format conversion from pdf to png

[Yogi]

I'm feeling really stupid and I'm not getting this to work. I'm
uploading multipage pdf files and I want to generate png preview of
the first page. I don't wan't to do any resizing, just conversion from
pdf to png like

convert my_uploaded.pdf[0] my_uploaded.png

I've tried to pass all kinds of combinations of options to paperclip
but haven't succeeded. How should this be tackled?


tia,
Yogi