Merge pull request #23 from bruno-j-nicoletti/dev/bruno/colourMaths

Added simple arithmatic operators to artist::colour and a test

lib/include/artist/color.hpp

@@ -34,6 +34,11 @@ namespace cycfi::artist
    constexpr bool operator==(color const& a, color const& b);
    constexpr bool operator!=(color const& a, color const& b);
 
+   constexpr color operator+(color const& a, color const& b);
+   constexpr color operator-(color const& a, color const& b);
+   constexpr color operator*(color const& a, float b);
+   constexpr color operator*(float a, color const& b);
+
    ////////////////////////////////////////////////////////////////////////////
    // Inlines
    ////////////////////////////////////////////////////////////////////////////
@@ -176,6 +181,26 @@ namespace cycfi::artist
       return r;
    }
 
+   constexpr color operator+(color const& a, color const& b)
+   {
+     return color(a.red + b.red, a.green + b.green, a.blue + b.blue, a.alpha + b.alpha*(1.0-a.alpha));
+   }
+
+   constexpr color operator-(color const& a, color const& b)
+   {
+     return color(a.red - b.red, a.green - b.green, a.blue - b.blue, a.alpha + b.alpha*(1.0-a.alpha));
+   }
+
+   constexpr color operator*(color const& a, float b)
+   {
+     return color(a.red * b, a.green * b, a.blue * b, a.alpha);
+   }
+
+   constexpr color operator*(float a, color const& b)
+   {
+     return color(a * b.red, a * b.green, a * b.blue, b.alpha);
+   }
+
    ////////////////////////////////////////////////////////////////////////////
    // Common colors
    ////////////////////////////////////////////////////////////////////////////

test/main.cpp

@@ -986,4 +986,21 @@ TEST_CASE("Misc")
 }
 
 
-
+TEST_CASE("Color Maths")
+{
+  color a(0.2, 0.25, 0.5, 1.0);
+  color b(0.5, 0.6, 0.1, 1.0);
+
+  auto check = [&](color result, color check)
+  {
+    REQUIRE_THAT(result.red, Catch::WithinRel(check.red, 0.001f));
+    REQUIRE_THAT(result.green, Catch::WithinRel(check.green, 0.001f));
+    REQUIRE_THAT(result.blue, Catch::WithinRel(check.blue, 0.001f));
+    REQUIRE_THAT(result.alpha, Catch::WithinRel(check.alpha, 0.001f));
+  };
+
+  check(a + b, color(0.7, 0.85, 0.6, 1.0));
+  check(a - b, color(-0.3, -0.35, 0.4, 1.0));
+  check(a * 2, color(0.4, 0.5, 1.0, 1.0));
+  check(2 * a, color(0.4, 0.5, 1.0, 1.0));
+}