QUESTION: What is an EPS file?
ANSWER: EPS stands for Encapsulated PostScript. EPS is a standard file format for importing and exporting graphics and formatted text. Many page-layout applications, word-processing applications, and illustration applications have features that allow you to create (export) EPS files and use (import) EPS files. The Adobe Acrobat software also allows you to create EPS files.
An EPS file usually has a filename extension of .eps or .epsf. Sample filenames for EPS files are:
myfile.eps
myfile.epsf
An EPS file is a PostScript file, but an EPS file has some special characteristics that a "regular" PostScript file does not have. Some of the most important special characteristics are:
- An EPS file always describes a single page — never more than one page.
- The information in an EPS file is structured in a way that allows an importing application to discover the size and shape of the page described in the EPS file. An importing application needs to know the size and shape of the page in order to position the page properly and in order to render the page at the proper size. (The importing application might allow for re-sizing and re-positioning the imported page, but it needs to know the dimensions up front.)
- There are some PostScript commands that would cause technical problems if used in an EPS file; therefore, these commands are considered "illegal" for EPS files.
- Most EPS files contain a crude representation of their contents in bitmap format. This bitmap code is usually referred to as "preview" code. The bitmap-format preview code is included because many applications that import EPS files can't read and understand PostScript code; such applications use the bitmap-format preview code to display pictures of EPS files on the screen. (Computer programs can understand bitmap-format code more easily than PostScript code.)
- When an EPS file containing preview code is printed, the printer generally does not use the preview code at all. Instead, the printer uses only the PostScript code in the EPS file to create text and graphics on the page. The preview code is generally used only for screen display.
Some EPS files cannot be printed without first being imported into an application and included in another document. If you send such an EPS file to your PostScript printer, your printer will appear to process the file (that is, the printer will give an indication that it is "busy"), but it won't print anything.
How do you create and use EPS files?
Procedures for exporting (creating) and importing (using) EPS files vary depending on the type of computer you're using and depending on the application you're using, but it usually works something like this:
- To create an EPS file, you'll start by 1) clicking on the "Print" command (the same command that you use to print documents on paper), or 2) clicking on an "Export" command, or 3) clicking on a "Save as" command.
At this point, you might need to make some selections in a dialog box. Then, you'll type a filename for the EPS file that will be created, and you'll click a button to kick off the file-creation process. - To use an EPS file, you'll click on a command called "Import," "Insert," "Place," or something similar; then you'll select the EPS file you want to use; then you'll click a button to kick off the file-import process.
In most cases, the application will then display a picture of the text and graphics in the EPS file. At that point, you'll use your mouse to make the text and graphics larger or smaller (if required) and to position the text and graphics in the desired position on the page.
How can you include a page on another page?
We've said that an EPS file is a single-page file that you import into an application and place on a page in a document that you're creating.
If the concept of EPS files is new to you, you might be wondering what you'd gain by placing a page on another page. For example, you might be thinking, "Wouldn't the second page just cover up the first page?"
The answer is, "Not necessarily."
You see, even though an EPS file is a one-page file, that one page might be a very small page. For example, many EPS files contain logos — and a logo is often just a fraction of an inch wide and a fraction of an inch tall.
Another key concept to understand is that — when you are importing an EPS file into an application — the dimensions of the page that the EPS file contains aren't really important anyway, because you'll typically resize it after you've imported it. Because of the way PostScript code works, the text and graphics in most EPS files look perfectly fine even if you shrink down the EPS file to a fraction of its original size or blow up the EPS file so that it is many times larger than its original size. So even if you have an EPS file containing a logo that is 8 1/2" wide and 11" tall, you can use that logo on an 8 1/2" x 11" page in another document by importing the EPS file and shrinking it down until it's the size you want.
Most EPS files are not editable
Most EPS files are of the "look-but-don't-touch" variety. That is: you can include them in your documents by importing them into an application, but — except for resizing them and repositioning them — you can't modify them. At least, you can't modify them with general-purpose page-layout applications, word-processing applications, or illustration applications. Some special-purpose software does support limited modification of some PostScript files and EPS files.
Adobe Illustrator EPS Files are editable
Adobe Illustrator EPS files are specially formatted such that they can be edited extensively and easily, with the right software. Adobe Illustrator EPS files can be created and edited by some illustration applications and a few other types of applications. Two widely used illustration applications are Adobe Illustrator and CorelDRAW, both of which allow you to create and edit Adobe Illustrator EPS files.
Adobe Illustrator EPS files generally cannot be created or edited by page-layout applications and word-processing applications.
If you are a programmer, and if you want technical information about how to write programs that create EPS file or use EPS files, turn to the PostScript Language Reference Manual.