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