please help me with follow rewrite rule.

[digginchina]

here is the structure:
/images/thumbnails/
/watermark

i use follow rewrite rule to add a watermark on my pictures.

rewrite ^/images/(.*)\.jpg /wm/wm.php?$request_filename;

i found it will rewrite with images/*.jpg and image/thumbnails/*.jpg,
but actually i only wanna rewrite images/*.jpg, not subdirectories. then
i change it to:

rewrite ^/images/(.[^/])\.jpg /watermark/image.php?$request_filename;

my opinion is fit all character except "/" so that i can remove all
subdirectories from the rewrite rule. 

but unfortunately, it doesn't work well, /images/*.jpg can't be rewrited
too.

is there anybody help me with this case?

thanks a lot.
regards
solo

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,137829,137829#msg-137829