Add diamond structuring element

modules/imgproc/test/test_structuring_element.cpp

@@ -0,0 +1,17 @@
+#include "test_precomp.hpp"
+
+namespace opencv_test { namespace {
+
+TEST(MorphShapes, getStructuringElementDiamond)
+{
+    cv::Mat element = cv::getStructuringElement(cv::MORPH_DIAMOND, cv::Size(5,5));
+    cv::Mat expected = (cv::Mat_<uchar>(5,5) <<
+        0,0,1,0,0,
+        0,1,1,1,0,
+        1,1,1,1,1,
+        0,1,1,1,0,
+        0,0,1,0,0);
+    EXPECT_EQ(0, cvtest::norm(element, expected, cv::NORM_INF));
+}
+
+}} // namespace