Qt+OpenCV打开视频文件并在窗口界面上显示

1、新建一个Qt Widgets Application，工程配置文件（.pro文件）内容如下：

#-------------------------------------------------
#
# Project created by QtCreator 2018-12-11T12:57:12
#
#-------------------------------------------------

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = QtOpenVideo
TEMPLATE = app


SOURCES += main.cpp\
        mainwindow.cpp

HEADERS  += mainwindow.h

FORMS    += mainwindow.ui

INCLUDEPATH += C:\opencv\build\include \
               C:\opencv\build\include\opencv \
               C:\opencv\build\include\opencv2

CONFIG(debug, debug|release):
{
LIBS += -LC:\opencv\build\x86\vc11\lib\
-lopencv_calib3d249d \
-lopencv_contrib249d \
-lopencv_core249d \
-lopencv_features2d249d \
-lopencv_flann249d \
-lopencv_gpu249d \
-lopencv_highgui249d \
-lopencv_imgproc249d \
-lopencv_legacy249d \
-lopencv_ml249d \
-lopencv_nonfree249d \
-lopencv_objdetect249d \
-lopencv_ocl249d \
-lopencv_photo249d \
-lopencv_stitching249d \
-lopencv_superres249d \
-lopencv_ts249d \
-lopencv_video249d \
-lopencv_videostab249d
}

2、main.cpp内容如下：

#include "mainwindow.h"
#include 

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

    return a.exec();
}

3、mainwiodow.h内容如下

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include 
#include 
#include 
#include 
#include 

#include 
#include 
#include 
#include 

#include 

using namespace cv;
using namespace std;

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void ReadFrame();

    void on_btnOpenVideo_clicked();

    void on_btnCloseVideo_clicked();

private:
    Ui::MainWindow *ui;
    QTimer *timer;
    VideoCapture capture;
    Mat frame;
    Mat result_frame;
};

#endif // MAINWINDOW_H

4、mainwindow.cpp内容如下

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    timer = new QTimer(this);
    connect(timer,SIGNAL(timeout()),this,SLOT(ReadFrame()));
}

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

void MainWindow::ReadFrame()
{
    if(capture.isOpened())
    {
        capture >> frame;
        if(!frame.empty())
        {
            cvtColor(frame, result_frame, CV_BGR2RGB);     //  OpenCV中Mat读入的图像是BGR格式，要转换为RGB格式
            cv::resize(result_frame, result_frame, Size(640, 480));

            // 将抓取到的帧，转换为QImage格式。QImage::Format_RGB888不同的摄像头用不同的格式。
            QImage image((const uchar*)result_frame.data, result_frame.cols, result_frame.rows, QImage::Format_RGB888);
            ui->label->setPixmap(QPixmap::fromImage(image));    //  将图片显示到label上
            ui->label->resize( ui->label->pixmap()->size());    //  将label控件resize到fame的尺寸
        }
    }

}

void MainWindow::on_btnOpenVideo_clicked()
{
    QString file_name = QFileDialog::getOpenFileName(this, tr("Open Video"), ".", tr("Video File(*.avi *.mp4 *.h264)"));

    capture.open(file_name.toStdString());

    timer->start(25);   //  开始计时，每隔25毫秒更新一次，超时则发出timeout()信号
}

void MainWindow::on_btnCloseVideo_clicked()
{
    timer->stop();      //  停止读取数据。

    //  释放内存；
    capture.release();
    frame.release();
}