[cairo] fill question

[Angelo Dureghello]

Dear all,

i have the following issue:
i load from a png file a picture, with some circles with 3 px borders, 
and with transparency outside and inside the circles.
I would need to set this image as gtk window background, but with an 
opaque "inner" of the circles. Otherwise the window will stay 
transparent inside them, and i need to draw things on them.

Any help is very appreciated.
Thanks
Angelo