Usually when you print to a PostScript file you end up capturing all of the
PostScript code that is sent to the printer to create the page. (Remember
that what you send to the printer is a PostScript program that the printer
runs to create the page).
EPS files (Encapsulated PostScript) are designed and intended to be brought
into other documents which will then be sent as a whole to a PostScript
printer. As a result they only contain the PostScript code necessary to
produce whatever image they contain and **not** all of the PostScript header
information, etc. that gets sent to the printer.
EPS files may (and often do) contain a preview image - a low resolution
bitmap version of the actual file. A lot of programs use that preview on the
screen to help you place the image on the page. When they print, they print
at full resolution, but the previews often look really bad.
Finally, EPS images can contain either bitmap or vector data. Bitmap data
does not scale particularly well since you have to either duplicate pixels
or remove pixels to change the size. Vector data (HPGL files are also vector
data) are essentially a stream of endpoints and draw/move commands so they
scale really well. As a result you can have some EPS files that scale really
well and some that don't. On top of that, some graphics file conversions
will require that a vector file be rendered to a bitmap when it is
converted, which creates the scaling problem.
Chris
J. Chris Johnston
Polymers Branch, Materials Division (216) 433-5029
NASA Lewis Research Center (216) 433-5033 fax
21000 Brookpark Rd. MS 105-1 James.C.Johnston@lerc.nasa.gov
Cleveland, OH 44135
Resistance is Futile!