An interface for focus and zoom related camera settings. More...

Inheritance diagram for QCameraFocus:

Public Typedefs
using	FocusModes = QFlags< FocusMode >

Public Types
enum	FocusMode

enum	FocusPointMode

Public Signals
void	digitalZoomChanged (double value)

void	focusZonesChanged ()

void	maximumDigitalZoomChanged (double value)

void	maximumOpticalZoomChanged (double value)

void	opticalZoomChanged (double value)

Public Signals inherited from QObject
void	destroyed (QObject *obj=nullptr)

void	objectNameChanged (const QString &objectName)

Public Methods
QPointF	customFocusPoint () const

double	digitalZoom () const

FocusModes	focusMode () const

QCameraFocus::FocusPointMode	focusPointMode () const

QCameraFocusZoneList	focusZones () const

bool	isAvailable () const

bool	isFocusModeSupported (FocusModes mode) const

bool	isFocusPointModeSupported (QCameraFocus::FocusPointMode mode) const

double	maximumDigitalZoom () const

double	maximumOpticalZoom () const

double	opticalZoom () const

void	setCustomFocusPoint (const QPointF &point)

void	setFocusMode (FocusModes mode)

void	setFocusPointMode (QCameraFocus::FocusPointMode mode)

void	zoomTo (double opticalZoom, double digitalZoom)

Public Methods inherited from QObject
	QObject (QObject *parent=nullptr)

	~QObject ()

bool	blockSignals (bool block)

const QList< QObject * > &	children () const

bool	connect (const QObject *sender, const QString &signalMethod, const QString &location, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

bool	connect (const QObject *sender, const QString &signalMethod, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

bool	disconnect (const QObject *receiver, const QString &slotMethod=QString ()) const

bool	disconnect (const QString &signalMethod, const QString &location, const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const

bool	disconnect (const QString &signalMethod=QString (), const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const

void	dumpObjectInfo ()

void	dumpObjectTree ()

QList< QString >	dynamicPropertyNames () const

virtual bool	event (QEvent *event)

virtual bool	eventFilter (QObject watched, QEvent event)

template<typename T >
T	findChild (const QString &childName=QString ()) const

template<class T >
QList< T >	findChildren (const QRegularExpression &regExp, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

template<class T >
QList< T >	findChildren (const QString &childName=QString (), Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

bool	inherits (const QString &className) const

void	installEventFilter (QObject *filterObj)

bool	isWidgetType () const

bool	isWindowType () const

void	killTimer (int id)

const QMetaObject *	metaObject () const

void	moveToThread (QThread *targetThread)

QString	objectName () const

QObject *	parent () const

template<class T = QVariant>
T	property (const QString &name) const

void	removeEventFilter (QObject *obj)

void	setObjectName (const QString &name)

void	setParent (QObject *parent)

bool	setProperty (const QString &name, const QVariant &value)

bool	signalsBlocked () const

int	startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)

QThread *	thread () const

Properties
	customFocusPoint

	digitalZoom

	focusMode

	focusPointMode

	focusZones

	opticalZoom

Properties inherited from QObject
	objectName

Friends
class	QCamera

Additional Inherited Members
Public Slots inherited from QObject
void	deleteLater ()

Static Public Methods inherited from QObject
static bool	connect (const QObject sender, const QMetaMethod &signalMethod, const QObject receiver, const QMetaMethod &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

static bool	connect (const QObject sender, const QString &signalMethod, const QObject receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection, const QString &location=QString ())

static bool	connect (const QObject sender, const QString &signalMethod, const QString &location, const QObject receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool	connect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver receiver, SlotReturn (SlotClass::slotMethod)(SlotArgs...), Qt::ConnectionType type=Qt::AutoConnection)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool	connect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, T slotLambda, Qt::ConnectionType type=Qt::AutoConnection)

static bool	disconnect (const QObject sender, const QMetaMethod &signalMethod, const QObject receiver, const QMetaMethod &slotMethod)

static bool	disconnect (const QObject sender, const QString &signalMethod, const QObject receiver, const QString &slotMethod)

static bool	disconnect (const QObject sender, const QString &signalMethod, const QString &location, const QObject receiver, const QString &slotMethod)

static bool	disconnect (const QObject sender, std::nullptr_t, const QObject receiver, std::nullptr_t)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver receiver, SlotReturn (SlotClass::slotMethod)(SlotArgs...))

