CMS (color management system) is a general term for a structure which allows color to be managed as described in the previous pages.

A CMS is based on:

• profiles which describe the devices gamut;
• conversions from a source profile to a destination profile (gamut mapping);
• styles of gamut mapping: rendering intent;
• software for the conversion: color engine.

The open CMS technology currently used with MacOS and Windows are:

• the technology standardised by the International Color Consortium (ICC);
  • in MacOS, it is implemented in ColorSync (now version 3) which deals with color management according to ICC specifications;
  • in Windows 98 and 2000, it is ICM (Image Color Management, now version 2);
  • in Windows 95 and NT there is no CMS implemented at operating system level.
• the technology supported in the latest versions of PostScript, known as PostScript Color Management (PCM).

Each of these systems uses its own idea of profile, rendering intent and color engine. The two are not in conflict, however, but rather complement and supplement each other.

This is due to the fact that color management based on ICC specifications is performed on-host (i.e. on a computer, within an application, before printing or at most within the print driver), whereas PostScript color management is performed in-rip (i.e. esclusively in the print phase, within a PostScript Level 3 rip).

The CMS can (or rather should) be implemented at operating system level. This way, the relevant part of the operating system can offer a common method of controlling and converting colors between devices to all the applications and devices, and to the other components of the operating system.

Specifically, it can offer a common user interface, a common format for the profiles (e.g. ICC), a common color engine (and if necessary the means to use others) and the means to access the API (application programming interface). In other words, it enables the applications to use the most common functions and routines that the CMS has already implemented.

The applications themselves may also have a color management structure which can use the facilities made available by the operating system.

There are also stand-alone applications (or sets of applications) which offer functions similar to those of the system CMS, but which work at least partly independently from it.

Official Apple ColorSync pages.