From 6e3d68d3af68296a9ded7d2ea9a21c663a1d2b02 Mon Sep 17 00:00:00 2001
From: Thomas Churchman <thomas@churchman.nl>
Date: Thu, 24 Apr 2025 16:47:07 +0200
Subject: [PATCH] Add absolute conversion matrices for ACES2065-1

Continuing the addition of absolute color conversion matrices. See also
https://github.com/linebender/color/pull/156.
---
 color/src/colorspace.rs | 44 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/color/src/colorspace.rs b/color/src/colorspace.rs
index d2dd249..916c1bd 100644
--- a/color/src/colorspace.rs
+++ b/color/src/colorspace.rs
@@ -848,6 +848,50 @@ impl ColorSpace for Aces2065_1 {
         matvecmul(&LINEAR_SRGB_TO_ACES2065_1, src)
     }
 
+    fn to_linear_srgb_absolute(src: [f32; 3]) -> [f32; 3] {
+        // XYZ_to_lin_sRGB * ACES2065_1_to_XYZ
+        const ACES2065_1_TO_LINEAR_SRGB: [[f32; 3]; 3] = [
+            [
+                54_120_196_967_290_615. / 21_154_043_450_084_358.,
+                -320_017_885_460_000. / 285_865_452_028_167.,
+                -564_067_687_050. / 1_439_638_182_257.,
+            ],
+            [
+                -65_267_199_138_999_760. / 234_786_371_866_236_861.,
+                320_721_924_808_012_000. / 234_786_371_866_236_861.,
+                -2_987_552_619_450. / 31_956_767_642_063.,
+            ],
+            [
+                -581_359_048_862_990. / 33_857_690_407_037_013.,
+                -457_168_407_800_000. / 3_077_971_855_185_183.,
+                4_981_730_664_150. / 4_608_369_457_879.,
+            ],
+        ];
+        matvecmul(&ACES2065_1_TO_LINEAR_SRGB, src)
+    }
+
+    fn from_linear_srgb_absolute(src: [f32; 3]) -> [f32; 3] {
+        // XYZ_to_ACES2065_1 * lin_sRGB_to_XYZ
+        const LINEAR_SRGB_TO_ACES2065_1: [[f32; 3]; 3] = [
+            [
+                26_324_697_889_654. / 60_805_826_029_215.,
+                95_867_335_448_462. / 255_384_469_322_703.,
+                34_545_867_731_048. / 182_417_478_087_645.,
+            ],
+            [
+                1_068_725_544_495_979. / 11_952_668_021_931_000.,
+                9_008_998_273_654_297. / 11_033_232_020_244_000.,
+                2_110_950_307_239_113. / 20_490_288_037_596_000.,
+            ],
+            [
+                267_367_106. / 13_953_194_325.,
+                2_967_477_727. / 25_115_749_785.,
+                33_806_406_089. / 35_879_642_550.,
+            ],
+        ];
+        matvecmul(&LINEAR_SRGB_TO_ACES2065_1, src)
+    }
+
     fn clip([r, g, b]: [f32; 3]) -> [f32; 3] {
         [
             r.clamp(-65504., 65504.),