template<class Sender , class SignalClass , class... SignalArgs, class Receiver >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, std::nullptr_t slotMethod=nullptr)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, T slotMethod)

static QMetaObject &	staticMetaObject ()

static QString	tr (const char text, const char comment=nullptr, std::optional< int > numArg=std::optional< int >())

Protected Methods inherited from QObject
virtual void	childEvent (QChildEvent *event)

virtual void	connectNotify (const QMetaMethod &signalMethod) const

virtual void	customEvent (QEvent *event)

virtual void	disconnectNotify (const QMetaMethod &signalMethod) const

bool	isSignalConnected (const QMetaMethod &signalMethod) const

int	receivers (const QString &signal) const

QObject *	sender () const

int	senderSignalIndex () const

virtual void	timerEvent (QTimerEvent *event)

Related Functions inherited from QObject
T	qobject_cast (QObject *object)

	QObjectList

Detailed Description

The QCameraFocus class provides an interface for focus and zoom related camera settings.

On hardware that supports it this class lets you adjust the focus or zoom (both optical and digital). This also includes things like "Macro" mode for close up work (e.g. reading barcodes, or recognizing letters), or "touch to focus" indicating an interesting area of the viewfinder for the hardware to attempt to focus on.

QCameraFocus *focus = camera->focus();
focus->setFocusPointMode(QCameraFocus::FocusPointCustom);
 
// a point near the bottom left, 25% away from the corner, near that shiny vase
focus->setCustomFocusPoint(QPointF(0.25f, 0.75f));

Zooming can be accomplished in a number of ways - usually the more expensive but higher quality approach is an optical zoom, which allows using the full extent of the camera sensor to gather image pixels. In addition it is possible to digitally zoom, which will generally just enlarge part of the sensor frame and throw away other parts. If the camera hardware supports optical zoom this should generally always be used first. The maximumOpticalZoom() method allows this to be checked. The zoomTo() method allows changing both optical and digital zoom at once.

focus->zoomTo(3.0, 4.0); // super zoom

Some notes on autofocus

Some hardware supports a movable focus lens assembly, and typically this hardware also supports automatically focusing via some heuristic. You can influence this via the FocusPointMode setting - typically the center of the frame is brought into focus, but some hardware also supports focusing on any faces detected in the frame, or on a specific point (usually provided by a user in a "touch to focus" scenario).

This class (in combination with QCameraFocusZone) can expose information on what parts of the camera sensor image are in focus or are being used for autofocusing via the focusZones() property.

focus->setFocusPointMode(QCameraFocus::FocusPointAuto);
QList<QCameraFocusZone> zones = focus->focusZones();
 
for (QCameraFocusZone zone : zones) {
    if (zone.status() == QCameraFocusZone::Focused) {
        // Draw a green box at zone.area()
 
    } else if (zone.status() == QCameraFocusZone::Selected) {
        // This area is selected for autofocusing, but is not in focus
        // Draw a yellow box at zone.area()
    }
}

See also: QCameraFocusZone

Member Typedef Documentation

QCameraFocus::FocusModes

Typedef for QFlags<FocusMode>. Refer to QCameraFocus::FocusMode for documentation.

Member Enumeration Documentation

enum QCameraFocus::FocusMode

Indicates how the camera will focus.

Constant	Value	Description
QCameraFocus::ManualFocus	0x1	Manual or fixed focus mode.
QCameraFocus::HyperfocalFocus	0x02	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.
QCameraFocus::InfinityFocus	0x04	Focus strictly to infinity.
QCameraFocus::AutoFocus	0x8	One-shot auto focus mode.
QCameraFocus::ContinuousFocus	0x10	Continuous auto focus mode.
QCameraFocus::MacroFocus	0x20	One shot auto focus to objects close to camera.

enum QCameraFocus::FocusPointMode

Indicates how the camera selects a focus point.

Constant	Value	Description
QCameraFocus::FocusPointAuto	0	Automatically select one or multiple focus points.
QCameraFocus::FocusPointCenter	1	Focus to the frame center.
QCameraFocus::FocusPointFaceDetection	2	Focus on faces in the frame.
QCameraFocus::FocusPointCustom	3	Focus to the custom point, defined by QCameraFocus::customFocusPoint property.

