QCameraImageCapture Class

The QCameraImageCapture class is used for the recording of media content. More...

Header: #include <QCameraImageCapture>
qmake: QT += multimedia
Inherits: QObject and QMediaBindableInterface

Public Types

enum CaptureDestination { CaptureToFile, CaptureToBuffer }
flags CaptureDestinations
enum DriveMode { SingleImageCapture }
enum Error { NoError, NotReadyError, ResourceError, OutOfSpaceError, NotSupportedFeatureError, FormatError }


Public Functions

QCameraImageCapture(QMediaObject *mediaObject, QObject *parent = nullptr)
virtual ~QCameraImageCapture()
QMultimedia::AvailabilityStatus availability() const
QVideoFrame::PixelFormat bufferFormat() const
QCameraImageCapture::CaptureDestinations captureDestination() const
QImageEncoderSettings encodingSettings() const
QCameraImageCapture::Error error() const
QString errorString() const
QString imageCodecDescription(const QString &codec) const
bool isAvailable() const
bool isCaptureDestinationSupported(QCameraImageCapture::CaptureDestinations destination) const
bool isReadyForCapture() const
void setBufferFormat(const QVideoFrame::PixelFormat format)
void setCaptureDestination(QCameraImageCapture::CaptureDestinations destination)
void setEncodingSettings(const QImageEncoderSettings &settings)
QList<QVideoFrame::PixelFormat> supportedBufferFormats() const
QStringList supportedImageCodecs() const
QList<QSize> supportedResolutions(const QImageEncoderSettings &settings = QImageEncoderSettings(), bool *continuous = nullptr) const

Reimplemented Public Functions

virtual QMediaObject *mediaObject() const override

Public Slots

void cancelCapture()
int capture(const QString &file = QString())


void bufferFormatChanged(QVideoFrame::PixelFormat format)
void captureDestinationChanged(QCameraImageCapture::CaptureDestinations destination)
void error(int id, QCameraImageCapture::Error error, const QString &errorString)
void imageAvailable(int id, const QVideoFrame &frame)
void imageCaptured(int id, const QImage &preview)
void imageExposed(int id)
void imageMetadataAvailable(int id, const QString &key, const QVariant &value)
void imageSaved(int id, const QString &fileName)
void readyForCaptureChanged(bool ready)

Reimplemented Protected Functions

virtual bool setMediaObject(QMediaObject *mediaObject) override

Detailed Description

The QCameraImageCapture class is a high level images recording class. It's not intended to be used alone but for accessing the media recording functions of other media objects, like QCamera.

camera = new QCamera;

viewfinder = new QCameraViewfinder();


imageCapture = new QCameraImageCapture(camera);

//on half pressed shutter button

//on shutter button pressed

//on shutter button released

See also QCamera.

Member Type Documentation

enum QCameraImageCapture::CaptureDestination
flags QCameraImageCapture::CaptureDestinations

QCameraImageCapture::CaptureToFile0x01Capture the image to a file.
QCameraImageCapture::CaptureToBuffer0x02Capture the image to a buffer for further processing.

The CaptureDestinations type is a typedef for QFlags<CaptureDestination>. It stores an OR combination of CaptureDestination values.

enum QCameraImageCapture::DriveMode

QCameraImageCapture::SingleImageCapture0Drive mode is capturing a single picture.

enum QCameraImageCapture::Error

QCameraImageCapture::NoError0No Errors.
QCameraImageCapture::NotReadyError1The service is not ready for capture yet.
QCameraImageCapture::ResourceError2Device is not ready or not available.
QCameraImageCapture::OutOfSpaceError3No space left on device.
QCameraImageCapture::NotSupportedFeatureError4Device does not support stillimages capture.
QCameraImageCapture::FormatError5Current format is not supported.

Property Documentation

readyForCapture : const bool

This property holds whether the service is ready to capture a an image immediately.

Calling capture() while readyForCapture is false is not permitted and results in an error.

Access functions:

bool isReadyForCapture() const

Notifier signal:

void readyForCaptureChanged(bool ready)

Member Function Documentation

QCameraImageCapture::QCameraImageCapture(QMediaObject *mediaObject, QObject *parent = nullptr)

Constructs a media recorder which records the media produced by mediaObject.

The parent is passed to QMediaObject.

[signal] void QCameraImageCapture::bufferFormatChanged(QVideoFrame::PixelFormat format)

Signal emitted when the buffer format for the buffer image capture has changed.

[slot] void QCameraImageCapture::cancelCapture()

Cancel incomplete capture requests. Already captured and queused for proicessing images may be discarded.

[slot] int QCameraImageCapture::capture(const QString &file = QString())

Capture the image and save it to file. This operation is asynchronous in majority of cases, followed by signals QCameraImageCapture::imageExposed(), QCameraImageCapture::imageCaptured(), QCameraImageCapture::imageSaved() or QCameraImageCapture::error().

If an empty file is passed, the camera backend choses the default location and naming scheme for photos on the system, if only file name without full path is specified, the image will be saved to the default directory, with a full path reported with imageCaptured() and imageSaved() signals.

QCamera saves all the capture parameters like exposure settings or image processing parameters, so changes to camera parameters after capture() is called do not affect previous capture requests.

