The magazine of the Melbourne PC User Group PostScript - For the bookshelf Major Keary

Creating PostScript files is easy. Just use a PostScript printer driver (you don't need a physical printer) and print-to-file from any application that provides a print function (word processor, DTP, graphics, and so on). There is plenty of software-some free-that will convert a PostScript file to PDF. Even printing on non-PostScript printers can be achieved with software emulation, such as provided by GhostScript. GSView, which runs under GhostScript, is a GUI implementation and can be used to print or display PostScript and EPS files, and will convert a PostScript file to EPS.

EPS stands for "encapsulated PostScript". EPS files contain a "bounding box" that specifies a rectangle that contains the image, text, or a combination of both; these files can be "placed" by DTP applications (as well as modern word processors and many other applications). Open an EPS file with a text editor and you will see something like %%BoundingBox: 153 153 459 560 somewhere near the top of the file. Not all PostScript files can be converted to EPS, but there is not room here to discuss the format in detail.

Why would anyone want to hand craft a PostScript file? It helps users understand the format and can make it easier to detect the source of output problems, something-from personal experience-easier said than done. There are a number of routines that one can create with short PostScript files, but which are not easy to achieve otherwise.

For those who want an introduction to writing PostScript programs or PostScript files, or just want to learn about it, there is a dearth of literature in print. There have been some good books, but they are out of print. You may find something in the secondhand bookshops, but be warned that searching for "postscript" on book vendor sites can throw up a lot of extraneous data.

As far as I am aware the only introductory title presently in print is Adobe's PostScript Language Tutorial and Cookbook. Published in 1985, it is presently in its 26th printing-a remarkable record for a computer-related title. The PostScript language, if nothing else, is stable. Regardless of enhancements to the language, this text is still fully relevant to fundamental programming. The book is in two parts: a tutorial that explains programming basics, and a cookbook that demonstrates a range of solutions to particular problems.

For example, suppose you want to create an outline font; the cookbook section contains a PostScript program (including how to re-encode a character set) that will convert an existing 'filled' Type 1 font into an outline font. Want to make a small caps font? It is not simply a matter of going down two points, as most DTP applications do. Typographically correct small caps requires a change in weight as well as size. The book provides a routine to create proper small cap fonts. There are a number of other font manipulation programs-such as setting fractions-that should be of special interest, and value, to anyone involved in typographic design. There is also a program for setting vertical text.

A number of graphics routines are also included. They provide excellent templates for creating particular effects and logos. There is also a program for creating a poster composed of several A4 sheets that can be joined together.

For those who want to know how it all works, the tutorial section explains the PostScript stack and arithmetic, the PostScript coordinate system, graphics, loops, arrays, clipping, and how to draw lines and filled shapes. The meaning and use of mysterious operators (such as mul, pstack, translate, grestore, and pop) are well explained with examples. Anyone with a general interest in learning about programming should find the tutorial quite helpful for its clear descriptions of how the most commonly used operators work.

One does not have to be a programming expert to make use of PostScript, especially for a limited repertoire of routines, such as font manipulation or the creation of simple graphics. For those who want a solution to a particular problem this book may be all they need. Those who want to master PostScript will find it a valuable introduction.
 

Adobe Systems: PostScript Language Tutorial and Cookbook ISBN 0-201-10179-3 Published by Addison-Wesley, 243 pp., RRP $57.95 incl. GST

The definitive resource, of course, is Adobe's PostScript Language Reference Manual. It is complete, but assumes the reader is already familiar with PostScript programming.

This is an image created by the accompanying program:

The file is in two parts, procedures and the program. The first ten lines set up two definitions: "/inch {72 mul} def" is a common method of translating inches into 1/72-inch units used by PostScript's coordinate system; the other defines the wedge shape used to make up the image.

The rest of the file is procedural; in a surprisingly small space it tells PostScript how and where to place the wedges, and the fill for each one. Once a user gets the hang of the way in which this routine (one of many in the cookbook section) is organised, other designs can be created. By using GSView one can see the result of any change without the hassles of printing.

The Tutorial and Cookbook won't turn you into a PostScript expert, but it will show you how to do some useful things. As an introduction to further study of PostScript it is highly recommended.

Reprinted from the April 2003 issue of PC Update, the magazine of Melbourne PC User Group, Australia

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