laser-lovers@uw-beaver (01/26/85)
From: Ken Olum <KDO@SRI-KL> As I understand it the Postscript language does not have ANY FACILITY WHATSOEVER for dealing with any kind of bitmap. You can't download fonts in bitmap format, nor can you download rasters such as screen images. As far as I am concerned, this makes such a printer well-nigh useless. On the other hand it depends a lot on your application. It would really be much nicer if Post script dominated other languages completely. It would also help Adobe sell their printers. Does anyone know the story on getting Metafont fonts into a Postscript printer? I have heard a rumor that there exists a program that will do this, on the other hand I've heard another rumor that no program has ever been written to get the spline-representation out of Metafont, which would seem to be a prerequisite. In regards to the supposed advantages of Postscript, converting splines to rasters is *SLOW* and presumably makes the printer much slower than the basic print-rate of the interface when doing something complicated although I don't have any timing figures. In addition the a spline-to-raster has parameters (e.g. how much darkness to turn on the bit) and better fonts can be produced if these parameters are twiddled, presumably based on the print engine. Having all this stuff done in ROM keeps you from being able to deal with it in any way. I don't see having the fonts in ROM as a feature -- we have a Symbolics LGP for which we use entirely downloaded fonts and the speed of the engine still dominates the speed of the download. On the other hand the LaserWriter is supposed to go on a serial interface which would be a lot slower (also error-prone -- do they have a reliable protocol for it?). Ken
laser-lovers@uw-beaver (01/26/85)
From: Brian Reid <reid@Glacier> I worked so hard to be reasonable on my morning message; maybe I should get back to normal and flame like crazy so people would listen. As I said, PostScript can do anything you want with bitmaps, including scaling and rotating them. The Apple LaserWriter implementation of PostScript can use any of the Macintosh screen fonts directly. You can download full-page rasters, 4-bit rasters, or anything in between. I can't imagine why anybody in their right mind would want to put Computer Modern fonts into a PostScript printer when it has real fonts. This is an aesthetic reason. There is certainly no technological reason why you cannot do this. Converting splines to rasters might or might not be slow (it's much faster than you think), but the PostScript printers all have font caches in them. The font cache in the Apple LaserWriter is bigger than the entire font memory in my Imagen 12/240 printer. If you have a cache you only have to do the conversion once. After you have printed a page or two in some font, all of the rasters are in the cache and the printer runs at full speed. I don't think you have a glimmer of an understanding of what a major-league printer the PostScript engines are, or you wouldn't even think about comparing them to, say, Symbolics printers. They are a completely new and different breed of printer and you really should not flame them out until you understand what they are, or better yet until you try one. Brian Reid Stanford