qt opencv打开摄像头录取视频 截图 的代码

以下是使用Qt和OpenCV打开摄像头，录取视频和截图的代码：

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <opencv2/opencv.hpp>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private slots:
    void on_pushButton_OpenCamera_clicked();
    void on_pushButton_Record_clicked();
    void on_pushButton_Screenshot_clicked();

private:
    Ui::MainWindow *ui;
    cv::VideoCapture cap;
    cv::VideoWriter writer;
    bool isRecording;
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFileDialog>
#include <QMessageBox>

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

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

void MainWindow::on_pushButton_OpenCamera_clicked()
{
    if(!cap.isOpened()){
        cap.open(0);
        if(cap.isOpened()){
            ui->pushButton_OpenCamera->setText("Close Camera");
        }
        else{
            QMessageBox::warning(this, "Error", "Failed to open camera.");
        }
    }
    else{
        cap.release();
        ui->pushButton_OpenCamera->setText("Open Camera");
    }
}

void MainWindow::on_pushButton_Record_clicked()
{
    if(!cap.isOpened()){
        QMessageBox::warning(this, "Error", "Please open camera first.");
        return;
    }

    if(!isRecording){
        QString filename = QFileDialog::getSaveFileName(this, "Save Video", ".", "Videos (*.avi)");
        if(filename.isEmpty()){
            return;
        }
        writer.open(filename.toStdString(), cv::VideoWriter::fourcc('M', 'J', 'P', 'G'), 25.0, cv::Size(cap.get(cv::CAP_PROP_FRAME_WIDTH), cap.get(cv::CAP_PROP_FRAME_HEIGHT)));
        if(!writer.isOpened()){
            QMessageBox::warning(this, "Error", "Failed to save video.");
            return;
        }
        isRecording = true;
        ui->pushButton_Record->setText("Stop Record");
    }
    else{
        writer.release();
        isRecording = false;
        ui->pushButton_Record->setText("Start Record");
    }
}

void MainWindow::on_pushButton_Screenshot_clicked()
{
    if(!cap.isOpened()){
        QMessageBox::warning(this, "Error", "Please open camera first.");
        return;
    }

    cv::Mat frame;
    cap.read(frame);
    if(frame.empty()){
        QMessageBox::warning(this, "Error", "Failed to get frame.");
        return;
    }

    QString filename = QFileDialog::getSaveFileName(this, "Save Screenshot", ".", "Images (*.png *.jpg)");
    if(filename.isEmpty()){
        return;
    }
    cv::imwrite(filename.toStdString(), frame);
}

这个代码利用了Qt的UI设计，包含了三个按钮：打开摄像头，开始/停止录制和截图。打开摄像头使用OpenCV的VideoCapture类，录制视频使用VideoWriter类，截图则是读取一帧图像并使用imwrite函数保存。

希望这个代码对你有所帮助！