【QT常用技术讲解】opencv实现指定分辨率打开摄像头

前言

        上一篇分享了QT自带媒体模块实现摄像头的操作，第三方库opencv的图像处理方面，功能更丰富，本篇分享与上一篇相似的功能，不分享其他的图像处理功能。

效果图

功能讲解

摄像头下拉框

void MainWindow::refreshCameraList()
{ui->cameraComboBox->clear();cameraList.clear();// 获取可用摄像头列表QList<QCameraInfo> cameras = QCameraInfo::availableCameras();for(int i = 0; i < cameras.size(); ++i) {cameraList.append(qMakePair(i, cameras[i].description()));ui->cameraComboBox->addItem(cameras[i].description());}
}

在初始化函数中进行调用refreshCameraList()。

分辨率下拉框

使用QT的媒体模块，内容与上一篇一样，代码如下：

QList<QSize> MainWindow::getSupportedResolutions(const QCameraInfo &cameraInfo) {QList<QSize> resolutions;// 创建临时摄像头对象获取分辨率QCamera tempCamera(cameraInfo);// 使用QEventLoop等待摄像头加载完成QEventLoop loop;QTimer timer;timer.setSingleShot(true);QObject::connect(&tempCamera, &QCamera::stateChanged, [&](QCamera::State state) {if (state == QCamera::LoadedState) {loop.quit();}});QObject::connect(&timer, &QTimer::timeout, [&]() {if (loop.isRunning()) {qWarning() << "Camera loading timed out";loop.quit();}});tempCamera.load();timer.start(2000); // 2秒超时loop.exec();if (tempCamera.state() == QCamera::LoadedState) {QList<QCameraViewfinderSettings> supportedSettings = tempCamera.supportedViewfinderSettings();if (supportedSettings.isEmpty()) {qWarning() << "No supported viewfinder settings for camera:" << cameraInfo.description();// 备用方法：尝试通过图像捕获获取分辨率QCameraImageCapture imageCapture(&tempCamera);QList<QSize> imageResolutions = imageCapture.supportedResolutions();if (!imageResolutions.isEmpty()) {resolutions = imageResolutions;} else {// 提供一些常见分辨率作为备选resolutions << QSize(640, 480)<< QSize(800, 600)<< QSize(1024, 768)<< QSize(1280, 720)<< QSize(1920, 1080);}} else {// 提取分辨率并手动去重（不使用QSet）for (const QCameraViewfinderSettings &setting : supportedSettings) {if (setting.resolution().isValid() &&setting.resolution().width() > 0 &&setting.resolution().height() > 0) {// 检查是否已存在相同分辨率bool alreadyExists = false;for (const QSize &existing : resolutions) {if (existing == setting.resolution()) {alreadyExists = true;break;}}if (!alreadyExists) {resolutions.append(setting.resolution());}}}}// 按面积排序（从小到大）std::sort(resolutions.begin(), resolutions.end(), [](const QSize &a, const QSize &b) {return a.width() * a.height() < b.width() * b.height();});} else {qWarning() << "Failed to load camera for resolution detection:" << cameraInfo.description();// 提供一些默认分辨率resolutions << QSize(640, 480)<< QSize(800, 600)<< QSize(1024, 768)<< QSize(1280, 720)<< QSize(1920, 1080);}tempCamera.unload();return resolutions;
}void MainWindow::updateResolutionComboBox(const QCameraInfo &cameraInfo) {qDebug() << "Updating resolution combo box for camera:" << cameraInfo.description();// 在状态栏显示加载信息statusBar()->showMessage("正在获取摄像头支持的分辨率...");// 使用单次定时器异步获取分辨率，避免界面卡顿QTimer::singleShot(100, [this, cameraInfo]() {QList<QSize> resolutions = getSupportedResolutions(cameraInfo);ui->comboBox_resolution->clear();if (resolutions.isEmpty()) {ui->comboBox_resolution->addItem("默认分辨率");statusBar()->showMessage("无法获取分辨率列表，将使用默认分辨率", 3000);} else {for (const QSize &resolution : resolutions) {QString resText = QString("%1 x %2").arg(resolution.width()).arg(resolution.height());ui->comboBox_resolution->addItem(resText, resolution);}statusBar()->showMessage(QString("找到 %1 个支持的分辨率").arg(resolutions.size()), 3000);}});
}void MainWindow::on_camera_selection_changed(int index) {if (index < 0 || index >= cameras.size()) return;ui->comboBox_resolution->clear();// 获取选中的摄像头QCameraInfo cameraInfo = cameras.at(index);updateResolutionComboBox(cameraInfo);
}

在初始化函数中引用

// 如果有摄像头，默认选择第一个并获取其分辨率if (ui->cameraComboBox->count() > 0) {// 手动调用分辨率获取函数，而不是通过信号触发QTimer::singleShot(100, [this]() {int index = ui->cameraComboBox->currentIndex();if (index >= 0 && index < cameras.size()) {QCameraInfo cameraInfo = cameras.at(index);updateResolutionComboBox(cameraInfo);}});}

打开/关闭摄像头

两个功能合并到一个按钮中，适合界面紧凑的布局。

void MainWindow::on_startBtn_clicked()
{if(!capture) {int selectedCam = ui->cameraComboBox->currentIndex();if(selectedCam < 0 || selectedCam >= cameraList.size()) return;std::cout << __LINE__ << "==" << cameraList[selectedCam].first << std::endl;capture = new cv::VideoCapture(cameraList[selectedCam].first);QSize selectedRes = ui->comboBox_resolution->currentData().toSize();// 设置分辨率并检查是否设置成功if(!capture->set(cv::CAP_PROP_FRAME_WIDTH, selectedRes.width()) ||!capture->set(cv::CAP_PROP_FRAME_HEIGHT, selectedRes.height())) {QString showstr=QString("该摄像头不支持分辨率:%1x%2").arg(selectedRes.width()).arg(selectedRes.height());QMessageBox::warning(this, "警告",showstr );delete capture;capture = nullptr;return;}if(!capture->isOpened()) {delete capture;capture = nullptr;return;}timer->start(33); // 30fpsui->startBtn->setText("停止");} else {timer->stop();capture->release();delete capture;capture = nullptr;ui->startBtn->setText("开始");ui->videoLabel->clear();}
}