python: add bindings for convenience color functions.

Co-authored-by: Vladimír Vondruš <mosra@centrum.cz>

src/python/magnum/math.vector.h

@@ -533,6 +533,19 @@ template<class T> void color3(py::class_<Math::Color3<T>, Math::Vector3<T>>& c)
             return Math::Color3<T>::fromSrgb(srgb);
         }, "Create linear RGB color from 24-bit sRGB representation", py::arg("srgb"))
 
+        .def_static("red", &Math::Color3<T>::red,
+            "Red color", py::arg("red") = Math::Implementation::fullChannel<T>())
+        .def_static("green", &Math::Color3<T>::green,
+            "Green color", py::arg("green") = Math::Implementation::fullChannel<T>())
+        .def_static("blue", &Math::Color3<T>::blue,
+            "Blue color", py::arg("blue") = Math::Implementation::fullChannel<T>())
+        .def_static("cyan", &Math::Color3<T>::cyan,
+            "Cyan color", py::arg("red") = T(0))
+        .def_static("magenta", &Math::Color3<T>::magenta,
+            "Magenta color", py::arg("green") = T(0))
+        .def_static("yellow", &Math::Color3<T>::yellow,
+            "Yellow color", py::arg("blue") = T(0))
+
         /* Accessors */
         .def("to_srgb_int", &Math::Color3<T>::toSrgbInt,
              "Convert to 32-bit integral sRGB representation")
@@ -583,6 +596,31 @@ template<class T> void color4(py::class_<Math::Color4<T>, Math::Vector4<T>>& c)
             return Math::Color4<T>::fromSrgb(srgb, a);
         }, "Create linear RGBA color from 32-bit sRGB a alpha representation", py::arg("srgb"), py::arg("a") = Math::Implementation::fullChannel<T>())
 
+        .def_static("red", &Math::Color4<T>::red,
+            "Red color",
+            py::arg("red") = Math::Implementation::fullChannel<T>(),
+            py::arg("alpha") = Math::Implementation::fullChannel<T>())
+        .def_static("green", &Math::Color4<T>::green,
+            "Green color",
+            py::arg("green") = Math::Implementation::fullChannel<T>(),
+            py::arg("alpha") = Math::Implementation::fullChannel<T>())
+        .def_static("blue", &Math::Color4<T>::blue,
+            "Blue color",
+            py::arg("blue") = Math::Implementation::fullChannel<T>(),
+            py::arg("alpha") = Math::Implementation::fullChannel<T>())
+        .def_static("cyan", &Math::Color4<T>::cyan,
+            "Cyan color",
+            py::arg("red") = T(0),
+            py::arg("alpha") = Math::Implementation::fullChannel<T>())
+        .def_static("magenta", &Math::Color4<T>::magenta,
+            "Magenta color",
+            py::arg("green") = T(0),
+            py::arg("alpha") = Math::Implementation::fullChannel<T>())
+        .def_static("yellow", &Math::Color4<T>::yellow,
+            "Yellow color",
+            py::arg("blue") = T(0),
+            py::arg("alpha") = Math::Implementation::fullChannel<T>())
+
         /* Accessors */
         .def("to_srgb_alpha_int", &Math::Color4<T>::toSrgbAlphaInt,
              "Convert to 32-bit integral sRGB + linear alpha representation")

src/python/magnum/test/test_math.py

@@ -355,6 +355,22 @@ class Color3_(unittest.TestCase):
         self.assertEqual(c2, Color3(0.5, 0.75, 1.0))
         self.assertEqual(c3, Color3(0.5, 0.75, 1.0))
 
+    def test_init_primaries(self):
+        red  = Color3.red(0.5)
+        cyan = Color3.cyan(0.5)
+        self.assertEqual(red,  Color3(0.5, 0.0, 0.0))
+        self.assertEqual(cyan, Color3(0.5, 1.0, 1.0))
+
+        green   = Color3.green(0.5)
+        magenta = Color3.magenta(0.5)
+        self.assertEqual(green,   Color3(0.0, 0.5, 0.0))
+        self.assertEqual(magenta, Color3(1.0, 0.5, 1.0))
+
+        blue   = Color3.blue(0.5)
+        yellow = Color3.yellow(0.5)
+        self.assertEqual(blue,   Color3(0.0, 0.0, 0.5))
+        self.assertEqual(yellow, Color3(1.0, 1.0, 0.5))
+
     def test_srgb(self):
         # Cross-checked with C++ tests
         a = Color3.from_srgb(0xf32a80)
@@ -409,6 +425,22 @@ class Color4_(unittest.TestCase):
         self.assertEqual(e4, Color4(0.5, 0.75, 0.875, 0.9))
         self.assertEqual(e5, Color4(0.5, 0.75, 0.875, 0.9))
 
+    def test_init_primaries(self):
+        red  = Color4.red(0.5, 0.75)
+        cyan = Color4.cyan(0.5, 0.75)
+        self.assertEqual(red,  Color4(0.5, 0.0, 0.0, 0.75))
+        self.assertEqual(cyan, Color4(0.5, 1.0, 1.0, 0.75))
+
+        green   = Color4.green(0.5, 0.75)
+        magenta = Color4.magenta(0.5, 0.75)
+        self.assertEqual(green,   Color4(0.0, 0.5, 0.0, 0.75))
+        self.assertEqual(magenta, Color4(1.0, 0.5, 1.0, 0.75))
+
+        blue   = Color4.blue(0.5, 0.75)
+        yellow = Color4.yellow(0.5, 0.75)
+        self.assertEqual(blue,   Color4(0.0, 0.0, 0.5, 0.75))
+        self.assertEqual(yellow, Color4(1.0, 1.0, 0.5, 0.75))
+
     def test_srgb(self):
         # Cross-checked with C++ tests
         a = Color4.from_srgb(0xf32a80)