LAB to RGB Converter (CIE L*a*b* Color Space)

CIE L*a*b* (CIELAB) is a color space defined by the International Commission on Illumination that describes all perceivable colors. L represents lightness (0 = black, 100 = white), a represents the green-red axis, and b represents the blue-yellow axis. Unlike RGB which is device-dependent, LAB is designed to approximate human vision, making it the standard for color science and print production.

The LAB color space is larger than the sRGB color space used by most monitors. Some LAB values describe colors that are physically real but cannot be displayed on a standard sRGB screen. When a LAB color falls outside the sRGB gamut, the RGB values would need to go below 0 or above 255, requiring clipping. The out-of-gamut warning indicates that the displayed color is an approximation of the true LAB color.

D65 is a standard illuminant defined by the CIE that represents average daylight with a correlated color temperature of approximately 6504K. It serves as the reference white point for sRGB and most modern displays. The choice of illuminant affects how LAB values map to XYZ coordinates during conversion — using a different illuminant like D50 (common in print) would produce different RGB results from the same LAB input.

The conversion follows a two-step pipeline. First, LAB values are converted to CIE XYZ tristimulus values using the inverse of the CIELAB formulas with the D65 white point reference. Then, XYZ values are transformed to linear RGB using the sRGB color matrix, and finally a gamma correction curve (the sRGB transfer function) is applied to produce the final 0-255 RGB values. This ensures perceptually accurate color reproduction on sRGB displays.