QCameraImageCapture::capture returns the capture Id parameter, used with imageExposed(), imageCaptured() and imageSaved() signals.

See also isReadyForCapture().

[signal] void QCameraImageCapture::captureDestinationChanged(QCameraImageCapture::CaptureDestinations destination)

Signal emitted when the capture destination has changed.

[signal] void QCameraImageCapture::error(int id, QCameraImageCapture::Error error, const QString &errorString)

Signals that the capture request id has failed with an error and errorString description.

Note: Signal error is overloaded in this class. To connect to this signal by using the function pointer syntax, Qt provides a convenient helper for obtaining the function pointer as shown in this example:

connect(cameraImageCapture, QOverload<int, QCameraImageCapture::Error, const QString &>::of(&QCameraImageCapture::error),
    [=](int id, QCameraImageCapture::Error error, const QString &errorString){ /* ... */ });

[signal] void QCameraImageCapture::imageAvailable(int id, const QVideoFrame &frame)

Signal emitted when QCameraImageCapture::CaptureToBuffer is set and the frame with request id is available.

[signal] void QCameraImageCapture::imageCaptured(int id, const QImage &preview)

Signal emitted when QAbstractVideoSurface is used as a viewfinder and the frame with request id was captured, but not processed and saved yet. Frame preview can be displayed to user.

[signal] void QCameraImageCapture::imageExposed(int id)

Signal emitted when the frame with request id was exposed.

[signal] void QCameraImageCapture::imageMetadataAvailable(int id, const QString &key, const QVariant &value)

Signals that a metadata for an image with request id is available. Also includes the key and value of the metadata.

This signal is emitted between imageExposed and imageSaved signals.

[signal] void QCameraImageCapture::imageSaved(int id, const QString &fileName)

Signal emitted when QCameraImageCapture::CaptureToFile is set and the frame with request id was saved to fileName.

[signal] void QCameraImageCapture::readyForCaptureChanged(bool ready)

Signals that a camera's ready for capture state has changed.

Note: Notifier signal for property readyForCapture.

[virtual] QCameraImageCapture::~QCameraImageCapture()

Destroys images capture object.

QMultimedia::AvailabilityStatus QCameraImageCapture::availability() const

Returns the availability of this functionality.

QVideoFrame::PixelFormat QCameraImageCapture::bufferFormat() const

Returns the buffer image capture format being used.

See also supportedBufferFormats() and setBufferFormat().

QCameraImageCapture::CaptureDestinations QCameraImageCapture::captureDestination() const

Returns the image capture destination being used.

See also isCaptureDestinationSupported() and setCaptureDestination().

QImageEncoderSettings QCameraImageCapture::encodingSettings() const

Returns the image encoder settings being used.

See also setEncodingSettings().

QCameraImageCapture::Error QCameraImageCapture::error() const

Returns the current error state.

See also errorString().

QString QCameraImageCapture::errorString() const

Returns a string describing the current error state.

See also error().

QString QCameraImageCapture::imageCodecDescription(const QString &codec) const

Returns a description of an image codec.

bool QCameraImageCapture::isAvailable() const

Returns true if the images capture service ready to use.

bool QCameraImageCapture::isCaptureDestinationSupported(QCameraImageCapture::CaptureDestinations destination) const

Returns true if the image capture destination is supported; otherwise returns false.

See also captureDestination() and setCaptureDestination().

[override virtual] QMediaObject *QCameraImageCapture::mediaObject() const

Reimplements: QMediaBindableInterface::mediaObject() const.

See also setMediaObject().

void QCameraImageCapture::setBufferFormat(const QVideoFrame::PixelFormat format)

Sets the buffer image capture format to be used.

See also bufferFormat(), supportedBufferFormats(), and captureDestination().

void QCameraImageCapture::setCaptureDestination(QCameraImageCapture::CaptureDestinations destination)

Sets the capture destination to be used.

See also isCaptureDestinationSupported() and captureDestination().

void QCameraImageCapture::setEncodingSettings(const QImageEncoderSettings &settings)

Sets the image encoding settings.

If some parameters are not specified, or null settings are passed, the encoder choose the default encoding parameters.

See also encodingSettings().

[override virtual protected] bool QCameraImageCapture::setMediaObject(QMediaObject *mediaObject)

Reimplements: QMediaBindableInterface::setMediaObject(QMediaObject *object).

See also mediaObject().

QList<QVideoFrame::PixelFormat> QCameraImageCapture::supportedBufferFormats() const

Returns the list of supported buffer image capture formats.

See also bufferFormat() and setBufferFormat().

QStringList QCameraImageCapture::supportedImageCodecs() const

Returns a list of supported image codecs.

QList<QSize> QCameraImageCapture::supportedResolutions(const QImageEncoderSettings &settings = QImageEncoderSettings(), bool *continuous = nullptr) const

Returns a list of resolutions images can be encoded at.

If non null image settings parameter is passed, the returned list is reduced to resolution supported with partial settings like image codec or quality applied.

If the encoder supports arbitrary resolutions within the supported range, *continuous is set to true, otherwise *continuous is set to false.

See also QImageEncoderSettings::resolution().

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