mac xcode工程，新增的opencv头文件报错：
with <opencv2/core/core.hpp> file not found with <angled> include, use "quotes" instead.
解决方法：https://stackoverflow.com/questions/17465902/use-of-external-c-headers-in-objective-c
路径设置好后，还要将：Always Search User Paths设置为Yes：
