QCamera Class

The QCamera class provides interface for system camera devices.

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Publié le 26 janvier 2024 - Mis à jour le 26 janvier 2024

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QCamera Class▲

Header: QCamera
CMake:

find_package(Qt6 REQUIRED COMPONENTS Multimedia)

target_link_libraries(mytarget PRIVATE Qt6::Multimedia)
qmake: QT += multimedia
Inherited By:
Instantiated By: qml-qtmultimedia-camera.xml
Inherits: QObject
Group: QCamera is part of multimedia, multimedia_camera

Detailed Description▲

QCamera can be used within a QMediaCaptureSession for video recording and image taking.

You can use QCameraDevice to list available cameras and choose which one to use.

Sélectionnez

const QList&lt;QCameraDevice&gt; cameras = QMediaDevices::videoInputs();
for (const QCameraDevice &amp;cameraDevice : cameras) {
    if (cameraDevice.description() == "mycamera")
        camera = new QCamera(cameraDevice);
}

On hardware that supports it, QCamera lets you adjust the focus and zoom. This also includes functionality such as a "Macro" mode for close up work (e.g. reading barcodes, or recognizing letters), or "touch to focus" - indicating an interesting area of the image for the hardware to attempt to focus on.

Sélectionnez

camera-&gt;setFocusPointMode(QCamera::FocusModeManual);
camera-&gt;setCustomFocusPoint(QPointF(0.25f, 0.75f)); // A point near the bottom left, 25% away from the corner, near that shiny vase

The minimumZoomFactor() and maximumZoomFactor() methods provide the range of supported zoom factors. The zoomTo() method allows changing the zoom factor.

Sélectionnez

camera-&gt;setZoomFactor(3.0);

After capturing the raw data for a camera frame, the camera hardware and software performs various image processing tasks to produce the final image. This includes compensating for ambient light color, reducing noise, as well as making some other adjustments to the image.

You can control many of these processing steps through the Camera properties. For example, you can set the white balance (or color temperature) used for processing images:

Sélectionnez

camera-&gt;setWhiteBalanceMode(QCamera::WhiteBalanceFluorescent);

For more information on image processing of camera frames, see Camera Image Processing.

See the camera overview for more information.

Member Type Documentation▲

enum QCamera::Error▲

This enum holds the last error code.

Constant	Value	Description
QCamera::NoError	0	No errors have occurred.
QCamera::CameraError	1	An error has occurred.

enum QCamera::ExposureMode▲

Constant	Value	Description
QCamera::ExposureAuto	0	Automatic mode.
QCamera::ExposureManual	1	Manual mode.
QCamera::ExposurePortrait	2	Portrait exposure mode.
QCamera::ExposureNight	3	Night mode.
QCamera::ExposureSports	4	Spots exposure mode.
QCamera::ExposureSnow	5	Snow exposure mode.
QCamera::ExposureBeach	6	Beach exposure mode.
QCamera::ExposureAction	7	Action mode. Since 5.5
QCamera::ExposureLandscape	8	Landscape mode. Since 5.5
QCamera::ExposureNightPortrait	9	Night portrait mode. Since 5.5
QCamera::ExposureTheatre	10	Theatre mode. Since 5.5
QCamera::ExposureSunset	11	Sunset mode. Since 5.5
QCamera::ExposureSteadyPhoto	12	Steady photo mode. Since 5.5
QCamera::ExposureFireworks	13	Fireworks mode. Since 5.5
QCamera::ExposureParty	14	Party mode. Since 5.5
QCamera::ExposureCandlelight	15	Candlelight mode. Since 5.5
QCamera::ExposureBarcode	16	Barcode mode. Since 5.5

enum QCamera::Feature▲

flags QCamera::Features

Describes a set of features supported by the camera. The returned value can be a combination of:

Constant	Value	Description
QCamera::Feature::ColorTemperature	0x1	The Camera supports setting a custom colorTemperature.
QCamera::Feature::ExposureCompensation	0x2	The Camera supports setting a custom exposureCompensation.
QCamera::Feature::IsoSensitivity	0x4	The Camera supports setting a custom isoSensitivity.
QCamera::Feature::ManualExposureTime	0x8	The Camera supports setting a manual exposure Time.
QCamera::Feature::CustomFocusPoint	0x10	The Camera supports setting a custom focus point.
QCamera::Feature::FocusDistance	0x20	The Camera supports setting the focusDistance property.

