac OS X protects itself by checking the integrity of a font when it is displayed or printed. Apple calls this Font Validation. If the operating system detects a corrupt font, it will be automatically deactivated.

  • Apple Advanced Typography (AAT) is a Mac OS X system–level feature that supports (for programs written to make use of it) sophisticated typographic capabilities previously found only in typesetting applications such as QuarkXpress. Included in these capabilities: kerning (customizing the spacing between certain pairs of letters), tracking (adjusting the spacing between groups of letters and entire blocks of text), ligatures (two or more letters combined into one character), and a mind-boggling list of others. And all this is available even to humble applications like TextEdit.

  • Font Book. Panther contains this new font management utility, described in detail later in this Chapter.

  • Mac OS X protects against the font corruption that plagued Mac OS 9. In Mac OS 9, if two fonts happened to have the same font ID number, the operating system attempted to resolve the conflict by assigning a new number to one of them. However, sometimes more than just the number would get changed, and the font file became corrupted, leading to mysterious problems, crashed systems, and much sadness.

    But Mac OS X does not try to alter fonts, so the chance of corruption is greatly reduced. Font corruption can still happen in Mac OS X, but at least the OS is not a contributing factor. Check any fonts for corruption that you import from an older system, as well as those purchased from smaller font foundries, using one of the font utilities mentioned later in this Chapter. And it’s not a bad precaution to periodically check all the fonts on your system, just in case.

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Mac OS X Bible, Panther Edition
Mac OS X Bible, Panther Edition
ISBN: 0764543997
EAN: 2147483647
Year: 2003
Pages: 290

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