In my project I need to detect rotated and non-rotated faces in real time. I read original articles and try to use common implementation in matlab and openCV. And as I understood Haar features are not rotation invariant. What should I do for successes detection of rotated faces ? I have some ideas about it. Which is more 'real'?

1. Try to rotate original image with some angle step
2. Train own classifier on rotated examples
3. Use any modified Viola Jones Algorithm from research articles
4. Use another algorithm (like SURF, KLT.)

In my project I need to detect rotated and non-rotated faces in real time. I read original articles and try to use common implementation in matlab and openCV. And as I understood Haar features are not rotation invariant. What should I do for successes detection of rotated faces ? I have some ideas about it. Which is more 'real'?

1. Try to rotate original image with some angle step
2. Train own classifier on rotated examples
3. Use any modified Viola Jones Algorithm from research articles
4. Use another algorithm (like SURF, KLT, Skin based face detection)