Rob McDougall writes:

>[Wirt Atmar wrote:]
>> Indeed, when we first gave serious thought to adopting PostScript -- and
>later
>> again thought of completely abandoning PCL (for a whole raft of reasons, but
>> most especially the inability of HP to produce two printers that acted
>> precisely the same) ...
>
>The PCL problem you describe was solved many years ago when the PCL 5
>imaging model was standardised.  Now the same PCL prints the same way on
>all PCL printers.  We have many customers that create forms for HP
>LaserJet III's (a reasonable lowest common denominator) and then print
>them on all manor of 4's, 5's and 6's.  No problem.

Well, no *big* problem. There are a few differences between the LJ III
and later printers having to do with the internal font sets and the fact
that font selection is ambiguous. Also, limiting yourself to the LJ III
feature set means not using HPGL/2 in forms, thus severely limiting the
kinds of graphics that can be included without resorting to bitmaps.

HP publishes a 135-page catalog of differences among its PCL printers.
This catalog does not include the HP 5000 series, which have their own
uncataloged foibles -- and which, incidentally, are PCL 4 rather than PCL
5 printers.

These differences are a huge headache for people trying to write
graphics-oriented printer drivers. If I were in Wirt's place, I would
have made the same decision he did.

>
>[snip]
>> >  >But the
>> >  >quality of output is significantly (to greatly) better.
>> >
>> >  This is misleading in the extreme.
>>
>> ... I was
>> speaking about overall aesthetic image quality. There is a simple, objective
>> test to my statement. Count the number of books, magazines, newspapers,
>> advertisements, catalogs, etc. that are put together using PCL -- and
>>compare that number to PostScript-produced documents. ...
>
>I think this statistic is misleading.  I don't believe that the fact
>that high end publications are produced using Postscript is directly
>related to the quality of its output.  ... High end layout packages all
>support Postscript because that's what the high end printing presses
>support.  The only reason they support Postscript is because that's what
>they've always supported.

No; high-end layout packages and printing presses support PostScript
because it's inherently device-independent. A PostScript program is a
precise, resolution-independent mathematical description of the contents
of a page; a PCL data stream is whatever HP says it is, meaning different
things to different printers at different times. There have been several
HP-sanctioned attempts at creating PCL imagesetters (essentially very
precise, high-end printers that produce the negatives or plates for
printing), and none have gotten very far simply because there's no point
in sending imprecise instructions a high-precision device.

PCL 6 does not share this failing; in fact, PCL 6 looks a lot like
binary-encoded PostScript. It still has the resource-management issues
that PostScript users solved a long time ago, but it's a big step toward
a graphics system that can actually be trusted to produce the same output
twice in a row.

-- Bruce


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