libgui|Image: Color mixing helper

skyjake · Sep 1, 2019 · 0eddee8 · 0eddee8
1 parent e83aa94
commit 0eddee8
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diff --git a/doomsday/libs/gui/include/de/graphics/image.h b/doomsday/libs/gui/include/de/graphics/image.h
@@ -118,6 +118,7 @@ class LIBGUI_PUBLIC Image : public ISerializable
     }
     static Vec4f hsv(Color color);          // normalized HSV
     static Color fromHsv(const Vec4f &hsv); // normalized HSV
+    static Color mix(Color a, Color b, Color m);
 
 public:
     Image();

diff --git a/doomsday/libs/gui/src/graphics/image.cpp b/doomsday/libs/gui/src/graphics/image.cpp
@@ -1465,4 +1465,19 @@ Image::Color Image::fromHsv(const Vec4f &hsv)
     return (rgb.min(Vec4f(1, 1, 1, 1)).max(Vec4f()) * 255.f + Vec4f(.5f, .5f, .5f, .5f)).toVec4ub();
 }
 
+Image::Color Image::mix(Color a, Color b, Color m)
+{
+    const duint mr = m.x;
+    const duint mg = m.y;
+    const duint mb = m.z;
+    const duint ma = m.w;
+
+    int red   = (b.x * mr + a.x * (255u - mr)) / 255u;
+    int green = (b.y * mg + a.y * (255u - mg)) / 255u;
+    int blue  = (b.z * mb + a.z * (255u - mb)) / 255u;
+    int alpha = (b.w * ma + a.w * (255u - ma)) / 255u;
+
+    return makeColor(red, green, blue, alpha);
+}
+
 } // namespace de