make lab_to_xyz f32 friendly to match the spec

packages/color-helpers/dist/index.mjs

@@ -44,7 +44,7 @@ function multiplyMatrices(_,t){return[_[0]*t[0]+_[1]*t[1]+_[2]*t[2],_[3]*t[0]+_[
  * @license W3C https://www.w3.org/Consortium/Legal/2015/copyright-software-and-document
  * @copyright This software or document includes material copied from or derived from https://github.com/w3c/csswg-drafts/blob/main/css-color-4/conversions.js. Copyright © 2022 W3C® (MIT, ERCIM, Keio, Beihang).
  * @see http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html
- */function Lab_to_XYZ(_){const t=24389/27,o=216/24389,e=(_[0]+16)/116,r=_[1]/500+e,a=e-_[2]/200;return[(Math.pow(r,3)>o?Math.pow(r,3):(116*r-16)/t)*n[0],(_[0]>8?Math.pow((_[0]+16)/116,3):_[0]/t)*n[1],(Math.pow(a,3)>o?Math.pow(a,3):(116*a-16)/t)*n[2]]}
+ */function Lab_to_XYZ(_){const t=24389/27,o=216/24389,e=_[0]/116,r=_[1]/500,a=_[2]/200,i=e+16/116,l=i+r,u=i-a;return[(Math.pow(l,3)>o?Math.pow(l,3):(e+r)*(116/t))*n[0],(_[0]>8?Math.pow((_[0]+16)/116,3):_[0]/t)*n[1],(Math.pow(u,3)>o?Math.pow(u,3):116/t*(e-a))*n[2]]}
 /**
  * @license W3C https://www.w3.org/Consortium/Legal/2015/copyright-software-and-document
  * @copyright This software or document includes material copied from or derived from https://github.com/w3c/csswg-drafts/blob/main/css-color-4/conversions.js. Copyright © 2022 W3C® (MIT, ERCIM, Keio, Beihang).
@@ -108,8 +108,11 @@ function XYZ_to_OKLab(_){const t=multiplyMatrices(i,_);return multiplyMatrices(l
  * @copyright This software or document includes material copied from or derived from https://github.com/w3c/csswg-drafts/blob/main/css-color-4/conversions.js. Copyright © 2022 W3C® (MIT, ERCIM, Keio, Beihang).
  */function XYZ_to_lin_sRGB(_){return multiplyMatrices(Y,_)}
 /**
- * Convert an array of linear-light rec2020 RGB  in the range 0.0-1.0
- * to gamma corrected form ITU-R BT.2020-2 p.4
+ * Convert an array of linear-light rec2020 RGB in the range 0.0-1.0
+ * to gamma corrected form.
+ * Reference electro-optical transfer function from Rec. ITU-R BT.1886 Annex 1
+ * with b (black lift) = 0 and a (user gain) = 1
+ * defined over the extended range, not clamped
  *
  * @license W3C https://www.w3.org/Consortium/Legal/2015/copyright-software-and-document
  * @copyright This software or document includes material copied from or derived from https://github.com/w3c/csswg-drafts/blob/main/css-color-4/conversions.js. Copyright © 2022 W3C® (MIT, ERCIM, Keio, Beihang).
@@ -149,7 +152,9 @@ function XYZ_to_OKLab(_){const t=multiplyMatrices(i,_);return multiplyMatrices(l
 /**
  * Convert an array of rec2020 RGB values in the range 0.0 - 1.0
  * to linear light (un-companded) form.
- * ITU-R BT.2020-2 p.4
+ * Reference electro-optical transfer function from Rec. ITU-R BT.1886 Annex 1
+ * with b (black lift) = 0 and a (user gain) = 1
+ * defined over the extended range, not clamped
  *
  * @license W3C https://www.w3.org/Consortium/Legal/2015/copyright-software-and-document
  * @copyright This software or document includes material copied from or derived from https://github.com/w3c/csswg-drafts/blob/main/css-color-4/conversions.js. Copyright © 2022 W3C® (MIT, ERCIM, Keio, Beihang).

packages/color-helpers/scripts/hashes.json

@@ -1,6 +1,6 @@
 [
 	"384d52db3fcd98381e18743e1eba590a",
-	"a69bf3dc21cfcc876c80ee311ca85f90",
+	"00493f00572bf1f5c2303f948422c1c7",
 	"094c9859b0960c4e394947cc4832b54f",
 	"c9e2f2a3b2cba543a01cb8aa5d77c04a",
 	"7aba804ac76ce5d733956b4251194344",

packages/color-helpers/src/conversions/gam-2020.ts

@@ -1,8 +1,11 @@
 import type { Color } from '../types/color';
 
