使用cocoaPod
pod 'OpenCV'

在使用到的地方 ViewController 改为c++编译模式（后缀变为.mm）

由于 OpenCV 和 UIKit 冲突，要把导入的头文件 放在 文件的最前面

include "opencv2/core.hpp"

include "opencv2/imgproc.hpp"

include "opencv2/imgcodecs.hpp"

include "opencv2/highgui.hpp"

include <opencv2/imgcodecs/ios.h>

include <opencv2/imgproc/imgproc.hpp>

import "ViewController.h"