Bit-exact Nearest Neighbor Resizing

* bit exact resizeNN

* change the value of method enum

* add bitexact-nn to ResizeExactTest

* test to compare with non-exact version

* add perf for bit-exact resizenn

* use cvFloor-equivalent

* 1/3 scaling is not stable for floating calculation

* stricter test

* bugfix: broken data in case of 6 or 12bytes elements

* bugfix: broken data in default pix_size

* stricter threshold

* use raw() for floor

* use double instead of int

* follow code reviews

* fewer cases in perf test

* center pixel convention

ADD yolov4 in models.yml

* Fix ONNX loading in issues opencv#17516, opencv#17531

* Add tests for Linear and Matmul layers

* Disable tests for IE versions lower than 20.4

* Skip unstable tests with OpenCL FP16 on Intel GPU

* Add correct test filtering for OpenCL FP16 tests

[GSoC] Add siamrpnpp.py

* Updated base branch with siamrpnpp.py

* Addition of Parsers

* Merged to using few ONNX files, Changes to Parsers, Links to Repo

* Deleted whitespace

* Adjusting flake8 error

* Fixes according to review

* Fix according to review

* Addition of OpenVINO backends and Computation target devices

* Fix on backend after review

* Fixes after review

* Remove extra white space

* Removed Repeated Varaibles

Add CV_LOG_DEBUG.

 - AVDISCARD_NONINTRA flag is supported only for FFMPEG libraries pack

Use camera intrinsic matrix everywhere. Add cameramatrix, distcoeffs and distcoeffsfisheye macros to avoid copy/paste errors.

* Fixed centering issue with make_cicle_pattern and make_acircle_pattern()

* Fixed issue where asymmetric circles were not at 45 degree angles. Also fixed support for inch measurement by converting parsing to usage of floating points for page size

* Fixed copy-paste error from experimental workspace

- fixes proper initialization of non-trivial variable

- OpenCL kernel cleanup processing is asynchronous and can be called even after forced clFinish()
- buffers are released later in asynchronous mode
- silence these false positive cases for asynchronous cleanup

* add the HH4 mode
* option to display disparity with a color map
* display current settings in the title bar
* don't close app when wanting to take screenshots

reformatting

Improve initialization performance of Brisk

fix formatting

Improve initialization performance of Brisk

formatting

Improve initialization performance of Brisk

make a lookup table for ring

use cosine/sine lookup table for theta in brisk and utilize trig identity

fix ring lookup table

use cosine/sine lookup table for theta in brisk and utilize trig identity

formatting

use cosine/sine lookup table for theta in brisk and utilize trig identity

move scale radius product to ring loop to ensure it's not recomputed for each rot

revert change

move scale radius product to ring loop to ensure it's not recomputed for each rot

remove rings lookup table

move scale radius product to ring loop to ensure it's not recomputed for each rot

fix formatting of for loop

move scale radius product to ring loop to ensure it's not recomputed for each rot

use sine/cosine approximations for brisk lookup table.

add documentation for sine/cosine lookup tables

Improve initialization performance of BRISK

* 8-bit SIFT descriptors

* use clearer parameter

* update docs

* propagate type info

* overload function for avoiding ABI-break

* bugfix: some values are undefined when CV_SIMD is absent