1）.pro文件

#-------------------------------------------------

#

# Project created by QtCreator 2014-05-18T12:56:52

#

#-------------------------------------------------

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = myQTDemo

TEMPLATE = app

SOURCES += main.cpp\

        mainwindow.cpp

HEADERS  += mainwindow.h

FORMS    += mainwindow.ui

INCLUDEPATH+=d:\opencv249\include\opencv\

                    d:\opencv249\include\opencv2\

                    d:\opencv249\include

LIBS+=d:\opencv249\lib\libopencv_calib3d249.dll.a\

        d:\opencv249\lib\libopencv_contrib249.dll.a\

        d:\opencv249\lib\libopencv_core249.dll.a\

        d:\opencv249\lib\libopencv_features2d249.dll.a\

        d:\opencv249\lib\libopencv_flann249.dll.a\

        d:\opencv249\lib\libopencv_gpu249.dll.a\

        d:\opencv249\lib\libopencv_highgui249.dll.a\

        d:\opencv249\lib\libopencv_imgproc249.dll.a\

        d:\opencv249\lib\libopencv_legacy249.dll.a\

        d:\opencv249\lib\libopencv_ml249.dll.a\

        d:\opencv249\lib\libopencv_objdetect249.dll.a\

        d:\opencv249\lib\libopencv_video249.dll.a

2）.h文件

#ifndef MAINWINDOW_H

#define MAINWINDOW_H

#include <QMainWindow>

#include <opencv2/core/core.hpp>

#include <opencv2/highgui/highgui.hpp>

namespace Ui {

class MainWindow;

}

class MainWindow : public QMainWindow

{

    Q_OBJECT

public:

    explicit MainWindow(QWidget *parent = 0);

    ~MainWindow();

    cv::Mat image,image2;

      QImage img;

private slots:

    void on_pushButton_clicked();

    void on_pushButton_2_clicked();

private:

    Ui::MainWindow *ui;

};

#endif // MAINWINDOW_H

3）.cpp文件

#include "mainwindow.h"

#include "ui_mainwindow.h"

#include "mainwindow.h"

#include "ui_mainwindow.h"

#include <QString>

#include <QFileDialog>

#include <QMessageBox>

#include <opencv/cv.h>

#include <QTextCodec>

using namespace cv;

MainWindow::MainWindow(QWidget *parent) :

    QMainWindow(parent),

    ui(new Ui::MainWindow)

{

    ui->setupUi(this);

}

MainWindow::~MainWindow()

{

    delete ui;

}

void MainWindow::on_pushButton_clicked()

{

    QString filename = QFileDialog::getOpenFileName(this,tr("Open Image"),"",tr("Image File(*.bmp *.jpg *.jpeg *.png)"));

    QTextCodec *code = QTextCodec::codecForName("gb18030");

    std::string name = code->fromUnicode(filename).data();

    image = cv::imread(name);

    if(!image.data)

    {

        QMessageBox msgBox;

        msgBox.setText(tr("image data is null"));

        msgBox.exec();

    }

    else

    {

        cv::cvtColor(image,image2,CV_BGR2RGB);

        img = QImage((const unsigned char*)(image2.data),image.cols,image.rows, image.step,  QImage::Format_RGB888);

        ui->label->clear();

        ui->label->setPixmap(QPixmap::fromImage(img));

        //ui->processPushButton->setEnabled(true);

        ui->label->resize(ui->label->pixmap()->size());

    }

}

void MainWindow::on_pushButton_2_clicked()

{

    // cv::flip(image,image,1);

    Mat gray;

    cvtColor(image,gray,CV_BGR2GRAY);

    // cvtColor(gray,gray,CV_bg)

  //  imshow("li",gray);

    // cv::cvtColor(image,image,CV_BGR2RGB);

    //      img = QImage((const unsigned char*)(image.data),image.cols,image.rows,image.cols*image.channels(),  QImage::Format_RGB888);

    img = QImage((const unsigned char*)(gray.data),gray.cols,gray.rows,gray.step,  QImage::Format_Indexed8);

    ui->label->setPixmap(QPixmap::fromImage(img));

}