内容

公共类型
公共函数
相关非成员
详细描述

QGradient 类

The QGradient class is used in combination with QBrush 以指定渐变填充。更多...

头：	#include <QGradient>
qmake:	QT += gui
继承者：	QConicalGradient , QLinearGradient ，和 QRadialGradient

所有成员列表，包括继承成员

公共类型

enum	CoordinateMode { LogicalMode, StretchToDeviceMode, ObjectBoundingMode }
enum	Spread { PadSpread, RepeatSpread, ReflectSpread }
enum	Type { LinearGradient, RadialGradient, ConicalGradient, NoGradient }

公共函数

CoordinateMode	coordinateMode () const
void	setColorAt (qreal position , const QColor & color )
void	setCoordinateMode (CoordinateMode mode )
void	setSpread (Spread method )
void	setStops (const QGradientStops & stopPoints )
Spread	spread () const
QGradientStops	stops () const
类型	type () const
bool	operator!= (const QGradient & gradient ) const
bool	operator== (const QGradient & gradient ) const

typedef	QGradientStop
typedef	QGradientStops

详细描述

The QGradient class is used in combination with QBrush 以指定渐变填充。

Qt currently supports three types of gradient fills:

Linear gradients interpolate colors between start and end points.
简单 radial gradients interpolate colors between a focal point and end points on a circle surrounding it.
Extended radial gradients interpolate colors between a center and a focal circle.
Conical gradients interpolate colors around a center point.

A gradient's type can be retrieved using the type () function. Each of the types is represented by a subclass of QGradient :

QLinearGradient	QRadialGradient	QConicalGradient

The colors in a gradient are defined using stop points of the QGradientStop type; i.e., a position and a color. Use the setColorAt () function to define a single stop point. Alternatively, use the setStops () function to define several stop points in one go. Note that the latter function 替换 the current set of stop points.

It is the gradient's complete set of stop points (accessible through the stops () function) that describes how the gradient area should be filled. If no stop points have been specified, a gradient of black at 0 to white at 1 is used.

A diagonal linear gradient from black at (100, 100) to white at (200, 200) could be specified like this:

    QLinearGradient linearGrad(QPointF(100, 100), QPointF(200, 200));
    linearGrad.setColorAt(0, Qt::black);
    linearGrad.setColorAt(1, Qt::white);

A gradient can have an arbitrary number of stop points. The following would create a radial gradient starting with red in the center, blue and then green on the edges:

    QRadialGradient radialGrad(QPointF(100, 100), 100);
    radialGrad.setColorAt(0, Qt::red);
    radialGrad.setColorAt(0.5, Qt::blue);
    radialGrad.setColorAt(1, Qt::green);

It is possible to repeat or reflect the gradient outside its area by specifiying the spread method 使用 setSpread () function. The default is to pad the outside area with the color at the closest stop point. The currently set spread method can be retrieved using the spread () 函数。 QGradient::Spread enum defines three different methods:


PadSpread	RepeatSpread	ReflectSpread

注意， setSpread () function only has effect for linear and radial gradients. The reason is that the conical gradient is closed by definition, i.e. the conical gradient fills the entire circle from 0 - 360 degrees, while the boundary of a radial or a linear gradient can be specified through its radius or final stop points, respectively.

The gradient coordinates can be specified in logical coordinates, relative to device coordinates, or relative to object bounding box coordinates. The coordinate mode can be set using the setCoordinateMode () function. The default is LogicalMode , where the gradient coordinates are specified in the same way as the object coordinates. To retrieve the currently set coordinate mode 使用 coordinateMode ().

另请参阅 The Gradients Example and QBrush .

成员类型文档编制

enum QGradient:: CoordinateMode

This enum specifies how gradient coordinates map to the paint device on which the gradient is used.

常量	值	描述
`QGradient::LogicalMode`	`0`	This is the default mode. The gradient coordinates are specified logical space just like the object coordinates.
`QGradient::StretchToDeviceMode`	`1`	In this mode the gradient coordinates are relative to the bounding rectangle of the paint device, with (0,0) in the top left corner, and (1,1) in the bottom right corner of the paint device.
`QGradient::ObjectBoundingMode`	`2`	In this mode the gradient coordinates are relative to the bounding rectangle of the object being drawn, with (0,0) in the top left corner, and (1,1) in the bottom right corner of the object's bounding rectangle.

该枚举在 Qt 4.4 引入或被修改。

enum QGradient:: Spread

Specifies how the area outside the gradient area should be filled.

常量	值	描述
`QGradient::PadSpread`	`0`	The area is filled with the closest stop color. This is the default.
`QGradient::RepeatSpread`	`2`	The gradient is repeated outside the gradient area.
`QGradient::ReflectSpread`	`1`	The gradient is reflected outside the gradient area.

另请参阅 spread () 和 setSpread ().

enum QGradient:: Type

Specifies the type of gradient.

常量	值	描述
`QGradient::LinearGradient`	`0`	Interpolates colors between start and end points ( QLinearGradient ).
`QGradient::RadialGradient`	`1`	Interpolate colors between a focal point and end points on a circle surrounding it ( QRadialGradient ).
`QGradient::ConicalGradient`	`2`	Interpolate colors around a center point ( QConicalGradient ).
`QGradient::NoGradient`	`3`	No gradient is used.

另请参阅 type ().

成员函数文档编制

CoordinateMode QGradient:: coordinateMode () const

Returns the coordinate mode of this gradient. The default mode is LogicalMode .

该函数在 Qt 4.4 引入。

另请参阅 setCoordinateMode ().

void QGradient:: setColorAt ( qreal position , const QColor & color )

Creates a stop point at the given position 采用给定 color . The given position must be in the range 0 to 1.

另请参阅 setStops () 和 stops ().

void QGradient:: setCoordinateMode ( CoordinateMode mode )

Sets the coordinate mode of this gradient to mode . The default mode is LogicalMode .

该函数在 Qt 4.4 引入。

另请参阅 coordinateMode ().

void QGradient:: setSpread ( Spread method )

Specifies the spread method that should be used for this gradient.

Note that this function only has effect for linear and radial gradients.

另请参阅 spread ().

void QGradient:: setStops (const QGradientStops & stopPoints )

Replaces the current set of stop points with the given stopPoints . The positions of the points must be in the range 0 to 1, and must be sorted with the lowest point first.

另请参阅 setColorAt () 和 stops ().

Spread QGradient:: spread () const

Returns the spread method use by this gradient. The default is PadSpread .

另请参阅 setSpread ().

QGradientStops QGradient:: stops () const

Returns the stop points for this gradient.

If no stop points have been specified, a gradient of black at 0 to white at 1 is used.

另请参阅 setStops () 和 setColorAt ().

Type QGradient:: type () const

Returns the type of gradient.

bool QGradient:: operator!= (const QGradient & gradient ) const

返回 true if the gradient is the same as the other gradient specified; otherwise returns false .

该函数在 Qt 4.2 引入。

另请参阅 operator== ().

bool QGradient:: operator== (const QGradient & gradient ) const