OpenCV：VideoCapture类

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <iostream>

using namespace std;
using namespace cv;

int main()
{
	//打开视频文件：其实就是建立一个VideoCapture结构
	VideoCapture capture("C:/Projects/test.avi");
	//检测是否正常打开:成功打开时，isOpened返回ture
	if(!capture.isOpened())
		cout<<"fail to open!"<<endl;
	//获取整个帧数
	long totalFrameNumber = capture.get(CV_CAP_PROP_FRAME_COUNT);
	cout<<"整个视频共"<<totalFrameNumber<<"帧"<<endl;


	//设置开始帧()
	long frameToStart = 300;
	capture.set( CV_CAP_PROP_POS_FRAMES,frameToStart);
	cout<<"从第"<<frameToStart<<"帧开始读"<<endl;


	//设置结束帧
	int frameToStop = 400;

	if(frameToStop < frameToStart)
	{
		cout<<"结束帧小于开始帧，程序错误，即将退出！"<<endl;
		return -1;
	}
	else
	{
		cout<<"结束帧为：第"<<frameToStop<<"帧"<<endl;
	}


	//获取帧率
	double rate = capture.get(CV_CAP_PROP_FPS);
	cout<<"帧率为:"<<rate<<endl;



	//定义一个用来控制读取视频循环结束的变量
	bool stop = false;
	//承载每一帧的图像
	Mat frame;
	//显示每一帧的窗口
	namedWindow("Extracted frame");
	//两帧间的间隔时间:
	//int delay = 1000/rate;
	int delay = 1000/rate;


	//利用while循环读取帧
	//currentFrame是在循环体中控制读取到指定的帧后循环结束的变量
	long currentFrame = frameToStart;


	//滤波器的核
	int kernel_size = 3;
	Mat kernel = Mat::ones(kernel_size,kernel_size,CV_32F)/(float)(kernel_size*kernel_size);

	while(!stop)
	{
		//读取下一帧
		if(!capture.read(frame))
		{
			cout<<"读取视频失败"<<endl;
			return -1;	
		}
		
		//这里加滤波程序
		imshow("Extracted frame",frame);
		filter2D(frame,frame,-1,kernel);

		imshow("after filter",frame);
		cout<<"正在读取第"<<currentFrame<<"帧"<<endl;
		//waitKey(int delay=0)当delay ≤ 0时会永远等待；当delay>0时会等待delay毫秒
		//当时间结束前没有按键按下时，返回值为-1；否则返回按键


		int c = waitKey(delay);
		//按下ESC或者到达指定的结束帧后退出读取视频
		if((char) c == 27 || currentFrame > frameToStop)
		{
			stop = true;
		}
		//按下按键后会停留在当前帧，等待下一次按键
		if( c >= 0)
		{
			waitKey(0);
		}
		currentFrame++;
	
	}
	//关闭视频文件
	capture.release();
	waitKey(0);
	return 0;
}