PyrDown: Fix bug #12961 (#13672)
* Force unaligned pointer and create test
* More cross-platform solution
* MSVC expects a proper order
* Remove useless clang macro
* Return vector of MetaArg instead of MatDesc and fix test with ADL check
* Fix construction of vector
* Change names and tests according to review
Also add GAPI_EXPORTS prefix for two ostream operators
* Add version of descr_of function taking vector of Mat
* Overload descr_of function for cv::Mat
* Add template function instead of copypasting and change tests a little
* __shfl_up_sync with proper mask value for CUDA >= 9
* BlockScanInclusive for CUDA >= 9
* compatible_shfl_up for use in integral.hpp
* Use CLAHE in cudev
* Add tests for BlockScan
* Add Operator override for multi-channel Mat with literal constant.
* simple test
* Operator overloading channel constraint for primitive types
* fix some test for #13586
- Before this PR, following tests failed on some platform.
CUDA_OptFlow/FarnebackOpticalFlow.Accuracy/19
CUDA_OptFlow/FarnebackOpticalFlow.Accuracy/23
- The algorithm now recognizes the OPTFLOW_USE_INITIAL_FLOW flag.
Previously, when the flag was set, it did not use the flow data
passed as input, instead used some garbage data in memory.
- More strict test limit.
Improve stitching detailed (#13584)
* Added block size getter/setters
* Added a bunch of new features to the stitching_detailed sample
* Do not required XFEATURES2D for default use
* Add support for akaze features in stitching_detailed
* Improved sample logs
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