Contents

init(labWhitePoint:blackPoint:range:)

Creates a device-independent color space that is relative to human color perception, according to the CIE L*a*b* standard.

Declaration

init?(labWhitePoint whitePoint: UnsafePointer<CGFloat>, blackPoint: UnsafePointer<CGFloat>?, range: UnsafePointer<CGFloat>?)

Parameters

  • whitePoint:

    An array of 3 numbers that specify the tristimulus value, in the CIE 1931 XYZ-space, of the diffuse white point.

  • blackPoint:

    An array of 3 numbers that specify the tristimulus value, in CIE 1931 XYZ-space, of the diffuse black point.

  • range:

    An array of 4 numbers that specify the range of valid values for the a* and b* components of the color space. The a* component represents values running from green to red, and the b* component represents values running from blue to yellow.

Return Value

A new L*a*b* color space, or NULL if unsuccessful. In Objective-C, you’re responsible for releasing this object by calling CGColorSpaceRelease.

Discussion

The CIE L*a*b* space is a nonlinear transformation of the Munsell color notation system (a system which specifies colors by hue, value, and saturation—or “chroma”—values), designed to match perceived color difference with quantitative distance in color space. The L* component represents the lightness value, the a* component represents values running from green to red, and the b* component represents values running from blue to yellow. This roughly corresponds to the way the human brain is thought to decode colors. Colors in a device-independent color space should appear the same when displayed on different devices, to the extent that the capabilities of the device allow.

See Also

Creating Color Spaces