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4. PRINCIPLE COLOUR MANAGEMENT SYSTEMS

Any description of CMS at present can be no more than a snapshot of a rapidly evolving scene. A wide range of organisations are concerned with CMS, from the providers of the systems, the application developers who incorporate some of the systems in their products, through to the suppliers of colour i/o devices and colour products such as film. Many of the organisations are collaborating through two bodies.

One body is the International Color Consortium (ICC), with members such as Adobe, Agfa, Apple, Kodak, Microsoft, Silicon Graphics, Sun and Taligent. The ICC has concerned itself with defining a standard device profiling system to enable inter-operability of systems via tagged files. Work is proceeding on extending industry standard image formats to support these new profiles.

Another body, the Open Systems Color Association, is concerning itself with the provision of standardised device characterisation, i.e. the provision of device profiles in the ICC format. OSCA is an association of peripheral and colour product producers such as Agfa, DuPont, Fuji-film and so-on.

As a result of this industry activity it can be expected that there will be many new products available in the near future, or adaptations of existing propriety systems as they start to conform to the ICC standards.

Another cause of developments is the original platform for many systems. Due to the early dominance of Apple in the DTP arena, CMS were aimed at the Apple market. This is now changing and suppliers are addressing PC support, but it is still true that a wider variety of systems are available on a Mac platform than a PC.

The following sub-sections describe CMS which are available as 'free-standing' items or in conjunction with other application packages via OEM arrangements. CMS for whom the information was obtained by their incarnation in an application package are discussed in the following section.

4.1 Pantone

Pantone has been addressing the problem of Colour Standards for decades. Concentrating on the printing industry they developed the Pantone Colour Matching System. These are standard palettes with unique reference codes to enable collaborators to specify precisely which shade of colour they are to use. The Pantone colour books contain examples of how the Pantone colours appear on both matt and glossy finishes. There are palettes of spot colours that are produced using specific dyes, and a set of definitions for Process Colours. These definitions give a palette of Process Colours, i.e. colours produced from primary mixtures, and the precise mix of Cyan, Magenta, Yellow and Black required to produce them. This Process Colour palette differs from the Pantone Spot colours as it is not possible to produce the spot palette exactly. There is a gamut of colours that can be produced using a four colour system and many spot colours lie outside it. As a possible solution to this problem Pantone is working on HEXACHROME, a six colour process colour definition. This will hopefully cover about 80% of the Pantone spot colour palette. However, currently it is Pantone's CMYK system that is of interest to the computer industry.

With the introduction of electronic typesetting and desktop publication systems Pantone came forward and provided a solution to the software industry for the problem of colour matching across devices. They offer to license software packages and printers for the Pantone process colours. If a supplier has such a license they are given a set of look up tables that define how the process colour is to be composed on given printers. Due to each make of printer having different characteristics, each printer needs its own unique table. These look-up tables serve the same function as the physical colour books. A Pantone licensed package will be able to render the Pantone process colours accurately on all Pantone registered printers. A Pantone register on a printer essentially means there is a Pantone colour table for it.

Pantone then took this one stage further and addressed the problem of collaborators requiring precise colour fidelity over a range of software packages, They have produced a tool, ColorDrive. ColorDrive is essentially a clearing house for Mac desktop colour. It is designed to import and export colour palettes between different packages. It also allows the import and export of PICT and TIFF files for colour correction and the export of those files back to the package. For Pantone registered printers, the palette gives the precise CMYK mix. However, packages can be run in conjunction with non-Pantone printers. In these cases, ColorDrive is ColorSync compatible (see below), giving the Pantone color in a standard CMYK colour mix.

All Pantone colours are supported. Where the colour is outside the gamut of the process colour space, ColorDrive gives the closest approximation. ColorDrive supports RGB, CMYK, CIE and YIQ colour spaces. Among the packages it supports are Adobe Photoshop, Adobe Illustrator, Aldus Freehand, Aldus Pagemaker, CorelDraw, Micrographx Designer and QuarkXpress.

4.2 ColorSync

ColorSync is a solution for Apple MacIntosh. It is an operating system extension that provides colour matching capability to the existing QuickDraw graphics market. ColorSync functions as a generic CMS as outlined in section 2 above. Apple provide ColorSync software as part of its device drivers and will also license it to third-party peripheral manufacturers.

Due to different devices having different gamuts, it is not enough just to define a palette in device independent terms. When a colour cannot be produced exactly on a device, some means of coming up with the 'best possible' match is required. This role is fulfilled in ColorSync by the Colour Matching Modules.

QuickDraw is a utility that stands between an application and a device. ColorSync stands behind QuickDraw. Because Apple wanted to provide an architecture where third-party developers could add value, ColorSync utilises a component manager that stands between it and modules that handle colour matching methods. Third-party Colour Management Systems can also be linked into the Component Manager to provide specific solutions. Efi (see later) and Kodak colour management modules can be incorporated easily.

ColorSync's default Apple-developed CMM was designed to provide good matching results without requiring a large primary memory. There are four options for the matching calculation including Spot and Photographic.

Add-on colour palettes for Pantone and other such named colour palettes can be incorporated if the named colour palette is provided in terms of CIE XYZ values.

The ColorSync Management extensions also support the device calibration systems currently available from third-party developers such as SuperMac, Radius and Raster Ops. With these the user can create an accurate profile for a device. Apple have co-operated with Adobe so that future PostScript drivers will incorporate the ability to include device profiles.

ColorSync is therefore essentially a colour space definition and a set of profiles describing how to render colours on various devices. It comes with some default profiles, but can be extended. The extensions can take the form of more sophisticated colour matching algorithms, or the means by which new device profiles can be created.

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