ProLab: perceptually uniform projective colour coordinate system

TL;DR

ProLab is a new perceptually uniform 3D projective colour space derived from CIE XYZ, offering improved uniformity over CIELAB and better noise properties, facilitating linear colour analysis.

Contribution

We introduce proLab, a novel projective colour coordinate system that enhances perceptual uniformity and noise characteristics compared to existing spaces.

Findings

ProLab outperforms CIELAB in perceptual uniformity according to STRESS metric.

ProLab's angular errors are normalized for human colour discrimination thresholds.

Shot noise in proLab is more homoscedastic than in CAM16-UCS.

Abstract

In this work, we propose proLab: a new colour coordinate system derived as a 3D projective transformation of CIE XYZ. We show that proLab is far ahead of the widely used CIELAB coordinate system (though inferior to the modern CAM16-UCS) according to perceptual uniformity evaluated by the STRESS metric in reference to the CIEDE2000 colour difference formula. At the same time, angular errors of chromaticity estimation that are standard for linear colour spaces can also be used in proLab since projective transformations preserve the linearity of manifolds. Unlike in linear spaces, angular errors for different hues are normalized according to human colour discrimination thresholds within proLab. We also demonstrate that shot noise in proLab is more homoscedastic than in CAM16-UCS or other standard colour spaces. This makes proLab a convenient coordinate system in which to perform linear colour analysis.