Check Image exists

The code you write work perfectly for this

http://example.com/images/200x180

If user pass only width, I have to assume that it is squre like this
http://example.com/images/200 means http://example.com/images/200x200

And I try to modify your htaccess code

    # request URL is for images
    RewriteCond %{REQUEST_URI}  ^/images/([^x]+)x([^/]+)/? [NC]
    # disable storage loops
    RewriteCond %{REQUEST_URI}  !storage [NC]
    # check for file exists
    RewriteCond %{REQUEST_URI} -f
    RewriteRule .*   /storage/%1/%1x%2.png [L][OR]
    RewriteRule .*   /storage/%1/%1x%1.png [L]

Is this correct?