opencv-视频处理--画线（越线、拌线）

视频处理中，经常有做一些行人、车辆或者其它运动物体越线检测，越界检测。

原视频流：

下面用opencv介绍两种方式，画直线（越线、拌线）：

第一种：固定第一帧,或者暂停视频，在固定的一帧中完成画直线的功能

#include<iostream>
using namespace std;

#include<opencv2\core\core.hpp>
#include<opencv2\highgui\highgui.hpp>
#include<opencv2\imgproc\imgproc.hpp>
using namespace cv;

/*--------------------------------定义鼠标事件--画直线--------------------------*/
bool got_line = false;
//全局变量
Point beginPoint=Point(0,0);//--注意这个有一个初始化的(0,0)
bool got_beigin_point = false;
Point endPoint=Point(0,0);//--注意这个有一个自己默认的初始化(0,0)
void mouseLineHandler(int event, int x, int y, int flags, void *param)
{
	switch(event)
	{
	case CV_EVENT_LBUTTONDOWN:
		beginPoint = Point(x,y);
		endPoint = beginPoint;
		got_beigin_point = true;
		break;
	case   CV_EVENT_MOUSEMOVE:
		if(got_beigin_point)
		{
			endPoint = Point(x,y);
		}
		break;
	case CV_EVENT_LBUTTONUP:
		got_line = true;
		endPoint = Point(x,y);
		break;
	default:
		break;
	}
}
/*---------------------------------------------------------------------------------------------*/
 int main(int argc,char*argv[])
 {
	 //读取视频
	 VideoCapture video(argv[1]);

	 //判断视频是否打开
	 if( !video.isOpened())
		 return 0;

	 //视频中的第一帧
	 Mat firstFrame;

	 Mat frame;

	 //读取视频的第一帧
	 video>>frame;

	 //复制到firstFrame中
	 frame.copyTo(firstFrame);

	 //register
	 namedWindow("video",1);
	 setMouseCallback("video",mouseLineHandler,NULL);

	 //画线
	 while(!got_line)
	 {
		 firstFrame.copyTo(frame);
		 line(frame,beginPoint,endPoint,Scalar(255,0,0),2);
		 imshow("video",frame);
		 if(waitKey(50) == ‘q‘)//---------很重要
			 break;
	 }
	 //remove callback
	 setMouseCallback("video",NULL,NULL);

	 //视频继续
	 for(;;)
	 {
		  video>>frame;
		  line(frame,beginPoint,endPoint,Scalar(255,255,0),2);
		  imshow("video",frame);
		  if(waitKey(33) == ‘q‘)
			  break;
	 }
	 return 0;
 }
 /*-----------------------------------------------------------------*/

【结果】：最好亲手试一下，才能看出区别

第二种：不影响视频播放的情况下，完成画直线的功能

#include<iostream>
using namespace std;

#include<opencv2\core\core.hpp>
#include<opencv2\highgui\highgui.hpp>
#include<opencv2\imgproc\imgproc.hpp>
using namespace cv;

/*--------------------------------定义鼠标事件--画直线--------------------------*/
bool got_line = false;
//全局变量
Point beginPoint=Point(0,0);//--注意这个有一个初始化的(0,0)
bool got_beigin_point = false;
Point endPoint=Point(0,0);//--注意这个有一个自己默认的初始化(0,0)
void mouseLineHandler(int event, int x, int y, int flags, void *param)
{
	switch(event)
	{
	case CV_EVENT_LBUTTONDOWN:
		beginPoint = Point(x,y);
		endPoint = beginPoint;
		got_beigin_point = true;
		break;
	case   CV_EVENT_MOUSEMOVE:
		if(got_beigin_point)
		{
			endPoint = Point(x,y);
		}
		break;
	case CV_EVENT_LBUTTONUP:
		got_line = true;
		endPoint = Point(x,y);
		break;
	default:
		break;
	}
}
/*---------------------------------------------------------------------------------------------*/
 int main(int argc,char*argv[])
 {
	 //读取视频
	 VideoCapture video(argv[1]);

	 //判断视频是否打开
	 if( !video.isOpened())
		 return 0;

	 //视频帧
	 Mat frame;

	 //register
	 namedWindow("video",1);
	 setMouseCallback("video",mouseLineHandler,NULL);

	 //画直线
	 for(;;)
	 {
		 video>>frame;
		  line(frame,beginPoint,endPoint,Scalar(0,255,255),2);
		   imshow("video",frame);
		   if(got_line)
			   break;
		   if(waitKey(50)==‘q‘)
			   break;
	 }

	 //remove callback
	 setMouseCallback("video",NULL,NULL);

	 //视频继续
	 for(;;)
	 {
		  video>>frame;
		  line(frame,beginPoint,endPoint,Scalar(0,255,255),2);
		  imshow("video",frame);
		  if(waitKey(33) == ‘q‘)
			  break;
	 }
	 return 0;
 }
 /*-----------------------------------------------------------------*/

【结果】：