Methods of description and synthesis of facial expression based on isodensity maps are proposed in this paper. Previous methods have almost been based on the Facial Action Coding System (FACS), which describes facial expression using feature points extracted from facial parts such as eyes, nose, mouth, etc. However it is very difficult to extract such feature points, and to describe changes in density in variations such as wrinkles with feature points only. In contrast to these methods, isodensity maps are adopted in this paper as able to represent density variation of facial images and level planes. To describe facial expression, the physical state of a face must be described, and a tree structure, which is constructed based on the relationship among the loops of isodensity maps, is used for that purpose in this paper. Facial expression is synthesized by the characteristic points which are extracted from level planes. By using this method, changes of expression on the cheek and around the mouth are represented well between successive frames. The prospects of using these proposed methods for describing and synthesizing facial expression are very promising.
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