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This article first appeared in the May 1998 issue of the Louisville Computer News. It was written by Lee Larson.
It has always struck me as odd that graphics professionals-people whose livelihood depends on getting PostScript printers to do everything but sing and dance-have embraced a computer that at its heart knows nothing about PostScript. From the very first 128K Macintosh until today, the graphics language at the heart of the Macintosh has been QuickDraw, and not PostScript. Everything you see on the Macintosh screen is put there because of QuickDraw and not PostScript. It's up to your software and the LaserWriter printer driver to quickly and accurately translate QuickDraw to PostScript when your work is put to paper. This QuickDraw to PostScript translation has taken years to perfect and many programs have little bugs that are hard to track down.
For the last few months I've been annoyed by a small translation bug. A couple of weeks ago, it finally became clear the problem wasn't going to go away on its own, so I decided to track it down. The method I used could benefit others with similar problems.
One of the tasks I'm always doing is generating complex mathematical graphs for inclusion in technical papers. The program usually used to generate the graphs is an amazingly versatile and powerful mathematical development system from Wolfram Research called Mathematica. Even though the graphs generated by Mathematica are very good, they're not quite perfect, so I copy them as PICT files on the clipboard and paste them into Deneba Software's graphics program Canvas for a final tweak. Then, the tweaked picture is saved in encapsulated PostScript format so it can be inserted into the final paper, which is usually written in Textures, from Blue Sky Research.
At the end, when the final encapsulated PostScript file was used, there was a vexing problem; the screen display and the printed output didn't quite match. For example, on the screen the minus signs correctly displayed as en-dashes (option+hyphen), while on the printout, the minus signs were printed as em-dashes (option+shift+hyphen), which are too wide. There were several other such problems, none of which were show-stopping, but all of which were irksome. Since the files had no problems when printed from a StyleWriter, which is a QuickDraw printer, and had the problems when printed to a PostScript printer, the problem had to be in the QuickDraw to PostScript translation.
A PostScript file is nothing more than a text file containing a program written in the PostScript programming language. Machine-generated PostScript, such as that from Canvas is not meant for people to read. The files are huge and have no comments to tell you what is what inside the file. But, there are a few tools to help.
The first thing I did was open a few problem files with the text editor BBEdit Pro 4.5 to have a look around. This didn't help much because the files are so large. Besides, if I made any changes, I had to print the file to see if it made any difference, and this meant killing trees as well as having to go all the way across the room to pick up the paper.
To save trees, a good tool for the job is MacGS 1.0, a completely free port of GhostScript 5.10 and related tools to the Macintosh. GhostScript is a freeware PostScript language interpreter which started out in the Unix world and has since been ported to many other systems. It understands PostScript level 2 and does a decent screen preview of pure PostScript files. Besides this, it will convert a pure PostScript file to PICT and can convert PostScript files to and from PDF format. MacGS can be downloaded at http://www.cs.wisc.edu/~ghost/mac/index.html.
Using these two programs, I could make a change in the raw PostScript file with BBEdit Pro and immediately see the result on the screen in MacGS. It didn't take long to isolate the problems.
I've written to Deneba about several small bugs in their encapsulated PostScript translator, and I've also got a small script for BBedit Pro which fixes my PostScript files until Deneba gets around to revising Canvas.
An irony in all this is that Mathematica does all its internal graphics as PostScript. So, the process I went through used Mathematica to translate its internal PostScript to QuickDraw (PICT) for Canvas. Then Canvas changed it back into PostScript (EPSF) again. It would be so much cleaner, if the Macintosh could use PostScript for both printing and screen display.
