[css-color-4] update inlined copy of sample code

Author: svgeesus

css-color-4/Overview.bs

@@ -2534,7 +2534,11 @@ Default Style Rules</h2>
 <em>This section is not normative.</em>
 
 <pre class="lang-javascript">
-	<!-- imported 4 Mar  2019-->
+	<!-- imported 30 Oct  2019-->
+	// Sample code for color conversions
+	// Conversion can also be done using ICC profiles and a Color Management System
+	// For clarity, a library is used for matrix manipulations
+
 	// sRGB-related functions
 
 	function lin_sRGB(RGB) {
@@ -2591,21 +2595,21 @@ Default Style Rules</h2>
 
 
 	function lin_P3(RGB) {
-		// convert an array of display-p3 RGB values in the range 0.0 - 1.0
+		// convert an array of image-p3 RGB values in the range 0.0 - 1.0
 		// to linear light (un-companded) form.
 
 		return lin_sRGB(RGB);	// same as sRGB
 	}
 
 	function gam_P3(RGB) {
-		// convert an array of linear-light display-p3 RGB  in the range 0.0-1.0
+		// convert an array of linear-light image-p3 RGB  in the range 0.0-1.0
 		// to gamma corrected form
 
 		return gam_sRGB(RGB);	// same as sRGB
 	}
 
 	function lin_P3_to_XYZ(rgb) {
-		// convert an array of linear-light display-p3 values to CIE XYZ
+		// convert an array of linear-light image-p3 values to CIE XYZ
 		// using  D65 (no chromatic adaptation)
 		// http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html
 		var M = math.matrix([
@@ -2634,7 +2638,7 @@ Default Style Rules</h2>
 	function lin_ProPhoto(RGB) {
 		// convert an array of prophoto-rgb values in the range 0.0 - 1.0
 		// to linear light (un-companded) form.
-		// Transfer curve is gamma 1.0 with a small linear portion
+		// Transfer curve is gamma 1.8 with a small linear portion
 		return RGB.map(function (val) {
 			if (val < 0.031248) {
 				return val / 16;
@@ -2647,7 +2651,7 @@ Default Style Rules</h2>
 	function gam_ProPhoto(RGB) {
 		// convert an array of linear-light prophoto-rgb  in the range 0.0-1.0
 		// to gamma corrected form
-		// Transfer curve is gamma 1.0 with a small linear portion
+		// Transfer curve is gamma 1.8 with a small linear portion
 		return RGB.map(function (val) {
 			if (val > 0.001953) {
 				return Math.pow(val, 1/1.8);
@@ -2673,36 +2677,38 @@ Default Style Rules</h2>
 	function XYZ_to_lin_ProPhoto(XYZ) {
 		// convert XYZ to linear-light prophoto-rgb
 		var M = Math.matrix([
-			[  1.3457989731028281,  -0.25558010007997534,  -0.05110628506753401 ],
-			[ -0.5446224939028347,   1.5082327413132781,    0.02053603239147973 ],
-			[  0.0,                  0.0,                   1.2119675456389454  ]
+		  [  1.3457989731028281,  -0.25558010007997534,  -0.05110628506753401 ],
+		  [ -0.5446224939028347,   1.5082327413132781,    0.02053603239147973 ],
+		  [  0.0,                  0.0,                   1.2119675456389454  ]
 		]);
 
 		return Math.multiply(M, XYZ).valueOf();
 	}
 
 	// a98-rgb functions
 
-	function lin_a98-rgb(RGB) {
+	function lin_a98rgb(RGB) {
 		// convert an array of a98-rgb values in the range 0.0 - 1.0
 		// to linear light (un-companded) form.
 		return RGB.map(function (val) {
-			return Math.pow(val, 563/256);
+		  return Math.pow(val, 563/256);
 		});
 	}
 
-	function gam_a98-rgb(RGB) {
+	function gam_a98rgb(RGB) {
 		// convert an array of linear-light a98-rgb  in the range 0.0-1.0
 		// to gamma corrected form
 		return RGB.map(function (val) {
 			return Math.pow(val, 256/563);
 		});
 	}
 
-	function lin_a98-rgb_to_XYZ(rgb) {
-		// convert an array of linear-light prophoto-rgb values to CIE XYZ
+	function lin_a98rgb_to_XYZ(rgb) {
+		// convert an array of linear-light a98-rgb values to CIE XYZ
 		// using  D50 (so no chromatic adaptation needed afterwards)
 		// http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html
+		// which has greater numerical precsion than section 4.3.5.3 of
+		// https://www.adobe.com/digitalimag/pdfs/AdobeRGB1998.pdf
 		var M = Math.matrix([
 		[ 0.5766690429101305,   0.1855582379065463,   0.1882286462349947  ],
 		[ 0.29734497525053605,  0.6273635662554661,   0.07529145849399788 ],
@@ -2712,8 +2718,8 @@ Default Style Rules</h2>
 		return Math.multiply(M, rgb).valueOf();
 	}
 
-	function XYZ_to_lin_a98-rgb(XYZ) {
-		// convert XYZ to linear-light prophoto-rgb
+	function XYZ_to_lin_a98rgb(XYZ) {
+		// convert XYZ to linear-light a98-rgb
 		var M = Math.matrix([
 		[  2.0415879038107465,    -0.5650069742788596,   -0.34473135077832956 ],
 		[ -0.9692436362808795,     1.8759675015077202,    0.04155505740717557 ],
@@ -2726,7 +2732,7 @@ Default Style Rules</h2>
 	//Rec. 2020-related functions
 
 	function lin_2020(RGB) {
-		// convert an array of Rec. 2020 RGB values in the range 0.0 - 1.0
+		// convert an array of rec-2020 RGB values in the range 0.0 - 1.0
 		// to linear light (un-companded) form.
 		const α = 1.09929682680944 ;
 		const β = 0.018053968510807;
@@ -2742,7 +2748,7 @@ Default Style Rules</h2>
 	//check with standard this really is 2.4 and 1/2.4, not 0.45 was wikipedia claims
 
 	function gam_2020(RGB) {
-		// convert an array of linear-light Rec. 2020 RGB  in the range 0.0-1.0
+		// convert an array of linear-light rec-2020 RGB  in the range 0.0-1.0
 		// to gamma corrected form
 		const α = 1.09929682680944 ;
 		const β = 0.018053968510807;
@@ -2757,7 +2763,7 @@ Default Style Rules</h2>
 	}
 
 	function lin_2020_to_XYZ(rgb) {
-		// convert an array of linear-light Rec. 2020 values to CIE XYZ
+		// convert an array of linear-light rec-2020 values to CIE XYZ
 		// using  D65 (no chromatic adaptation)
 		// http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html
 		var M = math.matrix([
@@ -2771,7 +2777,7 @@ Default Style Rules</h2>
 	}
 
 	function XYZ_to_lin_2020(XYZ) {
-		// convert XYZ to linear-light Rec. 2020
+		// convert XYZ to linear-light rec-2020
 		var M = math.matrix([
 			[1.7166511879712674,   -0.35567078377639233, -0.25336628137365974],
 			[-0.6666843518324892,   1.6164812366349395,   0.01576854581391113],