1. A method for determining a lean angle of a body, comprising: obtaining a position of a head; determining a plurality of search region spaced with an angle around the head; calculating a value of an energy function for each search region; and determining the lean angle of a search region with a largest or smallest value of the energy function as the lean angle of the body, wherein calculating the value of the energy function for each search region comprises: calculating a coverage feature indicating an area of foreground pixel in the search region, an edge feature indicating a direction consistency of the search region and the body and a symmetry feature indicating an eudipleural symmetry of image in the search region; and calculating the value of the energy function based on at least one of the coverage feature, the edge feature, and the symmetry feature.