Rewriting jpg with specific google referer to 1 pixel gif

If I understand correctly, nginx doesn’t do multiple conditions in an
‘if’
or nested if’s.

Based on some of the ideas being tossed around in this thread
(http://www.webmasterworld.com/google/4537063-11-30.htm) I’d like to
rewrite serve up a one pixel gif to whenever both of the two following
conditions are met:

  1. The http referer is http://www.google./blank.html() and then

  2. the requested asset is a jpg

What’s the best performance way to handle that?

  • I suck at regex, so I just put the asterix there to signify catching
    any
    of the google country domains.

Thanks for any suggestions.