Add new Mat constructor (#10808)

* Add new Mat constructor

* Fix build error

* Fix build error

* Fixed the code about 4 comments

* Fixed three comments

* delete previous local declaration

* fix build error

modules/core/include/opencv2/core/mat.hpp

@@ -989,6 +989,10 @@ public:
     */
     template<typename _Tp, typename = typename std::enable_if<std::is_arithmetic<_Tp>::value>::type>
     explicit Mat(const std::initializer_list<_Tp> list);
+
+    /** @overload
+    */
+    template<typename _Tp> explicit Mat(const std::initializer_list<int> sizes, const std::initializer_list<_Tp> list);
 #endif
 
 #ifdef CV_CXX_STD_ARRAY
@@ -2208,6 +2212,7 @@ public:
 
 #ifdef CV_CXX11
     Mat_(std::initializer_list<_Tp> values);
+    explicit Mat_(const std::initializer_list<int> sizes, const std::initializer_list<_Tp> values);
 #endif
 
 #ifdef CV_CXX_STD_ARRAY

modules/core/include/opencv2/core/mat.inl.hpp

@@ -584,6 +584,18 @@ Mat::Mat(const std::initializer_list<_Tp> list)
         return;
     Mat((int)list.size(), 1, traits::Type<_Tp>::value, (uchar*)list.begin()).copyTo(*this);
 }
+
+template<typename _Tp> inline
+Mat::Mat(const std::initializer_list<int> sizes, const std::initializer_list<_Tp> list)
+    : Mat()
+{
+    size_t size_total = 1;
+    int *sz = (int*)sizes.begin();
+    for(auto s : sizes)
+        size_total *= s;
+    CV_Assert(list.size() != 0 || size_total == list.size());
+    Mat((int)sizes.size(), sz, traits::Type<_Tp>::value, (uchar*)list.begin()).copyTo(*this);
+}
 #endif
 
 #ifdef CV_CXX_STD_ARRAY
@@ -1629,6 +1641,11 @@ template<typename _Tp> inline
 Mat_<_Tp>::Mat_(std::initializer_list<_Tp> list)
     : Mat(list)
 {}
+
+template<typename _Tp> inline
+Mat_<_Tp>::Mat_(const std::initializer_list<int> sizes, std::initializer_list<_Tp> list)
+    : Mat(sizes, list)
+{}
 #endif
 
 #ifdef CV_CXX_STD_ARRAY

modules/core/test/test_mat.cpp

@@ -1719,17 +1719,23 @@ TEST(Mat, from_initializer_list)
 {
     Mat A({1.f, 2.f, 3.f});
     Mat_<float> B(3, 1); B << 1, 2, 3;
+    Mat_<float> C({3}, {1,2,3});
 
     ASSERT_EQ(A.type(), CV_32F);
     ASSERT_DOUBLE_EQ(cvtest::norm(A, B, NORM_INF), 0.);
+    ASSERT_DOUBLE_EQ(cvtest::norm(A, C, NORM_INF), 0.);
+    ASSERT_DOUBLE_EQ(cvtest::norm(B, C, NORM_INF), 0.);
 }
 
 TEST(Mat_, from_initializer_list)
 {
     Mat_<float> A = {1, 2, 3};
     Mat_<float> B(3, 1); B << 1, 2, 3;
+    Mat_<float> C({3}, {1,2,3});
 
     ASSERT_DOUBLE_EQ(cvtest::norm(A, B, NORM_INF), 0.);
+    ASSERT_DOUBLE_EQ(cvtest::norm(A, C, NORM_INF), 0.);
+    ASSERT_DOUBLE_EQ(cvtest::norm(B, C, NORM_INF), 0.);
 }