“…Different strategies have been proposed to generate local parts. According to the level of granularity, part-based target representation can be categorized into three levels: top level (holistic target models [10][11][12]), middle level (superpixels [1,5,3] and patches [13,2,6,9]), and bottom level (keypoints [7,14,15] and pixels [16,17]). Each level target representation has its pros and cons.…”