[css-color-4] update inline transfer functions for extended

Author: svgeesus

css-color-4/Overview.bs

@@ -3313,14 +3313,18 @@ and ''xyz''.</h3>
 			</table>
 
 			<pre class="lang-javascript">
-			var Cl;
-			if (C <= 0.04045)
-				Cl = C / 12.92;
-			else
-				Cl = Math.pow((C + 0.055) / 1.055, 2.4);
+			let sign = c < 0? -1 : 1;
+			let abs = Math.abs(c);
+
+			if (abs < 0.04045) {
+				cl = c / 12.92;
+			}
+			else {
+				cl = sign * (Math.pow((abs + 0.055) / 1.055, 2.4));
+			}
 			</pre>
-			C is the gamma-encoded red, green or blue component.
-			Cl is the corresponding linear-light component.
+			c is the gamma-encoded red, green or blue component.
+			cl is the corresponding linear-light component.
 
 			<figure>
 				<img src="images/sRGB-prim-sec.svg" width=540 height=520
@@ -3472,13 +3476,19 @@ and ''xyz''.</h3>
 				</table>
 
 				<pre class="lang-javascript">
-					var Cl;
-					if (C <= (16/512))
-						Cl = C / 16;
-					else
-						Cl = Math.pow(C, 1.8);
-					</pre>
-					C is the red, green or blue component.
+					const E = 16/512;
+					let sign = c < 0? -1 : 1;
+					let abs = Math.abs(c);
+
+					if (abs <= E) {
+						cl =  c / 16;
+					}
+					else {
+						cl = sign * Math.pow(c, 1.8);
+					}
+				</pre>
+				c is the gamma-encoded red, green or blue component.
+				cl is the corresponding linear-light component.
 
 				<figure>
 					<img src="images/prophoto-prim-sec.svg" width=780 height=760
@@ -3523,7 +3533,7 @@ and ''xyz''.</h3>
 				<tr><th>Green chromaticity</th><td>0.170</td><td>0.797</td></tr>
 				<tr><th>Blue chromaticity</th><td>0.131</td><td>0.046</td></tr>
 				<tr><th>White chromaticity</th><td>0.31272</td><td>0.32903</td><td>(D65)</td></tr>
-				<tr><th>Transfer function</th><td colspan="2">1/2.4 (see note)</td></tr>
+				<tr><th>Transfer function</th><td colspan="2">see below</td></tr>
 				<tr><th>Image state</th><td colspan="2">display-referred</td></tr>
 				<tr>
 					<th>Percentages</th>
@@ -3532,16 +3542,21 @@ and ''xyz''.</h3>
 			</table>
 
 			<pre class="lang-javascript">
-				const α = 1.09929682680944;
-				const β = 0.018053968510807,
-				var Cl;
-				if (C < β * 4.5)
-					Cl = C / 4.5;
-				else
-					Cl = Math.pow((val + α -1 ) / α, 1/4.5);
-				</pre>
-				C is the gamma-encoded red, green or blue component.
-				Cl is the corresponding linear-light component.
+				const α = 1.09929682680944 ;
+				const β = 0.018053968510807;
+
+				let sign = c < 0? -1 : 1;
+				let abs = Math.abs(c);
+
+				if (abs < β * 4.5 ) {
+					cl = c / 4.5;
+				}
+				else {
+					cl = sign * (Math.pow((abs + α -1 ) / α, 1/0.45));
+				}
+			</pre>
+			c is the gamma-encoded red, green or blue component.
+			cl is the corresponding linear-light component.
 
 			<figure>
 				<img src="images/2020-prim-sec.svg" width=670 height=580