            writer = vtkPNMWriter()
        elif ext == '.ps':
            if rgba:
                rgba = False
            writer = vtkPostScriptWriter()
        elif ext == '.tiff':
--
            writer = vtkPNMWriter()
        elif ext == '.ps':
            if rgba:
                rgba = False
            writer = vtkPostScriptWriter()
        elif ext == '.tiff':
