LibWeb/CSS: Add support for the `rec2020` color space in `color()`

This color space is often used as a reference in WPT tests, having
support for it makes us pass 15 new tests:
  - css/css-color/rec2020-001.html
  - css/css-color/rec2020-002.html
  - css/css-color/rec2020-003.html
  - css/css-color/rec2020-004.html
  - css/css-color/rec2020-005.html
  - css/css-color/predefined-011.html
  - css/css-color/predefined-012.html

Libraries/LibGfx/Color.cpp

@@ -476,6 +476,33 @@ Color Color::from_pro_photo_rgb(float r, float g, float b, float alpha)
     return from_xyz50(x, y, z, alpha);
 }
 
+// https://www.w3.org/TR/css-color-4/#predefined-rec2020
+Color Color::from_rec2020(float r, float g, float b, float alpha)
+{
+    auto to_linear = [](float c) -> float {
+        auto constexpr alpha = 1.09929682680944;
+        auto constexpr beta = 0.018053968510807;
+
+        u8 sign = c < 0 ? -1 : 1;
+        auto absolute = abs(c);
+
+        if (absolute < beta * 4.5)
+            return c / 4.5;
+
+        return sign * (pow((absolute + alpha - 1) / alpha, 1 / 0.45));
+    };
+
+    auto linear_r = to_linear(r);
+    auto linear_g = to_linear(g);
+    auto linear_b = to_linear(b);
+
+    float x = 0.63695805 * linear_r + 0.14461690 * linear_g + 0.16888098 * linear_b;
+    float y = 0.26270021 * linear_r + 0.67799807 * linear_g + 0.05930172 * linear_b;
+    float z = 0.00000000 * linear_r + 0.02807269 * linear_g + 1.06098506 * linear_b;
+
+    return from_xyz65(x, y, z, alpha);
+}
+
 Color Color::from_xyz50(float x, float y, float z, float alpha)
 {
     // See commit description for these values

Libraries/LibGfx/Color.h

@@ -187,6 +187,7 @@ public:
     static Color from_lab(float L, float a, float b, float alpha = 1.0f);
     static Color from_linear_srgb(float r, float g, float b, float alpha = 1.0f);
     static Color from_pro_photo_rgb(float r, float g, float b, float alpha = 1.0f);
+    static Color from_rec2020(float r, float g, float b, float alpha = 1.0f);
     static Color from_xyz50(float x, float y, float z, float alpha = 1.0f);
     static Color from_xyz65(float x, float y, float z, float alpha = 1.0f);
 

Libraries/LibWeb/CSS/StyleValues/CSSColor.cpp

@@ -25,6 +25,8 @@ CSSColorValue::ColorType color_type_from_string_view(StringView color_space)
         return CSSColorValue::ColorType::sRGBLinear;
     if (color_space == "prophoto-rgb"sv)
         return CSSColorValue::ColorType::ProPhotoRGB;
+    if (color_space == "rec2020"sv)
+        return CSSColorValue::ColorType::Rec2020;
     if (color_space == "xyz-d50"sv)
         return CSSColorValue::ColorType::XYZD50;
     if (color_space == "xyz"sv || color_space == "xyz-d65")
@@ -88,6 +90,9 @@ Color CSSColor::to_color(Optional<Layout::NodeWithStyle const&>) const
     if (color_type() == ColorType::ProPhotoRGB)
         return Color::from_pro_photo_rgb(c1, c2, c3, alpha_val);
 
+    if (color_type() == ColorType::Rec2020)
+        return Color::from_rec2020(c1, c2, c3, alpha_val);
+
     if (color_type() == ColorType::XYZD50)
         return Color::from_xyz50(c1, c2, c3, alpha_val);
 

Libraries/LibWeb/CSS/StyleValues/CSSColor.h

@@ -21,7 +21,7 @@ public:
     virtual Color to_color(Optional<Layout::NodeWithStyle const&>) const override;
     virtual String to_string() const override;
 
