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Managing Color With ColorSync


Glossary

absolute colorimetric matching A rendering intent that is used for a device-independent color space in which the result is an idealized print viewed on a perfect paper having a large dynamic range and color gamut. In reality, paper cannot reproduce densities less than a particular minimum density.

abstract profile A profile that allows applications to perform special color effects independent of the devices on which the effects are rendered. Abstract space profiles perform affects between two PCS color spaces. See also profile , color space profile , device profile , and named color space profile .

additive color theory The process of mixing red, green, and blue lights, which are each approximately one-third of the visible spectrum. Additive color theory explains how red, green, and blue light can be added to make white light.

animated color A color that the Palette Manager uses for special animation effects. Animated colors work only on devices that have a color table; that is, they do not work on direct devices.

application-owned dialog box A dialog box, created by an application, for presenting a color picker.

arbitrated CMM A CMM selected by the ColorSync Manager from the available source and destination profiles to perform a specified operation. Compare with default CMM , key CMM , and preferred CMM .

brightness A term in color theory used to describe differences in the intensity of light reflected from or transmitted by a color image. Also known as value . The hue of an object may be blue, but the adjectives dark or light distinguish the brightness of one object from another. Compare with hue and saturation.

calibration The process of setting a device's parameters according to its factory standards. Compare with characterization .

characterization The process of learning the color character of a monitor so that a profile can be created to describe it. Compare with calibration .

CIE-based color spaces Color spaces that allow color to be expressed in a device-independent way, unlike RGB colors, which vary with display, and scanner characteristics and CMYK colors, which vary with printer, ink, and paper characteristics. CIE-based color spaces result from work carried out in 1931 by the Commission Internationale d'Eclairage (CIE). These color spaces are also referred to as device-independent color spaces.

CMM See color management module.

CMS See color management system.

CMY space A color space in which cyan, magenta, and yellow are the three primary colors. Used for some low-end printers.

CMYK space A color space in which cyan, magenta, and yellow are the three primary colors. Unlike CMY space, the CMYK color space models the way inks or dyes are applied to paper in printing, in which black ink is overprinted in darker areas to give a better appearance.

color channel See color component.

color component A dimension of a color value expressed as a numeric value. For the ColorSync Manager, depending on the color space, a color value may consist of one, two, three, four, or eight components, also referred to as channels.

color-component value A value that represents the color of a component. Each component of a color space has a color-component value. A color-component value can vary from 0 to 65,535 (0xFFFF), although the numerical interpretation of that range is different for different color spaces. In most cases, color-component intensities are interpreted numerically as varying between 0 and 1.0. See also color space and color value.

color conversion The process of converting colors from one color space to another in a mathematically reversible way.

color gamut See gamut.

color management module (CMM) A component, also referred to as a CMM, that carries out the actual color matching and gamut-checking processes based on requests resulting from calls a program makes to the ColorSync Manager API. An application or driver can supply its own CMM or it can use the robust default CMM that Apple supplies. A CMM interprets the information stored in a profile .

color management system (CMS) Software that provides consistent color across peripheral devices and across operating-system platforms by converting colors from the color space of one device to the color space of another device.

Color Manager A set of system software functions that supply color-selection support for Color QuickDraw. Most applications never need to call the Color Manager directly.

color matching The process of adjusting or matching converted colors appropriately to achieve maximum similarity from the gamut of one color space to the other. Color matching always involves color conversion, whereas color conversion may not entail color matching. Matching also involves devices, and may not be reversible.

color space An environment in which colors are represented, ordered, compared, or computed. A color space specifies how color information is represented. It defines a multidimensional space whose dimensions, or components, represent intensity values.

color space profile A profile that contains the data necessary to convert color values between a PCS and a non-device color space (such as L*a*b to or from L*u*v, or XYZ to or from Yxy), as necessary for color matching. Color space profiles provide a convenient means for CMMs to convert between different nondevice profiles. See also profile , abstract profile , device profile , and named color space profile .

ColorSync A platform-independent color management system from Apple Computer that provides services for fast, consistent, and accurate desktop color calibration, proofing, and reproduction.

