G-API Expose all imgproc operations to python

* Expose imgproc operations

* Fix alignment

G-API Expose all core operations to python

* Expose all G-API core operations to python

* Fix typo in python gapi types test

* GAPI: fix various gapi related typos

Fixes source comments and documentation related to gapi code.

* Fix source typos

* Fixed typos requested

* Follow-up typo fix

GAPI: Move Resize kernel from core to imgproc

* Move Resize kernel from core to imgproc

* Applied style comments

* Adding backward compatibility

* Applied Asya PR

1) Document GFrame/MediaFrame (and also other G-API types)
- Added doxygen comments for GMat, GScalar, GArray<T>, GOpaque classes;
- Documented GFrame and its host-side counterpart MediaFrame;
- Added some more notes to the data type classes.

2) Give @brief descriptions to most of the cv::gapi::* namespaces

3) Make some symbols private
- These structures are mainly internal and shouldn't be used directly

G-API: New python operations API

* Reimplement test using decorators

* Custom python operation API

* Remove wip status

* python: support Python code in bindings (through loader only)

* cleanup, skip tests for Python 2.x (not supported)

* python 2.x can't skip unittest modules

* Clean up

* Clean up

* Fix segfault python3.9
Co-authored-by: NAlexander Alekhin <alexander.a.alekhin@gmail.com>

[G-API] Introduce cv.gin/cv.descr_of for python

* Implement cv.gin/cv.descr_of

* Fix macos build

* Fix gcomputation tests

* Add test

* Add using to a void exceeded length for windows build

* Add using to a void exceeded length for windows build

* Fix comments to review

* Fix comments to review

* Update from latest master

* Avoid graph compilation to obtain in/out info

* Fix indentation

* Fix comments to review

* Avoid using default in switches

* Post output meta for giebackend

[G-API] Multiple return/note fix

* Fix doxygen:
 - multiple return
 - multiple notes

* Addressing comments
 - divide description of split(merge)3/4

[G-API]: kmeans() Standard Kernel Implementation

* cv::gapi::kmeans kernel implementation
 - 4 overloads:
    - standard GMat - for any dimensionality
    - GMat without bestLabels initialization
    - GArray<Point2f> - for 2D
    - GArray<Point3f> - for 3D
 - Accuracy tests:
   - for every input - 2 tests
   1) without initializing. In this case, no comparison with cv::kmeans is done as kmeans uses random auto-initialization
   2) with initialization
   - in both cases, only 1 attempt is done as after first attempt kmeans initializes bestLabels randomly

* Addressing comments
 - bestLabels is returned to its original place among parameters
 - checkVector and isPointsVector functions are merged into one, shared between core.hpp & imgproc.hpp by placing it into gmat.hpp (and implementation - to gmat.cpp)
 - typos corrected

* addressing comments
 - unified names in tests
 - const added
 - typos

* Addressing comments
 - fixed the doc note
 - ddepth -> expectedDepth, `< 0 ` -> `== -1`

* Fix unsupported cases of input Mat
 - supported: multiple channels, reversed width
 - added test cases for those
 - added notes in docs
 - refactored checkVector to return dimentionality along with quantity

* Addressing comments
 - makes chackVector smaller and (maybe) clearer

* Addressing comments

* Addressing comments
 - cv::checkVector -> cv::gapi::detail

* Addressing comments
 - Changed checkVector: returns bool, quantity & dimensionality as references

* Addressing comments
 - Polishing checkVector
 - FIXME added

* Addressing discussion
 - checkVector: added overload, separate two different functionalities
 - depth assert - out of the function

* Addressing comments
 - quantity -> amount, dimensionality -> dim
 - Fix typos

* Addressing comments
 - fix docs
 - use 2 variable's definitions instead of one (for all non-trivial variables)

[G-API] Wrap GArray

* Wrap GArray for output

* Collect in/out info in graph

* Add imgproc tests

* Add cv::Point2f

* Update test_gapi_imgproc.py

* Fix comments to review

[G-API]: fitLine() Standard Kernel Implementation

* fitLine API (Mat, 32S, 32F) (2D, 3D)

