利用QT中QTimer進行重新整理。

//main.cpp
#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

//mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
     timer   = new QTimer(this);
    QObject::connect(timer,SIGNAL(timeout()),this,SLOT(readFrameSlot()));
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_pushButton_clicked()
{
    capture.open(0);//"1.avi"
       if( !capture.isOpened())
       {
          qDebug()<< "open camera error"<<endl;
          this->close();
       }
       else
       {
        timer->start(33);

       }
}

void MainWindow::on_pushButton_2_clicked()
{
    timer->stop();
    ui->label->setPixmap(QPixmap());
     this->close();
}
void MainWindow::readFrameSlot()
{
    capture >> frame;
    if(!frame.empty())
    {
        img = QImage((const unsigned char*)(frame.data),frame.cols,frame.rows,
                     QImage::Format_RGB888).rgbSwapped();
        img = img.scaled(
                            ui->label->width(),
                            ui->label->height(),
                            Qt::IgnoreAspectRatio,
                            Qt::FastTransformation
                        );//調整圖片大小，使圖片和顯示的label控制元件一樣大
        ui->label->setPixmap(QPixmap::fromImage(img));
    }
}
 

//mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QDialog>
#include <QDebug>
#include <QTimer>
#include <QImage>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
using namespace cv;
namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
    Mat frame;//video frame
      VideoCapture capture;

      QTimer *timer;
      QImage img;

private slots:
      void on_pushButton_clicked();

      void on_pushButton_2_clicked();
      void readFrameSlot();
private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H