The Bitstream TrueDoc Imaging System is the best solution available for developers looking for a total font rendering solution. It reliably handles the processing of fonts in all the popular industry standard font formats and delivers industry leading performance and code size compression. TrueDoc Imaging System has been widely implemented in servers, operating systems, applications and printers, and it boasts a long list of satisfied customers. Now, with its optional companion products and its support of Bitstream's next-generation TrueDoc PFR font data structure, TrueDoc Imaging System is smaller, faster and more flexible than ever.

In their implementations of TDIS, customers may choose from the following industry standard font processors: TrueType, PostScript Type 1, HP PCLeo, Bitstream Speedo, and the Bitstream TrueDoc Character Shape Player (or CSP). Output modules include BlackWriter, WhiteWriter, QuickWriter, GrayWriter, 2D Writer, and the OutlineWriter. If needed, developers can also choose from a series of Resident Font Sets that emulate industry standard font suites in operating systems and popular PostScript and HP PCL devices. Resident Font Sets are supplied as highly compacted TrueDoc Portable Font Resource (PFR) files.

Figure 1. TrueDoc Imaging System Architecture

Unified Front-End API
The TDIS unified front-end (UFE) API accepts calls from the host computer's operating system, application, or driver. It routes the information to the appropriate font processor. Bitstream has engineered the UFE and the font processors to operate on one set of API calls, maximizing efficiency and performance. The UFE passes character requests (including point size, rotation angle, etc.) to the appropriate font processors in the TDIS architecture.

Character Mapping Table
Fonts in different formats and from different platforms are encoded, mapped and identified in different ways (direct index, HP MSL, PostScript character set, Unicode, etc.). The character mapping tables let the appropriate TDIS font processors identify characters in any of the industry standard character sets and map them to their corresponding Bitstream character IDs. The character mapping tables ensure that proper characters are imaged, regardless of which operating system or font format the host uses.

Font Processors
TrueDoc Imaging System supports five font processors:

TrueType Processor
The TrueType processor in TDIS is licensed from Apple Computer but has been optimized by Bitstream's engineers to support vertical composition and to increase performance. The TrueType processor interprets TrueType font data and passes scaled outlines to the output module.

PostScript Type 1 Processor
Developed by Bitstream, this PostScript Type 1 font processor can function in either a PostScript or non-PostScript environment. The PostScript Type 1 processor interprets Type 1 font data and passes scaled outlines to the output module.

HP PCLeo Processor
A line and arc processor, the PCLeo processor interprets PCL encapsulated outline font data and passes scaled outlines to the output module.

Bitstream Speedo Processor
To maintain backwards compatibility, TDIS supports Speedo, which was used as the resident font technology in earlier versions of 4-in-1. The Speedo processor interprets Speedo font data and passes scaled outlines to the output module. While Speedo fonts already enjoyed a significant compression and performance advantage over other font formats, the new TrueDoc PFR font data structure offers even better font compression and performance.

Bitstream TrueDoc Character Shape Player (CSP)
In TDIS, the TrueDoc Character Shape Player (CSP) replaces the Speedo font processor as the resident font technology. The TrueDoc CSP processes resident font TrueDoc PFRs (or downloaded PFRs), and passes scaled outlines to the output module.

Output Modules
The TrueDoc Imaging System's modular design lets OEM and ISV customers implement the output module/s required for their specific products. Output modules receive scaled font outlines from the Font Processors and generate bitmaps (or outlines in the case of the OutlineWriter). Bitstream delivers the TrueDoc Imaging System with the following output module options:

BlackWriter
To generate characters quickly without high memory requirements, the tool of choice is the BlackWriter scan conversion module. This module simply turns on every pixel whose center falls within the character shape outline. For printers offering 600 dpi resolution or better, the BlackWriter module provides high-quality images at the fastest speeds.

GrayWriter
A multi-bit-per-pixel output module, the GrayWriter supports up to 64 gray levels for anti-aliasing. It is best for use on color or gray-scale screens, printers or other output devices.

QuickWriter
The QuickWriter offers the optimum balance between quality and performance. It runs only 10 to 20% slower than the BlackWriter module but produces higher quality type on low- to medium-resolution devices, particularly at small type sizes.

