chromashift/
lch.rs

1use crate::{Lab, ToAlpha, round_dp};
2use core::fmt;
3
4/// A cylindrical colour space representing within the CIE colour space.
5/// The components are:
6/// - Lightness / Luminance - a number between 0.0 and 100.0
7/// - Chroma - a number between 0.0 and 150.0
8/// - Hue - a number between 0.0 and 360.0
9/// - Alpha - a number between 0.0 and 100.0
10#[derive(Debug, Clone, Copy, PartialEq)]
11pub struct Lch {
12	pub lightness: f64,
13	pub chroma: f64,
14	pub hue: f64,
15	pub alpha: f32,
16}
17
18impl Lch {
19	pub fn new(lightness: f64, chroma: f64, hue: f64, alpha: f32) -> Self {
20		Self {
21			lightness: lightness.clamp(0.0, 100.0),
22			chroma: chroma.clamp(0.0, 150.0),
23			hue: hue.rem_euclid(360.0),
24			alpha: alpha.clamp(0.0, 100.0),
25		}
26	}
27}
28
29impl ToAlpha for Lch {
30	fn to_alpha(&self) -> f32 {
31		self.alpha
32	}
33}
34
35impl fmt::Display for Lch {
36	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
37		let Self { lightness, chroma, hue, alpha } = self;
38		write!(f, "lch({}% {} {}", round_dp(*lightness, 2), round_dp(*chroma, 5), round_dp(*hue, 2))?;
39		if *alpha < 100.0 {
40			write!(f, " / {}", round_dp(*alpha as f64, 2))?;
41		}
42		write!(f, ")")
43	}
44}
45
46impl From<Lab> for Lch {
47	fn from(value: Lab) -> Self {
48		let Lab { lightness, a, b, alpha } = value;
49		let chroma = (a * a + b * b).sqrt();
50		let hue = b.atan2(a).to_degrees();
51		let hue = if hue < 0.0 { hue + 360.0 } else { hue }; // Normalize to [0, 360)
52		Lch::new(lightness, chroma, hue, alpha)
53	}
54}
55
56impl From<Lch> for Lab {
57	fn from(value: Lch) -> Self {
58		let Lch { lightness, chroma, hue, alpha } = value;
59		let h_rad = hue.to_radians();
60		Lab::new(lightness, chroma * h_rad.cos(), chroma * h_rad.sin(), alpha)
61	}
62}
chromashift/lch.rs

chromashift/
lch.rs
