[css-color] relative color syntax, components descriptor

Author: svgeesus

css-color-4/Overview.bs

@@ -3824,6 +3824,39 @@ Specifying a color profile: the ''@color-profile'' at-rule</h3>
 			but fall just inside the gamut.
 	</dl>
 
+	<pre class=descdef for="@color-profile">
+		Name: components
+		Value: <<ident>>#
+		For: @color-profile
+		Initial: n/a
+	</pre>
+
+	Color profiles can define color spaces which contain a varying number of components.
+	For example, a Cyan, Magenta, Yellow and Black (CMYK) profile
+	has four components
+	named c, m, y and k
+	While a four-component additive screen profile
+	might use four components
+	named r, g, y and b.
+
+	The value of this descriptor is a comma-separated list of <<ident>> tokens.
+	Each <<ident>>> names a component,
+	in the order in which they are used in the color profile,
+	while the total number of tokens defines the number of components.
+
+	<div class="example" id="ex-components-cmyk">
+		This descriptor declares that there are four components named cyan, magenta, yellow and black:
+		<pre>components: cyan, magenta, yellow, black</pre>
+		while this descriptor opts for terser names:
+		<pre>components: c,m,y,k</pre>
+	</div>
+
+	<div class="example" id="ex-components-cmykogv">
+		This descriptor declares that there are seven components
+		named cyan, magenta, yellow, black, orange, green and violet:
+		<pre>components: cyan, magenta, yellow, black, orange, green, violet</pre>
+	</div>
+
 <h3 id="cal-cmyk">
 	CSS and print: using calibrated CMYK and other printed color spaces</h3>
 

css-color-5/Overview.bs

@@ -1054,6 +1054,43 @@ the allowed [=channel keywords=] are:
 	</pre>
 </div>
 
+<h4 id="relative-color">Relative color-function colors</h4>
+
+The grammar of the ''color()'' function is extended as follows:
+
+<pre class='prod'>
+	<dfn>color()</dfn> = color( [from <<color>>]? <<colorspace-params>> [ / <<alpha-value>> ]? )
+	<dfn>colorspace-params</dfn> = [<<custom-params>> | <<predefined-rgb-params>> | <<xyz-params>>]
+	<dfn>custom-params</dfn> = <<dashed-ident>> [ <<number>> | <<percentage>> ]#
+	<dfn>predefined-rgb-params</dfn> = <<predefined-rgb>> [ <<number>> | <<percentage>> ]{3}
+	<dfn>predefined-rgb</dfn> = srgb | display-p3 | a98-rgb | prophoto-rgb | rec2020
+	<dfn>xyz-params</dfn> = xyz <<number>>{3}
+</pre>
+
+Within a [=relative color=] syntax ''color()'' function using <<custom-params>>,
+the number and name of the allowed [=channel keywords=] are defined by the
+'@color-profile/components' descriptor on the corresponding ''@color-profile'',
+if present;
+otherwise, no relative color manipulation is valid.
+
+They are all <<percentage>>s that correspond to the [=origin color's=] channels
+	after its conversion to the color space of the color profile.
+
+Within a [=relative color=] syntax ''color()'' function using <<predefined-rgb-params>>,
+the allowed [=channel keywords=] are:
+
+* <dfn value for="color()">r</dfn>, <dfn value for="color()">g</dfn>, and <dfn value for="color()">b</dfn>
+	are all <<percentage>>s
+	that correspond to the [=origin color's=] red, green, and blue channels
+	after its conversion to the predefined RGB color space.
+
+Within a [=relative color=] syntax ''color()'' function using <<xyz-params>>,
+the allowed [=channel keywords=] are:
+
+* <dfn value for="color()">x</dfn>, <dfn value for="color()">x</dfn>, <dfn value for="color()">x</dfn> are all <<number>>s
+	that correspond to the [=origin color's=] X, Y and Z channels
+	after its conversion to relative, D50-adapted CIE XYZ color space.
+
 
 
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