PostScript is a language that describes the content of one or more pages. To actually use that description to print on paper or make a printing plate, a program is needed that interprets (or renders) the data, turning it into something that a printer, imagesetter or CtP system can output on media. This interpretation is done by a system that is called a RIP (Raster Image Processor) or renderer.
If every application on the market would use its own way of describing what the content of a page looks like, you would have to buy a RIP for every separate application (a QuarkXPress RIP, an Illustrator RIP, a Corel Draw RIP,..). To avoid this problem the input data are encoded in a standardized page description language or PDL. There are several PDLs. The most common ones are:
- PostScript (which is mainly used in graphic arts)
- PCL (for office use)
- HPGL (typically used to drive plotters for Computer Aided Design).
The remainder of this article focuses on PostScript RIPs.
Hardware versus software RIPs
In essence, a RIP is a software program running on some kind of computer. Twenty years ago, all RIPs ran on dedicated hardware, computers that were designed to only run the RIP software and that didn’t necessarily include a keyboard, screen or mouse. Such RIPs are called hardware RIPs. You can still find them in laser printers and other ‘cheaper’ devices. These build-in RIPs are also called PostScript controllers.
Nowadays a lot of RIPs run on generic PCs or Macs and behave just like any other application. These RIPs are called software RIPs. They may still include special hardware like a card to connect to the output device. To prevent piracy, software RIPs often include a security key like a dongle.
Adobe and not-so-Adobe PostScript RIPs
Since PostScript was developed by Adobe, they are the most important company creating PostScript RIPs. These RIPs are sold to the OEM market: Adobe create the core code of the RIP (which is nowadays called the CPSI or APPE in the latest generation) and sell it to any company looking for a PostScript solution. An imagesetter manufacturer then buys this code and adds both the necessary hardware to interface with their imagesetter and the extra software to control the software and add functionality.
Of course Adobe is not the only company that creates RIPs. Other companies have jumped on the bandwagon to create so-called PostScript clones. These are RIPs that conform to the Adobe PostScript standard. The most important ones are created by Global Graphics. Their RIP is called Harlequin and they also sell an alternative called the Jaws RIP. Ghostscript is a freeware PostScript interpreter from Alladin. Its commercial nephew is used in products like the popular BESTColor RIP.