apache mod-rewrite file name change

This is probably straight forward for someone who know apache mod rewrite and regex but that someone is not me. This is what I am looking for : I just want to re-route image开发者_StackOverflow中文版,css requests to one shared repository image/css file. e.g. we have 6-7 sites which can be on same server or different. Currently, image looks like this /img/site1_header.jpg, all I want is that internally this request should become /img/header.jpg so basically remove the variable 'site1' (or site2,site 3)

Any help appreciated.

thanks

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I haven't tested it, but I expect it will look something like:

RewriteEngine On
RewriteRule ^(.*)/(site[0-9]*_)(.*)$ $1/$2 [PT,L]