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

modules/core/test/test_arithm.cpp

@@ -2225,4 +2225,21 @@ TEST(Core_ConvertTo, regression_12121)
     }
 }
 
+TEST(Core_MeanStdDev, regression_multichannel)
+{
+    {
+        uchar buf[] = { 1, 2, 3, 4, 5, 6, 7, 8,
+                        3, 4, 5, 6, 7, 8, 9, 10 };
+        double ref_buf[] = { 2., 3., 4., 5., 6., 7., 8., 9.,
+                             1., 1., 1., 1., 1., 1., 1., 1. };
+        Mat src(1, 2, CV_MAKETYPE(CV_8U, 8), buf);
+        Mat ref_m(8, 1, CV_64FC1, ref_buf);
+        Mat ref_sd(8, 1, CV_64FC1, ref_buf + 8);
+        Mat dst_m, dst_sd;
+        meanStdDev(src, dst_m, dst_sd);
+        EXPECT_EQ(0, cv::norm(dst_m, ref_m, NORM_L1));
+        EXPECT_EQ(0, cv::norm(dst_sd, ref_sd, NORM_L1));
+    }
+}
+
 }} // namespace