RewriteEngine on
RewriteCond %{HTTP_REFERER} !^http://domain.com/.*$      [NC]
RewriteCond %{HTTP_REFERER} !^http://domain.com$      [NC]
RewriteCond %{HTTP_REFERER} !^https://domain.com/.*$      [NC]
RewriteCond %{HTTP_REFERER} !^https://domain.com$      [NC]
RewriteRule .*\.(jpg|jpeg|gif|png|bmp)$ - [F,NC]