Please enable pre-commit hook to avoid whitespace issues: https://github.com/opencv/opencv/wiki/How_to_contribute#q3-i-was-asked-to-remove-whitespace-issues-how-can-i-do-that

This patch should go into 3.4 branch first. We will merge changes from 3.4 into master regularly (weekly/bi-weekly).

So, please:

• change "base" branch of this PR: master => 3.4 (use "Edit" button near PR title)
• rebase your commits from master onto 3.4 branch. For example:
  git rebase -i --onto upstream/3.4 upstream/master
  (check list of your commits, save and quit (Esc + "wq" + Enter)
  where upstream is configured by following this GitHub guide and fetched (git fetch upstream).
• push rebased commits into source branch of your fork (with --force option)

Note: no needs to re-open PR, apply changes "inplace".

I pushed rebased commits

Thank you. I tried to rebase but got a conflict. I guess something like git cherry-pick would have worked.