* Complete fitLine kernel & accuracy tests
 - initialization for vectors of cv::Point and Mats via vectors added
 - comparison functions for Vec<T, n> added:
   - straight average difference comparison
   - comparison by equasion for 2d line
 - stream overload for cv::DistanceTypes added

* Fix precommit warnings

* Fix docs

* Address comments
Try to fix warning

* Disable warning in tests

[G-API]: findContours() and boundingRect() Standard Kernels Implementation

* Add findContours() standard kernel
 - API and documentation provided:
   - as OpenCV provides two overloads whether to calculate hierarchy or not, but they differ by only the output in sight of G-API, two different G-API functions and kernels implemented
   - G-API Imgproc documentation divided into more parts according to imgproc module parts
   - some typos connected with division into parts corrected
 - `GArray<GArray<U>>` overload for `get_out` function provided to coonvert correctly into `vector<vector<U>>`
 - OCV backend supported
 - accuracy tests provided

* Add boundingRect() standard kernel
     - API and documentation provided:
       - GOpaque<Rect> used as an output
       - as OpenCV provides two possibilities whether to take a gray-scale image or a set of 2D points (`Point2i` or `Point2f` supported), three different overloads of a single G-API function and three kernels implemented
          - for a gray-scale image the overload via `GMat`
          - for a set of `Point2i` - the one via GArray<`Point2i`>
          - set of `Point2f` -> GArray<`Point2f`>
     - OCV backend supported
     - accuracy tests provided
       - comparison function for Rects provided
     - some typos in `gapi_tests_common` corrected

* Fix precommit windows warnings

* - Addressing comments:
   - split tests
 - Fix Windows warnings

* Static_cast for warnings

* - Remove randomness
 - Fix unnecessary precision losses

* - Forgot reference for RNG

* addressing comments

* equalizeHist -> no group

* `const` addedin new functions

* Address suggestions:
 - Hierarchical -> H
 - added cv::GMatDesc::isVectorPoins()
 - added support of giving a set of points to boundingRect()

* Addressing comments
 - IoU comparison function added for Rects
 - isPointsVector moved from a GMatDesc method to a separate function in imgproc.hpp
 - enums instead of int
 - typos corrected

* Addressing comments
 - findContours: Point offset -> GOpaque<Point>
 - removed "straight" comparison for Rects, IoU available only
 - changed vectors initialization -> fix Debug test run
 - Some typos

* added comment for later upgrades

* Fix not to corrupt docs by FIXME

* Addressing commens
 - overload without offset added (as a temporary workaround)
 - checkMetaForFindingContours -> validateFindingContoursMeta
 - added ostream overload for enums used in tests

[G-API]: morphologyEx() Standard Kernel Implementation

* cv::gapi::morphologyEx() kernel
 - implemented (without separate 3x3 version)
 - tests added: check only different operations, not kernels/borders

* Address comments: add `const` where needed

* Replaced fundamental tyeps -> enums where needed
 - added operator<< overload for cv::MorphTypes for tests output

[G-API Wrap streaming

* Wrap streaming

* Fix build

* Add comments

* Remove comment

* Fix comments to review

* Add test for python pull overload

GAPI: Addition new Color conversion kernels to CPU backend.

* Add BGR2RGB kernel to CPU backend

* Add BGR2I420 and RGB2I420 kernels to CPU backend

* Add I4202BGR and I4202RGB kernels to CPU backend

* fix documentation for cv::gapi::blur

* remove dst parameter and move ksize parameter to its correct position

G-API: Laplacian and bilateralFilter standard kernels

* Added Laplacian kernel and tests

* Added: Laplacian kernel, Bilateral kernel (CPU, GPU); Performance and accuracy tests for this kernels

* Changed tolerance for GPU test

* boner

* Some changes with alignment; Tests's parameters are the same as for OCV

* Cut tests

* Compressed tests

* Minor changes (rsrt bb)

