The search for color spaces with faithful hue angles, part 1

When we work in a color space for image manipulation, we are implicitly trusting that the geometry of that space reflects something about human perception. That trust matters most when the operation depends on directional structure. Gamut mapping is a good example. Many practical approaches preserve hue by moving colors along rays or along constant hue directions while adjusting lightness or chroma to fit within a destination gamut. If the hue angles in the working space do not correspond well to perceived hue, those operations introduce hue shifts that are visible and often objectionable. That is the motivation for looking carefully at how different color spaces represent hue, not just in a qualitative sense, but in a way that can be measured and compared. My starting point here was to ask how well constant Munsell hue trajectories are represented in several candidate spaces. The Munsell system is not perfect, but it remains a useful reference for perceptual hue organization. If a…