Path: utzoo!attcan!uunet!mcsun!hp4nl!media01!pkr
From: pkr@media01.UUCP (Peter Kriens)
Newsgroups: comp.lang.postscript
Subject: open pre-press interface OPI 1.1
Keywords: postscript tiff image pre-press pagemaker
Message-ID: <1289@media01.UUCP>
Date: 13 Jul 90 13:49:07 GMT
Organization: Mediasystemen, Netherlands
Lines: 40

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[ OPI is a defintion from ALDUS [Pagemaker] that allows
[ the manipulation of high res pictures in postscript while
[ the end user uses a low res version. The spec can be
[ obtained from Aldus: Developers Desk, Aldus Corporation, 
[ 411 First Avenue South, Seattle, Washington 98104 (206)-628-6593
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While writing software for using the Aldus
OPI defintion for high def pictures in postscript,
we have found something peculiar. Is there anybody
who can verify those facts for us?

In OPI you specify the original size of the picture
in pixels. Now it seems to me that pixels are a nasty
way of measuring sizes. If I make a low res version
from my picture and give it to the end user, he will
use quite a different resolution than what I store
on the main system. I do not want to include the low
res in a high res tiff file because then I would still
need to send all the data to the user.

So what now is the meaning of the pixels? Are they specified
in the low res or in the high res. And if they are in the
high res, how does the user know [or its application] what
measuring system to use.

I think the best solution would be if the image size and
cropping rectangle could be specified in 1/72 of in inch,
recalculation of these values to the pixels is quite
easy if you know the dpi. And the dpi is a mandatory field
in a scanned TIFF picture.

Anybody any suggestions or comments on this problem?

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