CIELABiin
CIELABiin is a hypothetical extension of the CIELAB color space proposed to include an illumination-invariant dimension alongside the standard L*, a*, and b* coordinates. Unlike the conventional space, which maps colors to perceptual coordinates under a fixed reference illuminant, CIELABiin adds a fourth coordinate i that encodes how a color's appearance is expected to persist across changes in lighting and viewing angle. The four coordinates are L*, a*, b*, and i, with L*, a*, and b* defined as in CIELAB, and i defined by an empirical or learned model calibrated from reflectance and illumination data. In practice, i is constrained to the range [0,1], where higher values indicate greater invariance to illumination variation.
The transformation to CIELABiin combines the standard CIELAB transformation from XYZ with a separate estimation of
Applications for CIELABiin are mostly in theoretical color science, digital archiving, and color-critical workflows where consistent
See also: CIELAB, CIE color spaces, color appearance models.