luminance
Source set: Common
public fun Color.luminance(): FloatReturns the relative luminance of this color.
Based on the formula for relative luminance defined in WCAG 2.0, W3C Recommendation 11 December 2008.
Return
A value between 0 (darkest black) and 1 (lightest white)
Throws: IllegalArgumentException
If the this color's color space does not use the RGB color model
