QGraphicsTransform¶
Inherited by: QGraphicsRotation, QGraphicsScale
Note
This class was introduced in Qt 4.6
Detailed Description¶
The PySide.QtGui.QGraphicsTransform class is an abstract base class for building advanced transformations on QGraphicsItems.
As an alternative to QGraphicsItem::transform, PySide.QtGui.QGraphicsTransform lets you create and control advanced transformations that can be configured independently using specialized properties.
PySide.QtGui.QGraphicsItem allows you to assign any number of PySide.QtGui.QGraphicsTransform instances to one PySide.QtGui.QGraphicsItem . Each PySide.QtGui.QGraphicsTransform is applied in order, one at a time, to the PySide.QtGui.QGraphicsItem it’s assigned to.
PySide.QtGui.QGraphicsTransform is particularly useful for animations. Whereas QGraphicsItem.setTransform() lets you assign any transform directly to an item, there is no direct way to interpolate between two different transformations (e.g., when transitioning between two states, each for which the item has a different arbitrary transform assigned). Using PySide.QtGui.QGraphicsTransform you can interpolate the property values of each independent transformation. The resulting operation is then combined into a single transform which is applied to PySide.QtGui.QGraphicsItem .
Transformations are computed in true 3D space using PySide.QtGui.QMatrix4x4 . When the transformation is applied to a PySide.QtGui.QGraphicsItem , it will be projected back to a 2D PySide.QtGui.QTransform . When multiple PySide.QtGui.QGraphicsTransform objects are applied to a PySide.QtGui.QGraphicsItem , all of the transformations are computed in true 3D space, with the projection back to 2D only occurring after the last PySide.QtGui.QGraphicsTransform is applied. The exception to this is PySide.QtGui.QGraphicsRotation , which projects back to 2D after each rotation to preserve the perspective effect around the X and Y axes.
If you want to create your own configurable transformation, you can create a subclass of PySide.QtGui.QGraphicsTransform (or any or the existing subclasses), and reimplement the pure virtual PySide.QtGui.QGraphicsTransform.applyTo() function, which takes a pointer to a PySide.QtGui.QMatrix4x4 . Each operation you would like to apply should be exposed as properties (e.g., customTransform->setVerticalShear(2.5)). Inside you reimplementation of PySide.QtGui.QGraphicsTransform.applyTo() , you can modify the provided transform respectively.
PySide.QtGui.QGraphicsTransform can be used together with QGraphicsItem.setTransform() , QGraphicsItem.setRotation() , and QGraphicsItem.setScale() .
- class PySide.QtGui.QGraphicsTransform([parent=None])¶
Parameters: parent – PySide.QtCore.QObject Constructs a new PySide.QtGui.QGraphicsTransform with the given parent .
- PySide.QtGui.QGraphicsTransform.applyTo(matrix)¶
Parameters: matrix – PySide.QtGui.QMatrix4x4 This pure virtual method has to be reimplemented in derived classes.
It applies this transformation to matrix .
- PySide.QtGui.QGraphicsTransform.update()¶
Notifies that this transform operation has changed its parameters in such a way that PySide.QtGui.QGraphicsTransform.applyTo() will return a different result than before.
When implementing you own custom graphics transform, you must call this function every time you change a parameter, to let PySide.QtGui.QGraphicsItem know that its transformation needs to be updated.
