第一个m文件：构造、训练BP神经网络并计算其识别率；第二个文件将进行人脸检测。注意：orl人脸数据库需要在网上下载。(The function of the first m file is to construct and train the BP neural network and calculate its recognition rate. The second is the detection of face. Note: the ORL face database needs to be downloaded from the Internet.)