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From: glenn@heaven.woodside.ca.us (Glenn Reid)
Newsgroups: comp.lang.postscript
Subject: Re: Landscape EPS files.
Message-ID: <334@heaven.woodside.ca.us>
Date: 1 Dec 90 23:42:45 GMT
References: <1990Nov22.210919.27574@ccs.carleton.ca> <1990Nov25.024943.27731@Neon.Stanford.EDU>
Reply-To: glenn@heaven.woodside.ca.us (Glenn Reid)
Organization: RightBrain Software, Woodside, CA
Lines: 55

In article <1990Nov25.024943.27731@Neon.Stanford.EDU> rokicki@Neon.Stanford.EDU (Tomas G. Rokicki) writes:
>   - Landscape EPS images, when incoporated, will still be landscape.
>     I presume this is what is desired.
>   - Note that the bounding box of a landscape graphic is still measured
>     in portrait mode.
>
>In other words, from the perspective of the importing application, landscape
>and portrait graphics are both handled precisely identically.

Landscape EPS images are a very tricky thing, indeed.

It is my opinion that there is no such thing as a landscape EPS file.
Landscape is an invented concept whereby you map a PostScript image
to a physical sheet of paper by choosing to print it rotated.  An
EPS file should not contain "90 rotate 0 -612 translate" or the
equivalent, because the EPS file itself does not know how it will
be used, or whether it will be printed or cropped and scaled to
fit in some newsletter.

Now there *is* a distinction between an EPS file and a PostScript
print file; the latter has been prepared by printing by some application
or print spooler, and it is perfectly reasonable for it to contain
a landscape invocation at that point, but it also may *not* be an
EPS file any longer (it may or may not be, depending on what the file
contains).

In a display environment it can be very important for a previewing
application to understand something of the semantics of Landscape.
For example, a Preview application like the one on the NeXT computer
might want to rotate the screen image so it will read "correctly"
on the screen when previewing, rather than expecting you to turn your
head 90 degrees.  This is done on the NeXT by an extra comment that
is added to the header of the file that looks like this:

	%%Orientation: Landscape

	or 

	%%Orientation: Portrait

This further requires that all the applications rotate the same way
to get to landscape mode, else some of them may be upside-down.

But again, this is used only for files that are intended to be printed,
and which may be intercepted by the Preview application instead; the
previewer does its best to emulate the printing process in an intelligent
way, including compensating for the "90 rotate 0 -612 translate" or
whatever.

I don't think that EPS files should ever contain that kind of code; it
is enough that their aspect ratio can be divined from the bounding box
and mapped to a landscape page by the importing application if so
desired.

Glenn Reid


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