1.1 What is PostScript?
1.2 What is the difference between PostScript Levels 1, 2, and 3?
1.3 What is Direct PostScript?
1.4 What are the advantages?
1.5 What is the TinyDict?
2.1 How do I typeset?
2.2 What software do I need?
2.3 Isn’t a word-processor just as good?
2.4 What else do I need to know?
2.5 How are page files extracted from a typeset book file?
3.1 Where can I find more information on PostScript?
PostScript is a programming language to describe the position, size, and shape of any lines and text placed on a page. It was devised by Chuck Geschke and John Warnock, the founders of Adobe Systems Inc. and released in 1984. The resulting written instructions are like the co-ordinates for finding buried treasure; so many paces north; so many east, and so on. The distances are measured in typesetter’s points of 1/72 of an inch and an interpreter in a PostScript device rasterises the instructions into the necessary microscopic dots to be correctly placed on the paper or film. It is the de facto industry standard for print and publishing technologies.
PDF is, essentially, a form of PostScript that has been optimized, tokenised and compressed. There are a few extra bells and whistles, too.
Level 2 is an extension of the original Level 1 commands. Most of the additions are to do with colour printing; sophisticated methods of manipulating fonts and graphics; printer operators; or Display PostScript instructions for NeXT computers. All PostScript printers are supposed to be backwardly compatible, although some Level 1 commands have degenerated into Level 2 jargon, so that, for example, manual feed true has been transmogrified into 2 setpapertray.
PostScript 3 integrates PostScript, the Adobe Portable Document Format and the creation of Web pages into one progamming language.
Direct PostScript is a means of addressing the interpreter in a PostScript printer directly, without relying upon third-party DTP software, such as InDesign or Quark XPress, to convert text and illustrations into the PostScript language. This is done by creating a PostScript program: a series of instructions that the interpreter in your printer understands. The file is therefore a list of text commands, and does not represent itself graphically until the page is printed (or a software interpreter produces an on-screen display).
By way of analogy: most people are familiar with HTML for making web-pages: a series of codes are used to instruct the web browser how to display the page. The HTML file is text, and is not displayed graphically until the browser creates the page. In the same way, the PostScript instructions are not carried out until the page is printed or distilled. (However, PostScript is much more sophisticated than HTML!)
Most contemporary desktop printing software has been developed for the pre-press production of packaging, advertisements and glossy magazines. These require sophisticated printing techniques, handling such things as trapping; dot gain; colour separation and the black art of colour-management. Additional imposition software is then required to arrange the pages into groups of 16 or 32 on flats, with the necessary calculations made for the triple mysteries of skewing, bottling, and creep.
Such applications are unnecessary for the laser printing of continuously paged text in traditional book form, such as novels, biographies, and plays, where the text flows from page to page and all formatting must be global over many thousands of words. The on-screen scrolling of even sixteen DTP pages is time-consuming, and any editing has an irritating iterative effect. Direct PostScript files are smaller, print faster, and are ideal for archived Book on Demand printing.
The TinyDict is a PostScript dictionary that provides everything you need for typesetting text directly in PostScript.
Text to be typeset is given some simple codes from an accompanying typesetting dictionary and the file is sent to a laser printer which interprets and prints the page. After proofing, the book file may be separated into individual page files and re-combined into ‘printer’s pairs’ to make front and back sections or ‘signatures’ for printing in book form, such as 16/1 : 2/15, etc. Typesetting is quick as no mousework is needed to select fonts, styles or sizes from often obscure menus or palettes.
On most computers, a good text editor with Line Unwrap and Search and Replace facilities is normally sufficient, although a good, extendable spell checker is also useful. Some systems will need software to send the PostScript file to the printer; others, such as Mac and Unix, can send the file directly to the printer through the OS.
The ability to generate PDFs from PostScript is also useful: Macs have this facility built-in; but they and other systems may benefit from the use of Ghostscript, Adobe's own Distiller, or one of the many shareware/freeware offerings to be found on the Internet. PCs may require Adobe's PostScript driver.
A more extensive, though by no means exhaustive, list of suitable software is to found here.
No. Most word-processors offer limited typographic control over text, and do not lend themselves to printing in paged booklet order. Professional DTP software that does have the required capabilities is often far too expensive for 'casual' use. In any case, the files are saved in proprietary formats that change each year, sometimes for no better reason that to make you buy the new version of the software.
Direct PostScript pages are much more easily sectioned for front and back printing by a text editor than by a word processor. There is less tedious on-screen page scrolling and the files are independent of software or system. This means they can be printed or edited almost anywhere, without needing software translators, and they may be archived for the foreseeable future. Of course, direct PS files may be typed using a word-processor, but should be saved as Ascii text files (.txt) before being send directly to the PostScript printer.
Adobe recommends PostScript files include Document Structuring Convention comments. These consist of additional information, ignored by most PostScript interpreters, about the make-up of the file. They are mostly 'read' by software that processes PostScript. They consist of a header, markers for where pages start and end, and so forth. Their main purpose is to ensure that imposition software and print spoolers can manipulate PS files, although PostScript files will print quite happily without most of them. Those shown below are the minimum needed for a conforming file.
%!PS-Adobe-2.0
%%Title: Direct PostScript FAQ
%%BoundingBox: 0 0 597 842 % A4: lower left xy: upper right xy %
%%Creator: David Byram-Wigfield
%%For: Cappella Archive
%%Date: 17:11:97
%%EndComments % no colon %
%%Page: i 1 % colon - label - page number %
file script here
%%EndPage % no colon %
%%Trailer % no colon %
showpage % in Tinydict close command %
%%EOF % followed by a return
The %! opening characters wake up the laser printer, and the Bounding Box records the size of a graphic or page of text. It is essential for an Encapsulated PostScript file and to enable it to be displayed in some viewers. Notice the colons; they are important. EPS files will also add EPSF-1.2 (or 2.0) to the first line. The Adobe and EPSF numbers refer to the DSC version being used; some older graphics programs will only open EPSF-1.2. More recent software may prefer Adobe-3.0 and EPSF 3.0.
Typeset pages may be imposed into Printer’s Pairs for stapled or sewn booklets by cutting and pasting each page into one of two files in its proper sequence. The front (odd) file being in facing page pairs of
16-1 : 14-3 : 12-5 : 10-7 ;
the back (even) file as
2-15 : 4-13 : 6-12 : 8-9.
The first page number of each file must always be the odd number of the pairing or the facing pages may emerge opposite handed. If Tinydict typeset files are passed through Distiller and re-saved as PostScript files, then DSC information will have been added.
Imposition software can use DSC instructions like %%Page header and each successive %%Page: to reorder the pages. Each separate page file should have a %%Trailer, as well as the DSC Header shown above, or it may not work.
Try the free Cappella Archive ebook: Practical PostScript (.pdf)
Full technical documentation on PostScript is provided by Adobe here.
PostScript™ is a trademark of Adobe Systems Inc. which may be registered in certain jurisdictions.
All URLs correct at time of publishing.