The QTransform class specifies 2D transformations of a coordinate system. 更多...
This class can be pickled.
The QTransform class specifies 2D transformations of a coordinate system.
A transformation specifies how to translate, scale, shear, rotate or project the coordinate system, and is typically used when rendering graphics.
QTransform differs from QMatrix (obsolete) in that it is a true 3x3 matrix, allowing perspective transformations. QTransform's toAffine () method allows casting QTransform to QMatrix (obsolete) . If a perspective transformation has been specified on the matrix, then the conversion will cause loss of data.
QTransform is the recommended transformation class in Qt.
A QTransform object can be built using the setMatrix (), scale (), rotate (), translate () 和 shear () functions. Alternatively, it can be built by applying basic matrix operations . The matrix can also be defined when constructed, and it can be reset to the identity matrix (the default) using the reset () 函数。
The QTransform class supports mapping of graphic primitives: A given point, line, polygon, region, or painter path can be mapped to the coordinate system defined by this matrix using the map () function. In case of a rectangle, its coordinates can be transformed using the mapRect () function. A rectangle can also be transformed into a polygon (mapped to the coordinate system defined by this matrix), using the mapToPolygon () 函数。
QTransform provides the isIdentity () function which returns true if the matrix is the identity matrix, and the isInvertible () function which returns true if the matrix is non-singular (i.e. AB = BA = I). The inverted () 函数返回 an inverted copy of this matrix if it is invertible (otherwise it returns the identity matrix), and adjoint () returns the matrix's classical adjoint. In addition, QTransform provides the determinant () function which returns the matrix's determinant.
Finally, the QTransform class supports matrix multiplication, addition and subtraction, and objects of the class can be streamed as well as compared.
When rendering graphics, the matrix defines the transformations but the actual transformation is performed by the drawing routines in QPainter .
默认情况下， QPainter operates on the associated device's own coordinate system. The standard coordinate system of a QPaintDevice has its origin located at the top-left position. The x values increase to the right; y values increase downward. For a complete description, see the coordinate system 文档编制。
QPainter has functions to translate, scale, shear and rotate the coordinate system without using a QTransform. For example:
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void SimpleTransformation.paintEvent(QPaintEvent *) { QPainter painter(this); painter.setPen(QPen(Qt.blue, 1, Qt.DashLine)); painter.drawRect(0, 0, 100, 100); painter.rotate(45); painter.setFont(QFont("Helvetica", 24)); painter.setPen(QPen(Qt.black, 1)); painter.drawText(20, 10, "QTransform"); } |
Although these functions are very convenient, it can be more efficient to build a QTransform and call QPainter.setTransform () if you want to perform more than a single transform operation. For example:
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void CombinedTransformation.paintEvent(QPaintEvent *) { QPainter painter(this); painter.setPen(QPen(Qt.blue, 1, Qt.DashLine)); painter.drawRect(0, 0, 100, 100); QTransform transform; transform.translate(50, 50); transform.rotate(45); transform.scale(0.5, 1.0); painter.setTransform(transform); painter.setFont(QFont("Helvetica", 24)); painter.setPen(QPen(Qt.black, 1)); painter.drawText(20, 10, "QTransform"); } |
A QTransform object contains a 3 x 3 matrix. The m31 ( dx ) and m32 ( dy ) elements specify horizontal and vertical translation. The m11 and m22 elements specify horizontal and vertical scaling. The m21 and m12 elements specify horizontal and vertical shearing . And finally, the m13 and m23 elements specify horizontal and vertical projection, with m33 as an additional projection factor.
QTransform transforms a point in the plane to another point using the following formulas:
x' = m11*x + m21*y + dx y' = m22*y + m12*x + dy if (is not affine) { w' = m13*x + m23*y + m33 x' /= w' y' /= w' }
The point (x, y) is the original point, and (x', y') is the transformed point. (x', y') can be transformed back to (x, y) by performing the same operation on the inverted () matrix.
The various matrix elements can be set when constructing the matrix, or by using the setMatrix () function later on. They can also be manipulated using the translate (), rotate (), scale () 和 shear () convenience functions. The currently set values can be retrieved using the m11 (), m12 (), m13 (), m21 (), m22 (), m23 (), m31 (), m32 (), m33 (), dx () 和 dy () 函数。
Translation is the simplest transformation. 设置 dx and dy will move the coordinate system dx units along the X axis and dy units along the Y axis. Scaling can be done by setting m11 and m22 . For example, setting m11 to 2 and m22 to 1.5 will double the height and increase the width by 50%. The identity matrix has m11 , m22 ，和 m33 set to 1 (all others are set to 0) mapping a point to itself. Shearing is controlled by m12 and m21 . Setting these elements to values different from zero will twist the coordinate system. Rotation is achieved by setting both the shearing factors and the scaling factors. Perspective transformation is achieved by setting both the projection factors and the scaling factors.
