ProLab: perceptually uniform projective colour coordinate system
This work provides a new colour space for researchers and practitioners in colour science and image processing, offering improved perceptual uniformity and homoscedastic noise properties for linear colour analysis.
This paper introduces proLab, a new colour coordinate system derived from CIE XYZ using a 3D projective transformation. It achieves superior perceptual uniformity compared to CIELAB, as indicated by the STRESS metric against CIEDE2000, while also offering more homoscedastic shot noise than CAM16-UCS and other standard colour spaces.
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.