Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!uwmcsd1!ig!agate!pasteur!ames!coherent!dplatt
From: dplatt@coherent.com (Dave Platt)
Newsgroups: comp.sys.mac
Subject: Re: HP DeskJet Drivers?
Message-ID: <6443@coherent.com>
Date: 8 Jul 88 22:18:39 GMT
References: <46100177@uxe.cso.uiuc.edu> <694@ttrdf.UUCP>
Reply-To: dplatt@coherent.com (Dave Platt)
Distribution: comp
Organization: Coherent Thought Inc., Palo Alto CA
Lines: 84

In article <694@ttrdf.UUCP> fjo@ttrdf.UUCP (Frank Owen ) writes:

> This is an O.K. solution, but not the best one. The Imagewriter LQ has
> resolution of 216x216 dpi, while the DeskJet does 300 dpi. Asside from
> the possible scaling problems, it would be nice if you could get
> true 300 dpi output on the DeskJet.  The Grappler is also a piece of
> hardware, ( extra $) which is really not necessary.

Agreed, in general... although I suspect that any third-party Mac driver
capable of doing a really-nice 300 DPI image is likely to cost about the
same as a Grappler.  GDT Softworks' driver-set for the DeskJet costs
about $100, and it doesn't give 300 DPI graphics.

>    The correct solution is to write a DeskJet driver that gets
> "Choosen" like the Apple drivers.

Yup... something like the ImageWriter LQ driver, but a bit more so.
It'll probably be memory-hungry, but is definitely the best approach in
the long run.

GDT is apparently thinking seriously of writing such a beast.

>                                          I have begun working on such a 
> beast, but have been discouraged by the lack of documentation from Apple
> on how to do it.

Earle Horton's articles on his daisy-wheel driver, published in
MacTutor, may be useful.

>                     Then, as soon as I thought I had it all figured out, and
> actually went out and bought a DeskJet, I find out that Cricket software will 
> be coming out with a driver Real Soon Now.   HP is endorsing their driver
> for the PaintJet, and so will probably do the same for the DeskJet.

Hmmm... when I called Cricket, I was told that their drivers are
designed to work only with their own software... they're special-purpose
graphics drivers and aren't suitable for general-purpose use.  I was
also told that they don't have a set date for the production of the
DeskJet driver.  If I was told wrong, I'd be very interested to know the
real facts of the matter!

> From the article I have read, Cricket's drivers apparently 
> extend QuickDraw to do some PostScript-type operations like text 
> rotation.

Yummie!

>            Sounds like this will be a good product when it comes out.
> The output quality should be at least as good as the LaserWrite SC.
> Oh well, perhaps my driver will end up in the public domain.
> 
>    As an aside, the DeskJet is really a nice printer. HP should be
> commended on their design. The only gripe I have is it's relatively
> slow speed at drawing graphics. Since this is the way it will be driven in
> a Mac environment, it's really too bad.  

Hmmm.  I have a suspicion that the speed limitation may be due to the
fact that the driver must shove a _lot_ of data over a medium-speed
serial link.  At 300 dots/inch, arbitrary bit-graphics (anything that
couldn't meaningfully be compressed) would require the transmission of
90,000 bits per square inch... at 9600 baud, that's almost 9 seconds!
I don't know what the actual interface speed is, but I'd be a bit
surprised if it's >19,200 baud.  At this speed, an 8-by-10 image of
arbitrary bit-graphics would require over 300 seconds (5 minutes) to
download the bits.

This is certainly a worse-case scenario, of course.  I haven't studied
HP-GL, but I infer that it contain support for both compressed
graphics (e.g. handling solid areas of black, white, or a fixed
pattern), "cursor" positioning, and perhaps some object-oriented
capabilities as well (e.g. "draw a line from point (a,b) to point
(c,d)").  An "optimal" DeskJet driver would make use of all of these
abilities, as well as the DJ's built-in fonts where applicable, and
would seek to minimize the total number of bytes shipped down to the
printer.  Not an easy job to do right... especially if the printer
doesn't have enough memory to hold an entire page-image at once, and
must be sent the data broken down into bands.


-- 
Dave Platt                                             VOICE: (415) 493-8805
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