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

enum QCamera::FlashMode▲

Constant	Value	Description
QCamera::FlashOff	0	Flash is Off.
QCamera::FlashOn	1	Flash is On.
QCamera::FlashAuto	2	Automatic flash.

enum QCamera::FocusMode▲

Constant	Value	Description
QCamera::FocusModeAuto	0	Continuous auto focus mode.
QCamera::FocusModeAutoNear	1	Continuous auto focus mode on near objects.
QCamera::FocusModeAutoFar	2	Continuous auto focus mode on objects far away.
QCamera::FocusModeHyperfocal	3	Focus to hyperfocal distance, with the maximum depth of field achieved. All objects at distances from half of this distance out to infinity will be acceptably sharp.
QCamera::FocusModeInfinity	4	Focus strictly to infinity.
QCamera::FocusModeManual	5	Manual or fixed focus mode.

enum QCamera::TorchMode▲

Constant	Value	Description
QCamera::TorchOff	0	Torch is Off.
QCamera::TorchOn	1	Torch is On.
QCamera::TorchAuto	2	Automatic torch.

enum QCamera::WhiteBalanceMode▲

Constant	Value	Description
QCamera::WhiteBalanceAuto	0	Auto white balance mode.
QCamera::WhiteBalanceManual	1	Manual white balance. In this mode the white balance should be set with setColorTemperature()
QCamera::WhiteBalanceSunlight	2	Sunlight white balance mode.
QCamera::WhiteBalanceCloudy	3	Cloudy white balance mode.
QCamera::WhiteBalanceShade	4	Shade white balance mode.
QCamera::WhiteBalanceTungsten	5	Tungsten (incandescent) white balance mode.
QCamera::WhiteBalanceFluorescent	6	Fluorescent white balance mode.
QCamera::WhiteBalanceFlash	7	Flash white balance mode.
QCamera::WhiteBalanceSunset	8	Sunset white balance mode.

Property Documentation▲

active : bool▲

Describes whether the camera is currently active.

Access functions:

bool isActive() const
void setActive(bool active)

Notifier signal:

void activeChanged(bool)

cameraDevice : QCameraDevice▲

Returns the QCameraDevice object associated with this camera.

Access functions:

cameraDevice() const
void setCameraDevice(const &cameraDevice)

Notifier signal:

void cameraDeviceChanged()

cameraFormat : QCameraFormat▲

Returns the camera format currently used by the camera.

Access functions:

cameraFormat() const
void setCameraFormat(const &format)

Notifier signal:

void cameraFormatChanged()

colorTemperature : int▲

Returns the current color temperature if the current white balance mode is WhiteBalanceManual. For other modes the return value is undefined.

Access functions:

int colorTemperature() const
void setColorTemperature(int colorTemperature)

Notifier signal:

void colorTemperatureChanged() const

customFocusPoint : QPointF▲

This property represents the position of the custom focus point, in relative frame coordinates: QPointF(0,0) points to the left top frame point, QPointF(0.5,0.5) points to the frame center.

The custom focus point property is used only in FocusPointCustom focus mode.

You can check whether custom focus points are supported by querying supportedFeatures() with the Feature.CustomFocusPoint flag.

Access functions:

customFocusPoint() const
void setCustomFocusPoint(const &point)

Notifier signal:

void customFocusPointChanged()

[read-only] error : const Error▲

Returns the error state of the camera.

Access functions:

error() const

Notifier signal:

void errorChanged()

[read-only] errorString : const QString▲

Returns a human readable string describing a camera's error state.

Access functions:

errorString() const

Notifier signal:

void errorChanged()

exposureCompensation : float▲

Exposure compensation in EV units.

Exposure compensation property allows to adjust the automatically calculated exposure.

Access functions:

float exposureCompensation() const
void setExposureCompensation(float ev)

Notifier signal:

void exposureCompensationChanged(float value)

exposureMode : QCamera::ExposureMode▲

This property holds the exposure mode being used.

Access functions:

exposureMode() const
void setExposureMode( mode)

Notifier signal:

void exposureModeChanged()

[read-only] exposureTime : const float▲

Camera's exposure time in seconds.

