huepreserving

Huepreserving refers to a class of color transformations that maintain the hue component of colors while allowing changes to other attributes such as lightness and chroma. Hue describes the color type (for example red, green, or blue) and is often represented as an angle in a polar representation of chromaticity. A huepreserving operation aims to keep that angle fixed so the color category remains recognizable after processing.

In practice, huepreserving can be achieved by performing edits in color spaces that separate hue from lightness and chroma, or by using perceptually uniform representations. Common approaches include converting to spaces like CIE LCh or OKLab, where the data are expressed as lightness, chroma, and hue. Adjustments can then be applied to lightness or chroma while leaving hue unchanged, before converting back to an RGB or device space. Some workflows also rely on cylindrical coordinates in HSL or HSV, but these can be less robust to gamut clipping and perceptual nonuniformities, potentially causing small hue drifts.

Applications of huepreserving transformations include color correction and grading, recoloring of objects in images and 3D textures, and any workflow where maintaining the original color identity is important while changing brightness or saturation. Limitations include the risk of hue shifts due to gamut clipping, metamerism, or interpolation in nonuniform color spaces. Careful choice of color space and clipping strategies helps minimize perceptual hue changes.

See also color management, color spaces, perceptual uniformity.