# these rules ensure you aren't clobbering legit requests (like to image.php)
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d

# just in case, exclude the admin directory
RewriteCond %{REQUEST_URI} !^/admin

# rewrite
RewriteRule ^(.*)$ image.php?query=$1 [L]

RewriteCond %{REQUEST_URI} !^/admin
RewriteRule (.*) image.php?query=$1