1. A computer-implemented method comprising: obtaining an image of a face of a subject; automatically detecting a symmetry line of the face in the image, wherein the symmetry line intersects at least a mouth region of the face, wherein the symmetry line is a non-vertical line that is tilted by an angle, wherein said automatically detecting comprises: obtaining a pair of points; and minimizing a value of a symmetry operator to determine parameters of the symmetry line, wherein a value of the symmetry operator depends on the angle and a center point, wherein said minimizing is performed with respect to a variety of potential points as the center point, wherein the variety of potential points are points in between a first point of the pair of points and a second point of the pair of points; and automatically locating a facial feature of the face using the symmetry line, wherein said automatically detecting the symmetry line comprises: computing a value of the symmetry operator S(x, y, θ)=∫ (x 1 ,y 1 )ϵΩ |m(x 1 , y 1 )−m(x 2 , y 2 )|, wherein m is an intensity value of the image in a point, wherein (x 2 , y 2 ) is a reflection of a point (x 1 , y 1 ) over the symmetry line, wherein θ is the angle, wherein (x 2 , y 2 ) is determined based on (x 1 , y 1 ) using θ, and wherein Ω is half a circle with center at (x, y) and a radius in accordance with a size of the face.