Merge remote-tracking branch 'upstream/3.4' into merge-3.4

modules/core/test/test_arithm.cpp

@@ -2166,6 +2166,15 @@ TEST(Core_Norm, IPP_regression_NORM_L1_16UC3_small)
     EXPECT_EQ((double)20*cn, cv::norm(a, b, NORM_L1, mask));
 }
 
+TEST(Core_Norm, NORM_L2_8UC4)
+{
+    // Tests there is no integer overflow in norm computation for multiple channels.
+    const int kSide = 100;
+    cv::Mat4b a(kSide, kSide, cv::Scalar(255, 255, 255, 255));
+    cv::Mat4b b = cv::Mat4b::zeros(kSide, kSide);
+    const double kNorm = 2.*kSide*255.;
+    EXPECT_EQ(kNorm, cv::norm(a, b, NORM_L2));
+}
 
 TEST(Core_ConvertTo, regression_12121)
 {