How to align face images c++ opencv
I am developing a C++ application for face authentication. First, I have to detect the face and pre-process the image.
- For face detection I have used the HaarCascadeClassifier. The problem is that the this tool or this algorithm gives me a facial region detected by a little bit large rectangle that englobes hair and some of the background. Is there a solution to change the dimension of this rectangle? I used "frontalfacecascaadclassifier.xml".
- For face pre-processing i want to do face alignment exactly like this technique. How would I go about accomplishing this?
Answer
Finding the accurate position of the eyes in a given image is far from trivial. The Haar-cascades for finding the eyes in OpenCV produce too many false positive to be useful, moreover this approach won't be robust to image rotation (it may compensate slight rotation though, I don't know the training images). If I were you I'd start a breadth-first search on http://scholar.google.com for relevant papers of this research area.
You'll need a robust head pose estimation for aligning face images. I did some research myself and I think sharing algorithms and code is useful here. The most interesting approaches I have seen are:
Gary B. Huang, Vidit Jain, and Erik Learned-Miller. Unsupervised joint alignment of complex images. International Conference on Computer Vision (ICCV), 2007. (Project page), (PDF Online available), (Source code)
X. Zhu, D. Ramanan. Face Detection, Pose Estimation and Landmark Localization in the Wild Computer Vision and Pattern Recognition (CVPR) Providence, Rhode Island, June 2012. (Project page), (PDF Online available), (Source code)