commit 956aa23: [Project] Css: Fix HSL conversion

[Vsevolod Stakhov]

Author: Vsevolod Stakhov
Date: 2021-03-04 20:34:58 +0000
URL: https://github.com/rspamd/rspamd/commit/956aa233ad9536a5d2ca8b1ed6924b15cd5fee10

[Project] Css: Fix HSL conversion

---
 src/libserver/css/css_value.cxx | 42 ++++++++++++++++++++++-------------------
 src/libserver/css/css_value.hxx |  2 +-
 2 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/src/libserver/css/css_value.cxx b/src/libserver/css/css_value.cxx
index f00543615..c0ed9242c 100644
--- a/src/libserver/css/css_value.cxx
+++ b/src/libserver/css/css_value.cxx
@@ -158,17 +158,11 @@ constexpr static inline auto h_component_convert(const css_parser_token &tok)
 			else if (dbl < 0) {
 				dbl = 0;
 			}
-			ret = (dbl / 100.0) * 360.0;
+			ret = (dbl / 100.0);
 		}
 		else {
-			if (dbl > 360) {
-				dbl = 360;
-			}
-			else if (dbl < 0) {
-				dbl = 0;
-			}
-
-			ret = dbl;
+			dbl = ((((int)dbl % 360) + 360) % 360); /* Deal with rotations */
+			ret = dbl / 360.0; /* Normalize to 0..1 */
 		}
 	}
 
@@ -210,6 +204,8 @@ constexpr static inline auto sl_component_convert(const css_parser_token &tok)
 static inline auto hsl_to_rgb(double h, double s, double l)
 	-> css_color
 {
+	css_color ret;
+
 	constexpr auto hue2rgb = [](auto p, auto q, auto t) -> auto {
 		if (t < 0.0) {
 			t += 1.0;
@@ -217,25 +213,33 @@ static inline auto hsl_to_rgb(double h, double s, double l)
 		if (t > 1.0) {
 			t -= 1.0;
 		}
-		if (t < 1.0/6.0) {
+		if (t * 6. < 1.0) {
 			return p + (q - p) * 6.0 * t;
 		}
-		if (t < 0.5) {
+		if (t * 2. < 1) {
 			return q;
 		}
-		if (t < 2.0/3.0) {
+		if (t * 3. < 2.) {
 			return p + (q - p) * (2.0/3.0 - t) * 6.0;
 		}
-		return p * 255.0;
+		return p;
 	};
 
-	css_color ret;
+	if (s == 0) {
+		/* Achromatic */
+		ret.r = l;
+		ret.g = l;
+		ret.b = l;
+	}
+	else {
+		auto q = l <= 0.5 ? l * (1.0 + s) : l + s - l * s;
+		auto p = 2.0 * l - q;
+		ret.r = (std::uint8_t) (hue2rgb(p, q, h + 1.0 / 3.0) * 255);
+		ret.g = (std::uint8_t) (hue2rgb(p, q, h) * 255);
+		ret.b = (std::uint8_t) (hue2rgb(p, q, h - 1.0 / 3.0) * 255);
+	}
 
-	auto q = l < 0.5 ? l * (1.0 + s) : l + s - l * s;
-	auto p = 2.0 * l - q;
-	ret.r = (std::uint8_t)hue2rgb(p, q, h + 1.0/3.0);
-	ret.g = (std::uint8_t)hue2rgb(p, q, h);
-	ret.b = (std::uint8_t)hue2rgb(p, q, h - 1.0/3.0);
+	ret.alpha = 255;
 
 	return ret;
 }
diff --git a/src/libserver/css/css_value.hxx b/src/libserver/css/css_value.hxx
index a8152ed10..5f9fa0cee 100644
--- a/src/libserver/css/css_value.hxx
+++ b/src/libserver/css/css_value.hxx
@@ -36,7 +36,7 @@ struct alignas(int) css_color {
 
 	std::uint8_t alpha;
 
-	constexpr css_color(std::uint8_t _r, std::uint8_t _g, std::uint8_t _b, std::uint8_t _alpha = 255) :
+	css_color(std::uint8_t _r, std::uint8_t _g, std::uint8_t _b, std::uint8_t _alpha = 255) :
 	 	r(_r), g(_g), b(_b), alpha(_alpha) {}
 	css_color() = default;
 };