Math: default alpha parameter also for Color4::fromHSV().

Not sure why this was omitted.

src/Magnum/Math/Color.h

@@ -438,7 +438,7 @@ class Color4: public Vector4<T> {
             return Color4<T>(Implementation::fromHSV<T>(hsv), a);
         }
         /** @overload */
-        constexpr static Color4<T> fromHSV(Deg<FloatingPointType> hue, FloatingPointType saturation, FloatingPointType value, T alpha) {
+        constexpr static Color4<T> fromHSV(Deg<FloatingPointType> hue, FloatingPointType saturation, FloatingPointType value, T alpha = Implementation::fullChannel<T>()) {
             return fromHSV(std::make_tuple(hue, saturation, value), alpha);
         }
 

src/Magnum/Math/Test/ColorTest.cpp

@@ -313,6 +313,10 @@ void ColorTest::hsvOverflow() {
 void ColorTest::hsvAlpha() {
     CORRADE_COMPARE(Color4ub::fromHSV(std::make_tuple(230.0_degf, 0.749f, 0.427f), 23), Color4ub(27, 40, 108, 23));
     CORRADE_COMPARE(Color4ub::fromHSV(230.0_degf, 0.749f, 0.427f, 23), Color4ub(27, 40, 108, 23));
+
+    /* Default alpha */
+    CORRADE_COMPARE(Color4ub::fromHSV(std::make_tuple(230.0_degf, 0.749f, 0.427f)), Color4ub(27, 40, 108, 255));
+    CORRADE_COMPARE(Color4ub::fromHSV(230.0_degf, 0.749f, 0.427f), Color4ub(27, 40, 108, 255));
 }
 
 void ColorTest::swizzleType() {