CIELABin

CIELABin is a term used in color science to describe a method for encoding and indexing colors by partitioning the CIELAB color space into discrete bins. The aim is to produce a perceptually uniform and compact representation that supports efficient color quantization, retrieval, and palette creation.

Definition and method: The technique quantizes each of the CIELAB channels (L*, a*, b*) using fixed bin widths ΔL*, Δa*, Δb*. After converting an input color from sRGB to CIELAB using a standard illuminant (commonly D65) and the CIE 1976 L*a*b* formula, the bin indices are computed as i = floor((L* - Lmin)/ΔL*), j = floor((a* - amin)/Δa*), k = floor((b* - bmin)/Δb*). The resulting triplet (i, j, k) serves as a color bin key and can be packed into a single integer or used as a compound index. A representative color can be recovered by mapping the bin to its center values.

Implementation notes: Bin sizes determine trade-offs between color fidelity and palette size. Narrow bins preserve detail but yield large bin counts; wider bins compress more aggressively. The method depends on the chosen white point and observer data, and results may vary with device ICC profiles.

Applications and variants: CIELABin is used for palette extraction, fast color-based indexing and search, and image quantization. Variants may employ adaptive binning, non-uniform bin shapes aligned with perceptual contours, or integration with color management pipelines.

Status: CIELABin is not a formally standardized technique; discussions appear in experimental literature and algorithm discussions. As with any color-quantization method, results depend on color management, viewing conditions, and the target application.