What is PostScript

PostScript is a standard printer language written by Adobe to ensure consistency of formatted text and page layout from one device to the next. PostScript is the standard for the graphics industry. Non-PostScript printers all have unique print drivers that will each handle text and graphics differently and all communicate differently with your computer (try sending to a dot matrix or laser printer using an inkjet printer driver, or vis-à-vis and you will find either the printer spits out garbage or produces an error in your application). Generic PostScript files can be sent directly to any PostScript device regardless of the manufacturer, as they all interpret the code the same. A very thin line (0.1 point) on a high-resolution printer such as a Linotronic 330 (printing at 2540 DPI) will be almost invisible, however it may appear to be about 0.3 points thick on a 300 DPI laser printer. When switching between Non PostScript print drivers it is normal for text to re-flow ending up in an overflow condition, and for graphics (pictures and objects drawn with MS Publisher's drawing tools) to change position on the page, for this reason always use Publisher's Design Checker as well as carefully checking all items in your publication yourself whenever you change print drivers. On the PC text will sometimes re-flow when using a PostScript printer as well, this is the reason it is best to target the final output printer before you start your Publication. This is not a problem with the Mac platform because it is device independent. Publisher 2000 and Publisher 2002 (Publisher XP) are also device independent when running on Windows 98 and later or Windows 2000.

An EPS (Encapsulated PostScript) file is a placeable image that is based on PostScript code, and can only be printed on a PostScript device. When you place an EPS file in Publisher, or any other program, all you will normally see is the 'placeable header'. The 'placeable header', if there is one, will be a low-resolution bitmap image. In some cases all that will be displayed is an 'X', or a reference to the file. Some Printing Companies will want an EPS so they can place it into another program, like PageMaker, in order to print or colour separate the file. MS Publisher produces a composite RGB PostScript code when in full colour mode, which is not compatible with commercial printing and must be forced at the RIP.

Unfortunately PostScript has become more complex in recent years, and there are some differences between genuine Adobe PostScript and other PostScript. The original PostScript language is often referred to as Level 1 PostScript, and can be correctly interpreted by most PostScript devices (some Level 3 devices may not correctly interpret it). Level 2 PostScript devices can interpret Level 1 code, but obviously Level 1 PostScript devices may not interpret Level 2 PostScript correctly and will often error out (this will be dependant on the features of the PostScript code called upon). Level 2 PostScript devices may not interpret Level 3 PostScript correctly even if they don't error out. Some Level 2 PostScript devices will accept True Type fonts in Native (Type 42) format, some will need the fonts converted to curves (or Bitmaps, however curves will give better results), the settings to control this are in the driver set-up. Level 2 code is more efficient than Level 1 PostScript code. All level 3 devices will accept True Type fonts sent in native (Type 42) format, and the print drivers should be set to send the fonts in that format unless problems occur printing the fonts. Level 3 code is more efficient than level 3 code and is able to do more things.

If you open a PostScript file as text in MS Word (or other text editor) some of it may make sense. The PostScript file should start similar to this:

%!PS-Adobe-3.0
%%Title: Microsoft Word - Document1
%%Creator: PSCRIPT.DRV Version 4.0
%%CreationDate: 06/09/01 01:25:36
%%BoundingBox: 1 1 612 792 
%%Pages: (atend)
%%PageOrder: Special
%%Requirements: 
%%DocumentNeededFonts: (atend)
%%DocumentSuppliedFonts: (atend)
%%DocumentData: Clean7Bit
%%LanguageLevel: 1
%%EndComments

HP PostScript printers put proprietary code before this (and at the end of the PostScript file) that may cause problems with some PostScript devices, MS Word (or other text editor) can be used to remove this. The end of a PostScript file should look similar to this:

%%Trailer
%%DocumentNeededFonts: 
%%DocumentSuppliedFonts: Arial Unicode MS
%%+ Times New Roman
Pscript_Win_Driver_Incr dup /terminate get exec
savelevel0 restore 
%%Pages: 2
(%%[ LastPage ]%%) =
%%EOF

You will find that sometimes Arial will get substituted for Helvetica and Times New Roman will get substituted for Times, this can be overridden when setting up your print driver, in fact I recommend not letting your driver substitute fonts, as there are some subtle differences. Although different printers have different fonts resident on the chipset (which the driver will not include in a PostScript file) all PostScript printers have the 'Base 13' PostScript (Type 1) fonts built into the chipset. These base fonts are:

If a font needed to print the file is not included in the PostScript file and is not resident at the printer the file is sent to the printer will use Courier (the default font). For this reason if you don't have the correct driver for the PostScript printer the file will be printed on (or don't know what printer it will be printed on) it is best to use a generic or basic PostScript Print driver, ones I find reliable in most cases are:

Linotronic 330 (available on the Windows CD)
MS Publisher Imagesetter
MS Publisher Color Printer

PostScript files can be viewed and printed using GSview from Gohstscript. 

Click here to download Gohstscript or visit their website http://www.cs.wisc.edu/~ghost/index.html