From 837e42e07d52333bd790f81df3c2f5600b115faa Mon Sep 17 00:00:00 2001
From: Nadia Barbosa <nadiabarbosa@me.com>
Date: Thu, 11 Apr 2019 17:00:10 -0700
Subject: [ios, macos] Premultiply color values for mgl_color

Fixes https://github.com/mapbox/mapbox-gl-native/issues/14329
---
 platform/ios/src/UIColor+MGLAdditions.mm | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

(limited to 'platform/ios/src/UIColor+MGLAdditions.mm')

diff --git a/platform/ios/src/UIColor+MGLAdditions.mm b/platform/ios/src/UIColor+MGLAdditions.mm
index 7c1fbddc20..5a4b5cf06e 100644
--- a/platform/ios/src/UIColor+MGLAdditions.mm
+++ b/platform/ios/src/UIColor+MGLAdditions.mm
@@ -6,7 +6,8 @@
 {
     CGFloat r, g, b, a;
     [self getRed:&r green:&g blue:&b alpha:&a];
-    return { (float)r, (float)g, (float)b, (float)a };
+    // Premultiply 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 +18,13 @@
 
 + (UIColor *)mgl_colorWithColor:(mbgl::Color)color
 {
-    return [UIColor colorWithRed:color.r green:color.g blue:color.b alpha:color.a];
+    // Since CIColor expects color values to be non-multiplied, we transform them here
+    // to non-premultiplied values
+    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
-- 
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