Module `Hugin.Color`

Perceptually uniform OKLCH colors.

Perceptually uniform colors.

Colors are represented internally in the OKLCH color space. All operations (lighten, darken, mix) produce perceptually uniform results: equal numerical steps yield equal perceived differences.

Constructors accept common input formats (sRGB, hex) and convert to OKLCH on creation. The reverse conversion to_rgba is called only at render time.

Types

type t

The type for colors in OKLCH space. Components are lightness [0, 1], chroma [0, ~0.4], hue [0, 360), and alpha [0, 1].

Constructors

val oklch : l:float -> c:float -> h:float -> unit -> t

oklch ~l ~c ~h () is the fully opaque OKLCH color with lightness l, chroma c, and hue h (in degrees).

val oklcha : l:float -> c:float -> h:float -> a:float -> unit -> t

oklcha ~l ~c ~h ~a () is like oklch with alpha a.

val rgb : r:float -> g:float -> b:float -> unit -> t

rgb ~r ~g ~b () is the fully opaque color with sRGB components r, g, b in [0, 1], converted to OKLCH.

val rgba : r:float -> g:float -> b:float -> a:float -> unit -> t

rgba ~r ~g ~b ~a () is like rgb with alpha a.

val hex : string -> t

hex s is the color parsed from the hex string s. Accepts "#RRGGBB" and "#RRGGBBAA" formats.

Raises Invalid_argument if s is not a valid hex color.

Accessors

val lightness : t -> float

lightness c is the OKLCH lightness of c in [0, 1].

val chroma : t -> float

chroma c is the OKLCH chroma of c in [0, ~0.4].

val hue : t -> float

hue c is the OKLCH hue of c in degrees [0, 360).

val alpha : t -> float

alpha c is the alpha of c in [0, 1].

Converting

val to_rgba : t -> float * float * float * float

to_rgba c is (r, g, b, a) with sRGB components in [0, 1]. Values are clamped to the sRGB gamut.

Operations

val with_alpha : float -> t -> t

with_alpha a c is c with alpha set to a.

val lighten : float -> t -> t

lighten amount c is c with lightness increased by amount, clamped to [0, 1].

val darken : float -> t -> t

darken amount c is c with lightness decreased by amount, clamped to [0, 1].

val mix : float -> t -> t -> t

mix ratio a b is the perceptual blend of a and b. ratio is the interpolation factor: 0.0 gives a, 1.0 gives b. Hue is interpolated along the shortest arc.

Named colors

The default named colors follow the Okabe-Ito palette, designed to be distinguishable under all forms of color-vision deficiency.

val orange : t

val sky_blue : t

val green : t

val yellow : t

val blue : t

val vermillion : t

val purple : t

val black : t

val white : t

val gray : t

Formatting

val pp : Stdlib.Format.formatter -> t -> unit

pp formats the color as oklch(L C H / A).