查看ncnn中模型为type_layer_name的feature map尺寸
std::string type_layer_name = "face_rpn_type_prob_reshape_stride" + std::to_string(RPNs_[i]);
ex.extract(class_layer_name.c_str(), class_mat);
int width = class_mat.w;
int height = class_mat.h;
原文：https://www.cnblogs.com/shuimuqingyang/p/13984106.html