regex - URL rewriting for images with different domains -

i want use urls followings :

http://mydomain.com/320x200/server/path/to/my/image.jpg 

where can find 3 parameters retrieve rewriting :

1. 320x200 : optional parameter, can 2 numbers (like "320x200"), or single number (like "320x") or empty (only "x")
2. server : required (this specific parameter find server image hosted, not matter case)
3. path/to/my/image.jpg : required

and rewrite domain followings :

http://myotherdomain.com/320/200/server/path/to/my/image.jpg 

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i tried following rewrite rules not working :

rewriterule ^([0-9]+)x([0-9]+)/([a-za-z0-9]+)/([a-za-z0-9/.]+)$ htp://myotherdomain.com/$1/$2/$3/$4 [l]

rewriterule ^([0-9]+)x/([a-za-z0-9]+)/([a-za-z0-9/.]+)$ htp://myotherdomain.com/$1/$2/$3 [l]

rewriterule ^x/([a-za-z0-9]+)/([a-za-z0-9/.]+)$ htp://myotherdomain.com/$1/$2 [l]

why not working ?

the 3 regex working when tested through website regexplanet.com

i tried clear browser cache, restart apache, remove cookies, ... still not working !

thanks help

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edit :

finally, problem .htaccess file not correctly saved (don't know why).

i closed , opened .htaccess again, ok !

you should divide work grouping. don't bother converting x / don't capture it.

rewriterule ^([0-9]+)x([0-9]+/)([a-za-z0-9]+)/([a-za-z0-9/.]+)$ http://myotherdomain.com/$1/$2$3/$4 [l]  rewriterule ^([a-za-z0-9]+)/([a-za-z0-9/.]+)$ http://myotherdomain.com/$1/$2 [l] 

• ([0-9]+) captures 2 resolutions parameters individually.
• (?:....)? non capturing grouping rendered optional.

edit:

the optionality trap. don't use -> second rule.

if other domain end being same domain:

rewritecond %{request_uri} ![0-9]+/[0-9]+.*$ 

will prevent loops.