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From: bryce@COGSCI.BERKELEY.EDU (Bryce Nesbitt)
Newsgroups: comp.sys.amiga
Subject: Re: dvi2iff
Message-ID: <8708290951.AA14964@cogsci.berkeley.edu>
Date: Sat, 29-Aug-87 05:51:55 EDT
Article-I.D.: cogsci.8708290951.AA14964
Posted: Sat Aug 29 05:51:55 1987
Date-Received: Sun, 30-Aug-87 07:47:26 EDT
Sender: usenet@ucbvax.BERKELEY.EDU
Organization: Institute of Cognitive Studies, UC Berkeley
Lines: 55
Keywords: graphics, aspect ratios, GfxBASE

In article <> rminnich@udel.EDU (Ron Minnich) typed:
>
> ...So, with no further ado, Can someone tell me:
> Exact width and height of Amiga monitor
> pixels/inch of 1080 monitor when in 640x400
>
There is a better way!	In GFXBase there are two UWORDS, NormalDPMX and
NormalDPMY.  (gb_NormalDPMX and Y for assembly programmers).  DPM stands
for "Dots Per Meter".  On a standard V1.2 Kickstart they come out to:

NormalDPMX  = $0500 or decimal 1280
NormalDPMY  = $044A or decimal 1098

This seems to be optimized for the 1080 monitor, though users of other
monitors could certainly change these fields.  It is very possible that if
the OS detects a PAL system instead of NTSC, it will adjust.

There are other fields too look at as well, read your V1.2
graphics/GfxBase.h include file.  Especially note NormalDisplayRows and
NormalDisplayColums.  *That* or an Intuition GetScreenData() call is an
absolute *must* for a program that opens a custom screen.  I have 704
pixels of horizonal resolution, and I want to see all of it in all programs
I use!

My 1080 monitor takes 26.5 cm to display 704 pixels horizontal and 19.2 cm
to do 460 pixels vertical.  That's an aspect ratio of about 11:10.  My
monitor is no longer "factory fresh", it has been modified to shrink the
picture so I can add more pixels using "morerows" or "scnsizer".
Measurement accuracy is +-5mm.  Trust GfxBase, I'll adjust for my weird
display as needed.

Normal DPMX and Y would be good candidates for a future preferences item so
the setting of these fields would be automatic on powerup.  The only real
problem with this is that it can't adjust for different densities on two or
more separate displays.  (If you had two sets of graphics chips, two sets
of chip ram and two monitors both with differing densities this would
loose.)
--------
Personally, I'd very much like to see the next generation of Amiga chips
have an adjusted "dot clock" such that (hi-res interlace) pixels end up
exactly *square* on the screen instead of the 10:11 ratio that we have
now.  Artists, CAD system designers, desktop publisher designers, etc. would
*love* this.

No particular change would be needed except for slightly slowing the rate
at which pixels are cranked out to the display.  The display would get
slightly wider for the same number of pixels.  While this would affect nuts
like me who have crammed our displays into the borders, normal 1080 users
and users of TV sets would not loose anything.

-----
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