VTK: Copy Image Data and run stuff in the background

I spent quite some time to figure out how to copy image data. I am setting up a pipeline in a Java method but want a copy of the image data in one of the fields, hence:

public void runSegmentation() {
//set up progress bar and hourglass cursor
progressBar = new ProgressBar("Segementation");
progressBar.OpenProgressBar();
currentSegmentation.setProgressBar(progressBar);
renWin.setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));

if (!currentSegmentation.is3D()) {
 //set up pipeline

 vtkImageReslice reslice2 = new vtkImageReslice();
 reslice2.SetOutputExtent(actor.GetDisplayExtent());
 reslice2.SetInput(canvas.GetOutput());
 reslice2.Update();

 currentSegmentation.setModel(reslice2.GetOutput()); //use the canvas as model;-)

 undo = true;
 slice = actor.GetSliceNumber();
 //copy the image
 undoImage = new vtkImageData();
 undoImage.DeepCopy(canvas.GetOutput());

}

//set up segmentation in the background 
SwingWorker worker =  new SwingWorker() {
 @Override
 public Object construct() {
  if (!currentSegmentation.is3D()) {
   currentSegmentation.Update();
   canvas.CopyImage(currentSegmentation.GetOutput());
  }
 return null;
 }

 @Override
 public void finished() {
  currentSegmentation.SetInput(null);
  currentSegmentation.setModel(null);
  pane.refresh(); //refresh view
  progressBar.CloseProgressBar();
  renWin.setCursor(transparentCursor);
 }

};

//run segmentation in the background
worker.start();

}
}

As you see I have thrown in some multithreading (segmenting data takes awfully long) but the code to copy the image data is essentially:

undoImage = new vtkImageData();
undoImage.DeepCopy(canvas.GetOutput());

I think DeepCopy is the right command but it took me a while. It might also be that the ImageCanvas is a weird construct though.