Here's the combined transformations example using basic matrix operations:
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void BasicOperations.paintEvent(QPaintEvent *) { double pi = 3.14; double a = pi/180 * 45.0; double sina = sin(a); double cosa = cos(a); QTransform translationTransform(1, 0, 0, 1, 50.0, 50.0); QTransform rotationTransform(cosa, sina, -sina, cosa, 0, 0); QTransform scalingTransform(0.5, 0, 0, 1.0, 0, 0); QTransform transform; transform = scalingTransform * rotationTransform * translationTransform; QPainter painter(this); painter.setPen(QPen(Qt.blue, 1, Qt.DashLine)); painter.drawRect(0, 0, 100, 100); painter.setTransform(transform); painter.setFont(QFont("Helvetica", 24)); painter.setPen(QPen(Qt.black, 1)); painter.drawText(20, 10, "QTransform"); } |
| 常量 | 值 |
|---|---|
| QTransform.TxNone | 0x00 |
| QTransform.TxTranslate | 0x01 |
| QTransform.TxScale | 0x02 |
| QTransform.TxRotate | 0x04 |
| QTransform.TxShear | 0x08 |
| QTransform.TxProject | 0x10 |
构造恒等矩阵。
All elements are set to zero except m11 and m22 (specifying the scale) and m13 which are set to 1.
另请参阅 reset ().
构造矩阵采用元素 m11 , m12 , m13 , m21 , m22 , m23 , m31 , m32 , m33 .
另请参阅 setMatrix ().
构造矩阵采用元素 m11 , m12 , m21 , m22 , dx and dy .
另请参阅 setMatrix ().
Constructs a matrix that is a copy of the given matrix . 注意： m13 , m23 ，和 m33 elements are set to 0, 0, and 1 respectively.
Returns the adjoint of this matrix.
Returns the matrix's determinant.
Returns the horizontal translation factor.
另请参阅 m31 (), translate ()，和 Basic Matrix Operations .
Returns the vertical translation factor.
另请参阅 translate () 和 Basic Matrix Operations .
Creates a matrix which corresponds to a scaling of sx horizontally and sy vertically. This is the same as QTransform ().scale(sx, sy) but slightly faster.
该函数在 Qt 4.5 引入。
Creates a matrix which corresponds to a translation of dx along the x axis and dy along the y axis. This is the same as QTransform ().translate(dx, dy) but slightly faster.
该函数在 Qt 4.5 引入。
Returns an inverted copy of this matrix.
If the matrix is singular (not invertible), the returned matrix is the identity matrix. If invertible is valid (i.e. not 0), its value is set to true if the matrix is invertible, otherwise it 被设为 false。
另请参阅 isInvertible ().
Returns true if the matrix represent an affine transformation, otherwise returns false.
Returns true if the matrix is the identity matrix, otherwise returns false.
另请参阅 reset ().
Returns true if the matrix is invertible, otherwise returns false.
另请参阅 inverted ().
Returns true if the matrix represents some kind of a rotating transformation, otherwise returns false.
另请参阅 reset ().
Returns true if the matrix represents a scaling transformation, otherwise returns false.
另请参阅 reset ().
Returns true if the matrix represents a translating transformation, otherwise returns false.
另请参阅 reset ().
Returns the horizontal scaling factor.
另请参阅 scale () 和 Basic Matrix Operations .
Returns the vertical shearing factor.
另请参阅 shear () 和 Basic Matrix Operations .
Returns the horizontal projection factor.
另请参阅 translate () 和 Basic Matrix Operations .
Returns the horizontal shearing factor.
另请参阅 shear () 和 Basic Matrix Operations .
Returns the vertical scaling factor.
另请参阅 scale () 和 Basic Matrix Operations .
Returns the vertical projection factor.
另请参阅 translate () 和 Basic Matrix Operations .
Returns the horizontal translation factor.
另请参阅 dx (), translate ()，和 Basic Matrix Operations .
Returns the vertical translation factor.
另请参阅 dy (), translate ()，和 Basic Matrix Operations .
Returns the division factor.
另请参阅 translate () 和 Basic Matrix Operations .
Maps the given coordinates x and y into the coordinate system defined by this matrix. The resulting values are put in * tx and * ty ，分别。
The coordinates are transformed using the following formulas:
x' = m11*x + m21*y + dx y' = m22*y + m12*x + dy if (is not affine) { w' = m13*x + m23*y + m33 x' /= w' y' /= w' }
The point (x, y) is the original point, and (x', y') is the transformed point.
另请参阅 Basic Matrix Operations .
这是重载函数。
创建和返回 QPointF object that is a copy of the given point, p , mapped into the coordinate system defined by this matrix.
这是重载函数。
创建和返回 QPoint object that is a copy of the given point , mapped into the coordinate system defined by this matrix. Note that the transformed coordinates are rounded to the nearest integer.
这是重载函数。
创建和返回 QLineF object that is a copy of the given line, l , mapped into the coordinate system defined by this matrix.
