QBrush Class Reference
[QtGui module]

Detailed Description

The QBrush class defines the fill pattern of shapes drawn by QPainter.

A brush has a style, a color, a gradient and a texture.

The brush style() defines the fill pattern using the Qt::BrushStyle enum. The default brush style is Qt::NoBrush (depending on how you construct a brush). This style tells the painter to not fill shapes. The standard style for filling is Qt::SolidPattern. The style can be set when the brush is created using the appropriate constructor, and in addition the setStyle() function provides means for altering the style once the brush is constructed.

The brush color() defines the color of the fill pattern. The color can either be one of Qt's predefined colors, Qt::GlobalColor, or any other custom QColor. The currently set color can be retrieved and altered using the color() and setColor() functions, respectively.

The gradient() defines the gradient fill used when the current style is either Qt::LinearGradientPattern, Qt::RadialGradientPattern or Qt::ConicalGradientPattern. Gradient brushes are created by giving a QGradient as a constructor argument when creating the QBrush. Qt provides three different gradients: QLinearGradient, QConicalGradient, and QRadialGradient - all of which inherit QGradient.

     QRadialGradient gradient(50, 50, 50, 50, 50);
     gradient.setColorAt(0, QColor::fromRgbF(0, 1, 0, 1));
     gradient.setColorAt(1, QColor::fromRgbF(0, 0, 0, 0));

     QBrush brush(gradient);

The texture() defines the pixmap used when the current style is Qt::TexturePattern. You can create a brush with a texture by providing the pixmap when the brush is created or by using setTexture().

Note that applying setTexture() makes style() == Qt::TexturePattern, regardless of previous style settings. Also, calling setColor() will not make a difference if the style is a gradient. The same is the case if the style is Qt::TexturePattern style unless the current texture is a QBitmap.

The isOpaque() function returns true if the brush is fully opaque otherwise false. A brush is considered opaque if:

• The alpha component of the color() is 255.
• Its texture() does not have an alpha channel and is not a QBitmap.
• The colors in the gradient() all have an alpha component that is 255.

To specify the style and color of lines and outlines, use the QPainter's pen combined with Qt::PenStyle and Qt::GlobalColor: QPainter painter(this); painter.setBrush(Qt::cyan); painter.setPen(Qt::darkCyan); painter.drawRect(0, 0, 100,100); painter.setBrush(Qt::NoBrush); painter.setPen(Qt::darkGreen); painter.drawRect(40, 40, 100, 100); Note that, by default, QPainter renders the outline (using the currently set pen) when drawing shapes. Use painter.setPen(Qt::NoPen) to disable this behavior.

For more information about painting in general, see The Paint System documentation.

See also Qt::BrushStyle, QPainter, and QColor.

Member Function Documentation

QBrush::QBrush ()

Constructs a default black brush with the style Qt::NoBrush (i.e. this brush will not fill shapes).

QBrush::QBrush ( Qt::BrushStyle style )

Constructs a black brush with the given style.

See also setStyle().

QBrush::QBrush ( const QColor & color, Qt::BrushStyle style = Qt::SolidPattern )

Constructs a brush with the given color and style.

See also setColor() and setStyle().

QBrush::QBrush ( Qt::GlobalColor color, Qt::BrushStyle style = Qt::SolidPattern )

Constructs a brush with the given color and style.

See also setColor() and setStyle().

QBrush::QBrush ( const QColor & color, const QPixmap & pixmap )

Constructs a brush with the given color and the custom pattern stored in pixmap.

The style is set to Qt::TexturePattern. The color will only have an effect for QBitmaps.

See also setColor() and setPixmap().

QBrush::QBrush ( Qt::GlobalColor color, const QPixmap & pixmap )

Constructs a brush with the given color and the custom pattern stored in pixmap.

The style is set to Qt::TexturePattern. The color will only have an effect for QBitmaps.

See also setColor() and setPixmap().

QBrush::QBrush ( const QPixmap & pixmap )

Constructs a brush with a black color and a texture set to the given pixmap. The style is set to Qt::TexturePattern.

See also setTexture().

QBrush::QBrush ( const QImage & image )

Constructs a brush with a black color and a texture set to the given image. The style is set to Qt::TexturePattern.

See also setTextureImage().

QBrush::QBrush ( const QBrush & other )

Constructs a copy of other.

