Qt 4.8: QGraphicsOpacityEffect Class Reference

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# QGraphicsOpacityEffect Class Reference

The QGraphicsOpacityEffect class provides an opacity effect. More...

     #include <QGraphicsOpacityEffect>

Inherits: QGraphicsEffect.

This class was introduced in Qt 4.6.

- List of all members, including inherited members

## Properties

- opacity : qreal
- opacityMask : QBrush

- 1 property inherited from QGraphicsEffect
- 1 property inherited from QObject

## Public Functions

| QGraphicsOpacityEffect ( QObject * parent = 0 )
| ~QGraphicsOpacityEffect ()
qreal | opacity () const
QBrush | opacityMask () const

- 3 public functions inherited from QGraphicsEffect
- 29 public functions inherited from QObject

## Public Slots

void | setOpacity ( qreal opacity )
void | setOpacityMask ( const QBrush & mask )

- 2 public slots inherited from QGraphicsEffect
- 1 public slot inherited from QObject

## Signals

void | opacityChanged ( qreal opacity )
void | opacityMaskChanged ( const QBrush & mask )

- 1 signal inherited from QGraphicsEffect
- 1 signal inherited from QObject

## Reimplemented Protected Functions

virtual void | draw ( QPainter * painter )

- 7 protected functions inherited from QGraphicsEffect
- 8 protected functions inherited from QObject

### Additional Inherited Members

- 7 static public members inherited from QObject
- 7 protected functions inherited from QGraphicsEffect
- 8 protected functions inherited from QObject

## Detailed Description

The QGraphicsOpacityEffect class provides an opacity effect.

An opacity effect renders the source with an opacity. This effect is useful for making the source semi-transparent, similar to a fade-in/fade-out sequence. The opacity can be modified using the setOpacity() function.

By default, the opacity is 0.7.

See also QGraphicsDropShadowEffect, QGraphicsBlurEffect, and QGraphicsColorizeEffect.

## Property Documentation

### opacity : qreal

This property holds the opacity of the effect.

The value should be in the range of 0.0 to 1.0, where 0.0 is fully transparent and 1.0 is fully opaque.

By default, the opacity is 0.7.

Access functions:

qreal | opacity () const
void | setOpacity ( qreal opacity )

Notifier signal:

void | opacityChanged ( qreal opacity )

See also setOpacityMask().

### opacityMask : QBrush

This property holds the opacity mask of the effect.

An opacity mask allows you apply opacity to portions of an element.

For example:

     ...
     QLinearGradient alphaGradient(rect.topLeft(), rect.bottomLeft());
     alphaGradient.setColorAt(0.0, Qt::transparent);
     alphaGradient.setColorAt(0.5, Qt::black);
     alphaGradient.setColorAt(1.0, Qt::transparent);
     QGraphicsOpacityEffect *effect = new QGraphicsOpacityEffect;
     effect->setOpacityMask(alphaGradient);
     ...

There is no opacity mask by default.

Access functions:

QBrush | opacityMask () const
void | setOpacityMask ( const QBrush & mask )

Notifier signal:

void | opacityMaskChanged ( const QBrush & mask )

See also setOpacity().

## Member Function Documentation

### QGraphicsOpacityEffect::QGraphicsOpacityEffect ( QObject * parent = 0 )

Constructs a new QGraphicsOpacityEffect instance. The parent parameter is passed to QGraphicsEffect's constructor.

### QGraphicsOpacityEffect::~QGraphicsOpacityEffect ()

Destroys the effect.

### void QGraphicsOpacityEffect::draw ( QPainter * painter )`[virtual protected]`

Reimplemented from QGraphicsEffect::draw().

### void QGraphicsOpacityEffect::opacityChanged ( qreal opacity )`[signal]`

This signal is emitted whenever the effect's opacity changes. The opacity parameter holds the effect's new opacity.

### void QGraphicsOpacityEffect::opacityMaskChanged ( const QBrush & mask )`[signal]`

This signal is emitted whenever the effect's opacity mask changes. The mask parameter holds the effect's new opacity mask.