OpenCV 如何打开摄像头获取图像数据？

代码运行环境：Qt 5.9.1 msvc2015 32bit OpenCV 3.3.0

#include "include/opencv2/opencv.hpp"

#include <iostream>

using namespace std;

using namespace cv;

int main(int argc, char *argv[])

{

#define 第一个摄像头 0

#define 第二个摄像头 1

#define 第三个摄像头 2

#define Esc 27

//#define 轮廓检测

//#define 灰度化

#define 旋转90度

    cv::VideoCapture capture;

    capture.open(第一个摄像头);

    if(!capture.isOpened())

    {

        return;

    }

    Mat frame;

#ifdef 轮廓检测

    Mat cannyDst;

#endif

//    capture.set(CV_CAP_PROP_FRAME_WIDTH, 1280);

//    capture.set(CV_CAP_PROP_FRAME_HEIGHT, 720);

//    capture.set(CV_CAP_PROP_FRAME_WIDTH, 640);

//    capture.set(CV_CAP_PROP_FRAME_HEIGHT, 480);

//    capture.set(CAP_PROP_FRAME_WIDTH,320);

//    capture.set(CAP_PROP_FRAME_HEIGHT,240);

//    capture.set(CAP_PROP_EXPOSURE,10);//设置曝光率

//    qDebug()<<capture.get(CV_CAP_PROP_FRAME_WIDTH)<<"x"<<capture.get(CV_CAP_PROP_FRAME_HEIGHT);

    double FPS, T;

    while(true)

    {

        T = (double)cv::getTickCount();

        capture >> frame;

        if(frame.empty())

            break;

        T = ((double)cv::getTickCount() - T) / cv::getTickFrequency();

        FPS = 1.0 / T;

        putText(frame, "FPS:"+std::to_string(FPS) , Point(30, 80), FONT_HERSHEY_TRIPLEX ,2, cvScalar(0, 0, 255, 0));//int(frame.rows*0.9)

//        qDebug()<<frame.cols<<"x"<<frame.rows;

#ifdef 旋转90度

        cv::transpose(frame,frame);

        flip(frame, frame, 1);

#endif

#ifdef 灰度化

        cv::cvtColor(frame, frame, CV_BGR2GRAY);

#endif

#ifdef 轮廓检测

    cv::Canny(frame, cannyDst, 0, 50, 3);

    cv::imshow("摄像头",cannyDst);

#else

    cv::imshow("摄像头",frame);

#endif

        //退出循环

        if (waitKey(1) == Esc)

        {

            break;

        }

    }

}