2D Writer
The Two-Dimensional BlackWriter (or 2D Writer) offers the highest quality output for low resolutions and small sizes. It runs 30 to 40% slower than the BlackWriter, but uses sophisticated scan conversion techniques (both x and y axes) to output the sharpest images.

WhiteWriter
The WhiteWriter compensates for the character erosion that occurs on thermal printers and white writers by adding a half-pixel layer around characters. This module enhances thin strokes in those devices where these attributes might otherwise be lost. The WhiteWriter is best for use with ion deposition and thermal printers.

OutlineWriter
The OutlineWriter serves vector-oriented graphics applications, plotters, and other vector devices. It is also the output module used in HP/GL-2 emulations.

Font Information Table
Page description languages (PDLs) typically request characters in one of two ways: One is by attribute (style, weight, etc.), the second is by name. Hewlett-Packard PCL requests characters by attribute, PostScript by name. The font information table (FIT) translates the requested typeface names or attributes into references for the appropriate typeface in the Resident Font Set. The FIT guarantees that the proper font prints, regardless of which PDL or protocol is used.

Resident Font Sets
Bitstream offers a wide range of Resident Font Sets to emulate popular HP LaserJet and PostScript printers. TDIS Resident Font Sets are provided as TrueDoc Portable Font Resources (PFRs) because of their small code size, fast performances, and excellent output quality.

Bitstream Font Navigator
Font Navigator is a powerful font management tool that allows users a quick and easy way to find, install, and organize fonts into manageable groups, This tool also features a way to view and print font samples. For developers looking to provide added value with low overhead; or for printer manufactures looking to emulate HP printers that ship with the HP FontSmart utility, Font Navigator is an ideal Windows font management utility.

TrueDoc PFR Manufacturing System
Bitstream knows that the future market for printers and software applications is shifting and changing directions constantly. Ideally, developers could easily customize their products for different geographic areas or specific markets. The Bitstream TrueDoc PFR Manufacturing System lets developers accomplish just that. By allowing companies to quickly and easily create new resident font sets for their products, Bitstream is removing one of the main barriers to fast and easy localization and specialization.

Technical Advantages

Performance
Bitstream's font processors have always been among the fastest in the industry, offering significant performance advantages over scalers from other sources. Now Bitstream's third-generation font system, TrueDoc, takes performance to an even higher level. TrueDoc offers some of the highest character generation speeds available today. In addition, Bitstream's PostScript Type 1 and TrueType processors offer performance equal to or better than similar processors from other vendors.

Small Code Size
Bitstream goes to great lengths to make sure that its code components are as small as possible. Bitstream engineers the most space-efficient combination of compacted fonts and font processors in the industry. Bitstream constantly improves the architecture and its components to ensure that it is as small as possible. For example, Bitstream's TDIS has helped developers build PCL 5e/PostScript emulation printer controllers in less than 2 MB of ROM.

For developers taking advantage of Font Navigator or TrueDoc PFR Resident Font Sets, the underlying TrueDoc Imaging Technology offers sophisticated compaction advantages found nowhere else in the industry.

TrueDoc's compaction is achieved through two main vehicles:

First, the recording process that the TrueDoc Character Shape Recorder (CSR) goes through in building Portable Font Resources (PFRs) is "intelligent." The CSR uses character subsetting and intelligent de-construction of compound characters over the entire font set to minimize the amount of data stored.

Second, the basic structure of the PFR is highly compact-the cubic Bézier format that TrueDoc uses stores character shapes with fewer control points (than other formats) while maintaining the highest level of quality. TrueDoc also uses a compact hint structure unique to Bitstream that also helps save space. A TrueDoc PFR containing the entire ASCII character set of Times and Helvetica (a total of 190 characters) is less than 13KB. This represents a better than 2-to-1 compression ratio over a PostScript Type 1 font file. It represents a better than 3-to-1 compression ratio over a TrueType font file.

Portability
Bitstream's TrueDoc Imaging System has already been successfully ported to printer controllers by leading developers such as Xionics. The SDK is provided as ANSI C and K & R source code, making it easily portable to any hardware configuration or software environment. There are no conflicts with word size, byte order, file I/O, precision, etc. Fixed point arithmetic routines are supplied to support all math requirements. The SDK is fully documented and Bitstream's engineers have years of experience working with customers to ensure a fast and trouble-free implementation.

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