In support of Optional Known Foreground Mask for Background Subtractors

[D00E]

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I agree to contribute to the project under Apache 2 License.
x To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
x The PR is proposed to the proper branch
x There is a reference to the original bug report and related work
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x Patch to opencv_extra has the same branch name.

The feature is well documented and sample code can be built with the project CMake

Description

Is in support to a pull request regarding, issue opencv/opencv#26476.
Core paired pull request: opencv/opencv#27810
This adds function templates inline with the pure virtual overloaded apply function present for background subtraction. Supporting the build of the pull request:

[asmorkalov]

@D00E Thanks a lot for the refresh. Looks like similar patch should be applied to cudabgsegm and cudalegacy modules too. See CI failures.

[D00E]

Thanks for the heads up, @asmorkalov , this has now been sorted :) should be ready to go

[asmorkalov]

There are CUDA build errors still:

opencv_contrib/modules/cudabgsegm/src/mog.cpp
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp:83:122: error: default argument missing for parameter 5 of 'virtual void {anonymous}::MOGImpl::apply(cv::InputArray, cv::InputArray, cv::OutputArray, double, cv::cuda::Stream&)'
   83 |         void apply(InputArray image, InputArray knownForegroundMask, OutputArray fgmask, double learningRate=-1, Stream& stream) CV_OVERRIDE;
      |                                                                                                                  ~~~~~~~~^~~~~~
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp:83:97: note: ...following parameter 4 which has a default argument
   83 |         void apply(InputArray image, InputArray knownForegroundMask, OutputArray fgmask, double learningRate=-1, Stream& stream) CV_OVERRIDE;
      |                                                                                          ~~~~~~~^~~~~~~~~~~~~~~
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp:137:10: error: 'BackgroundSubtractorMOGImpl' has not been declared
  137 |     void BackgroundSubtractorMOGImpl::apply(InputArray _image, InputArray _knownForegroundMask, OutputArray _fgmask, double learningRate){
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp: In function 'void {anonymous}::apply(cv::InputArray, cv::InputArray, cv::OutputArray, double)':
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp:143:32: error: invalid initialization of reference of type 'cv::OutputArray' {aka 'const cv::_OutputArray&'} from expression of type 'double'
  143 |         apply(_image, _fgmask, learningRate, Stream::Null());
      |                                ^~~~~~~~~~~~
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp:137:109: note: in passing argument 3 of 'void {anonymous}::apply(cv::InputArray, cv::InputArray, cv::OutputArray, double)'
  137 |     void BackgroundSubtractorMOGImpl::apply(InputArray _image, InputArray _knownForegroundMask, OutputArray _fgmask, double learningRate){
      |                                                                                                 ~~~~~~~~~~~~^~~~~~~
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp: At global scope:
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp:146:10: error: 'BackgroundSubtractorMOGImpl' has not been declared
  146 |     void BackgroundSubtractorMOGImpl::apply(InputArray _image, InputArray _knownForegroundMask, OutputArray _fgmask, double learningRate, Stream &stream){
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp: In function 'void {anonymous}::apply(cv::InputArray, cv::InputArray, cv::OutputArray, double, cv::cuda::Stream&)':
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp:152:52: error: no matching function for call to 'apply(const cv::_InputArray&, const cv::_OutputArray&, double&, cv::cuda::Stream&)'
  152 |         apply(_image, _fgmask, learningRate, stream);
      |                                                    ^
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp:137:10: note: candidate: 'void {anonymous}::apply(cv::InputArray, cv::InputArray, cv::OutputArray, double)'
  137 |     void BackgroundSubtractorMOGImpl::apply(InputArray _image, InputArray _knownForegroundMask, OutputArray _fgmask, double learningRate){
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp:137:109: note:   no known conversion for argument 3 from 'double' to 'cv::OutputArray' {aka 'const cv::_OutputArray&'}
  137 |     void BackgroundSubtractorMOGImpl::apply(InputArray _image, InputArray _knownForegroundMask, OutputArray _fgmask, double learningRate){
      |                                                                                                 ~~~~~~~~~~~~^~~~~~~
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp:146:10: note: candidate: 'void {anonymous}::apply(cv::InputArray, cv::InputArray, cv::OutputArray, double, cv::cuda::Stream&)'
  146 |     void BackgroundSubtractorMOGImpl::apply(InputArray _image, InputArray _knownForegroundMask, OutputArray _fgmask, double learningRate, Stream &stream){
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp:146:10: note:   candidate expects 5 arguments, 4 provided
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp: At global scope:
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp:83:14: warning: 'virtual void {anonymous}::MOGImpl::apply(cv::InputArray, cv::InputArray, cv::OutputArray, double, cv::cuda::Stream&)' used but never defined
   83 |         void apply(InputArray image, InputArray knownForegroundMask, OutputArray fgmask, double learningRate=-1, Stream& stream) CV_OVERRIDE;
      |              ^~~~~
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp:82:14: warning: 'virtual void {anonymous}::MOGImpl::apply(cv::InputArray, cv::InputArray, cv::OutputArray, double)' used but never defined
   82 |         void apply(InputArray image, InputArray knownForegroundMask, OutputArray fgmask, double learningRate=-1) CV_OVERRIDE;
      |              ^~~~~
/home/ci/opencv_contrib/modules/cudabgsegm/src/mog.cpp:146:10: warning: 'void {anonymous}::apply(cv::InputArray, cv::InputArray, cv::OutputArray, double, cv::cuda::Stream&)' defined but not used [-Wunused-function]
  146 |     void BackgroundSubtractorMOGImpl::apply(InputArray _image, InputArray _knownForegroundMask, OutputArray _fgmask, double learningRate, Stream &stream){
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~