copyright (c) 2020 JiaQi Xu S. Ren, K. He, R. Girshick, and J. Sun, Towards Real-Time Object Detection with Region Proposal Networks," IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 39, no. 6, pp. 1137-1149, 2015. DOI为10.1109/TPAMI.2016.2577031.