展示如何捕获静止图像或录制视频。
摄像头范例演示如何使用 Qt Multimedia 实现一些基本摄像头功能以获得静止图像和录制带音频的视频剪辑。
要运行范例从 Qt Creator ,打开 Welcome 模式,然后选择范例从 Examples 。更多信息,拜访 构建和运行范例 .
The example implements a
Camera
class that acts as our camera interface. It has a user interface, control functions, setting values and a means of defining the location where the image or video clip is to be saved. It will also store the image and video settings.
The Camera class uses:
The Camera constructor does some basic initialization of the user interface including disabling all buttons by default.
Camera::Camera() : ui(new Ui::Camera) { ui->setupUi(this); m_audioInput.reset(new QAudioInput); m_captureSession.setAudioInput(m_audioInput.get()); // Camera devices: videoDevicesGroup = new QActionGroup(this); videoDevicesGroup->setExclusive(true); updateCameras(); connect(&m_devices, &QMediaDevices::videoInputsChanged, this, &Camera::updateCameras); connect(videoDevicesGroup, &QActionGroup::triggered, this, &Camera::updateCameraDevice); connect(ui->captureWidget, &QTabWidget::currentChanged, this, &Camera::updateCaptureMode); connect(ui->metaDataButton, &QPushButton::clicked, this, &Camera::showMetaDataDialog); connect(ui->exposureCompensation, &QAbstractSlider::valueChanged, this, &Camera::setExposureCompensation); setCamera(QMediaDevices::defaultVideoInput()); } void Camera::setCamera(const QCameraDevice &cameraDevice) { m_camera.reset(new QCamera(cameraDevice)); m_captureSession.setCamera(m_camera.data()); connect(m_camera.data(), &QCamera::activeChanged, this, &Camera::updateCameraActive); connect(m_camera.data(), &QCamera::errorOccurred, this, &Camera::displayCameraError); if (!m_mediaRecorder) { m_mediaRecorder.reset(new QMediaRecorder); m_captureSession.setRecorder(m_mediaRecorder.data()); connect(m_mediaRecorder.data(), &QMediaRecorder::recorderStateChanged, this, &Camera::updateRecorderState); connect(m_mediaRecorder.data(), &QMediaRecorder::durationChanged, this, &Camera::updateRecordTime); connect(m_mediaRecorder.data(), &QMediaRecorder::errorChanged, this, &Camera::displayRecorderError); } if (!m_imageCapture) { m_imageCapture.reset(new QImageCapture); m_captureSession.setImageCapture(m_imageCapture.get()); connect(m_imageCapture.get(), &QImageCapture::readyForCaptureChanged, this, &Camera::readyForCapture); connect(m_imageCapture.get(), &QImageCapture::imageCaptured, this, &Camera::processCapturedImage); connect(m_imageCapture.get(), &QImageCapture::imageSaved, this, &Camera::imageSaved); connect(m_imageCapture.get(), &QImageCapture::errorOccurred, this, &Camera::displayCaptureError); } m_captureSession.setVideoOutput(ui->viewfinder); updateCameraActive(m_camera->isActive()); updateRecorderState(m_mediaRecorder->recorderState()); readyForCapture(m_imageCapture->isReadyForCapture()); updateCaptureMode(); m_camera->start(); } void Camera::keyPressEvent(QKeyEvent *event) { if (event->isAutoRepeat()) return; switch (event->key()) { case Qt::Key_CameraFocus: displayViewfinder(); event->accept(); break; case Qt::Key_Camera: if (m_doImageCapture) { takeImage(); } else { if (m_mediaRecorder->recorderState() == QMediaRecorder::RecordingState) stop(); else record(); } event->accept(); break; default: QMainWindow::keyPressEvent(event); } } void Camera::updateRecordTime() { QString str = tr("Recorded %1 sec").arg(m_mediaRecorder->duration() / 1000); ui->statusbar->showMessage(str); } void Camera::processCapturedImage(int requestId, const QImage &img) { Q_UNUSED(requestId); QImage scaledImage = img.scaled(ui->viewfinder->size(), Qt::KeepAspectRatio, Qt::SmoothTransformation); ui->lastImagePreviewLabel->setPixmap(QPixmap::fromImage(scaledImage)); // Display captured image for 4 seconds. displayCapturedImage(); QTimer::singleShot(4000, this, &Camera::displayViewfinder); } void Camera::configureCaptureSettings() { if (m_doImageCapture) configureImageSettings(); else configureVideoSettings(); } void Camera::configureVideoSettings() { VideoSettings settingsDialog(m_mediaRecorder.data()); if (settingsDialog.exec()) settingsDialog.applySettings(); } void Camera::configureImageSettings() { ImageSettings settingsDialog(m_imageCapture.get()); if (settingsDialog.exec() == QDialog::Accepted) settingsDialog.applyImageSettings(); } void Camera::record() { m_mediaRecorder->record(); updateRecordTime(); } void Camera::pause() { m_mediaRecorder->pause(); } void Camera::stop() { m_mediaRecorder->stop(); } void Camera::setMuted(bool muted) { m_captureSession.audioInput()->setMuted(muted); } void Camera::takeImage() { m_isCapturingImage = true; m_imageCapture->captureToFile(); } void Camera::displayCaptureError(int id, const QImageCapture::Error error, const QString &errorString) { Q_UNUSED(id); Q_UNUSED(error); QMessageBox::warning(this, tr("Image Capture Error"), errorString); m_isCapturingImage = false; } void Camera::startCamera() { m_camera->start(); } void Camera::stopCamera() { m_camera->stop(); } void Camera::updateCaptureMode() { int tabIndex = ui->captureWidget->currentIndex(); m_doImageCapture = (tabIndex == 0); } void Camera::updateCameraActive(bool active) { if (active) { ui->actionStartCamera->setEnabled(false); ui->actionStopCamera->setEnabled(true); ui->captureWidget->setEnabled(true); ui->actionSettings->setEnabled(true); } else { ui->actionStartCamera->setEnabled(true); ui->actionStopCamera->setEnabled(false); ui->captureWidget->setEnabled(false); ui->actionSettings->setEnabled(false); } } void Camera::updateRecorderState(QMediaRecorder::RecorderState state) { switch (state) { case QMediaRecorder::StoppedState: ui->recordButton->setEnabled(true); ui->pauseButton->setEnabled(true); ui->stopButton->setEnabled(false); ui->metaDataButton->setEnabled(true); break; case QMediaRecorder::PausedState: ui->recordButton->setEnabled(true); ui->pauseButton->setEnabled(false); ui->stopButton->setEnabled(true); ui->metaDataButton->setEnabled(false);
It seeks permissions for input device access:
Inputs are assigned:
UI signals are connected to slots that react to the triggering event:
However, most of the work is done when the setCamera() function is called, passing in a QCameraDevice .
setCamera()
sets up various connections between the user interface and the functionality of the Camera class using signals and slots. It also instantiates and initializes the
QCamera
,
QImageCapture
,和
QMediaRecorder
对象。
The still and video recording visual tabs are enabled:
Finally the start () function of the QCamera object is called.
Now that the camera is ready for user commands it waits for a suitable event. Such an event can be a key press of either the Qt::Key_CameraFocus or Qt::Key_Camera buttons on the application window.
Key_CameraFocus will simply display the preview and lock the camera settings.
Key_Camera
will either call
takeImage()
if doing an image capture, or call
record()
or
stop()
(if already recording) on the
QMediaRecorder
instance when recording video.