-    static constexpr Array s_supported_color_space = { "a98-rgb"sv, "display-p3"sv, "srgb"sv, "srgb-linear"sv, "prophoto-rgb"sv, "xyz"sv, "xyz-d50"sv, "xyz-d65"sv };
+    static constexpr Array s_supported_color_space = { "a98-rgb"sv, "display-p3"sv, "srgb"sv, "srgb-linear"sv, "prophoto-rgb"sv, "rec2020"sv, "xyz"sv, "xyz-d50"sv, "xyz-d65"sv };
 
 private:
     CSSColor(ColorType color_type, ValueComparingNonnullRefPtr<CSSStyleValue> c1, ValueComparingNonnullRefPtr<CSSStyleValue> c2, ValueComparingNonnullRefPtr<CSSStyleValue> c3, ValueComparingNonnullRefPtr<CSSStyleValue> alpha)

Libraries/LibWeb/CSS/StyleValues/CSSColorValue.h

@@ -35,6 +35,7 @@ public:
         sRGB, // This is used by CSSColor for color(srgb ...).
         sRGBLinear,
         ProPhotoRGB,
+        Rec2020,
         XYZD50,
         XYZD65,
     };

Tests/LibWeb/Ref/expected/wpt-import/css/css-color/rec2020-003-ref.html

@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Color 4: CSS Color 4: rec2020</title>
+<style>
+    body { background-color: grey; }
+    .test { background-color: rgb(99.993% 100% 100%); width: 12em; height: 12em; } /* color(rec2020 1 1 1) converted to sRGB */
+</style>
+<body>
+    <p>Test passes if you see a single square, and not two rectangles of different colors.</p>
+    <div class="test"></div>
+</body>

Tests/LibWeb/Ref/expected/wpt-import/css/css-color/rec2020-004-ref.html

@@ -0,0 +1,10 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Color 4: CSS Color 4: rec2020</title>
+<style>
+    .test { background-color: lab(85.7729% -160.7259 109.2319); width: 12em; height: 12em; } /* color(rec2020 0 1 0) converted to Lab */
+</style>
+<body>
+    <p>Test passes if you see a single square, and not two rectangles of different colors.</p>
+    <div class="test"></div>
+</body>

Tests/LibWeb/Ref/input/wpt-import/css/css-color/predefined-011.html

@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Color 4: predefined colorspaces, rec2020, decimal values</title>
+<link rel="author" title="Chris Lilley" href="mailto:chris@w3.org">
+<link rel="help" href="https://drafts.csswg.org/css-color-4/#predefined">
+<link rel="match" href="../../../../expected/wpt-import/css/css-color/greensquare-090-ref.html">
+<meta name="assert" content="Color function with explicit rec2020 value as decimal matches sRGB #009900">
+<style>
+    .test { background-color: red; width: 12em; height: 6em; margin-top:0}
+    .ref { background-color: #009900; width: 12em; height: 6em; margin-bottom: 0}
+    .test {background-color: color(rec2020 0.299218 0.533327 0.120785)}
+</style>
+<body>
+    <p>Test passes if you see a green square, and no red.</p>
+    <p class="ref"> </p>
+    <p class="test"> </p>
+</body>

Tests/LibWeb/Ref/input/wpt-import/css/css-color/predefined-012.html

@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Color 4: predefined colorspaces, rec2020, percent values</title>
+<link rel="author" title="Chris Lilley" href="mailto:chris@w3.org">
+<link rel="help" href="https://drafts.csswg.org/css-color-4/#predefined">
+<link rel="match" href="../../../../expected/wpt-import/css/css-color/greensquare-090-ref.html">
+<meta name="assert" content="Color function with explicit rec2020 value as percent matches sRGB #009900">
+<style>
+    .test { background-color: red; width: 12em; height: 6em; margin-top:0}
+    .ref { background-color: #009900; width: 12em; height: 6em; margin-bottom: 0}
+    .test {background-color: color(rec2020 29.9218% 53.3327% 12.0785%)}
+</style>
+<body>
+    <p>Test passes if you see a green square, and no red.</p>
+    <p class="ref"> </p>
+    <p class="test"> </p>
+</body>

