FACIAL SOFT BIOMETRICS - Library of Ph.D. Theses | EURASIP

69Chapter 6Soft biometrics for quantifying andpredicting facial aestheticsWith millions of images appearing daily on Facebook, Picasa, Flickr, or on different socialand dating sites, photographs are often seen as the carrier of the first and deciding impression of aperson. At the same time though, human perception of facial aesthetics in images is a priori highlysubjective. The nature of this perception has long been explored separately from psychologicaland photographical points of view, respectively focusing on the properties of the subject and ofthe image. The photographical point of view, corresponding to photo-quality assessment andenhancement, has recently attracted further attention, partly due to the vast amount of digitalimages that are now available, as well as due to the ease with which digital image manipulationcan now be achieved.6.1 Related workThe present work draws from former work in three areas, namely classical facial aesthetics,photo–quality and aesthetics and image processing based face recognition.6.1.1 Facial aestheticsThere are substantial amounts of works, both from psychological and sociological points ofview, studying human perception of facial attractiveness and beauty. Such perception is highlysubjective and is influenced by sociological and cultural factors and furthermore by individualpreferences. Although appreciation of beauty is subjective or in other words "beauty is in the eyeof the beholder", there are some characteristics that scientists have identified to evoke superiorpleasure when looking at. One such characteristic generally associated to beauty and perfection isthe golden ratio ϕ ≈ 1.6180339887. When this divine proportion appears in both nature or art,they are perceived harmonic and aesthetic, see [Doc05]. An attractive human face contains ϕ inseveral proportions, e.g face height / width and face height / location of eyes, see Figure 6.1.A further main characteristic is symmetry, which was evolutionary beneficial in its direct analogyto health [McK06]. Another sign for health and fertility is averageness of facial characteristics,not to be confused with faces of average persons. In [LR90] the authors present a studyshowing that mathematically average faces are considered beautiful. This study though contradictswith other theorems stating that attractiveness implies distinctive facial features. In termsof such features in literature following specifications are associated with beauty: a narrow face,