Add color from text parsing

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

@@ -5,6 +5,8 @@
 #include <psemek/geom/math.hpp>
 
 #include <cstdint>
+#include <string_view>
+#include <optional>
 
 namespace psemek::gfx
 {
@@ -205,4 +207,6 @@ namespace psemek::gfx
 		return generic_color{dark(c.c, darkness)};
 	}
 
+	std::optional<color_rgba> parse_color(std::string_view const & text);
+
 }

libs/gfx/source/color.cpp

@@ -0,0 +1,110 @@
+#include <psemek/gfx/color.hpp>
+
+#include <unordered_map>
+
+namespace psemek::gfx
+{
+
+	static std::unordered_map<std::string_view, color_rgba> const named_colors
+	{
+		{"black", {0, 0, 0, 255}},
+		{"white", {255, 255, 255, 255}},
+		{"grey", {127, 127, 127, 255}},
+
+		{"red", {255, 0, 0, 255}},
+		{"green", {0, 255, 0, 255}},
+		{"blue", {0, 0, 255, 255}},
+		{"cyan", {0, 255, 255, 255}},
+		{"magenta", {255, 0, 255, 255}},
+		{"yellow", {255, 255, 0, 255}},
+
+		{"dark_grey", {63, 63, 63, 255}},
+		{"light_grey", {191, 191, 191, 255}},
+
+		{"dark_red", {127, 0, 0, 255}},
+		{"dark_green", {0, 127, 0, 255}},
+		{"dark_blue", {0, 0, 127, 255}},
+		{"dark_cyan", {0, 127, 127, 255}},
+		{"dark_magenta", {127, 0, 127, 255}},
+		{"dark_yellow", {127, 127, 0, 255}},
+
+		{"light_red", {255, 127, 127, 255}},
+		{"light_green", {127, 255, 127, 255}},
+		{"light_blue", {127, 127, 255, 255}},
+		{"light_cyan", {127, 255, 255, 255}},
+		{"light_magenta", {255, 127, 255, 255}},
+		{"light_yellow", {255, 255, 127, 255}},
+	};
+
+	static bool all_hex(std::string_view const & text)
+	{
+		return std::all_of(text.begin(), text.end(), [](char c){
+			return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') || ('A' <= c && c <= 'F');
+		});
+	}
+
+	static std::uint8_t from_hex(char c)
+	{
+		if ('0' <= c && c <= '9')
+			return c - '0';
+		if ('a' <= c && c <= 'f')
+			return 10 + (c - 'a');
+		if ('A' <= c && c <= 'F')
+			return 10 + (c - 'A');
+		return 0;
+	}
+
+	static std::uint8_t from_hex(char c1, char c0)
+	{
+		return (from_hex(c1) * 16) | from_hex(c0);
+	}
+
+	std::optional<color_rgba> parse_color(std::string_view const & text)
+	{
+		if (auto it = named_colors.find(text); it != named_colors.end())
+			return it->second;
+
+		if (all_hex(text))
+		{
+			if (text.size() == 3)
+			{
+				return color_rgba{
+					17 * from_hex(text[0]),
+					17 * from_hex(text[1]),
+					17 * from_hex(text[2]),
+					255
+				};
+			}
+			else if (text.size() == 4)
+			{
+				return color_rgba{
+					17 * from_hex(text[0]),
+					17 * from_hex(text[1]),
+					17 * from_hex(text[2]),
+					17 * from_hex(text[3]),
+				};
+			}
+			else if (text.size() == 6)
+			{
+				return color_rgba{
+					from_hex(text[0], text[1]),
+					from_hex(text[2], text[3]),
+					from_hex(text[4], text[5]),
+					255
+				};
+			}
+			else if (text.size() == 8)
+			{
+				return color_rgba{
+					from_hex(text[0], text[1]),
+					from_hex(text[2], text[3]),
+					from_hex(text[4], text[5]),
+					from_hex(text[6], text[7]),
+				};
+			}
+		}
+
+		return std::nullopt;
+	}
+
+}