Add checks that prevents indexing an array by negative values.

* add eigen tensor conversion functions

* add eigen tensor conversion tests

* add support for column major order

* update eigen tensor tests

* fix coding style and add conditional compilation

* fix conditional compilation checks

* remove whitespace

* rearrange functions for easier reading

* reformat function documentation and add tensormap unit test

* cleanup documentation of unit test

* remove condition duplication

* check Eigen major version, not minor version

* restrict to Eigen v3.3.0+

* add documentation note and add type checking to cv2eigen_tensormap()

core: fix MatExpr::size() for gemm()

* core(test): MatExpr::size() test for gemm()

* core: fix MatExpr::size() for gemm()

- IPP/SSE4.2 works well

This reverts commit 3721c8bb
except changes in modules/dnn/test/test_tf_importer.cpp

* Add Operator override for multi-channel Mat with literal constant.

* simple test

* Operator overloading channel constraint for primitive types

* fix some test for #13586

Fix a bug in cv :: merge when array of 3-channel mat is input (#13544)

* Mat merge function bug fix - Bug fix of merge function of 3-channel vector <Mat> of 3 or 4 matrices

* Add Core_merge test for opencv#13544

* fixups

- support passing of `std::vector<KeyPoint>` via InputArray

* core(test): merge hang test

* core(merge/split): fix intrin optimization

* setTo_#10507

* setTo_Nan_10507

* setTo: update check / test for NaNs

* fix #9720

* Add regression test

* Fix calculation method for scale

* Make <array> #ifdef true for MSVC

I think MSVC had `std::array` for quite a while (possibly going back as far as VS 2012, but it's definitely there in 2015 and 2017. So I think `_MSC_VER` `1900` is a safe bet. Probably `1800` and maybe even `1700` could work as well but I can't test that locally.

* fix test

* 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

- removed tr1 usage (dropped in C++17)
- moved includes of vector/map/iostream/limits into ts.hpp
- require opencv_test + anonymous namespace (added compile check)
- fixed norm() usage (must be from cvtest::norm for checks) and other conflict functions
- added missing license headers

- CV_L2 -> relative NORM_L2
- eigenEps: 1e-6 ==> 1e-4
- evalEps: 1e-6 ==> 1e-5
- evecEps: 1e-3 ==> 5e-3
- RNG seed: 12345
- drop non-informative legacy test code (ts->printf, etc)

The original template based mat ptr for indexing is not implemented,
add the similar implementation as uchar type, but cast to
user-defined type from the uchar pointer.

Add constructors taking initializer_list for some of OpenCV data types (#9034)

* Add a constructor taking initializer_list for Matx

* Add a constructor taking initializer list for Mat and Mat_

* Add one more method to initialize Mat to the corresponding tutorial

* Add a note how to initialize Matx

* CV_CXX_11->CV_CXX11

Add support for std::array<T, N> (#8535)

* Add support for std::array<T, N>

* Add std::array<Mat, N> support

* Remove UMat constructor with std::array parameter

This test case uses a matrix with more dimensions than columns. Without
the fix in
https://github.com/opencv/opencv/pull/8448/commits/b45e784bebe318826bb48a41023db3fe1660d91e
this crashes with a segmentation fault, hangs or simply fails with wrong
values.

Currently, to select a submatrix of a N-dimensional matrix, it requires
two lines of code while only one line of code is required if using a 2D
array.

I added functionality to be able to select an N-dim submatrix using a
vector list instead of a Range pointer. This allows initializer lists to
be used for a one-line selection.