/Qt 5.11

QGraphicsBlurEffect Class

The QGraphicsBlurEffect class provides a blur effect. More...

Header: #include <QGraphicsBlurEffect>
qmake: QT += widgets
Since: Qt 4.6
Inherits: QGraphicsEffect

Public Types

enum BlurHint { PerformanceHint, QualityHint, AnimationHint }
flags BlurHints


Public Functions

QGraphicsBlurEffect(QObject *parent = nullptr)
virtual ~QGraphicsBlurEffect()
QGraphicsBlurEffect::BlurHints blurHints() const
qreal blurRadius() const

Reimplemented Public Functions

virtual QRectF boundingRectFor(const QRectF &rect) const override

Public Slots

void setBlurHints(QGraphicsBlurEffect::BlurHints hints)
void setBlurRadius(qreal blurRadius)


void blurHintsChanged(QGraphicsBlurEffect::BlurHints hints)
void blurRadiusChanged(qreal radius)

Reimplemented Protected Functions

virtual void draw(QPainter *painter) override

Additional Inherited Members

  • 1 public variable inherited from QObject
  • 10 static public members inherited from QObject
  • 7 protected functions inherited from QGraphicsEffect
  • 9 protected functions inherited from QObject
  • 2 protected variables inherited from QObject

Detailed Description

The QGraphicsBlurEffect class provides a blur effect.

A blur effect blurs the source. This effect is useful for reducing details, such as when the source loses focus and you want to draw attention to other elements. The level of detail can be modified using the setBlurRadius() function. Use setBlurHints() to choose the blur hints.

By default, the blur radius is 5 pixels. The blur radius is specified in device coordinates.

See also QGraphicsDropShadowEffect, QGraphicsColorizeEffect, and QGraphicsOpacityEffect.

Member Type Documentation

enum QGraphicsBlurEffect::BlurHintflags QGraphicsBlurEffect::BlurHints

This enum describes the possible hints that can be used to control how blur effects are applied. The hints might not have an effect in all the paint engines.

Constant Value Description
QGraphicsBlurEffect::PerformanceHint 0x00 Indicates that rendering performance is the most important factor, at the potential cost of lower quality.
QGraphicsBlurEffect::QualityHint 0x01 Indicates that rendering quality is the most important factor, at the potential cost of lower performance.
QGraphicsBlurEffect::AnimationHint 0x02 Indicates that the blur radius is going to be animated, hinting that the implementation can keep a cache of blurred verisons of the source. Do not use this hint if the source is going to be dynamically changing.

This enum was introduced or modified in Qt 4.6.

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

See also blurHints() and setBlurHints().

Property Documentation

blurHints : BlurHints

This property holds the blur hint of the effect.

Use the PerformanceHint hint to say that you want a faster blur, the QualityHint hint to say that you prefer a higher quality blur, or the AnimationHint when you want to animate the blur radius.

By default, the blur hint is PerformanceHint.

Access functions:

QGraphicsBlurEffect::BlurHints blurHints() const
void setBlurHints(QGraphicsBlurEffect::BlurHints hints)

Notifier signal:

void blurHintsChanged(QGraphicsBlurEffect::BlurHints hints)

blurRadius : qreal

This property holds the blur radius of the effect.

Using a smaller radius results in a sharper appearance, whereas a bigger radius results in a more blurred appearance.

By default, the blur radius is 5 pixels.

The radius is given in device coordinates, meaning it is unaffected by scale.

Access functions:

qreal blurRadius() const
void setBlurRadius(qreal blurRadius)

Notifier signal:

void blurRadiusChanged(qreal radius)

Member Function Documentation

QGraphicsBlurEffect::QGraphicsBlurEffect(QObject *parent = nullptr)

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

[virtual] QGraphicsBlurEffect::~QGraphicsBlurEffect()

Destroys the effect.

[signal] void QGraphicsBlurEffect::blurHintsChanged(QGraphicsBlurEffect::BlurHints hints)

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

Note: Notifier signal for property blurHints.

[signal] void QGraphicsBlurEffect::blurRadiusChanged(qreal radius)

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

Note: Notifier signal for property blurRadius.

[override virtual] QRectF QGraphicsBlurEffect::boundingRectFor(const QRectF &rect) const

Reimplemented from QGraphicsEffect::boundingRectFor().

[override virtual protected] void QGraphicsBlurEffect::draw(QPainter *painter)

Reimplemented from QGraphicsEffect::draw().

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Licensed under the GNU Free Documentation License, Version 1.3.