At some point, you may want to include some nice PostScript image into a document. There are a number of problems associated with this, but the main one is that your page layout program needs to know how big the image is, and how to move it to the correct place on the page. Encapsulated PostScript (EPS) is that part of Adobe’s Document Structuring Convention that provides this information.
The DSC is a special file format for PostScript documents. The full details for the DSC can (and should) be gotten from Adobe. If you are writing a PostScript printer driver or other utility which will be used by a large number of people to create or manipulate PostScript documents, do not even think about writing it without making it DSC-compliant. You will save yourself and your users a lot of headaches.
Although the full DSC is beyond the scope of this guide, the most basic rules can be explained. A DSC-compliant document is an ordinary PostScript document with a number of comments added. These comments provide information to any post-processors which work with the files. Some comments strictly provide information, others are used to structure the document into sections, which may be shuffled or processed in other ways by the post-processor.
Every DSC-compliant document is indicated by having the comment
%!PS-Adobe-3.0 as the first line. This comment is a flag to indicate that the
document is compliant. You should never use this comment unless your document
really is DSC compliant. There are many other parts to proper DSC. A document
which follows the DSC can be manipulated in many ways. In particular, post-processors
can shuffle the pages, print two or more pages on a side, and so on. The
printer drivers from some notable companies do not follow the DSC, and
their PostScript documents are, therefore, impossible to work with once
they’ve been generated.
An EPS file is a PostScript file which follows the DSC and which follows a couple of other rules. These rules can be summarized as follows:
%%Pagescomment must have a value of 0 or 1).
The BoundingBox comment is used in DSC to indicate where the actual
image will be on a page. The comment describes a rectangle which completely
encloses the image. The form of the comment is: %%BoundingBox: llx
lly urx ury. For instance, suppose I have an image
which extends from x=72 to x=144 and from y=150 to
y=170. The BoundingBox comment in the document should then be:
72 150 144 170.