Added l-alpha-beta

src/app/src/main.rs

@@ -25,10 +25,10 @@ fn main() {
     let g = 127;
     let b = 255;
     let rgb = Rgb::<u8>::new(r, g, b);
-    let jzazbz = Jzazbz::from_rgb(rgb, TransferFunction::Srgb);
-    println!("Jzczhz {:?}", jzazbz);
+    let lalphabeta = LAlphaBeta::from_rgb(rgb, TransferFunction::Srgb);
+    println!("LAlphaBeta {:?}", lalphabeta);
     println!("Rgb {:?}", rgb);
-    let restored = jzazbz.to_rgb(TransferFunction::Srgb);
+    let restored = lalphabeta.to_rgb(TransferFunction::Srgb);
     println!("Restored RGB {:?}", restored);
 
     let img = ImageReader::open("./assets/beach_horizon.jpg")

src/lalphabeta.rs

@@ -0,0 +1,71 @@
+/*
+ * // Copyright 2024 (c) the Radzivon Bartoshyk. All rights reserved.
+ * //
+ * // Use of this source code is governed by a BSD-style
+ * // license that can be found in the LICENSE file.
+ */
+use crate::{Rgb, TransferFunction, Xyz, SRGB_TO_XYZ_D65, XYZ_TO_SRGB_D65};
+use erydanos::{Exponential, Logarithmic};
+
+/// Represents l-alpha-beta colorspace
+#[derive(Debug, Copy, Clone, PartialOrd, PartialEq)]
+pub struct LAlphaBeta {
+    pub l: f32,
+    pub alpha: f32,
+    pub beta: f32,
+}
+
+impl LAlphaBeta {
+    #[inline]
+    /// Creates new instance
+    pub fn new(l: f32, alpha: f32, beta: f32) -> LAlphaBeta {
+        LAlphaBeta { l, alpha, beta }
+    }
+
+    /// Converts RGB to l-alpha-beta
+    #[inline]
+    pub fn from_rgb(rgb: Rgb<u8>, transfer_function: TransferFunction) -> LAlphaBeta {
+        let xyz = rgb.to_xyz(&SRGB_TO_XYZ_D65, transfer_function);
+        LAlphaBeta::from_xyz(xyz)
+    }
+
+    /// Converts XYZ to l-alpha-beta
+    #[inline]
+    pub fn from_xyz(xyz: Xyz) -> LAlphaBeta {
+        let l_lms = 0.3897 * xyz.x + 0.6890 * xyz.y - 0.0787 * xyz.z;
+        let m = -0.2298 * xyz.x + 1.1834 * xyz.y + 0.0464 * xyz.z;
+        let s = xyz.z;
+        let lp = if l_lms > 0. { l_lms.eln() } else { 0. };
+        let mp = if m > 0. { m.eln() } else { 0. };
+        let sp = if s > 0. { s.eln() } else { 0. };
+        let l = 0.5774 * lp + 0.5774 * mp + 0.5774 * sp;
+        let alpha = 0.4082 * lp + 0.4082 * mp - 0.8165 * sp;
+        let beta = 1.4142 * lp - 1.4142 * mp;
+        LAlphaBeta::new(l, alpha, beta)
+    }
+
+    /// Converts l-alpha-beta to XYZ
+    #[inline]
+    pub fn to_xyz(&self) -> Xyz {
+        let l_a = self.l * 0.577324;
+        let s_a = 0.408263 * self.alpha;
+        let p_b = 0.353557 * self.beta;
+        let lp = l_a + s_a + p_b;
+        let mp = l_a + s_a - p_b;
+        let sp = self.l * 0.577253 - 0.816526 * self.alpha;
+        let l = lp.eexp();
+        let m = mp.eexp();
+        let s = sp.eexp();
+        let x = 1.91024 * l - 1.11218 * m + 0.201941 * s;
+        let y = 0.370942 * l + 0.62905 * m + 5.13315e-6 * s;
+        let z = s;
+        Xyz::new(x, y, z)
+    }
+
+    /// Converts l-alpha-beta to RGB
+    #[inline]
+    pub fn to_rgb(&self, transfer_function: TransferFunction) -> Rgb<u8> {
+        let xyz = self.to_xyz();
+        xyz.to_rgb(&XYZ_TO_SRGB_D65, transfer_function)
+    }
+}

src/lib.rs

@@ -60,6 +60,7 @@ mod xyz_lab_to_image;
 mod xyz_target;
 mod xyz_transform;
 mod xyza_laba_to_image;
+mod lalphabeta;
 
 pub use concat_alpha::append_alpha;
 pub use gamma_curves::*;
@@ -172,3 +173,4 @@ pub use sigmoidal_to_image::sigmoidal_to_bgra;
 pub use sigmoidal_to_image::sigmoidal_to_rgb;
 pub use sigmoidal_to_image::sigmoidal_to_rgba;
 pub use taxicab::TaxicabDistance;
+pub use lalphabeta::LAlphaBeta;