PostScript Level 2 - "I never saw a purple cow…."

Folio: The Magazine for Magazine Management, August 1, 1990 by Liz Horton

ALIGUST 1990 63

New York City-Color a cow a luscious shade of lavender on your Macintosh screen, and you're apt to get lilac on your thermal printer, mauve on your neighbor's and maroon on your proof print. Now, with Postscript Level 2, comes the first comprehensive implementation of device-indendent color. That means the exact color you specify will turn up the same on any calibrated PostScript-compatible printer, typesetter or film recorder. As Paul Beyer of Soho Graphics said at a recent meeting of the New York Professional PostScript Users Group (NYPPTUG). Postscript Level 2 "drives a stake in the ground for device-independent color."

That's not all the new PostScript does. The first major upgrade since Postscript's release five years ago, it consolidates earlier extensions as well as addressing speed and half-toning quality issues with a number of new features.

Once extensions and now part of the package are the following:

* composite fonts, which let developers encode large character sets and handle non-horizontal writing modes-extremely useful for handling Japanese fonts;

* Display PostScript, which provides WYSIWYG screen views: and

* color extensions, including the CMYK color model and black generation and undercolor removal.

Among the new features:

* improved screening and half-toning algorithms, some of which are already being implemented in the Emerald RIP (these make throughput three to seven times faster and clear up some moire problems);

* compression/decompression conforming to JPEG standards, which reduce bulky Postscript files significantly and make it easier to process, archive and move them;

* improved memory management; and

* new color models supporting four CIE color spaces: CIE L*a*b*, CIE XYZ, CIEL, and CIEY.

The CIE color spaces, which specify color in a way related to human perception, were defined in 1931 by the CIE, an international committee on standards for the printing and publishing industries.

The first products with PostScript Level 2 won't appear until early 1991, although the Emerald RTP has been incorporated into imagesetters from a number of vendors, including Agfa Compugraphic's Selectset 5000 and Varityper's Series 4000. Users needn't worry about compatibility between the versions, says Jim King, Adobe's manager of advanced technology: just as TV programs normally in color can be run on black-and-white TVs, so Level 2 output will run on Level 1 devices.