Tests/LibWeb/Ref/input/wpt-import/css/css-color/rec2020-001.html

@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Color 4: rec2020</title>
+<link rel="author" title="Sam Weinig" href="mailto:weinig@apple.com">
+<link rel="help" href="https://drafts.csswg.org/css-color-4/#valdef-color-rec2020">
+<link rel="match" href="../../../../expected/wpt-import/css/css-color/greensquare-ref.html">
+<meta name="assert" content="rec2020 with no alpha">
+<style>
+    .test { background-color: red; width: 12em; height: 12em; }
+    .test { background-color: color(rec2020 0.235202 0.431704 0.085432); } /* green (sRGB #008000) converted to rec2020 */
+</style>
+<body>
+    <p>Test passes if you see a green square, and no red.</p>
+    <div class="test"></div>
+</body>

Tests/LibWeb/Ref/input/wpt-import/css/css-color/rec2020-002.html

@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Color 4: rec2020</title>
+<link rel="author" title="Sam Weinig" href="mailto:weinig@apple.com">
+<link rel="help" href="https://drafts.csswg.org/css-color-4/#valdef-color-rec2020">
+<link rel="match" href="../../../../expected/wpt-import/css/css-color/blacksquare-ref.html">
+<meta name="assert" content="rec2020 with no alpha">
+<style>
+    .test { background-color: red; width: 12em; height: 12em; }
+    .test { background-color: color(rec2020 0 0 0); } /* black (sRGB #000000) converted to rec2020 */
+</style>
+<body>
+    <p>Test passes if you see a black square, and no red.</p>
+    <div class="test"></div>
+</body>

Tests/LibWeb/Ref/input/wpt-import/css/css-color/rec2020-003.html

@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Color 4: rec2020</title>
+<link rel="author" title="Sam Weinig" href="mailto:weinig@apple.com">
+<link rel="help" href="https://drafts.csswg.org/css-color-4/#valdef-color-rec2020">
+<link rel="match" href="../../../../expected/wpt-import/css/css-color/rec2020-003-ref.html">
+<meta name="assert" content="rec2020 with no alpha">
+<style>
+    body { background-color: grey; }
+    .test { background-color: red; width: 12em; height: 6em; margin-top: 0; }
+    .ref { background-color: rgb(99.993% 100% 100%); width: 12em; height: 6em; margin-bottom: 0; } /* color(rec2020 1 1 1) converted to sRGB */
+    .test { background-color: color(rec2020 1 1 1); }
+</style>
+<body>
+    <p>Test passes if you see a single square, and not two rectangles of different colors.</p>
+    <div class="ref"></div>
+    <div class="test"></div>
+</body>

Tests/LibWeb/Ref/input/wpt-import/css/css-color/rec2020-004.html

@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Color 4: rec2020</title>
+<link rel="author" title="Sam Weinig" href="mailto:weinig@apple.com">
+<link rel="help" href="https://drafts.csswg.org/css-color-4/#valdef-color-rec2020">
+<link rel="match" href="../../../../expected/wpt-import/css/css-color/rec2020-004-ref.html">
+<meta name="assert" content="rec2020 with no alpha">
+<style>
+    .test { background-color: red; width: 12em; height: 6em; margin-top: 0; }
+    .ref { background-color: lab(85.7729% -160.7259 109.2319); width: 12em; height: 6em; margin-bottom: 0; } /* color(rec2020 0 1 0) converted to Lab */
+    .test { background-color: color(rec2020 0 1 0); }
+</style>
+<body>
+    <p>Test passes if you see a single square, and not two rectangles of different colors.</p>
+    <div class="ref"></div>
+    <div class="test"></div>
+</body>

Tests/LibWeb/Ref/input/wpt-import/css/css-color/rec2020-005.html

@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Color 4: rec2020</title>
+<link rel="author" title="Sam Weinig" href="mailto:weinig@apple.com">
+<link rel="help" href="https://drafts.csswg.org/css-color-4/#valdef-color-rec2020">
+<link rel="match" href="../../../../expected/wpt-import/css/css-color/greensquare-display-p3-ref.html">
+<meta name="assert" content="rec2020 outside the sRGB gamut">
+<style>
+    .test { background-color: red; width: 12em; height: 12em; }
+    .test { background-color: color(rec2020 0.431836 0.970723 0.079208); } /* green color(display-p3 0 1 0) converted to rec2020 */
+</style>
+<body>
+    <p>Test passes if you see a green square, and no red.</p>
+    <div class="test"></div>
+</body>