This idea occurred long ago to programmers at Adobe Systems, the originators of PostScript. In the late 1980's they designed a special PostScript interpreter, called Display PostScript, to be used for screen display instead of printing. The most well-known computer to use Display PostScript for its screen display was the famous black cube from NeXT. But, computers were not yet fast enough to efficiently handle Display PostScript, and NeXT failed to gain traction, in part because of an often lethargic screen. Now Apple owns NeXT and the next generation Apple operating system, Rhapsody, is based on NeXTStep. It was hoped by many people that Rhapsody would have Display PostScript as its screen driver. Alas, this will not happen because Adobe recently killed Display PostScript.
There are rumors that Apple has cloned Display PostScript for use with Rhapsody, but nobody at Apple has publicly admitted it.
The big news from Apple this month (besides their $55 million profit) was the release of QuickTime 3.0. Available for Mac OS, Windows 95 and Windows NT, this latest version of QuickTime significantly advances its video and audio capabilities. QuickTime 3 includes new compression technology and support for over 150 video effects and transitions approved by the Society of Motion Picture & Television Engineers. Roland Corporation's Sound Canvas sound set is also included, providing over 200 MIDI-compatible sounds and instruments. This new release supports most of the standard video, audio and still picture formats found on the Internet. QuickTime 3.0 was released in two different versions. A free version is available for downloading from Apple. A more capable release, for multimedia authors, called QuickTime Pro, is available for $29.99 from Apple. Details are at http://www.apple.com/quicktime/.
The great free on-line weekly Macintosh e-zine called TidBITS turned eight last month. It is one of the best sources for clear-headed Macintosh reporting. They've survived for over 425 issues, and have 68,000 readers in 120 countries. It's even translated every week into Dutch, French, German, Japanese, and Spanish. Thousands of us look forward to its appearance in our email boxes every Tuesday morning. You can subscribe by sending email to tidbits-on@tidbits.com. They also have a web site with more information at http://www.tidbits.com/.
There's a potentially killer bug in the Remove Office 98 utility that ships with Microsoft Office 98. Its purpose is to uninstall Office 98 from a computer, but under rare circumstances, it removes almost all the contents of the System Folder. Microsoft's first reaction to the bug was "well, then, don't remove Office 98!" But, there is an updater to Remove Office 98 out. Version 1.1 can be downloaded from Microsoft at http://www.microsoft.com/macoffice/productinfo/98dl/o98u.htm.
Graphic Converter 3.2.1 has been released. This is the Swiss-army-knife of Macintosh graphics programs, which imports about 100 graphics formats and outputs 40 of them. It should be in the toolkit of everyone who works with graphics. You can download it from http://www.lemkesoft.de. Graphics Converter is a $35 shareware program.
With the release of Mac OS 8.1, Apple also introduced the new file system for hard drives called HFS+. Many of us had painlessly converted our drives over to HFS+ when the change from Daylight Savings Time rolled around and caused some minor problems. It turns out that the older HFS file format stores the creation and modification dates of files in absolute time. In HFS+ they are stored as an offset from GMT. Because of this, when the Mac's time was backed up by an hour, the creation and modification times for all the files on any HFS+ volume also changed. The most common way to notice this was with backups. Most backup programs, such as Retrospect, do incremental backups by comparing modification dates of files already backed up with the dates of the files on the drive. Suddenly, none of the dates matched, so Retrospect wanted to back up all the files on the drive. This caused many of us to discover on Sunday or Monday morning that our tapes were filled to overflowing.
The Art Software Group will meet on May 23 1:004:00 in the Natural Science Building auditorium at the University of Louisville. Sweetwater Sound, Microrgrafx and Apple will be present to give demos. Promised Macintosh topics include a demonstration of the final release of Apple's new operating system called Rhapsody, demonstrations of a new unreleased G3 computer and a summary of the 1998 Apple Worldwide Developer Conference. For more information see their web site at http://www.aol.nu/.
The Louisville Computer Society will not meet in May because the usual meeting date falls on Memorial Day. Bob Smaracko from Apple will be present at the June 22 meeting to do an overview of all the new multi-media goodies. For more information, see the Louisville Computer Society's web page at http://www.aye.net/~lcs/.
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