nginx rewrite configuration

[goversation]

hi! i'm newbie so having a hard time!
I have a question about rewrite configure in nginx!

RULE is http://URL/[option]/http://URL .

I mean...
for example, 

if request is http://aaa.net/25X25/http://bbb.net/ccc.jpg ,
rewrite is /25X25/bbb.net.jpg

should i use regular expression?
please help me! 

thank you :D

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,245954,245954#msg-245954