Access functions:

float exposureTime() const

Notifier signal:

void exposureTimeChanged(float speed)

flashMode : QCamera::FlashMode▲

This property holds the flash mode being used.

Enables a certain flash mode if the camera has a flash.

Access functions:

flashMode() const
void setFlashMode( mode)

Notifier signal:

void flashModeChanged()

[read-only] flashReady : const bool▲

Indicates if the flash is charged and ready to use.

Access functions:

bool isFlashReady() const

Notifier signal:

void flashReady(bool ready)

focusDistance : float▲

This property return an approximate focus distance of the camera. The value reported is between 0 and 1, 0 being the closest possible focus distance, 1 being as far away as possible. Note that 1 is often, but not always infinity.

Setting the focus distance will be ignored unless the focus mode is set to FocusModeManual.

Access functions:

float focusDistance() const
void setFocusDistance(float d)

Notifier signal:

void focusDistanceChanged(float)

focusMode : FocusMode▲

This property holds the current camera focus mode.

Sets up different focus modes for the camera. All auto focus modes will focus continuously. Locking the focus is possible by setting the focus mode to FocusModeManual. This will keep the current focus and stop any automatic focusing.

Access functions:

focusMode() const
void setFocusMode( mode)

[read-only] focusPoint : const QPointF▲

Returns the point currently used by the auto focus system to focus onto.

Access functions:

focusPoint() const

Notifier signal:

void focusPointChanged()

[read-only] isoSensitivity : const int▲

This property holds the sensor ISO sensitivity.

Describes the ISO sensitivity currently used by the camera.

Access functions:

int isoSensitivity() const

Notifier signal:

void isoSensitivityChanged(int value)

manualExposureTime : int▲

Set the manual exposure time to seconds

Access functions:

float manualExposureTime() const
void setManualExposureTime(float seconds)

Notifier signal:

void manualExposureTimeChanged(float speed)

manualIsoSensitivity : int▲

Describes a manually set ISO sensitivity

Setting this property to -1 (the default), implies that the camera automatically adjusts the ISO sensitivity.

Access functions:

int manualIsoSensitivity() const
void setManualIsoSensitivity(int iso)

Notifier signal:

void manualIsoSensitivityChanged(int)

[read-only] maximumZoomFactor : const float▲

Returns the maximum zoom factor.

This will be 1.0 on cameras that do not support zooming.

Access functions:

float maximumZoomFactor() const

Notifier signal:

void maximumZoomFactorChanged(float)

[read-only] minimumZoomFactor : const float▲

Returns the minimum zoom factor.

This will be 1.0 on cameras that do not support zooming.

Access functions:

float minimumZoomFactor() const

Notifier signal:

void minimumZoomFactorChanged(float)

[read-only] supportedFeatures : const Features▲

Returns the features supported by this camera.

Access functions:

supportedFeatures() const

Notifier signal:

void supportedFeaturesChanged()

torchMode : QCamera::TorchMode▲

This property holds the torch mode being used.

A torch is a continuous source of light. It can be used during video recording in low light conditions. Enabling torch mode will usually override any currently set flash mode.

Access functions:

torchMode() const
void setTorchMode( mode)

Notifier signal:

void torchModeChanged()

whiteBalanceMode : WhiteBalanceMode▲

Returns the white balance mode being used.

Access functions:

whiteBalanceMode() const
void setWhiteBalanceMode( mode)

Notifier signal:

void whiteBalanceModeChanged() const

zoomFactor : float▲

This property holds the current zoom factor.

Gets or sets the current zoom factor. Values will be clamped between minimumZoomFactor and maximumZoomFactor.

Access functions:

float zoomFactor() const
void setZoomFactor(float factor)

Notifier signal:

void zoomFactorChanged(float)

Member Function Documentation▲

[explicit] QCamera::QCamera(QObject *parent = nullptr)▲

Construct a QCamera with a parent.

Selects the default camera on the system if more than one camera is available.

[explicit] QCamera::QCamera(const QCameraDevice &cameraDevice, QObject *parent = nullptr)▲

Construct a QCamera from a camera description cameraDevice and parent.

