Add ACEScg color space

AUTHORS

@@ -6,3 +6,4 @@
 # source control.
 Raph Levien
 Tom Churchman
+Jordan Johnson

color/.clippy.toml

@@ -1 +1 @@
-doc-valid-idents = ["ProPhoto", ".."]
+doc-valid-idents = ["ACEScg", "ACEScc", "ACEScct", "ProPhoto", ".."]

color/src/colorspace.rs

@@ -525,6 +525,60 @@ impl ColorSpace for Rec2020 {
     }
 }
 
+/// 🌌 The ACEScg color space.
+///
+/// This color space is defined by the Academy Color Encoding System [specification][acescg].
+///
+/// The ACEScg color space is a linear color space. The wide gamut makes this color space useful as
+/// a working space for computer graphics.
+///
+/// Other ACES color spaces include ACES2065-1, ACEScc, and ACEScct. This crate currently does not
+/// support these color spaces.
+///
+/// The ACEScg components are `[R, G, B]`. The components are bounded to `[-65504.0, 65504.0]`,
+/// though it is unusual to clip in this color space.
+///
+/// The conversion between D65 and the ACES whitepoint is done with the standard Bradford linear
+/// chromatic adaptation transform.
+///
+/// [acescg]: https://docs.acescentral.com/specifications/acescg/
+#[derive(Clone, Copy, Debug)]
+pub struct AcesCg;
+
+impl ColorSpace for AcesCg {
+    const IS_LINEAR: bool = true;
+
+    const TAG: Option<ColorSpaceTag> = Some(ColorSpaceTag::AcesCg);
+
+    fn to_linear_srgb(src: [f32; 3]) -> [f32; 3] {
+        // XYZ_to_lin_sRGB * ACESwp_to_D65 * ACEScg_to_XYZ
+        const ACESCG_TO_LINEAR_SRGB: [[f32; 3]; 3] = [
+            [1.705_051, -0.621_792_12, -0.083_258_87],
+            [-0.130_256_42, 1.140_804_8, -0.010_548_32],
+            [-0.024_003_36, -0.128_968_98, 1.152_972_3],
+        ];
+        matmul(&ACESCG_TO_LINEAR_SRGB, src)
+    }
+
+    fn from_linear_srgb(src: [f32; 3]) -> [f32; 3] {
+        // XYZ_to_ACEScg * D65_to_ACESwp * lin_sRGB_to_XYZ
+        const LINEAR_SRGB_TO_ACESCG: [[f32; 3]; 3] = [
+            [0.613_097_4, 0.339_523_15, 0.047379_45],
+            [0.070_193_72, 0.916_353_9, 0.013_452_4],
+            [0.020_615_59, 0.109_569_77, 0.869814_63],
+        ];
+        matmul(&LINEAR_SRGB_TO_ACESCG, src)
+    }
+
+    fn clip([r, g, b]: [f32; 3]) -> [f32; 3] {
+        [
+            r.clamp(-65504., 65504.),
+            g.clamp(-65504., 65504.),
+            b.clamp(-65504., 65504.),
+        ]
+    }
+}
+
 /// 🌌 The CIE XYZ color space with a 2° observer and a reference white of D50.
 ///
 /// Its components are `[X, Y, Z]`. The components are unbounded, but are usually positive.

color/src/lib.rs

@@ -102,8 +102,8 @@ mod floatfuncs;
 
 pub use color::{AlphaColor, HueDirection, OpaqueColor, PremulColor};
 pub use colorspace::{
-    A98Rgb, ColorSpace, ColorSpaceLayout, DisplayP3, Hsl, Hwb, Lab, Lch, LinearSrgb, Oklab, Oklch,
-    ProphotoRgb, Rec2020, Srgb, XyzD50, XyzD65,
+    A98Rgb, AcesCg, ColorSpace, ColorSpaceLayout, DisplayP3, Hsl, Hwb, Lab, Lch, LinearSrgb, Oklab,
+    Oklch, ProphotoRgb, Rec2020, Srgb, XyzD50, XyzD65,
 };
 pub use dynamic::{DynamicColor, Interpolator};
 pub use gradient::{gradient, GradientIter};

