Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site uw-beaver Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!ihnp4!houxm!vax135!cornell! uw-beaver!laser-lovers From: laser-lovers@uw-beaver Newsgroups: fa.laser-lovers Subject: LaserWriter and PostScript Message-ID: <626@uw-beaver> Date: Mon, 28-Jan-85 20:38:20 EST Article-I.D.: uw-beave.626 Posted: Mon Jan 28 20:38:20 1985 Date-Received: Wed, 30-Jan-85 05:26:32 EST Sender: daemon@uw-beaver Organization: U of Washington Computer Science Lines: 139 From: adobe!taft (Ed Taft) <adobe!t...@su-shasta.arpa> It is very gratifying to see the interest that has been generated among laser-lovers by the announcement of the Apple LaserWriter (as well as PostScript support for the Allied Linotronic 300 and Linotron 101 typesetters and beta-test delivery of the QMS 1200A PostScript printer). Naturally, we at Adobe Systems want to disseminate as much information as we can about these printers and about PostScript. However, Adobe is a small company; we don't have the resources to devote to detailed discussions (technical or otherwise) via net mail. Furthermore, since laser-lovers is distributed via the Arpanet, we are obligated not to discuss product plans or to promote products in this forum. Adobe's participation in laser-lovers discussions, therefore, will be limited to answering technical questions that are of general interest. Periodically (probably not more than once a week), I or some other member of Adobe's technical staff will respond to technical questions that have accumulated, concentrating on those that can't easily be answered by consulting the PostScript Language Manual. We won't respond to discussions about the relative merits of printer products. While I am on the subject of documentation, I should mention that the PostScript Language Manual, PostScript Cookbook, and Adobe font information (about 300 pages total) can be had by sending $30 to: Anne Brown Adobe Systems, Inc. 1870 Embarcadero Rd. Palo Alto, CA 94303 This documentation applies to all PostScript printers and does not include any information about the LaserWriter specifically. Apple will be selling a package called "Inside LaserWriter" that includes both the PostScript documentation and some additional information about the LaserWriter, AppleTalk protocols, and some other things (including a Mac diskette with various goodies). This can be ordered by sending $75 to: Apple Computer 467 Saratoga Ave. San Jose, CA 95129 I'm told that this will be available in about two weeks. (California residents should be sure to add sales tax.) Now for some responses to issues that have arisen in the laser-lovers discussions to date. In general, the information in Brian Reid's and Richard Furuta's messages has been quite accurate. I would like to elaborate on two topics: fonts and images. The conventional wisdom has long been that you can't produce high-quality characters at 300 bpi without bit tuning. Adobe has developed algorithms for automatic font scan conversion that, in our opinion, render the conventional wisdom obsolete. The results speak for themselves. Unfortunately, I can't discuss these algorithms because they are proprietary. The algorithms can be tuned to match the properties of different printing engines, such as the Canon engine in the LaserWriter versus the Xerox engine in the QMS 1200A. That is, a given character outline is converted into slightly different bitmaps on these two machines, even though their resolutions are the same. Adobe's fonts are uniformly scaled; no attempt is made to adjust the type style when going from one size to another. Our resident typographer (Sumner Stone) tells me that the practice of designing different typefaces for different sizes, while very common in the days of metal type, has largely fallen into disuse with the introduction of phototypesetters. A major exception to this is use of "display" typefaces for headlines, posters, and the like; as far as PostScript is concerned, these are entirely different fonts. The main algorithmic transformation in common use is anamorphic scaling, i.e., scaling by different amounts in x and y. Anamorphic scaling of arbitrary graphical objects, including characters, is supported in PostScript; and nothing precludes the possibility of defining fonts that select different descriptions for different sizes. However, none of these things is done automatically for any of the standard fonts. PostScript will give perfectly coordinated results among printers of all resolutions, because the font metrics are represented as floating point numbers that are resolution-independent. Maintaining fidelity between display and printer, however, is a much more difficult problem. At a minimum, one must have display fonts that are coordinated with the printer fonts. (A set of coordinated Mac display fonts will be sold with each LaserWriter.) For best results, one must use the printer's resolution-independent metrics for making formatting decisions such as breaking lines. Then, when placing text on the display, one must keep track of the difference between display and printer widths, and distribute this error in the white space between words. The Mac graphics software does not work this way at present; so the printed results are not always perfectly faithful to the display. Next, let's discuss images, of which bitmaps are a special case. The general case is a gray-level sampled image at an arbitrary resolution. PostScript can take such an image and render it on any resolution device by means of halftoning. (The halftoning technique is entirely under user control; but the default is a halftone screen appropriate for the given printer and resolution.) PostScript's imaging capability is intended primarily for use in rendering gray-scale graphical objects and scanned images such as photographs, and only secondarily for use in rendering user-supplied device-resolution bitmaps. Nevertheless, it is possible to define characters as bitmaps. For example, the Macintosh software synthesizes bitmap characters for Mac display fonts that don't have any printer equivalent. Needless to say, the results aren't as good as those obtained from the Adobe outline fonts. In general, PostScript is designed to work best when given high-level, device-independent descriptions of the desired results. Consider, for