emilk · January 21, 2021 09:45 · Jan 21, 2021
diff --git a/oklab.rs b/oklab.rs
@@ -0,0 +1,62 @@
+//! https://bottosson.github.io/posts/oklab/
+
+/// oklab from linear rgb (0-1 ranges)
+pub fn lab_from_rgb([r, g, b]: [f32; 3]) -> (f32, f32, f32) {
+    let x = 0.4121656120 * r + 0.5362752080 * g + 0.0514575653 * b;
+    let y = 0.2118591070 * r + 0.6807189584 * g + 0.1074065790 * b;
+    let z = 0.0883097947 * r + 0.2818474174 * g + 0.6302613616 * b;
+
+    let x = x.cbrt();
+    let y = y.cbrt();
+    let z = z.cbrt();
+
+    (
+        0.2104542553 * x + 0.7936177850 * y - 0.0040720468 * z,
+        1.9779984951 * x - 2.4285922050 * y + 0.4505937099 * z,
+        0.0259040371 * x + 0.7827717662 * y - 0.8086757660 * z,
+    )
+}
+
+/// linear rgb from oklab (0-1 ranges)
+pub fn rgb_from_lab((l, a, b): (f32, f32, f32)) -> [f32; 3] {
+    let x = l + 0.3963377774 * a + 0.2158037573 * b;
+    let y = l - 0.1055613458 * a - 0.0638541728 * b;
+    let z = l - 0.0894841775 * a - 1.2914855480 * b;
+
+    let x = x.powi(3);
+    let y = y.powi(3);
+    let z = z.powi(3);
+
+    [
+        4.0767245293 * x - 3.3072168827 * y + 0.2307590544 * z,
+        -1.2681437731 * x + 2.6093323231 * y - 0.3411344290 * z,
+        -0.0041119885 * x - 0.7034763098 * y + 1.7068625689 * z,
+    ]
+}
+
+/// 0-1 normalized lch from oklab.
+pub fn lch_from_lab((l, a, b): (f32, f32, f32)) -> (f32, f32, f32) {
+    use std::f32::consts::TAU;
+    let c = a.hypot(b);
+    let h = (b.atan2(a) + TAU) % TAU / TAU;
+    (l, c, h)
+}
+
+/// Oklab from 0-1 normalized lch.
+pub fn lab_from_lch((l, c, h): (f32, f32, f32)) -> (f32, f32, f32) {
+    use std::f32::consts::TAU;
+    let (sin_h, cos_h) = (h * TAU).sin_cos();
+    let a = c * cos_h;
+    let b = c * sin_h;
+    (l, a, b)
+}
+
+/// 0-1 normalized lch from linear rgb
+pub fn lch_from_rgb(rgb: [f32; 3]) -> (f32, f32, f32) {
+    lch_from_lab(lab_from_rgb(rgb))
+}
+
+/// linear rgb from 0-1 normalized lch
+pub fn rgb_from_lch(lch: (f32, f32, f32)) -> [f32; 3] {
+    rgb_from_lab(lab_from_lch(lch))
+}
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