ColorSync Manager A set of system software functions (or API) that provide device-independent color-matching and color conversion services for device drivers and applications; the implementation of ColorSync for the Mac OS.

color value A complete specification of a color in a given color space. Depending on the color space used, one, two, three, or four color-component values combine to make a color value.

courteous color A color that accepts whatever value the Color Manager determines is the closest match available in the color table. Compare tolerant color .

default CMM A CMM supplied with ColorSync that supports all the required and optional functions defined by the ColorSync Manager, and is therefore a suitable CMM of last resort when a specified CMM is not available or cannot perform a specified operation. Compare with arbitrated CMM , key CMM , and preferred CMM .

default system profile The system profile that serves as the default display profile, as well as the default profile for color conversion and matching operations for which no profile is specified. Unless the ColorSync Manager control panel is used to select a different profile, which must be an RGB profile, ColorSync uses the Apple 13-inch color display. See Setting Default Profiles for changes with ColorSync 2.5.

destination profile The profile that describes the characteristics of the output device for which the image is destined. The profile is used to color match the image to the device's gamut.

device-independent color spaces See CIE-based color spaces.

device link profile A profile that represents a one-way link or connection between devices. It can be created from a set of multiple profiles, such as various device profiles associated with the creation and editing of an image. Its not represent any device model, nor can it be embedded into images.

device profile A structure that contains the color characteristics of a given device in a particular state. See also profile , abstract profile , color space profile , and named color space profile .

explicit color A color that specifies an index value in the devices color table rather than an RGB color.

gamut The range of color that a device can produce, also referred to as the device's color gamut.

general purpose color-matching function One that uses a color world to characterize how to perform color-matching. also QuickDraw-specific color-matching function .

gray space A color space that typically has a single component, ranging from black to white.

HLS space A transformation of RGB space that allow colors to be described in terms more natural to an artist. The name HLS stands for hue, lightness, and saturation.

HSB space A transformation of RGB space that is analogous to HSV space. HSB stands for hue, saturation, and brightness. where brightness is synonymous with value in HSV space. Compare with HSV and HLS space.

HSV space A transformation of RGB space that allow colors to be described in terms more natural to an artist. The name HSV stands for hue, saturation, and value. Compare with HSB and HLS space.

hue The name of the color that places the color in its correct position in the spectrum. For example, if a color is described as blue, it is distinguished from yellow, red, green, or other colors. Compare with brightness and saturation.

indexed color space The color space used when drawing with indirectly specified colors.

inhibited color A color that is prevented from appearing on particular screens. Colors can be specifically inhibited on a 2-bit, 4-bit, and 8-bit color or grayscale screen.

interchange color space Device-independent color spaces that are used for the interchange of color data from the native color space of one device to the native color space of another device. Compare profile connection space (PCS) .

International Color Consortium (ICC) International color organization that publishes the International Color Consortium Profile Format Specification . The ICC Web site is at http://www.color.org .

inverse table A special data structure arranged by the Color Manager in such a manner that, given an arbitrary RGB color, the Color Manager can very rapidly look up its pixel value.

key CMM In a series of CMMs specified by a CMConcatProfileSet structure, the CMM indicated by the zero-based value of the structures keyIndex field. Compare with arbitrated CMM , default CMM , and preferred CMM .

L*a*b* space A nonlinear transformation (that is, a third-order approximation) of the Munsell color-notation system designed to match perceived color difference with quantitative distance in color space.

L*u*v* color space A nonlinear transformation of XYZ space used to create a perceptually linear color space. This color space was designed to match perceived color difference with quantitative distance in color space.

metamerism The capability of the human eye to perceive two or more visible spectra as the same color. See also trichromatic color vision .

named color space A color space in which each color has a name; colors are generally ordered so that each has an equal perceived distance from its neighbors in the color space.

named color space profile A profile that contains data for a list of named colors. The profile specifies a device color value and the corresponding CIE value for each color in the list. See also profile , abstract profile , color space profile , device profile , and named color space profile .

perceptual matching A rendering intent in which all the colors of a given gamut may be scaled to fit within another gamut. The colors maintain their relative positions, so the relationship between colors is maintained.

pixel value A number used by system software and a graphics device to represent a color. The translation from the color that an application specifies in an RGBColor data structure to a pixel value is performed at the time the application draws the color. The process differs for indexed and direct devices.