example, the MacDraw and MacPaint graphical models. In MacDraw, all the graphical entities (characters, lines, ellipses, etc.) retain their original identities. Printing a MacDraw document on a PostScript printer involves simply generating a PostScript description of those entities, which are then rendered at the full resolution of the printer. In contrast, everything in MacPaint is immediately converted to a display-resolution bitmap. Printing a MacPaint document requires sending the entire bitmap as an image. Not only does this take a long time, but the results are crude since they are still tied to Mac display resolution. (Some interpolation or "bit smoothing" does take place, but the improvement obtained is limited.) Device independence is achieved at a cost. Producing high-quality renditions of device-independent text, graphics, and images is computationally very intensive. This is why PostScript printers such as the LaserWriter must contain such a high-powered computer. Fortunately, the programming language base enables users to take maximum advantage of this power. Ed Taft Adobe Systems, Inc. Notices: PostScript is a trademark of Adobe Systems, Inc. LaserWriter and AppleTalk are trademarks of Apple Computer, Inc. Linotronic and Linotron are trademarks of Allied Corporation
Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site uw-beaver Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxb!houxm!vax135!cornell! uw-beaver!laser-lovers From: laser-lovers@uw-beaver Newsgroups: fa.laser-lovers Subject: PostScript update Message-ID: <881@uw-beaver> Date: Tue, 26-Feb-85 14:44:50 EST Article-I.D.: uw-beave.881 Posted: Tue Feb 26 14:44:50 1985 Date-Received: Thu, 28-Feb-85 20:06:03 EST Sender: daemon@uw-beaver Organization: U of Washington Computer Science Lines: 150 From: adobe!taft@Shasta (Ed Taft) Here is some additional information about PostScript and about the LaserWriter. As I said in my last message, Adobe will not participate in laser-lovers discussions about the relative merits of competing printer products, though we are glad to see such discussions take place. However, we will respond to technical questions about PostScript and about how it is being used. This message answers some questions that have been raised about fixing bugs, TeX support, and font handling. 1. Fixing bugs One person asked what plans Adobe has to fix bugs that are found in released printer products such as the LaserWriter. This is really a matter to be determined by the printer manufacturer rather than by Adobe. We are continuing to develop and improve PostScript, and we are naturally interested in seeing that the improvements be incorporated into printer products. What this means in terms of firmware retrofits to existing printers, I cannot say. Actually, we already know about several bugs in the LaserWriter; most of them are documented in the back of the LaserWriter Advanced User's Supplement (part of "Inside LaserWriter"). In general, these bugs are very obscure, and it's easy to avoid provoking them. To date, we have not discovered any bugs that are serious enough to warrant a firmware update in the near future. (We DO know of some serious bugs in the QMS 1200A PostScript printer, now in beta test. These bugs will be fixed before final product release.) We have the capability to "patch" many parts of the PostScript firmware, either by replacing two of the 16 ROM devices or by downloading replacement code into RAM from a host. This capability has already proven to be valuable: the entire package of AppleTalk software was introduced as a "patch" after the main body of PostScript had been frozen. We anticipate introducing various new capabilities in the form of programs that can be downloaded from a host. For example, we are already providing an alternative error handler that reports PostScript-level errors by printing a hardcopy page containing the error information in addition to sending the information to the host. This is included in both the "Inside LaserWriter" package and as part of TranScript. 2. TeX support We do not have the resources in-house to provide PostScript support for TeX. However, we are providing technical assistance to a few parties that have approached us about this. We prefer to let these outside parties make their own announcements about plans and availability. We expect that several flavors of TeX DVI to PostScript converters will emerge, from quick and dirty "preview" schemes to more robust and correct translations. At least one of these will support PostScript "specials", so that raw PostScript can be included in a TeX document for illustrations, scanned images, etc. TeX font support presents more interesting issues and alternatives. One possible solution is to teach TeX about Adobe's fonts (by building TFM files for them). This should be fine for many text applications, but the disparity between the character collections of the TeX and PostScript symbol fonts would make the setting of mathematics difficult. Another choice is to download TeX font bitmaps into a PostScript printer. This presents the usual challenges of storage management, etc, but should yield results familiar to users of TeX and TeX fonts on other systems. Eventually, Adobe hopes to offer outline descriptions of the standard Metafont/TeX fonts. We believe that we can generate acceptable outlines for a range of TeX fonts from high-resolution raster data. We expect to do this for a number of design sizes to allay the fears of Metafont enthusiasts. It will then be up to the TeX user and the DVI to PostScript translator to determine which set(s) of outlines to use. Of course, all of these approaches could be used in combination: Adobe Helvetica-Bold for chapter headings, your favorite rasters for AMR10, and an outline form of AMR for all the other sizes. As an aside, I should mention that Unilogic has announced plans to produce PostScript output from Scribe; and support for troff and ditroff is included as part of the TranScript package that has already been described in laser-lovers. 