[css-color-4] Interpolation between legacy sRGB colors is (once again) in sRGB space, for compatibility. #7949

svgeesus · svgeesus · commit a0a988606379 · 2025-06-04T14:51:03.000-04:00
diff --git a/css-color-4/Overview.bs b/css-color-4/Overview.bs
@@ -4770,7 +4770,6 @@ Color Space for Interpolation</h3>
 		gradient/gradient-eval-008.html
 		gradient/gradient-eval-009.html
 		gradient/gradient-none-interpolation.html
-		gradient/legacy-color-gradient.html
 		gradient/oklab-gradient.html
 		gradient/srgb-gradient.html
 		gradient/srgb-linear-gradient.html
@@ -4784,43 +4783,42 @@ Color Space for Interpolation</h3>
 	interpolation should take place in,
 	it defaults to Oklab.
 
-	<!--
-		The following removed by CSSWG resolution
-		https://github.com/w3c/csswg-drafts/issues/7948#issuecomment-1479941072
-
-		RESOLVED: change specification say browser MUST use OKLab color interpolation
-		for all colors, including legacy colors
-
-	 -->
-	<!-- However, user agents <em>may</em> handle interpolation
+	However, user agents <em>must</em> handle interpolation
 	between legacy sRGB color formats
 	(hex colors, named colors,
 	''rgb()'', ''hsl()'' or ''hwb()''
 	and the equivalent alpha-including forms)
 	in gamma-encoded sRGB space.
-	This provides Web compatibility; legacy sRGB content interpolates in the sRGB space by default.
+	This provides Web compatibility; 
+	legacy sRGB content interpolates in the sRGB space by default.
+
+	<wpt  pathprefix="css/css-images/">
+		gradient/legacy-color-gradient.html
+	</wpt>
 
 	This also means that authors can choose
 	to opt-in to better interpolation,
 	even between sRGB colors,
 	by using the non-legacy ''color(srgb r g b)'' form
-	for at least one of their colors. -->
+	for at least one of their colors,
+	or by explicitly specifying an [=interpolation color space=].
 
-	<!-- Now flip the previous paragraph,
-		authors that actually like sRGB interpolation can opt-in -->
+	<wpt>
+		/css/css-images/gradient/css-color-4-colors-default-to-oklab-gradient.html
+	</wpt>
 
-	Authors that prefer interpolation in sRGB
+	<!-- Authors that prefer interpolation in sRGB
 	in a particular instance
 	can opt-in to the old behavior
 	by explicitly specifying sRGB as the [=interpolation color space=],
-	for example on a particular gradient where that result is desired.
+	for example on a particular gradient where that result is desired. -->
 
 	If the colors to be interpolated are outside the gamut
 	of the [=interpolation color space=] ,
 	then once converted to that space,
 	they will contain out of range values.
 
-	These are not clipped, but the values are interpolated as-is.
+	These are not clipped; the values must be interpolated as-is.
 
 <h3 id="interpolation-missing">
 Interpolating with Missing Components</h3>
@@ -4893,6 +4891,10 @@ Interpolating with Missing Components</h3>
 	The Whiteness and Blackness components of HWB
 	have no analogs in other color spaces.
 
+	<wpt pathprefix="css/css-images/">
+		gradient/gradient-none-interpolation.html
+	</wpt>
+
 	<div class="example" id="ex-analogous-hue">
 		For example, if these two colors
 		are to be interpolated in OkLCh,