color/src/serialize.rs

@@ -86,6 +86,7 @@ impl core::fmt::Display for DynamicColor {
             ColorSpaceTag::A98Rgb => write_color_function(self, "a98-rgb", f),
             ColorSpaceTag::ProphotoRgb => write_color_function(self, "prophoto-rgb", f),
             ColorSpaceTag::Rec2020 => write_color_function(self, "rec2020", f),
+            ColorSpaceTag::AcesCg => write_color_function(self, "acescg", f),
             ColorSpaceTag::Hsl => write_legacy_function(self, "hsl", 1.0, f),
             ColorSpaceTag::Hwb => write_modern_function(self, "hwb", f),
             ColorSpaceTag::XyzD50 => write_color_function(self, "xyz-d50", f),

color/src/tag.rs

@@ -4,8 +4,8 @@
 //! The color space tag enum.
 
 use crate::{
-    A98Rgb, ColorSpace, ColorSpaceLayout, DisplayP3, Hsl, Hwb, Lab, Lch, LinearSrgb, Missing,
-    Oklab, Oklch, ProphotoRgb, Rec2020, Srgb, XyzD50, XyzD65,
+    A98Rgb, AcesCg, ColorSpace, ColorSpaceLayout, DisplayP3, Hsl, Hwb, Lab, Lch, LinearSrgb,
+    Missing, Oklab, Oklch, ProphotoRgb, Rec2020, Srgb, XyzD50, XyzD65,
 };
 
 /// The color space tag for dynamic colors.
@@ -44,6 +44,8 @@ pub enum ColorSpaceTag {
     ProphotoRgb,
     /// The [`Rec2020`] color space.
     Rec2020,
+    /// The [`AcesCg`] color space.
+    AcesCg,
     /// The [`XyzD50`] color space.
     XyzD50,
     /// The [`XyzD65`] color space.
@@ -67,8 +69,22 @@ impl ColorSpaceTag {
         matches!(
             (self, other),
             (
-                Srgb | LinearSrgb | DisplayP3 | A98Rgb | ProphotoRgb | Rec2020 | XyzD50 | XyzD65,
-                Srgb | LinearSrgb | DisplayP3 | A98Rgb | ProphotoRgb | Rec2020 | XyzD50 | XyzD65
+                Srgb | LinearSrgb
+                    | DisplayP3
+                    | A98Rgb
+                    | ProphotoRgb
+                    | Rec2020
+                    | AcesCg
+                    | XyzD50
+                    | XyzD65,
+                Srgb | LinearSrgb
+                    | DisplayP3
+                    | A98Rgb
+                    | ProphotoRgb
+                    | Rec2020
+                    | AcesCg
+                    | XyzD50
+                    | XyzD65
             ) | (Lab | Oklab, Lab | Oklab)
                 | (Lch | Oklch, Lch | Oklch)
         )
@@ -145,6 +161,7 @@ impl ColorSpaceTag {
             Self::A98Rgb => A98Rgb::from_linear_srgb(rgb),
             Self::ProphotoRgb => ProphotoRgb::from_linear_srgb(rgb),
             Self::Rec2020 => Rec2020::from_linear_srgb(rgb),
+            Self::AcesCg => AcesCg::from_linear_srgb(rgb),
             Self::XyzD50 => XyzD50::from_linear_srgb(rgb),
             Self::XyzD65 => XyzD65::from_linear_srgb(rgb),
             Self::Hsl => Hsl::from_linear_srgb(rgb),
@@ -167,6 +184,7 @@ impl ColorSpaceTag {
             Self::A98Rgb => A98Rgb::to_linear_srgb(src),
             Self::ProphotoRgb => ProphotoRgb::to_linear_srgb(src),
             Self::Rec2020 => Rec2020::to_linear_srgb(src),
+            Self::AcesCg => AcesCg::to_linear_srgb(src),
             Self::XyzD50 => XyzD50::to_linear_srgb(src),
             Self::XyzD65 => XyzD65::to_linear_srgb(src),
             Self::Hsl => Hsl::to_linear_srgb(src),
@@ -223,6 +241,7 @@ impl ColorSpaceTag {
             Self::A98Rgb => A98Rgb::clip(src),
             Self::ProphotoRgb => ProphotoRgb::clip(src),
             Self::Rec2020 => Rec2020::clip(src),
+            Self::AcesCg => AcesCg::clip(src),
             Self::XyzD50 => XyzD50::clip(src),
             Self::XyzD65 => XyzD65::clip(src),
             Self::Hsl => Hsl::clip(src),