1 files changed, 16 insertions, 2 deletions
diff --git a/platform/ios/src/UIColor+MGLAdditions.mm b/platform/ios/src/UIColor+MGLAdditions.mm
index 7c1fbddc20..68e77f5b10 100644
--- a/platform/ios/src/UIColor+MGLAdditions.mm
+++ b/platform/ios/src/UIColor+MGLAdditions.mm
@@ -6,7 +6,10 @@
 {
     CGFloat r, g, b, a;
     [self getRed:&r green:&g blue:&b alpha:&a];
-    return { (float)r, (float)g, (float)b, (float)a };
+    // UIColor provides non-premultiplied color components, so we have to premultiply each
+    // color component with the alpha value to transform it into a valid
+    // mbgl::Color which expects premultiplied color components.
+    return { static_cast<float>(r*a), static_cast<float>(g*a), static_cast<float>(b*a), static_cast<float>(a) };
 }
 
 - (mbgl::style::PropertyValue<mbgl::Color>)mgl_colorPropertyValue
@@ -17,7 +20,18 @@
 
 + (UIColor *)mgl_colorWithColor:(mbgl::Color)color
 {
-    return [UIColor colorWithRed:color.r green:color.g blue:color.b alpha:color.a];
+    // If there is no alpha value, return original color values.
+    if (color.a == 0.0f) {
+        return [UIColor colorWithRed:color.r green:color.g blue:color.b alpha:color.a];
+    }
+
+    // mbgl::Color provides premultiplied color components, so we have to convert color
+    // components to non-premultiplied values to return a valid UIColor object.
+    float red = static_cast<float>((color.r / color.a));
+    float green = static_cast<float>((color.g / color.a));
+    float blue = static_cast<float>((color.b / color.a));
+
+    return [UIColor colorWithRed:red green:green blue:blue alpha:color.a];
 }
 
 @end