[explicit] QCamera::QCamera(QCameraDevice::Position position, QObject *parent = nullptr)▲

Construct a QCamera which uses a hardware camera located a the specified position.

For example on a mobile phone it can be used to easily choose between front-facing and back-facing cameras.

If no camera is available at the specified position or if position is QCameraDevice::UnspecifiedPosition, the default camera is used.

[virtual] QCamera::~QCamera()▲

Destroys the camera object.

QMediaCaptureSession *QCamera::captureSession() const▲

Returns the capture session this camera is connected to, or a nullptr if the camera is not connected to a capture session.

use QMediaCaptureSession::setCamera() to connect the camera to a session.

void QCamera::errorOccurred(QCamera::Error error, const QString &errorString)▲

This signal is emitted when error state changes to error. A description of the error is provided as errorString.

void QCamera::exposureCompensationChanged(float value)▲

Signal emitted when the exposure compensation changes to value.

Notifier signal for property exposureCompensation.

float QCamera::exposureTime() const▲

Returns the current exposure time in seconds.

Getter function for property exposureTime.

void QCamera::exposureTimeChanged(float speed)▲

Signals that a camera's exposure speed has changed.

Notifier signal for property exposureTime.

void QCamera::flashReady(bool ready)▲

Signal the flash ready status has changed.

Notifier signal for property flashReady.

void QCamera::focusModeChanged()▲

Signals when the focusMode changes.

bool QCamera::isActive() const▲

Returns true if the camera is currently active.

Getter function for property active.

bool QCamera::isAvailable() const▲

Returns true if the camera can be used.

bool QCamera::isExposureModeSupported(QCamera::ExposureMode mode) const▲

Returns true if the exposure mode is supported.

bool QCamera::isFlashModeSupported(QCamera::FlashMode mode) const▲

Returns true if the flash mode is supported.

bool QCamera::isFlashReady() const▲

Returns true if flash is charged.

Getter function for property flashReady.

bool QCamera::isFocusModeSupported(QCamera::FocusMode mode) const▲

Returns true if the focus mode is supported by the camera.

bool QCamera::isTorchModeSupported(QCamera::TorchMode mode) const▲

Returns true if the torch mode is supported.

bool QCamera::isWhiteBalanceModeSupported(QCamera::WhiteBalanceMode mode) const▲

Returns true if the white balance mode is supported.

void QCamera::isoSensitivityChanged(int value)▲

Signal emitted when sensitivity changes to value.

Notifier signal for property isoSensitivity.

float QCamera::manualExposureTime() const▲

Returns the manual exposure time in seconds, or -1 if the camera is using automatic exposure times.

Getter function for property manualExposureTime.

float QCamera::maximumExposureTime() const▲

The maximal exposure time in seconds.

int QCamera::maximumIsoSensitivity() const▲

Returns the maximum ISO sensitivity supported by the camera.

float QCamera::minimumExposureTime() const▲

The minimal exposure time in seconds.

int QCamera::minimumIsoSensitivity() const▲

Returns the minimum ISO sensitivity supported by the camera.

void QCamera::setActive(bool active)▲

Turns the camera on if active is true, or off if it's false.

Setter function for property active.

void QCamera::setAutoExposureTime()▲

Use automatically calculated exposure time

void QCamera::setAutoIsoSensitivity()▲

Turn on auto sensitivity

void QCamera::setCameraDevice(const QCameraDevice &cameraDevice)▲

Connects the camera object to the physical camera device described by cameraDevice. Using a default constructed QCameraDevice object as cameraDevice will connect the camera to the system default camera device.

Setter function for property cameraDevice.

void QCamera::setCameraFormat(const QCameraFormat &format)▲

Tells the camera to use the format desribed by format. This can be used to define as specific resolution and frame rate to be used for recording and image capture.

Setter function for property cameraFormat.

void QCamera::setColorTemperature(int colorTemperature)▲

Sets manual white balance to colorTemperature. This is used when whiteBalanceMode() is set to WhiteBalanceManual. The units are Kelvin.

Setting a color temperature will only have an effect if WhiteBalanceManual is supported. In this case, setting a temperature greater 0 will automatically set the white balance mode to WhiteBalanceManual. Setting the temperature to 0 will reset the white balance mode to WhiteBalanceAuto.

