* Add HPX backend for OpenCV implementation
Adds hpx backend for cv::parallel_for_() calls respecting the nstripes chunking parameter. C++ code for the backend is added to modules/core/parallel.cpp. Also, the necessary changes to cmake files are introduced.
Backend can operate in 2 versions (selectable by cmake build option WITH_HPX_STARTSTOP): hpx (runtime always on) and hpx_startstop (start and stop the backend for each cv::parallel_for_() call)
* WIP: Conditionally include hpx_main.hpp to tests in core module
Header hpx_main.hpp is included to both core/perf/perf_main.cpp and core/test/test_main.cpp.
The changes to cmake files for linking hpx library to above mentioned test executalbles are proposed but have issues.
* Add coditional iclusion of hpx_main.hpp to cpp cpu modules
* Remove start/stop version of hpx backend
* Add functionality to filter homography decompositions
* documentation + small refactor
* fix comparing int to size_t (compiler warning)
* fix whitespace issues
* clarification of function return values in documentation
* refactor of function parameters and change in loop nesting
* cleanup useless .h, fix size_t to int compare, small refactor
* fix documentation and whitespace
* change output from return value to outputarray parameter
* update function docs to reflect changes in parameters
* whitespace
* failing test
* fixed warnings related to extended initialisers and improper types
* initialize vectors from arrays
* initialize vectors from arrays part 2
* fix whitespace
* fix trailing whitespace
* Include <inttypes.h> in test_filter_homography_decomp.cpp, should fix 'uint8_t' : undeclared identifier error
* updated the test (made it shorter and providing better diagnostic) and significantly improved implementation (get rid of heavy repeated and/or unnecessary operations)
* fixed compile warning; removed trailing whitespace
fixes handling of empty matrices in some functions (#11634)
* a part of PR #11416 by Yuki Takehara
* moved the empty mat check in Mat::copyTo()
* fixed some test failures
* make tmpRow proper size before copyTo to avoid reallocated tmpCol
* do the transposition without creating temporary array; replace TAB with spaces.
* revert the previous commit
