headEulerAngleY property
The rotation of the face about the vertical axis of the image.
Represented in degrees.
A face with a positive Euler Y angle is turned to the camera's right and to its left.
The Euler Y angle is guaranteed only when using the "accurate" mode setting of the face detector (as opposed to the "fast" mode setting, which takes some shortcuts to make detection faster).
Implementation
final double? headEulerAngleY;