Setter function for property colorTemperature.

void QCamera::setWhiteBalanceMode(QCamera::WhiteBalanceMode mode)▲

Sets the white balance to mode.

Setter function for property whiteBalanceMode.

void QCamera::setZoomFactor(float factor)▲

Zooms to a zoom factor factor at a rate of 1 factor per second.

Setter function for property zoomFactor.

void QCamera::start()▲

Starts the camera.

Same as setActive(true).

If the camera can't be started for some reason, the errorOccurred() signal is emitted.

void QCamera::stop()▲

Stops the camera. Same as setActive(false).

void QCamera::zoomTo(float factor, float rate)▲

Zooms to a zoom factor factor using rate.

The rate is specified in powers of two per second. At a rate of 1 it would take 2 seconds to go from a zoom factor of 1 to 4.

Using a specific rate is not supported on all cameras. If not supported, zooming will happen as fast as possible.

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QCamera Class

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QCamera Class▲

Detailed Description▲

Member Type Documentation▲

enum QCamera::Error▲

enum QCamera::ExposureMode▲

enum QCamera::Feature▲

enum QCamera::FlashMode▲

enum QCamera::FocusMode▲

enum QCamera::TorchMode▲

enum QCamera::WhiteBalanceMode▲

Property Documentation▲

active : bool▲

cameraDevice : QCameraDevice▲

cameraFormat : QCameraFormat▲

See Also▲

colorTemperature : int▲

customFocusPoint : QPointF▲

[read-only] error : const Error▲

[read-only] errorString : const QString▲

exposureCompensation : float▲

exposureMode : QCamera::ExposureMode▲

See Also▲

[read-only] exposureTime : const float▲

See Also▲

flashMode : QCamera::FlashMode▲

See Also▲

[read-only] flashReady : const bool▲

focusDistance : float▲

focusMode : FocusMode▲

See Also▲

[read-only] focusPoint : const QPointF▲

[read-only] isoSensitivity : const int▲

See Also▲

manualExposureTime : int▲

manualIsoSensitivity : int▲

[read-only] maximumZoomFactor : const float▲

[read-only] minimumZoomFactor : const float▲

[read-only] supportedFeatures : const Features▲

See Also▲

torchMode : QCamera::TorchMode▲

See Also▲

whiteBalanceMode : WhiteBalanceMode▲

zoomFactor : float▲

Member Function Documentation▲

[explicit] QCamera::QCamera(QObject *parent = nullptr)▲

[explicit] QCamera::QCamera(const QCameraDevice &cameraDevice, QObject *parent = nullptr)▲

[explicit] QCamera::QCamera(QCameraDevice::Position position, QObject *parent = nullptr)▲

[virtual] QCamera::~QCamera()▲

QMediaCaptureSession *QCamera::captureSession() const▲

void QCamera::errorOccurred(QCamera::Error error, const QString &errorString)▲

void QCamera::exposureCompensationChanged(float value)▲

float QCamera::exposureTime() const▲

void QCamera::exposureTimeChanged(float speed)▲

void QCamera::flashReady(bool ready)▲

void QCamera::focusModeChanged()▲

bool QCamera::isActive() const▲

bool QCamera::isAvailable() const▲

bool QCamera::isExposureModeSupported(QCamera::ExposureMode mode) const▲

bool QCamera::isFlashModeSupported(QCamera::FlashMode mode) const▲

bool QCamera::isFlashReady() const▲

bool QCamera::isFocusModeSupported(QCamera::FocusMode mode) const▲

bool QCamera::isTorchModeSupported(QCamera::TorchMode mode) const▲

bool QCamera::isWhiteBalanceModeSupported(QCamera::WhiteBalanceMode mode) const▲

void QCamera::isoSensitivityChanged(int value)▲

float QCamera::manualExposureTime() const▲

See Also▲

float QCamera::maximumExposureTime() const▲

int QCamera::maximumIsoSensitivity() const▲

float QCamera::minimumExposureTime() const▲

int QCamera::minimumIsoSensitivity() const▲

void QCamera::setActive(bool active)▲

See Also▲

void QCamera::setAutoExposureTime()▲

void QCamera::setAutoIsoSensitivity()▲

void QCamera::setCameraDevice(const QCameraDevice &cameraDevice)▲

See Also▲