How-to set resolution for png export?

[Richard Moll <richard moll pik-potsdam de>]

Hello,
I would like to export some of my Dia diagrams as .png's to include them in a OOo Impress presentation.

When exporting via GUI no resolution can be set (here on WinXP with v0.97-pre2) and the default (?) 
resolution ~400x180 is way too "pixelig".
In the help I found the command line syntax, which unfortunately doesn't work either:
C:\...>dia --export=test.png --size=600x --filter=png test.dia
Notice: User Interface type settings change will take after restart

** (dia.exe:2948): WARNING **: --size parameter unsupported for cairo-png filter
test.dia --> test.png


So is there a way to change the resolution or any other convenient way to import the diagrams into OOo?


TIA
Richard