Glossary

abstract profile

A profile for making color changes by transforming data within the profile connection space; it does not represent any device. The color space of the input and output data is that of the profile connection space, and so abstract profiles cannot be embedded in an image.

CIE

Commission Internationale de l'Éclairge (International Commission on Illumination).

CMM

See color manipulation module.

CMS

See color management system.

CMYK

Cyan, magenta, yellow, and black primaries, typically used to define color in printers. Black is included to increase the gamut and because it is difficult to get a true black by mixing cyan, magenta, and yellow. Including black also reduces the total amount of ink required and shortens drying times.

color gamut

The range of colors that can be produced by a particular device. When transforming color data from one device to another, the gamuts might not match. This is one source of color distortion. For information about how you can check for this effect, see “Checking Gamut Mapping”.

color management system

Software to facilitate manipulation of color images and ICC profiles to obtain appropriate transformed images.

color manipulation module

The software that performs the calculations necessary for color transformations.

color space

A system for specifying colors. The human visual system allows the description of all colors with the values of just three parameters; colors thus define an abstract volume. Exactly how coordinate axes are defined in the volume distinguishes color spaces from each other. For example, the set of phosphors and input values for each determines the color space of a monitor. The CIE has defined color spaces that attempt to more accurately reflect human perception of colors; the better known are referred to as CIEXYZ and CIELAB.

device-link profile

A profile that is useful if you repeatedly use a particular series of (device and non-device) profiles that begins and ends with device profiles; it concatenates the series and so defines a one-profile link between devices. Referred to as a DeviceLink profile in the ICC Profile Format Specification. Because of its device-specific nature, it does not make sense to embed this profile in an image file.

gamut mapping

If all colors are not mapped within the gamut of the output color space, which is determined by the output profile, a gamut mapping is needed to determine how to transform points in the input color space that would otherwise map out of gamut. Some of the things you can do in response to the need for gamut mapping are: change the input data, change profiles, set a flag.

ICC

International Color Consortium. See http://www.color.org, where you can find the ICC Profile Format Specification.

primary colors

The colorants that are combined to produce all colors in a device's gamut. Typically three primaries are needed, corresponding to the three dimensions of the color space.

profile

Characterizes a device's color space by specifying a mapping of it into either of two device-independent color spaces, CIELAB or CIEXYZ, developed by the CIE to describe color appearance. The Coloratura CMS uses the profile format described by the ICC Profile Format Specification, which can be found at http://www.color.org.

profile connection space

A color space based on the human visual system that allows a device independent description of color; it is used to characterize how colors are produced by input and output device color spaces and so allow color translation between devices. A device profile defines a mapping between the device's color space and the profile connection space and is defined by color measurements. The profile connection space uses either CIELAB or CIEXYZ color space. See the ICC Profile Format Specification, especially Annex A, for more details.

rendering intent

A tag in a profile to indicate how to reconcile differences between input and output gamuts when image data characterized by the profile are transformed. See the ICC Profile Format Specification for more details.

RGB

Red, green, and blue primary colors, typically used to specify colors on monitors or other devices that use additive color.

tag

Subsets of profile data that are defined by the ICC Profile Format Specification.

transform

Converts points from one color space to another: typically from the color space of an input device to that of an output device. A transform may include intermediate color adjustments. A transform is defined by a sequence of profiles and the computational algorithm in the CMM.