EPS Files

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Introduction

The EPS format (Encapsulated PostScript) was developed by Adobe as one of the file formats in its page description language, PostScript.
It is a vector format (not bitmap), thus inherently scalable and moderately device independent, which moves easily across platforms (the language itself is ASCII code).
Unless you have a computer equipped with Display PostScript, this means that you cannot see EPS files on screen. Some graphic packages (Illustrator, Freehand and Corel) can open most flavors of EPS. PhotoShop can convert to bitmaps some EPS files (but not all).

EPS vs. PS Files

Let us take the time to smash a widely encountered confusion. EPS files are not print files, that is they are not aimed at being dumped to a Postscript printer to get ink and text on paper.
The main difference with EPS files lies in this concept of encapsulation. This means that the file is made to be embedded in something (another file), even if some graphic packages chosen the EPS format or a close variant as their native data format. Let me also underline that an EPS file can't be more than a page (to fit in the target layout) and that a PS file, on the contrary, can hold several pages, up to a complete book.
On the other hand, you can instruct your printer driver to print to a file, that is to send all printing instructions to a file and not to a printer. These files are called print files, printer file, PRN files, Postscript files (and therefore often PS files). The confusion has therefore some deep roots.

Print Files

Just after saying that, let us precise that our programs are massively used to send layouts to Macintosh Service Bureaus, to get films. In this case, it makes perfectly sense to send print files. To avoid more confusion, we chose to discuss this question in a specific page on print files.

Preview Picture

When you place an EPS file in a layout program like PageMaker, or even in Word, you often only get a gray rectangle at the place of the graphic. It also happens that you get a very low-resolution picture. That worry mostly program testers and new users. However, the pictures print normally on a Postscript printer.

The cause lies in the preview pictures.
1) Simple EPS files have no preview at all.
2) The EPS file can have a preview picture embedded in the code. This preview is generally a TIFF picture. That is the way most PC programs work.
3) The preview picture can also be stored in another file, or in another stream or fork. That is the way most programs work on the Macintosh. Most Macintosh EPS files use a PICT preview stored in the resource fork. This preview picture gets lost most of the time when the file is transferred from a Macintosh to a PC.
Several graphic packages can save the EPS file with an embedded preview picture. InDesign, even on the Mac, does precisely that.
When you save the file, some programs allow you to select the type of preview picture. That way, you can spare many problems for the person that will open your work. You should check this point if you intend to exchange regularly files with somebody.

Fonts in EPS Files

There is a common belief that Xpress doesn't include the fonts in the EPS format. It seems that this is not quite true, but that other programs can't find the fonts information Xpress puts in the files.
If you look at the header of an EPS file produced in Corel Draw or PageMaker, you find an instruction:

	%%DocumentFonts: atend

This instruction is not recognized by Xpress. Instead, Xpress uses following code:

	%%DocumentFonts: Helvetica
	%%+ Helvetica-Bold
	Etc.

As Illustrator perfectly opens the EPS files created by Xpress, it seems that not everybody understands the commands to code fonts in an EPS file the same way. One can take as a rule to open the files in Illustrator (tested with versions 5 and 6 on the Macintosh) to get the fonts when you are crossing programs.

To Go Further...

If you're interested in the Postscript language, you should visit Aandi's site (Quite Inc.). Adobe site also offers numerous interesting things.