Summary of feature request description:

 Actual behaviour:
The VolumeVisualization functionality does not allow saving and restoring
transfer functions.


Expected behaviour:
VolumeVisualization should allow saving and restoring of transfer functions. 

Cause of the bug:
Feature request 

Proposed solution
Jens Poxleitner implemented serialization of TFs in QmitkDesignGalleries. This should be easy to port to VolumeVisualization.
We'll create a new FileWriter and FileReader to save and load mitktransferFunctions in XML-files.


Affected classes:
(mitkTransferfunction)
mitkTransferFunctionFileWriter / -Reader

How will the bugfix get tested?
Will be tested by some specific unit tests