QBrush::QBrush ( const QGradient & gradient )

Constructs a brush based on the given gradient.

The brush style is set to the corresponding gradient style (either Qt::LinearGradientPattern, Qt::RadialGradientPattern or Qt::ConicalGradientPattern).

QBrush::~QBrush ()

Destroys the brush.

const QColor & QBrush::color () const

Returns the brush color.

See also setColor().

const QGradient * QBrush::gradient () const

Returns the gradient describing this brush.

bool QBrush::isOpaque () const

Returns true if the brush is fully opaque otherwise false. A brush is considered opaque if:

• The alpha component of the color() is 255.
• Its texture() does not have an alpha channel and is not a QBitmap.
• The colors in the gradient() all have an alpha component that is 255.

const QMatrix & QBrush::matrix () const

Returns the current transformation matrix for the brush.

This function was introduced in Qt 4.2.

See also setMatrix().

void QBrush::setColor ( const QColor & color )

Sets the brush color to the given color.

Note that calling setColor() will not make a difference if the style is a gradient. The same is the case if the style is Qt::TexturePattern style unless the current texture is a QBitmap.

See also color().

void QBrush::setColor ( Qt::GlobalColor color )

This is an overloaded member function, provided for convenience.

Sets the brush color to the given color.

void QBrush::setMatrix ( const QMatrix & matrix )

Sets matrix as an explicit transformation matrix on the current brush. The brush transformation matrix is merged with QPainter transformation matrix to produce the final result.

This function was introduced in Qt 4.2.

See also matrix().

void QBrush::setStyle ( Qt::BrushStyle style )

Sets the brush style to style.

See also style().

void QBrush::setTexture ( const QPixmap & pixmap )

Sets the brush pixmap to pixmap. The style is set to Qt::TexturePattern.

The current brush color will only have an effect for monochrome pixmaps, i.e. for QPixmap::depth() == 1 (QBitmaps).

See also texture().

void QBrush::setTextureImage ( const QImage & image )

Sets the brush image to image. The style is set to Qt::TexturePattern.

Note the current brush color will not have any affect on monochrome images, as opposed to calling setTexture() with a QBitmap. If you want to change the color of monochrome image brushes, either convert the image to QBitmap with QBitmap::fromImage() and set the resulting QBitmap as a texture, or change the entries in the color table for the image.

This function was introduced in Qt 4.2.

See also textureImage() and setTexture().

void QBrush::setTransform ( const QTransform & matrix )

Sets matrix as an explicit transformation matrix on the current brush. The brush transformation matrix is merged with QPainter transformation matrix to produce the final result.

This function was introduced in Qt 4.3.

See also transform().

Qt::BrushStyle QBrush::style () const

Returns the brush style.

See also setStyle().

QPixmap QBrush::texture () const

Returns the custom brush pattern, or a null pixmap if no custom brush pattern has been set.

See also setTexture().

QImage QBrush::textureImage () const

Returns the custom brush pattern, or a null image if no custom brush pattern has been set.

If the texture was set as a QPixmap it will be converted to a QImage.

This function was introduced in Qt 4.2.

See also setTextureImage().

QTransform QBrush::transform () const

Returns the current transformation matrix for the brush.

This function was introduced in Qt 4.3.

See also setTransform().

QBrush::operator QVariant () const

Returns the brush as a QVariant

bool QBrush::operator!= ( const QBrush & brush ) const

Returns true if the brush is different from the given brush; otherwise returns false.

Two brushes are different if they have different styles, colors or pixmaps.

See also operator==().

QBrush & QBrush::operator= ( const QBrush & brush )

Assigns the given brush to this brush and returns a reference to this brush.

bool QBrush::operator== ( const QBrush & brush ) const

Returns true if the brush is equal to the given brush; otherwise returns false.

Two brushes are equal if they have equal styles, colors and pixmaps.

See also operator!=().

Related Non-Members

QDataStream & operator<< ( QDataStream & stream, const QBrush & brush )

This is an overloaded member function, provided for convenience.

Writes the given brush to the given stream and returns a reference to the stream.

See also Format of the QDataStream Operators.

QDataStream & operator>> ( QDataStream & stream, QBrush & brush )

This is an overloaded member function, provided for convenience.

Reads the given brush from the given stream and returns a reference to the stream.

See also Format of the QDataStream Operators.