Add color hex output

libs/gfx/include/psemek/gfx/color.hpp

@@ -163,6 +163,33 @@ namespace psemek::gfx
 		};
 	}
 
+	template <std::size_t N>
+	struct as_hex
+	{
+		geom::vector<std::uint8_t, N> color;
+
+		as_hex(geom::vector<std::uint8_t, N> const & color)
+			: color{color}
+		{}
+	};
+
+	template <typename OStream, std::size_t N>
+	OStream & operator << (OStream & os, as_hex<N> const & c)
+	{
+		static auto const hex_v = [](std::uint8_t value) -> char
+		{
+			if (value < 10)
+				return '0' + value;
+			else
+				return 'a' + (value - 10);
+		};
+
+		for (auto v : c.color.coords)
+			os << hex_v(v >> 4) << hex_v(v & 15);
+
+		return os;
+	}
+
 	struct generic_color
 	{
 		color_4f c;