OpenCV：使用VideoCapture类进行视频读取和显示-Mat

#include <stdio.h>
//#include "opencv2/core/core.hpp"
#include "opencv2/features2d/features2d.hpp"
//#include "opencv2/highgui/highgui.hpp"
#include "opencv2/nonfree/nonfree.hpp"
#ifndef _DEBUG
#pragma  comment(lib,"IlmImf.lib")   
#pragma  comment(lib,"libjasper.lib")    
#pragma  comment(lib,"libjpeg.lib")   
#pragma  comment(lib,"libpng.lib")       
#pragma  comment(lib,"libtiff.lib")  
#pragma  comment(lib,"zlib.lib")   
#pragma  comment(lib,"opencv_calib3d2411.lib")
#pragma  comment(lib,"opencv_contrib2411.lib")
#pragma  comment(lib,"opencv_core2411.lib")
#pragma  comment(lib,"opencv_features2d2411.lib")
#pragma  comment(lib,"opencv_flann2411.lib")
#pragma  comment(lib,"opencv_gpu2411.lib")
#pragma  comment(lib,"opencv_highgui2411.lib")
#pragma  comment(lib,"opencv_imgproc2411.lib")
#pragma  comment(lib,"opencv_legacy2411.lib")
#pragma  comment(lib,"opencv_ml2411.lib")
#pragma  comment(lib,"opencv_nonfree2411.lib")
#pragma  comment(lib,"opencv_objdetect2411.lib")
#pragma  comment(lib,"opencv_ocl2411.lib")
#pragma  comment(lib,"opencv_photo2411.lib")
#pragma  comment(lib,"opencv_stitching2411.lib")
#pragma  comment(lib,"opencv_superres2411.lib")
#pragma  comment(lib,"opencv_ts2411.lib")
#pragma  comment(lib,"opencv_video2411.lib")
#pragma  comment(lib,"opencv_videostab2411.lib")
#else
#pragma  comment(lib,"zlibd.lib")
#pragma  comment(lib,"IlmImfd.lib")
#pragma  comment(lib,"libjasperd.lib")
#pragma  comment(lib,"libjpegd.lib")
#pragma  comment(lib,"libpngd.lib")
#pragma  comment(lib,"libtiffd.lib")
#pragma  comment(lib,"opencv_calib3d2411d.lib")
#pragma  comment(lib,"opencv_contrib2411d.lib")
#pragma  comment(lib,"opencv_core2411d.lib")
#pragma  comment(lib,"opencv_features2d2411d.lib")
#pragma  comment(lib,"opencv_flann2411d.lib")
#pragma  comment(lib,"opencv_gpu2411d.lib")
#pragma  comment(lib,"opencv_highgui2411d.lib")
#pragma  comment(lib,"opencv_imgproc2411d.lib")
#pragma  comment(lib,"opencv_legacy2411d.lib")
#pragma  comment(lib,"opencv_ml2411d.lib")
#pragma  comment(lib,"opencv_nonfree2411d.lib")
#pragma  comment(lib,"opencv_objdetect2411d.lib")
#pragma  comment(lib,"opencv_ocl2411d.lib")
#pragma  comment(lib,"opencv_photo2411d.lib")
#pragma  comment(lib,"opencv_stitching2411d.lib")
#pragma  comment(lib,"opencv_superres2411d.lib")
#pragma  comment(lib,"opencv_ts2411d.lib")
#pragma  comment(lib,"opencv_video2411d.lib")
#pragma  comment(lib,"opencv_videostab2411d.lib")
#endif

#pragma comment(lib,"VFW32.lib")
//opencv中出现 runtime error! R6025-pure virtual function call的问题
//使用2.3版本后，常会出现如下图的问题：runtime error! R6025-pure virtual function call
//原因是在创建了新窗口到最后没有销毁掉，添加cvDestroyWindow（“名字”）或cvDestroyAllWindows（）则可
//
//这次通过一个读取视频的综合例子来介绍VideoCapture类的一些基本操作：
#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(int argn,char* argv[])
{
    if(argn==1)
        return 0;
    //打开视频文件：其实就是建立一个VideoCapture结构
    VideoCapture capture(argv[1]); // "D:/videos/PetsD2TeC2.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;
    cout<<"Press Enter to Continue..."<<endl;getchar();
    //设置开始帧()
    //long frameToStart = 300;
    long frameToStart = 1;
    capture.set( CV_CAP_PROP_POS_FRAMES,frameToStart);
    cout<<"从第"<<frameToStart<<"帧开始读"<<endl;
    cout<<"Press Enter to Continue..."<<endl;getchar();
    //设置结束帧
    //int frameToStop = 400;
    int frameToStop = totalFrameNumber-1;

    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(Hz)
    double rate = capture.get(CV_CAP_PROP_FPS);
    cout<<"帧率为:"<<rate<<endl;
    cout<<"Press Enter to Continue..."<<endl;getchar();
    //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:(ms)
    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
        else if( c >= 0)
        {
            waitKey(0);
        }
        currentFrame++;
    }
    //关闭视频文件
    capture.release();    
    cout<<"Press Any Key to Exit!"<<endl;
    waitKey(0);
    return 0;
}
//
//注释比较详尽，相信大家都能看得懂，这里再做几点补充：
//1.由于原视频是网络摄像头采集的，所以有很多雪花点，在这里进行了简单的均值滤波处理。
//2.虽然VideoCapture类中有grab（捕获下一帧）和retrieve（对该帧进行解码）操作，但是直接用read比较简单。
//3.get函数的功能很强大，可以获取关于视频的大部分信息，具体内容可以查看帮助手册。
//4.为了保证视频播放的流畅性，帧与帧之间加入了时延。这个时延是通过帧率算出来的。
//