[css-color-hdr] Add rec2100-linear, w3c#553

Author: svgeesus

css-color-hdr/Overview.bs

@@ -327,6 +327,56 @@ Predefined color spaces for HDR: {#predefined-HDR}
 
 	Issue: add black level lift Β as defined on same page?
 
+<dfn export>rec2100-linear</dfn> {#valdef-color-rec2100-linear}
+---------------------------
+
+	The ''rec2100-linear'' [[!Rec_BT.2100]] color space accepts three numeric parameters,
+	representing the red, green, and blue channels of the color,
+	with each having a nominal range of [0, 1]
+	regardless of the actual bit depth (10 or 12 bits per component).
+
+	The color with red, green and blue all at 1.0 
+	represents HDR Reference White with an absolute luminance of 
+	203 cd/m².
+
+	<pre class="lang-css">color(rec2100-linear 1 1 1)</pre>
+
+	<div class="example">
+		For example, the following color
+
+		<pre class="lang-css">color(rec2100-linear 9.852 9.852 9.852)</pre>
+
+		represents a white highlight 
+		with an absolute luminance
+		of 9.852 × 203 = 1,999 cd/m².
+	</div>
+
+	A linear-light electro-optical transfer function is used.
+
+	It has the following characteristics:
+	(The display primaries are the same as [[!Rec.2020]]):
+
+	<table>
+		<thead><td></td><td>x</td><td>y</td></thead>
+		<tr><th>Red chromaticity</th><td>0.708</td><td>0.292</td></tr>
+		<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 colspan="2">[=D65 whitepoint|D65=]</td></tr>
+		<tr><th>Transfer function</th><td colspan="2">Linear</td></tr>
+		<tr><th>White luminance</th><td colspan="2">203 cd/m²</td></tr>
+		<tr><th>Peak white luminance</th><td colspan="2">10,000 cd/m²</td></tr>
+		<tr><th>Black luminance</th><td colspan="2">0.001 cd/m²</td></tr>
+		<tr><th>Image state</th><td colspan="2">display-referred</td></tr>
+		<tr>
+			<th>Percentages</th>
+			<td  colspan="2">Allowed for R, G and B</td>
+		</tr>
+		<tr>
+			<th>Percent reference range</th>
+			<td>for R,G,B: 0% = 0.0, 100% = 1.0</td>
+		</tr>
+	</table>
+
 <dfn export>Jzazbz</dfn> {#Jzazbz}
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