Method Documentation

QPointF QCameraFocus::customFocusPoint ( ) const

Returns the value of the property.

double QCameraFocus::digitalZoom ( ) const

Returns the value of the property.

void QCameraFocus::digitalZoomChanged ( double value )

signal

Signal emitted when digital zoom value changes to new value.

FocusModes QCameraFocus::focusMode ( ) const

Returns the value of the property.

FocusPointMode QCameraFocus::focusPointMode ( ) const

Returns the value of the property.

QCameraFocusZoneList QCameraFocus::focusZones ( ) const

Returns the value of the property.

void QCameraFocus::focusZonesChanged ( )

signal

This signal is emitted when the set of zones used in autofocusing is changed. This can change when a zone is focused or loses focus, or new focus zones have been detected.

bool QCameraFocus::isAvailable ( ) const

Returns true if focus related settings are supported by this camera.

You may need to also check if any specific features are supported.

bool QCameraFocus::isFocusModeSupported ( FocusModes mode ) const

Returns true if the focus mode is supported by camera.

bool QCameraFocus::isFocusPointModeSupported ( QCameraFocus::FocusPointMode mode ) const

Returns true if focus point mode is supported.

double QCameraFocus::maximumDigitalZoom ( ) const

Returns the maximum digital zoom. This will be 1.0 on cameras that do not support digital zoom.

void QCameraFocus::maximumDigitalZoomChanged ( double value )

signal

Signal is emitted when the maximum supported digital value changes. The maximum supported zoom value can depend on other camera settings, like capture mode or resolution.

double QCameraFocus::maximumOpticalZoom ( ) const

Returns the maximum optical zoom. This will be 1.0 on cameras that do not support optical zoom.

void QCameraFocus::maximumOpticalZoomChanged ( double value )

signal

Signal is emitted when the maximum supported optical value changes.

double QCameraFocus::opticalZoom ( ) const

Returns the value of the property.

void QCameraFocus::opticalZoomChanged ( double value )

signal

Signal emitted when optical zoom value changes to new value.

void QCameraFocus::setCustomFocusPoint ( const QPointF & point )

Sets the value of the property to point.

void QCameraFocus::setFocusMode ( FocusModes mode )

Sets the value of the property to mode.

void QCameraFocus::setFocusPointMode ( QCameraFocus::FocusPointMode mode )

Sets the value of the property to mode.

void QCameraFocus::zoomTo	(	double	opticalZoom,
		double	digitalZoom
	)

Set the camera opticalZoom and digitalZoom values. Since there may be a physical component to move, the change in zoom value may not be instantaneous.

Property Documentation

QCameraFocus::customFocusPoint

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.

Properties	Class Methods
read	customFocusPoint
write	setCustomFocusPoint

QCameraFocus::digitalZoom

This property holds the current digital zoom value.

Properties	Class Methods
read	digitalZoom
notify	digitalZoomChanged

QCameraFocus::focusMode

This property holds the current camera focus mode. This controls the way the camera lens assembly is configured.

Properties	Class Methods
read	focusMode
write	setFocusMode

QCameraFocus::focusPointMode

This property holds the current camera focus point selection mode. If the camera focus mode is set to use an autofocusing mode, this property controls the way the camera will select areas of the frame to use for autofocusing.

Properties	Class Methods
read	focusPointMode
write	setFocusPointMode

QCameraFocus::focusZones

Returns the list of active focus zones.

If QCamera::FocusPointAuto or QCamera::FocusPointFaceDetection focus mode is selected this method returns the list of zones the camera is actually focused on. The coordinates system is the same as for custom focus points: QPointF(0,0) points to the left top frame point, QPointF(0.5,0.5) points to the frame center.

Properties	Class Methods
read	focusZones
notify	focusZonesChanged

QCameraFocus::opticalZoom

This property holds the current optical zoom value.

Properties	Class Methods
read	opticalZoom
notify	opticalZoomChanged

Public Typedefs

Public Types

Public Signals

Public Methods

Properties

Friends

Additional Inherited Members

Detailed Description

Some notes on autofocus

Member Typedef Documentation

Member Enumeration Documentation

Method Documentation

Property Documentation