What is "Encapsulated PostScript"
PostScript has over the years become a lingua franca of
powerful printers; since PostScript is also a powerful graphical
programming language, it is commonly used as an output medium for
drawing (and other) packages.
However, since PostScript is such a powerful language, some
rules need to be imposed, so that the output drawing may be included
in a document as a figure without "leaking" (and thereby destroying
the surrounding document, or failing to draw at all).
Appendix H of the PostScript Language Reference Manual (second
and subsequent editions), specifies a set of rules for PostScript to
be used as figures in this way. The important features are:
- certain "structured comments" are required; important ones are
the identification of the file type, and information about the
"bounding box" of the figure (i.e., the minimum rectangle
enclosing it);
- some commands are forbidden - for example, a
showpage
command will cause the image to disappear, in most TeX-output
environments; and
- "preview information" is permitted, for the benefit of things
such as word processors that don't have the ability to draw
PostScript in their own right - this preview information may be in
any one of a number of system-specific formats, and any viewing
program may choose to ignore it.
A PostScript figure that conforms to these rules is said to be in
"Encapsulated PostScript" format. Most (La)TeX packages for
including PostScript are structured to use Encapsulated PostScript;
which of course leads to much hilarity as exasperated (La)TeX users
struggle to cope with the output of drawing software whose authors
don't know the rules.
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=eps