Going to a single standard in the SI (metric) would be great; however, it
must be very simple, understandable and easy to say to meet the public's
needs and to be useful.
Stan Doore
----- Original Message -----
From: "Ziser, Jesse" <[EMAIL PROTECTED]>
To: "U.S. Metric Association" <[email protected]>
Sent: Tuesday, May 20, 2008 2:03 PM
Subject: [USMA:40950] Re: DPI
--- Pierre Abbat <[EMAIL PROTECTED]> wrote:
On Tuesday 20 May 2008 09:55, Patrick Moore wrote:
> It seems that today DPI for resolution is used worldwide by the computer
> industry, including printers. My googling in the last day has turned up
> an
> alternative, simply to specify pixels in micrometers. However, I fear
> that
> this alternative will require an ISO standard and decades before it
> becomes
> widely adopted. See these links:
> <http://www.iol.ie/~sob/tm/index.xhtml>
> <http://www.cl.cam.ac.uk/~mgk25/metric-typo>
> <http://en.wikipedia.org/wiki/Metric_typographic_units>
There are four separate issues here: the size of a printed pixel, the unit
used by PostScript, the dimension of a letter to use as the font size, and
the set of font sizes available in some software. For which dimension to
use,
see the links.
Plotters are, and have been since I was a kid, made with a resolution that
is
a round submultiple of 0.1 mm, typically 0.025 mm. I don't know if the
physical resolution of inkjet plotters is a submultiple of 0.1 mm, but I
do
know that the HPGL driver at my office, used with the last version of
AutoCAD
that was available for SCO, expresses distances in 25 µm units. This means
that both inches and millimeters are expressible as integers, but the
point
is not.
PostScript is perfectly capable of scaling by arbitrary factors, but if
you
want to make a document in millimeters, you have to specify it at the top
of
each page. To fix this, Adobe and whoever else writes PostScript-handling
software have to do three things:
1. Add a version of the PS-Adobe header that says that a document is
metric.
2. Add a flag to the PostScript interpreter (which ignores DSC) to specify
millimeters.
3. Modify the software to recognize the new header, so that BoundingBox
values
in millimeters are computed correctly.
For a set of font sizes, I suggest using the musical scale. Many ratios in
it
are close to ratios of small integers, and the ratio between two paper
sizes
such as A1 and B1 (before rounding to millimeters) is three half steps. As
PostScript can scale by arbitrary ratios, this can be implemented
independently of printer resolution.
An odd suggestion! Dealing with that system doesn't sound very appealing to
me. Factors of
2^(1/12)? That's even worse than working with feet, yards, rods, and so
forth. Why not just get
rid of the whole concept of a fixed set of font sizes (seriously, who still
uses mechanical type?)
and just let me tell the computer that I want my letters to be, say, 8.4 mm
tall? That would be
ideal to me.
