04-05-2012, 03:24 PM
A Robust Skin Color Based Face Detection Algorithm
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Introduction
Human face perception is currently an active
research area in the computer vision community.
Human face localization and detection is often the
first step in applications such as video surveillance,
human computer interface, face recognition and
image database management. Locating and tracking
human faces is a prerequisite for face recognition
and/or facial expressions analysis, although it
is often assumed that a normalized face image is
available. In order to locate a human face, the system
needs to capture an image using a camera and
a frame-grabber to process the image, search the
image for important features and then use these
features to determine the location of the face.
Color Models for Skin Color Classification
The study on skin color classification has
gained increasing attention in recent years due to
the active research in content-based image representation.
For instance, the ability to locate image
object as a face can be exploited for image coding,
editing, indexing or other user interactivity purposes.
Moreover, face localization also provides a
good stepping stone in facial expression studies.
YCbCr Color Space
YCbCr color space has been defined in response
to increasing demands for digital algorithms
in handling video information, and has since
become a widely used model in a digital video.
It belongs to the family of television transmission
color spaces. The family includes others such
as YUV and YIQ. YCbCr is a digital color system,
while YUV and YIQ are analog spaces for the
respective PAL and NTSC systems. These color
spaces separate RGB (Red-Green-Blue) into luminance
and chrominance information and are
useful in compression applications however the
specification of colors is somewhat unintuitive.
RGB Color Space
The RGB color space consists of the three
additive primaries: red, green and blue. Spectral
components of these colors combine additively to
produce a resultant color.
The RGB model is represented by a 3-dimensional
cube with red green and blue at the corners
on each axis (Figure 1). Black is at the origin. White
is at the opposite end of the cube. The gray scale
follows the line from black to white. In a 24-bit
color graphics system with 8 bits per color channel,
red is (255, 0, 0). On the color cube, it is (1, 0, 0).