From ea4f7c6b150079c697cab76d1a95c6f6e04ca5c8 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Thu, 19 Oct 2023 21:42:23 -0400
Subject: Implement the Oklab color space

---
 src/color.rs | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/main.rs  |  8 +++++--
 2 files changed, 81 insertions(+), 2 deletions(-)

diff --git a/src/color.rs b/src/color.rs
index 81d9689..90e68ce 100644
--- a/src/color.rs
+++ b/src/color.rs
@@ -275,3 +275,78 @@ impl ColorSpace for LuvSpace {
         Self(sum)
     }
 }
+
+/// [Oklab](https://bottosson.github.io/posts/oklab/) space.
+#[derive(Clone, Copy, Debug)]
+pub struct OklabSpace([f64; 3]);
+
+impl Index<usize> for OklabSpace {
+    type Output = f64;
+
+    fn index(&self, i: usize) -> &f64 {
+        &self.0[i]
+    }
+}
+
+impl From<Rgb8> for OklabSpace {
+    fn from(rgb8: Rgb8) -> Self {
+        let rgb = RgbSpace::from(rgb8);
+
+        let r = srgb_inv_gamma(rgb[0]);
+        let g = srgb_inv_gamma(rgb[1]);
+        let b = srgb_inv_gamma(rgb[2]);
+
+        let l = 0.4122214708 * r + 0.5363325363 * g + 0.0514459929 * b;
+        let m = 0.2119034982 * r + 0.6806995451 * g + 0.1073969566 * b;
+        let s = 0.0883024619 * r + 0.2817188376 * g + 0.6299787005 * b;
+
+        let l = l.cbrt();
+        let m = m.cbrt();
+        let s = s.cbrt();
+
+        Self([
+            0.2104542553 * l + 0.7936177850 * m - 0.0040720468 * s,
+            1.9779984951 * l - 2.4285922050 * m + 0.4505937099 * s,
+            0.0259040371 * l + 0.7827717662 * m - 0.8086757660 * s,
+        ])
+    }
+}
+
+impl Coordinates for OklabSpace {
+    type Value = f64;
+
+    fn dims(&self) -> usize {
+        self.0.dims()
+    }
+
+    fn coord(&self, i: usize) -> f64 {
+        self.0.coord(i)
+    }
+}
+
+impl Proximity for OklabSpace {
+    type Distance = EuclideanDistance<f64>;
+
+    fn distance(&self, other: &Self) -> Self::Distance {
+        euclidean_distance(&self.0, &other.0)
+    }
+}
+
+impl Metric for OklabSpace {}
+
+impl ColorSpace for OklabSpace {
+    fn average<I: IntoIterator<Item = Self>>(colors: I) -> Self {
+        let mut sum = [0.0, 0.0, 0.0];
+        let mut len: usize = 0;
+        for color in colors.into_iter() {
+            for i in 0..3 {
+                sum[i] += color[i];
+            }
+            len += 1;
+        }
+        for s in &mut sum {
+            *s /= len as f64;
+        }
+        Self(sum)
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index c651b23..09e335a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,7 +5,7 @@ pub mod hilbert;
 pub mod soft;
 
 use crate::color::source::{AllColors, ColorSource, ImageColors};
-use crate::color::{order, ColorSpace, LabSpace, LuvSpace, Rgb8, RgbSpace};
+use crate::color::{order, ColorSpace, LabSpace, LuvSpace, OklabSpace, Rgb8, RgbSpace};
 use crate::frontier::image::ImageFrontier;
 use crate::frontier::mean::MeanFrontier;
 use crate::frontier::min::MinFrontier;
@@ -69,6 +69,8 @@ enum ColorSpaceArg {
     Lab,
     /// CIE L*u*v* space.
     Luv,
+    /// Oklab space.
+    Oklab,
 }
 
 /// Error type for this app.
@@ -182,7 +184,7 @@ impl Args {
                 (@arg MODE: -l --selection +takes_value possible_value[min mean] "Specify the selection mode")
                 (@arg TARGET: -g --target +takes_value "Place colors on the closest pixels of the TARGET image")
             )
-            (@arg SPACE: -c --("color-space") default_value("Lab") possible_value[RGB Lab Luv] "Use the given color space")
+            (@arg SPACE: -c --("color-space") default_value("Lab") possible_value[RGB Lab Luv Oklab] "Use the given color space")
             (@arg WIDTH: -w --width +takes_value "The width of the generated image")
             (@arg HEIGHT: -h --height +takes_value "The height of the generated image")
             (@arg X: -x +takes_value "The x coordinate of the first pixel")
@@ -254,6 +256,7 @@ impl Args {
             "RGB" => ColorSpaceArg::Rgb,
             "Lab" => ColorSpaceArg::Lab,
             "Luv" => ColorSpaceArg::Luv,
+            "Oklab" => ColorSpaceArg::Oklab,
             _ => unreachable!(),
         };
 
@@ -334,6 +337,7 @@ impl App {
             ColorSpaceArg::Rgb => self.paint::<RgbSpace>(colors),
             ColorSpaceArg::Lab => self.paint::<LabSpace>(colors),
             ColorSpaceArg::Luv => self.paint::<LuvSpace>(colors),
+            ColorSpaceArg::Oklab => self.paint::<OklabSpace>(colors),
         }
     }
 
-- 
cgit v1.2.3