there is only a .cpp file for loading and saving transferfunctions:
mitkTransferFunctionPropertyDeserializer.cpp
mitkTransferFunctionPropertySerializer.cpp

Now I will add:
mitkTransferFunctionPropertyDeserializer.h
mitkTransferFunctionPropertySerializer.h

Then it is possible to use the functions "DeserializeTransferFunction()" and "SerializeTransferFunction()" in the class QmitkTransferFunctionGeneratorWidget.