A person’s lip shape holds much more importance than being a mere facial feature. Older studies of Petajan et al. and more recent works of Daubias , Goecke , and Nakata & Ando , have shown that the movement of the mouth plays a crucial role in speech detection. The Audio Visual Speech Recognition or AVSR and Mobile Phone Visual System for the hearing impaired or MPVS multimedia systems also rely on visual lip reading to function effectively . Further, lip shape and prints can be used as evidence for identifying persons for criminal and forensic purposes. Lip prints of a person remain the same throughout life as is evidenced from the researches of Williams , Sivapathasundharam et al , and Tsuchihashi . Hence, lip recognition methods have become increasingly popular in forensics . Victims as well as suspects can be identified using lip prints taken from objects at the crime scene such as cups, spoons, cigarettes and even clothing . Finally, the classification of lip shapes is needed to fulfil the growing demand for cosmetic lip surgery.
Several lip models have been developed over time, including Yuille, Cohen, and Hallinan , Guiard-Marigny, Adjoudani, and Benoit (1994), Rao and Mersereau (1994) and Hennecke, Prasad and Stork . So and So used the slant of the mouth and the fullness of lips to arrive at nine different mouth or lip shapes. Based on the end-point to mouth slant, lips have been classified into three types, namely: a) Upward, b) Flat, and c) Downward. Further, the thickness or fullness of the lips is also classified into three types, namely: a) heavy upper lip, b) heavy lower lip, and c) equal lips . Table 1 illustrates the different lip shapes thus arrived at:
Table 1
Cootes et al presented a similar model for the detection and tracking of visual speech data . Angular and linear dimensions along with cephalograms have been used in various studies to document lip vermillion qualitative evaluations. Some of the most prominent studies in this area are those of Neger , Holdaway , Lundstrom , Verdonck et al , and Bergman . However, while these studies took into account both hard as well as soft tissues, they failed to classify borders and commissures of lips in addition to differing from the actual shape of the lips. As a result, later researches such as Ricketts , Farkas , and Fernandez-Riviero et al incorporated the use of photographs to identify the lip vermillion shape. The Likert scale has also been used by several researchers to identify malformed lip shapes, especially in the case of cleft lips .
Never the less, all of these studies relied mainly on angular/ linear measurements and hence, several morphologically attributes such as pouts, flatness and flaps of the lips were not taken into consideration. Dr. Caroline Wilkinson developed a virtual facial reconstruction system by using lip and mouth morphology and acknowledges the importance of considering soft and hard tissues for classification . While complete human profiles can be approximately analyzed using the Fourier series , the detection of finer morphologic characteristics by evaluating the overall lip vermillion have not been conducted, although they are vital for orthodontic diagnoses .
While these models have been primarily aimed at speech recognition systems, they did not address a variety of lip shapes that were needed for the more glamorous field of cosmetic surgery. For the longest time, dentists and oral surgeons mainly conducted corrective surgery on patients having cleft lips for example. However, lip shapes soon gained a wider consumer base as people sought to acquire the perfect lips as represented in idealized concepts of beauty propagated by Hollywood. “I want to look like Angelina Jolie”, Dr. Robert Gordon quotes several clients . Popularly known as ‘Dr. Lips’, Gordon is credited with being the first doctor to develop a standardized lip classification template known as Vermillion Dollar Lips or VDL. The VDL identifies six main shapes of lips, namely: a) Classic, b) Rubina, c) Cupid, d) Pearlique, e) Hollywood, and f) Angelic. Gordon calls these shapes as ‘styles’ that women opting for cosmetic lip enhancement can choose from. The various lip styles and their characteristics are illustrated through Figure 1 .
Figure 1: VDL Lip Styles
The importance of lip shape classification has gone beyond cosmetic needs today. As Reddy notes, lip shape recognition and lip print identification have proven to be a cornerstone in the personal identification in forensic science and criminology . Further, the implications of lip classification and vermillion classification towards speech recognition is also great.
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