Make SparsePyrLKOpticalFlow::buildImagePyramid() public or free

[llschloesser]

System information (version)

• OpenCV => 4.1.2
• Operating System / Platform => Ubuntu 64 Bit
• Compiler => GCC

Detailed description

The overridden virtual function SparsePyrLKOpticalFlow::calc() accepts image pyramids as a possible input. However, there is currently no way to create and subsequently pass image pyramids as arguments because the member function SparsePyrLKOpticalFlow::buildImagePyramid() is protected. SparsePyrLKOpticalFlow::buildImagePyramid() should either be made public or made a free function such that the user can better manage system memory and compute resources and actually pass pyramids to SparsePyrLKOpticalFlow::calc().

Steps to reproduce

N/A

[czgdp1807]

Hi, @llschloesser
Can I work on this issue, if you aren't working on it, since no PR refers it?
As far as I have figured out, SparsePyrLKOpticalFlow doesn't have any(it's own or inherited) buildImagePyramid function. I observed that there is a buildOpticalFlowPyramid in opencv/modules/video/src/lkpyramid.cpp. Are you talking about this function? If so, then probably it's already free.
Otherwise, it would be great if you can direct me to the file where buildImagePyramid is defined/declared. Thanks.

[llschloesser]

@czgdp1807, please do work this issue. This is in reference to the CUDA class cv::cuda::SparsePyrLKOpticalFlow.

See: buildImagePyramid