From 3f22d5683a03f0bc7006744b04a50b4bc38f2918 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?H=C3=A9ctor=20Ram=C3=B3n=20Jim=C3=A9nez?= <hector@hecrj.dev>
Date: Wed, 6 Aug 2025 05:55:33 +0200
Subject: [PATCH] Expose `relative_luminance` as part of `Color`

---
 core/src/color.rs         |  7 +++++++
 core/src/theme/palette.rs | 10 ++--------
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/core/src/color.rs b/core/src/color.rs
index 65a47781..ad60592a 100644
--- a/core/src/color.rs
+++ b/core/src/color.rs
@@ -195,6 +195,13 @@ impl Color {
             ..self
         }
     }
+
+    /// Returns the relative luminance of the [`Color`].
+    /// https://www.w3.org/TR/WCAG21/#dfn-relative-luminance
+    pub fn relative_luminance(self) -> f32 {
+        let linear = self.into_linear();
+        0.2126 * linear[0] + 0.7152 * linear[1] + 0.0722 * linear[2]
+    }
 }
 
 impl From<[f32; 3]> for Color {
diff --git a/core/src/theme/palette.rs b/core/src/theme/palette.rs
index 08a80a26..77189730 100644
--- a/core/src/theme/palette.rs
+++ b/core/src/theme/palette.rs
@@ -716,17 +716,11 @@ fn is_readable(a: Color, b: Color) -> bool {
 
 // https://www.w3.org/TR/WCAG21/#dfn-contrast-ratio
 fn relative_contrast(a: Color, b: Color) -> f32 {
-    let lum_a = relative_luminance(a);
-    let lum_b = relative_luminance(b);
+    let lum_a = a.relative_luminance();
+    let lum_b = b.relative_luminance();
     (lum_a.max(lum_b) + 0.05) / (lum_a.min(lum_b) + 0.05)
 }
 
-// https://www.w3.org/TR/WCAG21/#dfn-relative-luminance
-fn relative_luminance(color: Color) -> f32 {
-    let linear = color.into_linear();
-    0.2126 * linear[0] + 0.7152 * linear[1] + 0.0722 * linear[2]
-}
-
 // https://en.wikipedia.org/wiki/Oklab_color_space#Conversions_between_color_spaces
 fn to_oklch(color: Color) -> Oklch {
     let [r, g, b, alpha] = color.into_linear();