Given a starting value and an ending value, QuickTime is able to figure out, for any moment in the duration of the animation, what the appropriate
value between those two values should be. This process is called tweening, and the track that contains the information needed to do the tweening
is called a .
QuickTime provides support for either simple linear interpolations of data or more complex tweening operations and operations.
For instance, the various types of path tweens allow us to derive values based on the shape of an arbitrary curve defined by a vector path.
And the list tween derives values from a list of atoms in an atom container, which can result in a series of discrete steps of non–continuous values.
Anyway, QTPlugin currently supports only linear interpolations of numerical or graphical data.
The QTPlugin provides the developers with the Tween Framework to add tween–based animation to their applications.
The Tween Framework, which is a set of classes,
handles all the tasks necessary to provide tweening by using either
or auto–running .
The QTPlgGraphicalTween class is part of the Tween Framework and allows you to perform
interpolation of graphical data. The type of the interpolated results depends on the
object instantiated (more details about the interpolation results
can be found into the section of this document).
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The QTPlgGraphicalTween class constructors are called when you create a new instance of the class, while
the ˜QTPlgGraphicalTween class destructor, is called automatically when the
class is no more in use. Also, you can invoke the class destructor by setting the instance of the class to nil.
Once a new class instance is returned, it is good practice to check the
class property to
be sure that the new object can be used.
The class provides you with the following initializer methods:
This is the default constructor. You specify the
you want to instantiate by setting
the
typeSelector with one of the
defined by the class
This is the copy constructor. The properties of the object to be copied will be used to initialize the
new class instance properties
specifies the starting and ending values used during the tweening operation. As these values are graphics objects, the class accepts as data source a
list containing two objects: that one with index
0 is interpreted as the starting value, that one with index
1) as the ending value. Any list of objects containing more than two objects will be rejected.
The type of the objects that must be contained into the
list reflects the
specified at initialization time with the appropriate
. You can find detailed informations about the
objects that are expected to be in the list in the
section of this document
the entry data must be two objects;
the result of the graphical interpolation is a
the entry data must be two objects;
the result of the graphical interpolation is a
the entry data must be two objects;
the result of the graphical interpolation is a
the entry data must be a list containing one object that represents the
and a QTPlgGraphicalTween
object of type kTypeMatrix; in this case the order followed to insert the objects does not matter.
The result of the graphical interpolation is a obtained by concatenating the
transformations produced by the with those one produced
by the matrix tweening
the entry data must be two objects (only the values of the
class property will be evaluated during the
tweening operation);
the result of the graphical interpolation is a object where the
property is set with the interpolated
color
the entry data must be two objects;
the result of the graphical interpolation is a object where
the resulting is obtained by
interpolating the red, green, and blue components of the source colors; the resulting value of the
property is not interpolated; rather,
it’s copied from the starting object into the tweened object
the entry data must be two objects;
the result of the graphical interpolation is a