Though people are good at face identification,
recognizing human face automatically by computer is
very difficult. Face recognition has been widely
applied in security system, credit-card verification,
and criminal identifications, teleconference and so on.
Face recognition is influenced by many complications,
such as the differences of facial expression, the light
directions of imaging, and the variety of posture, size
and angle. Even to the same people, the images taken
in different surroundings may be unlike. The problem
is so complicated that the achievement in the field of
automatic face recognition by computer is not as
satisfied as the finger prints. Facial feature extraction
has become an important issue in automatic
recognition of human faces. Detecting the basic
feature as eyes, nose and mouth exactly is necessary
for most face recognition methods.