* Returned types

Foumula fix 6

Foumula fix 7

     - opencv_gapi module is linked with opencv_video module (optional dependency)
     - kernels added to a new cv::gapi::video namespace and a brand new files created to provide gapi_video environment
     - there are 2 different kernels as G-API should provide GMat AND GArray<GMat> implementation: cv::calcOptFlowPyrLK doesn't calculate pyramids if vector<Mat> is given so just the cast GMat -> GArray<GMat> wouldn't represent all the cv:: functionality
     - tests to check both kernels (based on cv::video tests for cv::calcOpticalFlowPyrLK())
     - tests for internal purposes added
     - vectors<T> comparison in tests implemented
     - new (and old too) common test structures refactored to avoid code copypasting
     - "modules/gapi/test/common/gapi_video_tests_common.hpp" created to share some code snippets between perf and acc tests and avoid code copypasting

- cv::gapi::goodFeaturesToTrack() kernel is implemented
- tests (for exact check with cv::goodFeaturesToTrack() and for internal cases) are implemented
- a custom comparison function for vectors and a custom test fixture implemented
  - some posiible issues as wrong/inexact sorting of two compared vectors are
 not taken into account
- initializations of an input Mat using a picture from opencv_extra implemented (function from gapi_streaming_test used)

* Implement NV12toGray

* Snapshot

* Implement NV12toGray as compound kernel

* Update gapi_imgproc_tests_inl.hpp

* Remove YUV2Gray from public API

* G-API: Addressed various documentation issues

- Fixed various typos and missing references;
- Added brief documentaion on G_TYPED_KERNEL and G_COMPOUND_KERNEL macros;
- Briefly described GComputationT<>;
- Briefly described G-API data objects (in a group section).

* G-API: Some clean-ups in doxygen, also a chapter on Render API

* G-API: Expose more graph compilation arguments in the documentation

* G-API: Address documentation review comments

G-API planar kernels (#14917)

* Added resizeP with tests

* NV12 planar filters

* fix warnings in ResizeP test

* fix out mat ocv warning

* sz_on - > sz rename

* cpu tests new signature

* try to fix resizeP test

* trailing spaces remove

* doxygen doc fixed

* doxygen minor fix

* more doxygen fixes

* Doxygen corrected and extended after review.

Changed quotes to brackets when including public includes (#14741)

G-API: Implement color-convert kernels (#14513)

* Implement color-convert kernels

* Fix rgb2yuv422 reference version

* Fix comments to review

* Restore NV12toBGR in imgproc.hpp

* Add accuracy tests

* Fix doxygen

* Fix ref version yuv422

* Fix warnings

* Fix typos

* Fix simd version yuv422

* Fix warnings

* Fix compile error

* Fix warning

* Remove comment

* Add Sobel kernel which returns both dx and dy

* Splice dx and dy and extend add_border function

Also change some tests parameters

* Add borderValue parameter in test

* Introduces fluid kernel for sobelxy

Adds tests (basic and performance) on new backend

* Introduces BufHelper struct for some arithmetic

GAPI: Add normalize kernel in G-API (#13721)

* Add normalize kernel in G-API

In addition add several tests on new kernel

* Fix indentations and normalize test structure

* Move normalize kernel from imgproc to core

Set default parameter ddepth to -1

* Fix alignment

* Renamed Sobel operator GAPI kernel to match with OpenCV naming rules

* Fixed perf tests

* Small refactoring to check CI issue

* Refactored alignment for kernel wrappers in imgproc.hpp

* G-API Initial code upload

* Update G-API code base to Sep-24-2018

* The majority of OpenCV buildbot problems was addressed

* Update G-API code base to 24-Sep-18 EOD

* G-API code base update 25-Sep-2018

* Linux warnings should be resolved
* Documentation build should become green
* Number of Windows warnings should be reduced

* Update G-API code base to 25-Sep-18 EOD

* ARMv7 build issue should be resolved
* ADE is bumped to latest version and should fix Clang builds for macOS/iOS
* Remaining Windows warnings should be resolved
* New Linux32 / ARMv7 warnings should be resolved

* G-API code base update 25-Sep-2018-EOD2

* Final Windows warnings should be resolved now

* G-API code base update 26-Sep-2018

* Fixed issues with precompiled headers in module and its tests