* Fixing a bug in Canny implemetation when Sobel aperture size is 7.

* Fixing the bug in Canny accross variants and in test_canny.cpp

* Replacing a tab with white space

Add ocl version BackgroundSubtractorKNN (#10553)

* Add ocl version bgfg_knn

* Add ocl KNN perf test

* ocl KNN: Avoid unnecessary initializing when non-UMat parameters are used

* video: turn off OpenCL for color KNN on Intel devices

due performance degradation

* video: turn off KNN OpenCL on Apple devices with Intel iGPU

due process freeze during clBuildProgram() call

* Do not build protobuf if dnn is disabled

* Added BUILD_LIST cmake option to the cache

* Moved protobuf to the top level

* Fixed static build

* Fixed world build

* fixup! Fixed world build

* Introduces error throw for line drawn with THICKNESS=0

it fuse ocl kernels to reduce kernel enqueue
Signed-off-by: Li Peng <peng.li@intel.com>

Signed-off-by: Li Peng <peng.li@intel.com>

Signed-off-by: Li Peng <peng.li@intel.com>

- specify PKG_CONFIG_LIBDIR environment variable to new target SYSROOT

* Add a 512 bit codepath to the AVX512 fastConv function

this patch adds a 512 wide codepath to the fastConv() function for
AVX512 use.
The basic idea is to process the first N * 16 elements of the vector
with avx512, and then run the rest of the vector using the traditional
AVX2 codepath.

* dnn: use unaligned AVX512 load (OpenCV aligns data on 32-byte boundary)

* dnn: change "vecsize" condition for AVX512

* dnn: fix indentation