[vtkusers] Create image(files) without graphicwindow

[Thomas Faust]

I can write nice pictures from my renderwindow by using the vtkWindowToImageFilter to create vtkImageData a vtkImageWriter is using.
The requirement now is to write a image without having a window poping up in the screen. The program should read data from the disk, put it through the graphic pipeline and create an image that get written to the disk (e.g a JPEG).
Can I get a picture from the renderer without having a renderWindow?
Did anybody did something like this before?

I'd appreciate every help.