Offset printers need separate camera-ready copies for each ink they will use in printing a document. Aurora is a PostScript program for producing colour separates from a colour PostScript document. Aurora can be run from any type of computer, as it depends only on a black-and-white PostScript printer for its execution. It is capable of handling colour images as well as ordinary graphics, though image handling is very slow. ============================================================================= CONTENTS ======== The Aurora distribution consists of the files README This file. aurora The Aurora PostScript program. auroratx.ps A description of how Aurora works, its limitations, and examples showing what it will do. This document is suitable for printing on a colour printer, a Level 2 machine, viewing with a PostScript interpreter, or as a last resort, printing on an old Level 1 machine. The last page, containing several images, is extremely slow to output. cyan These four files allow selection of the primary colour magenta for a particular run of Aurora. Any colour used in yellow a document will be separated into these components, and black the amount of the selected primary will be output. red These three files are examples of how to select custom green colours. When used with Aurora, only precise matches blue to a custom colour are output (either as full black or as a shade of gray). 60.lpi When using the CMYK colours, it is useful to set up 71.lpi different screens for halftones of the different 85.lpi primaries. These files contain instructions obtained from the Adobe file server for establishing suitable screens for a desired dot density. The parameters used in these files may vary between machines, and you may find it necessary to consult the PPD file appropriate to your machine from the Adobe file server for more suitable numbers for setting colour screens on your hardware. ============================================================================= USAGE ===== It is necessary to send to the PostScript printer the file "aurora", followed by a colour primary selection, optionally a screen specification, and then the document itself. With some operating systems, it is best to join (or concatenate) the separate files into one before despatch to the printer. They must be treated as a single job by the PostScript printer. This procedure must be followed for each desired separate. For example, the files aurora magenta 60.lpi mydoc would be sent as a single file to the printer to print the magenta separate of "mydoc", using a 60 lines per inch screen. ============================================================================= Aurora is available by anonymous FTP from "ftp.adfa.oz.au" in directory "pub/postscript". Aurora may not be used for commercial purposes without the consent of the author. It may be freely transmitted provided the authorship and copyright notice is retained unmodified. Graham Freeman gfreeman@cs.adfa.oz.au