帮我写一个 qt+opencv的录屏软件 分辨率可选的，帧率30，视频格式mp4 的程序代码

好的，以下是程序代码:

#include <QCoreApplication>
#include <QFileDialog>
#include <QVBoxLayout>
#include <QHBoxLayout>
#include <QPushButton>
#include <QLabel>
#include <QMessageBox>
#include <opencv2/opencv.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/videoio.hpp>
#include <iostream>

using namespace cv;
using namespace std;

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    // Create GUI elements
    QWidget *widget = new QWidget;
    QVBoxLayout *layout = new QVBoxLayout;
    QHBoxLayout *buttonLayout = new QHBoxLayout;
    QLabel *resolutionLabel = new QLabel("Resolution:");
    QLabel *fpsLabel = new QLabel("FPS:");
    QComboBox *resolutionComboBox = new QComboBox;
    QComboBox *fpsComboBox = new QComboBox;
    QPushButton *startButton = new QPushButton("Start");
    QPushButton *stopButton = new QPushButton("Stop");

    // Add options to resolution and fps comboboxes
    resolutionComboBox->addItem("320x240");
    resolutionComboBox->addItem("640x480");
    resolutionComboBox->addItem("1280x720");
    resolutionComboBox->addItem("1920x1080");
    fpsComboBox->addItem("15");
    fpsComboBox->addItem("25");
    fpsComboBox->addItem("30");
    fpsComboBox->addItem("60");

    // Add GUI elements to layout
    buttonLayout->addWidget(startButton);
    buttonLayout->addWidget(stopButton);
    layout->addWidget(resolutionLabel);
    layout->addWidget(resolutionComboBox);
    layout->addWidget(fpsLabel);
    layout->addWidget(fpsComboBox);
    layout->addLayout(buttonLayout);
    widget->setLayout(layout);

    // Show the GUI
    widget->show();

    // Set up video capture
    VideoCapture cap(0);
    int frame_width = 0, frame_height = 0;
    double fps = 0;
    VideoWriter writer;

    // Connect start button
    QObject::connect(startButton, &QPushButton::clicked, [&]() {
        // Get selected resolution and fps
        QString resolutionText = resolutionComboBox->currentText();
        QString fpsText = fpsComboBox->currentText();

        // Parse resolution text
        QStringList resolutionList = resolutionText.split("x");
        if (resolutionList.size() != 2) {
            QMessageBox::warning(widget, "Error", "Invalid resolution");
            return;
        }
        frame_width = resolutionList[0].toInt();
        frame_height = resolutionList[1].toInt();

        // Parse fps text
        fps = fpsText.toDouble();
        if (fps <= 0) {
            QMessageBox::warning(widget, "Error", "Invalid FPS");
            return;
        }

        // Open video writer
        QString fileName = QFileDialog::getSaveFileName(widget, "Save video", "", "MP4 (*.mp4)");
        if (fileName.isEmpty()) {
            return;
        }
        writer.open(fileName.toStdString(), cv::VideoWriter::fourcc('m', 'p', '4', 'v'), fps, cv::Size(frame_width, frame_height), true);
        if (!writer.isOpened()) {
            QMessageBox::warning(widget, "Error", "Failed to open video writer");
            return;
        }

        // Start capturing frames
        Mat frame;
        cap.set(CAP_PROP_FRAME_WIDTH, frame_width);
        cap.set(CAP_PROP_FRAME_HEIGHT, frame_height);
        cap.set(CAP_PROP_FPS, fps);
        while (true) {
            cap.read(frame);
            if (frame.empty()) {
                break;
            }
            writer.write(frame);
            imshow("Recording", frame);
            if (waitKey(1) == 27) {
                break;
            }
        }

        // Release resources
        cap.release();
        writer.release();
        destroyAllWindows();
    });

    // Connect stop button
    QObject::connect(stopButton, &QPushButton::clicked, [&]() {
        cap.release();
        writer.release();
        destroyAllWindows();
    });

    return a.exec();
}

希望能够帮助到你！