Comparing PostScript and TrueType Fonts

The TrueType format was developed by Microsoft and Apple as an alternative to the Adobe Type 1 standard. TrueType is also an outline font technology, but it describes the outlines with quadratic curves (instead of cubic curves).
A cubic curve example (with Bézier control points)

And it differs from PostScript Type 1 in that the hinting process used to fine tune character appearance at small sizes and low resolutions is built into the font rather than into the rasteriser.

Hints or instructions tell the computer how to modify character outlines so they fit the grid of dots. In addition, dropouts have to be discovered and replaced. TrueType: instructions discover dropouts:

Both approaches have their merits. The TrueType one makes for a smaller and faster rasteriser, but at the expense of larger font files, whose final printed quality is much more dependent on the amount of effort and expertise put in by the type designer than are Type 1 fonts.

The more hints a designer puts into a TrueType font, the better it can be made to look, but at the same time, the font files get larger. On average, TrueType fonts are some 60-70 kbyte in size, while Type 1 equivalents are around 30-45 kbyte, so they take more space to store and longer to download.

Another benefit of putting the intelligence into the rasteriser rather than the font is that when you upgrade your rasteriser (when you buy a new printer), all your fonts look better. To make TrueType fonts look better, you'd have to upgrade all fonts! TrueType is supported on Macintosh and Windows 3.1, but the implementations are not identical, and even the base font sets came from different font vendors.

A frequently asked question at the computing center is: Across platforms, are the font metrics identical? The answer is NO. This is the reason for that users complain about different line and page breaks in the same document. Generally, two font technologies used at the same time do produce compatibility problems.

GOTO PostScript Font-Technologie (german).

Comparison with X11-Fonts

BDF

The Bitmap Distribution Format (BDF) is the standard format for distribution of fonts. It is an ASCII format so it can easily be edited it with your favourite editor or E-mailed to other users. As the name suggests, it stores bitmap fonts only. Another virtue of the BDF format is that most font format converters convert to or from this format. Means if you want to go from format A to format B, neither of which is BDF, then you are likely to convert A to BDF, then BDF to B. The BDF format is defined by Adobe. A document describing the format is available by ftp from Adobe's file server at "ps-file-server@adobe.com". It is also available in the standard X distribution. Look under ../X11R4(5)/mit/hardcopy/BDF. This document is also reproduced in any text describing the X standard.

SNF

The Server Normal Format (SNF) is an older format for bitmap fonts. The format is X Server and host dependent. This means that if you have two SNF files, their actual format may be different. Also, if you have an "snftobdf" utility, it may not be able to read font files from other systems. Convert to BDF format before you move it off the host system.

PCF

The Portable Compiled Font (PCF) format is a binary format for bitmap fonts. The binary contains sufficient information to be readable by other systems.

X11-Fonts

Bibliography

Adobe Systems

Adobe Type 1 Font Format, Addison-Wesley

Andre Jacques, Hersch Roger D. (editors)

Raster Imaging and Digital Typography, Cambridge Series on EP 1989

Apple Computer

TrueType Spec - The TrueType Font Format Specification

Hersch Roger D., Betrisey Claude

Model-based Matching and Hinting of Fonts, Swiss Federal Institute of Technology (EPFL) Lausanne