将“将图像另存为”链接到另一个图像？

I'm trying to protect images with a watermark, but I don't want to display the images on the website with the watermark. I created a php script that dynamically watermarks an image on the fly, but here's what I'd like to do with it:

I'd like for whenever someone right clicks and presses "save as" an image displayed on my website for it link to a different image that is watermarked. Is that possible? Should I go about this another way?

Any response in the right direction is greatly appreciated.

Here's an example: http://fatpita.net/?i=14453 When you save this image, the saved image is watermarked, but the website's image is not... I think they actually just mask the watermark on the website though.

Thanks!

What you are trying to achieve is not possible in a safe way.

If the browser gets the unwatermarked file the user can save that file - maybe not using "save image as" but e.g. through Firefox's "page info dialog which contains a full media list.

You can't do anything that the user can't fake. The site you mentioned doesn't either - the watermark is always there.

Look at the actual source:

<div style="position:relative;width:768px;margin:9px auto 0;">
    <a href="http://fatpita.net/?i=4011" id="image">
        click on the image for another random funny picture<br>
        <img src="images/image (14453).jpg?4011">
    </a>
    <div id="jpgCover">
    </div>
</div>

They are actually covering over the watermark in HTML. It is still there, but there is a div in the way making sure you can't see it.

Remember the user can always remove this watermark by an easy crop.