3. Font handling In connection with discussions about font downloading, it's important to understand a few things about how fonts work in PostScript. In particular, it's important to distinguish between the font description and the font cache. A font description is a collection of PostScript programs and data structures, organized in a particular way. It describes what the characters of the font look like in terms of standard PostScript graphical primitives (lines, curves, strokes, filled areas, images, etc.) Fonts provided by Adobe use a proprietary encoding that is compact and includes additional information that permits good-quality rendition in small point sizes at medium resolutions. Nevertheless, fonts themselves (whether Adobe-supplied or user-defined) are not primitive objects, but are built up from more basic graphical primitives. Though there are several different representations of fonts, the only thing that is really special about a font is that it conforms to a particular organization that is understood by PostScript's font machinery. This permits various optimizations to be performed that do not affect the appearance of the results but have a major effect on the efficiency with which those results are produced. The most important optimization is the font cache. This is a data structure that (unlike the font description) is essentially invisible to the PostScript programmer. When a particular character of a particular font is to be imaged, the font machinery first checks to see whether the bitmap for that character (at the correct size and orientation) already exists in the cache; if so, it uses the bitmap. If not, it executes the font description for the character, and stores the resulting bitmap in the cache for subsequent use. Imaging a cached character is typically 1000 times as fast as scan converting it from an outline. Font caching works regardless of whether a font description is built-in or downloaded, and regardless of whether the description consists of outlines, images (including device-resolution rasters), or whatever. Cached bitmaps for built-in or permanently-installed fonts survive from one print request to the next. In fact, idle time between print requests is utilized to scan convert and cache a "standard" selection of characters that may be specified at installation time. A downloadable font description can be introduced into a PostScript printer in one of two ways. It can be installed "permanently" (i.e., until the printer is next turned off); or it can be sent as part of an individual print request. In the latter case, the font description vanishes at the end of the print request, as do all other vestiges of that request. PostScript does not presently offer any mechanisms for automatic management of font descriptions. In general, it is the responsibility of spooling software to download fonts from a host and to determine which fonts should be permanent and which should be downloaded with individual print requests. For example, the TranScript package includes a spooler with such a font management capability. Ed Taft Adobe Systems, Inc. Notices: PostScript and TranScript are trademarks of Adobe Systems, Inc. LaserWriter is a trademark of Apple Computer, Inc. Scribe is a trademark of Unilogic, Ltd. TeX is a trademark of the American Mathematical Society.
Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site adobe.UUCP Path: utzoo!linus!philabs!prls!amdimage!amdcad!decwrl!Glacier!adobe!shore From: sh...@adobe.UUCP (Andrew Shore) Newsgroups: net.micro.mac,net.books Subject: PostScript books Message-ID: <662@adobe.UUCP> Date: Tue, 27-Aug-85 16:40:14 EDT Article-I.D.: adobe.662 Posted: Tue Aug 27 16:40:14 1985 Date-Received: Fri, 30-Aug-85 00:34:07 EDT Reply-To: sh...@adobe.UUCP (Andrew Shore) Organization: Adobe Systems, Palo Alto Lines: 61 Keywords: PostScript Adobe Systems is pleased and proud to announce the publication of two books on the PostScript language. The "PostScript Language Reference Manual" (ISBN 0-201-10174-2), and the "PostScript Language Tutorial and Cookbook" (ISBN 0-201-10179-3), are published by Addison-Wesley Publishing Company of Reading, Mass. PostScript, a device-independent page description language, is quickly becoming the industry standard for printing high-quality integrated text and graphics. PostScript has been incorporated into laser printers manufactured by Apple Computer, Allied Linotype, QMS Incorporated, and Dataproducts Corporation. PostScript Language Reference Manual ------------------------------------ This book is the complete definitive reference guide to the PostScript language. It begins with a discussion of the basic ideas that underlie PostScript, followed by comprehensive presentations of the language and its graphics and font facilities. The precise semantics of every PostScript operator is detailed in a convenient dictionary-like format. The manual concludes with four useful appendices on the standard fonts, implementation limits, structuring conventions, and the Apple LaserWriter. The PostScript Language Reference Manual represents substantial rewritting, reorganization, and additions to the information previously available as the PostScript Language Manual. The book is 336 pages, fully illustrated, and is available for $22.95. PostScript Language Tutorial and Cookbook ----------------------------------------- This book provides a thorough, clearly written guide to PostScript that outlines the features and capabilities of the language and shows practical ways to create useful PostScript programs. Using numerous annotated examples and short programs, the tutorial provides a step-by-step guided tour of PostScript, highlighting those qualities that make it such a unique and powerful language. The cookbook offers a collection of some of the most useful techniques and procedures available to PostScript programmers. The book is 256 pages, fully illustrated, and is available for $16.95. Both books were typeset entirely with PostScript (on the Linotype Linotronic 300 and Linotron 101 respectively), with no paste-up of any kind. The books, utilizing a complex book design, were formatted with the Scribe document production system and proofed on an Apple LaserWriter before final typesetting of camera-ready copy at Adobe Systems. These books should be available in bookstores soon. Most bookstores will accept orders using the ISBN (International Standard Book Number) codes given above. Adobe Systems will discontinue distribution of our older (3-hole bound) documentation, and begin distribution of these new books at list price plus shipping and handling. ----- Adobe Systems Incorporated