hello Alan_VB, due to how the web works this won't be possible to prevent. people can always view the source code of a page and extract/download selected resources.

If you are very much concern about copyright, then you can make a flash website instead of using html. But there also, screen shots and other tools are avaliable to fetch the image from screen. So, there is not much you can do about it.

Or place watermarks on your images. Or better yet, license them under CC!

I've built a ashx handler that only serves the image if the request comes from within one of my site's pages and I've also given it a parameter that will invalidate when the page is reloaded so taking the url from the source code isn't going to help anyone - I admit I can't do anything about screen capture but the page-info / media / save thing just makes it too easy to download the image I thought the mechanism would require a round trip to the server but it doesn't and the image shouldn't be cached since the source has query parameters.

I appreciate that I'm never going to be able to 100% prevent image theft but I'd like it to be less than trivially easy and this functionality as presented make it very simple for anyone with the slightest knowledge to get a good copy of the image (though I have water-marked it as well)

You would have to serve images by using a plugin like Flash that can retrieve the images via a secure connection to prevent or at least makes it more difficult for visitors to save the images (they could still make a screenshot).