I dont have an example now, but the script is smarter than the one you described.
suppose the setup at surpasshosting.com is as such:
Inside webpage a.html: <center><img src="http://www.surpasshosting.com/a.jpg"/></center>
Inside webpage b.html: <center><img src="http://www.surpasshosting.com/b.jpg"/></center>
Inside webpage c.html: <center><img src="http://www.surpasshosting.com/c.jpg"/></center>
etc... each only has an enlarged version of the image.
then to view the image a.jpg, the URL will be
http://surpasshosting.com/a.html OR
http://surpasshosting.com/a.jpg. For the latter case, we get redirected to the former URL. Thus we must be at the former URL to see the image. If we try to "save picture as", we will end up saving a.html with the HTML in the document. Renaming the extension wont help.
try this for the other pages and you get the same results.
i know it's possible to write .htaccess to manipulate the URL or redirect, but I just don't know how to do it, and if possible, also intercept the image download.