Change the interface of face landmark

[tegusi]

The interface is not definite so that python binding won't work.

resolves #1661

This pullrequest changes

landmark detector related files

[alalek]

No need to re-open PRs with the same topic. Just "force" push updated commits into your branch.

[alalek]

const reference for inputs

[alalek]

Thank you!

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

So, please:

• squash commits into one (for easy rebasing between branches)
• 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".

[tegusi]

OK, I have fixed the pr, so I just need to wait for the regular merge?

[LaurentBerger]

Thanks! I clone your repo and build opencv and python binding. first C++ example is good. I try to test python binding but I have got an exception :

OpenCV: terminate handler is called! The last OpenCV error is:
OpenCV(4.1.0-dev) Error: Assertion failed (channels() == CV_MAT_CN(dtype)) in cv::Mat::copyTo, file G:\Lib\opencv\modules\core\src\copy.cpp, line 254

my code is

path_to_opencv_extra ='f:/lib/' 
frame = cv.imread(path_to_opencv_extra + 'opencv_extra/testdata/cv/face/david1.jpg')
if frame is None:
    print("image not found")
    exit()
facemark = cv.face.createFacemarkLBF()
facemark.loadModel("F:/TestDNN/OpenFace/lbfmodel.yaml")
cascade = cv.CascadeClassifier(path_to_opencv_extra + 'opencv_extra/testdata/cv/face/lbpcascade_frontalface_improved.xml')
if cascade.empty() :
    print("cascade not found")
    exit()
faces = cascade.detectMultiScale(frame, 1.05,  2, cv.CASCADE_SCALE_IMAGE, (30, 30))
ok, landmarks = facemark.fit(frame, faces)

[LaurentBerger]

my python binding is here for facemarklbf

[alalek]

Looks good to me 👍

However it would be nice to add some Python tests in a separate PR (misc/python/test/test_facemark.py).