preferred CMM Starting with ColorSync 2.5, a user-selected CMM, chosen with the ColorSync control panel, that is used for all color checking and matching operations that the CMM can handle. Compare with arbitrated CMM , default CMM , and key CMM .

profile A structure that provides a means of defining the color characteristics of a given device in a particular state. A profile may contain measurements representing a color gamut, including information such as the lightest and darkest possible tones, and maximum densities for red, green, blue, cyan, magenta, and yellow. The International Color Consortium defines several different profile classes. Each profile class must include a different required set of information, but all of these classes follow the same format. See also abstract profile , color space profile , device profile , and named color space profile .

profile chromaticities Color values that define the extremes of saturation that the device can produce for its primary and secondary colors (red, green, blue, cyan, magenta, yellow).

profile connection space (PCS) A device-independent color space used as an intermediate when converting from one device-dependent color space to another. Profile connection spaces are typically based on spaces derived from CIE color spaces. Compare interchange color space .

profile identifier An abbreviated data structure that uniquely identifies, and possibly modifies, a profile in memory or on disk.

profile reference A unique reference to a profile, returned by ColorSync and based on a private data structure; the profile reference is the means by which your application identifies a profile and gains access to it.

QuickDraw-specific color-matching function One that uses QuickDraw to provide images showing consistent colors across displays. See also general purpose color-matching function .

reference white point A specific definition of what is considered white light represented in terms of XYZ space and usually based on the whitest light that can be generated by a given device.

relative colorimetric matching A rendering intent in which the colors that fall within the gamuts of both devices are left unchanged. Relative colorimetric matching allows some colors in both images to be exactly the same, which is useful when colors must match quantitatively. A disadvantage of relative colorimetric matching is that many colors may map to a single color resulting in tone compression.

rendering intent The approach taken when a CMM maps or translates the colors of an image to the color gamut of a destination device. Each profile supports four different rendering intents: perceptual matching, relative colorimetric matching, saturation matching, and absolute colorimetric matching.

RGB space A three-dimensional color space whose components are the red, green, and blue intensities that make up a given color. Compare sRGB space .

saturation The degree of hue in a color or a color's strength. A neutral gray is considered to have zero saturation. A saturated red would have the a color similar to apple red. Compare with brightness and hue.

saturation matching A rendering intent in which the relative saturation of colors is maintained from gamut to gamut. Colors outside the gamut are usually converted to colors with the same saturation, but different lightness, at the edge of the gamut.

source profile The profile that is associated with the image and describes the characteristics of the device on which the image was created.

sRGB space A three-dimensional color space that attempts to create a standard RGB space based on a calibrated, colorimetric RGB definition that calls for a gamma of 2.2, a white point of 6500 degrees K, and P-22 phosphors. Compare RGB space .

subtractive color theory The process of combining subtractive colorants such as inks or dyes. In this theory colorants of cyan, magenta, and yellow are used to subtract a portion of the white light that is illuminating an object.

system profile The profile that defines the color characteristics for the system's display device. The ColorSync Manager provides a control panel to allow the user to specify the system profile for the current display device.

trichromatic color vision The capacity of the human eye to responds equally to two or more sets of stimuli having different visible spectra. See also metamerism .

trichromatic color reproduction The process of inducing the illusion of a color using various amounts of only three primary colors: either red, green, and blue mixed additively or cyan, magenta, and yellow mixed subtractively.

tristimulus values An hypothetical set of primaries, XYZ, set up by the CIE that correspond to the way the eye's retina behaves. The term tristimulus comes from the fact that color perception results from the retina of the eye responding to three types of stimuli. After experimentation, the CIE set up a hypothetical set of primaries, XYZ, that correspond to the way the eye's retina behaves.

undercolor removal (UCR) The removal of excessive color densities when printing an image.

value See brightness.

XYZ color space The fundamental CIE-based color space that allows colors to be expressed as a mixture of the three tristimulus values X, Y, and Z.

Yxy color space A color space belonging to the XYZ base family that expresses the XYZ values in terms of x and y chromaticity coordinates, somewhat analogous to the hue and saturation coordinates of HSV space.


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