这是重载函数。
创建和返回 QLine object that is a copy of the given line , mapped into the coordinate system defined by this matrix. Note that the transformed coordinates are rounded to the nearest integer.
这是重载函数。
创建和返回 QPolygonF object that is a copy of the given polygon , mapped into the coordinate system defined by this matrix.
这是重载函数。
创建和返回 QPolygon object that is a copy of the given polygon , mapped into the coordinate system defined by this matrix. Note that the transformed coordinates are rounded to the nearest integer.
这是重载函数。
创建和返回 QRegion object that is a copy of the given region , mapped into the coordinate system defined by this matrix.
Calling this method can be rather expensive if rotations or shearing are used.
这是重载函数。
创建和返回 QPainterPath object that is a copy of the given path , mapped into the coordinate system defined by this matrix.
这是重载函数。
Maps the given coordinates x and y into the coordinate system defined by this matrix. The resulting values are put in * tx and * ty , respectively. Note that the transformed coordinates are rounded to the nearest integer.
创建和返回 QRectF object that is a copy of the given rectangle , mapped into the coordinate system defined by this matrix.
The rectangle's coordinates are transformed using the following formulas:
x' = m11*x + m21*y + dx y' = m22*y + m12*x + dy if (is not affine) { w' = m13*x + m23*y + m33 x' /= w' y' /= w' }
If rotation or shearing has been specified, this function returns the bounding rectangle. To retrieve the exact region the given rectangle maps to, use the mapToPolygon () function 代替。
另请参阅 mapToPolygon () 和 Basic Matrix Operations .
创建和返回 QPolygon representation of the given rectangle , mapped into the coordinate system defined by this matrix.
The rectangle's coordinates are transformed using the following formulas:
x' = m11*x + m21*y + dx y' = m22*y + m12*x + dy if (is not affine) { w' = m13*x + m23*y + m33 x' /= w' y' /= w' }
Polygons and rectangles behave slightly differently when transformed (due to integer rounding), so matrix.map(QPolygon(rectangle)) is not always the same as matrix.mapToPolygon(rectangle) .
另请参阅 mapRect () and Basic Matrix Operations .
Creates a transformation matrix, trans , that maps a four-sided polygon, one , to another four-sided polygon, two . Returns true if the transformation is possible; otherwise returns false.
This is a convenience method combining quadToSquare () 和 squareToQuad () methods. It allows the input quad to be transformed into any other quad.
另请参阅 squareToQuad () 和 quadToSquare ().
Creates a transformation matrix, trans , that maps a four-sided polygon, quad , to a unit square. Returns true if the transformation is constructed or false if such a transformation does not exist.
另请参阅 squareToQuad () 和 quadToQuad ().
Resets the matrix to an identity matrix, i.e. all elements are set to zero, except m11 and m22 (specifying the scale) and m33 which are set to 1.
另请参阅 QTransform (), isIdentity ()，和 Basic Matrix Operations .
Rotates the coordinate system counterclockwise by the given angle about the specified axis 并返回 reference to the matrix.
Note that if you apply a QTransform to a point defined in widget coordinates, the direction of the rotation will be clockwise because the y-axis points downwards.
The angle is specified in degrees.
另请参阅 setMatrix ().
Rotates the coordinate system counterclockwise by the given angle about the specified axis 并返回 reference to the matrix.
Note that if you apply a QTransform to a point defined in widget coordinates, the direction of the rotation will be clockwise because the y-axis points downwards.
The angle is specified in radians.
另请参阅 setMatrix ().
Scales the coordinate system by sx horizontally and sy vertically, and returns a reference to the matrix.
另请参阅 setMatrix ().
Sets the matrix elements to the specified values, m11 , m12 , m13 m21 , m22 , m23 m31 , m32 and m33 . Note that this function replaces the previous values. QTransform provides the translate (), rotate (), scale () 和 shear () convenience functions to manipulate the various matrix elements based on the currently defined coordinate system.
另请参阅 QTransform ().
Shears the coordinate system by sh horizontally and sv vertically, and returns a reference to the matrix.
另请参阅 setMatrix ().
Creates a transformation matrix, trans , that maps a unit square to a four-sided polygon, quad . Returns true if the transformation is constructed or false if such a transformation does not exist.
另请参阅 quadToSquare () 和 quadToQuad ().
返回 QTransform as an affine matrix.
警告： If a perspective transformation has been specified, then the conversion will cause loss of data.
Moves the coordinate system dx along the x axis and dy along the y axis, and returns a reference to the matrix.
另请参阅 setMatrix ().
Returns the transpose of this matrix.
Returns the transformation type of this matrix.
The transformation type is the highest enumeration value capturing all of the matrix's transformations. For example, if the matrix both scales and shears, the type would be TxShear , 因为 TxShear has a higher enumeration value than TxScale .
Knowing the transformation type of a matrix is useful for optimization: you can often handle specific types more optimally than handling the generic case.
