[ios, macos] Premultiply color values for mgl_color

Fixes https://github.com/mapbox/mapbox-gl-native/issues/14329

1 files changed, 7 insertions, 2 deletions

diff --git a/platform/darwin/test/MGLExpressionTests.mm b/platform/darwin/test/MGLExpressionTests.mm
index 06f06d8c6e..e7d1608018 100644
--- a/platform/darwin/test/MGLExpressionTests.mm
+++ b/platform/darwin/test/MGLExpressionTests.mm
@@ -282,9 +282,14 @@ using namespace std::string_literals;
         XCTAssertEqualObjects([expression expressionValueWithObject:nil context:nil], color);
     }
     {
-        MGLColor *color = [MGLColor mgl_colorWithColor:{ 255.0/255, 239.0/255, 213.0/255, 0.5 }]; // papayawhip
+        // Transform color components to non-premultiplied values
+        float alpha = 0.5;
+        float red = (255.0 * alpha) / 255;
+        float green = (239.0 * alpha) / 255;
+        float blue = (213.0 * alpha) / 255;
+        MGLColor *color = [MGLColor mgl_colorWithColor:{ red, green, blue, alpha }]; // papayawhip
         NSExpression *expression = [NSExpression expressionForConstantValue:color];
-        NSArray *jsonExpression = @[@"rgba", @255, @239, @213, @0.5];
+        NSArray *jsonExpression = @[@"rgba", @127.5, @119.5, @106.5, @0.5];
         XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
         XCTAssertEqualObjects([expression expressionValueWithObject:nil context:nil], color);
     }