You can set the image is a background and put a transparent gif or png as the image. This common, people then would download a blank image. I have also seen a javascript rightclick alert box that prevents saving with a warning. I'm not exactly sure how it was done though.

there are other ways to view the source and content other than right clicking the page
also if you watermark it could be as good for branding as it is as a deterrent

I'd say, instead of trying to find way to make it impossible/more difficult to steal images, try to find a way so that people don't even want to steal the images in the first place.

Watermarking is the best way for that I think. That way, you sort of "damage" the image, and the watermark is part of the image (impossible to detach), no matter how someone will get it (taking a screenshot is another way).

The downside is that it indeed looks a little bit less perfect on your website, but that's the price you'll have to pay.

@cnwtx: Yay, maybe something like this:

<figure>
   <img src="real-image.jpg" />
   <img class="watermark" src="watermark.jpg" />
</figure>

figure {position:relative;}
figure img.watermark {
  position:absolute;
  top:0px;
  left:0px;
}

/* Or... replace the <img class="watermark" ... /> and...
figure:after {
  content:url(watermark.jpg);
  position:absolute;
  top:0px;
  left:0px;
}
*/

PS: cnwtx, are you from Texas?

Yes, the watermark will make them more curious. Might be better to make watermark.jpg/png as transparent image that did not attract attention. That will make some spinning stars around their head when they realized that they save something that did not exist.

What about splitting the image into segments - I always though that would be a good idea.

Mainly because if it's in a bunch of segments the average user would never be arsed to try and put it back together again.

With an image and separate watermark, the thief can still go in the source code and download the actual image without the watermark.

Dividing the image into segments is quite a hassle to download and put back together, but it's also a hassle to create (cutting it up and putting every segment on the site). And without a watermark over it, Mr. Thief can just take a screenshot and crop the image.

Having the watermark as part of the image, it's impossible to separate the watermark from the image, so there's no way to get a clean image -- not by saving it, not by looking in the source code, not by taking a screenshot.

This is how stock photo companies do it, like iStockPhoto. If you look at any photo on their site, there's really no way an image can be taken without having the company's logo included in it (example: here). You'll have to clean it up really well in Photoshop if you want the actual image.

Maybe the best method is for them to fill a form in, sign a non ownership disclaimer and have the image taken to them by carrier pigeon.

@senff

It isn't impossible to remove the watermark, just very time consuming for some non-expert in Photoshop. I have removed them before and I would rather just pay for the image than spend the time trying to steal it. iStockPhoto does a good job because they have an x with different angles.

@cnwtx I would like to just try that.

A watermark is the only way.

All other ways are easily overcome using snipping tool.