 /**
- * Convert an array of linear-light rec2020 RGB  in the range 0.0-1.0
- * to gamma corrected form ITU-R BT.2020-2 p.4
+ * Convert an array of linear-light rec2020 RGB in the range 0.0-1.0
+ * to gamma corrected form.
+ * Reference electro-optical transfer function from Rec. ITU-R BT.1886 Annex 1
+ * with b (black lift) = 0 and a (user gain) = 1
+ * defined over the extended range, not clamped
  *
  * @license W3C https://www.w3.org/Consortium/Legal/2015/copyright-software-and-document
  * @copyright This software or document includes material copied from or derived from https://github.com/w3c/csswg-drafts/blob/main/css-color-4/conversions.js. Copyright © 2022 W3C® (MIT, ERCIM, Keio, Beihang).

packages/color-helpers/src/conversions/lab-to-xyz.ts

@@ -11,15 +11,20 @@ export function Lab_to_XYZ(Lab: Color): Color {
 	const κ = 24389 / 27;   // 29^3/3^3
 	const ε = 216 / 24389;  // 6^3/29^3
 
+	// Keep L out of L+16 for near-black precision
+	const lightness116 = Lab[0] / 116;
+	const a500 = Lab[1] / 500;
+	const b200 = Lab[2] / 200;
+
 	// compute f, starting with the luminance-related term
-	const f1 = (Lab[0] + 16) / 116;
-	const f0 = Lab[1] / 500 + f1;
-	const f2 = f1 - Lab[2] / 200;
+	const f1 = lightness116 + (16 / 116);
+	const f0 = f1 + a500;
+	const f2 = f1 - b200;
 
 	// compute xyz
 	return [
-		(Math.pow(f0, 3) > ε ? Math.pow(f0, 3) : (116 * f0 - 16) / κ) * D50[0],
+		(Math.pow(f0, 3) > ε ? Math.pow(f0, 3) : (lightness116 + a500) * (116 / κ)) * D50[0],
 		(Lab[0] > κ * ε ? Math.pow((Lab[0] + 16) / 116, 3) : Lab[0] / κ) * D50[1],
-		(Math.pow(f2, 3) > ε ? Math.pow(f2, 3) : (116 * f2 - 16) / κ) * D50[2],
+		(Math.pow(f2, 3) > ε ? Math.pow(f2, 3) : (lightness116 - b200) * (116 / κ)) * D50[2],
 	];
 }

packages/color-helpers/src/conversions/lin-2020.ts

@@ -3,7 +3,9 @@ import type { Color } from '../types/color';
 /**
  * Convert an array of rec2020 RGB values in the range 0.0 - 1.0
  * to linear light (un-companded) form.
- * ITU-R BT.2020-2 p.4
+ * Reference electro-optical transfer function from Rec. ITU-R BT.1886 Annex 1
+ * with b (black lift) = 0 and a (user gain) = 1
+ * defined over the extended range, not clamped
  *
  * @license W3C https://www.w3.org/Consortium/Legal/2015/copyright-software-and-document
  * @copyright This software or document includes material copied from or derived from https://github.com/w3c/csswg-drafts/blob/main/css-color-4/conversions.js. Copyright © 2022 W3C® (MIT, ERCIM, Keio, Beihang).

packages/css-color-parser/test/basic/powerless-exhaustive-double.mjs

@@ -0,0 +1,23 @@
+import assert from 'node:assert';
+import { reducePrecisionWholeValue } from '../util/serialize.mjs';
+import { color, computedValue } from '@csstools/css-color-parser';
+import { parse } from '../util/parse.mjs';
+
+{
+	const tests = [
+		['lch(from color(display-p3 0.1893689 0.18937814 0.18937561) l c h)', 'lch(19.99999973 0 none)'],
+		['color-mix(in lch, color(display-p3 0.1893689 0.18937814 0.18937561), lch(11 33 44))', 'lch(15.49999987 16.5 44)'],
+		['color-mix(in lch, color(display-p3 0.1893689 0.18937814 0.18937561))', 'lch(19.99999973 0 none)'],
+		['oklch(from color(display-p3 0.08610937692934956 0.08610188202042188 0.08610387292083356) l c h)', 'oklch(0.2 0.000004 359.99999992)'],
+		['color-mix(in oklch, color(display-p3 0.08610937692934956 0.08610188202042188 0.08610387292083356), oklch(0.11 0.33 0.44))', 'oklch(0.155 0.165002 0.21999996)'],
+		['color-mix(in oklch, color(display-p3 0.08610937692934956 0.08610188202042188 0.08610387292083356))', 'oklch(0.2 0.000004 359.99999992)'],
+	];
+
+	for (const test of tests) {
+		assert.deepStrictEqual(
+			reducePrecisionWholeValue(computedValue(color(parse(test[0])))),
+			test[1],
+			`"${test[0]}" : ${test[1]}`,
+		);
+	}
+}