If you don’t want other people to download images from your website, don’t put them online because – the way the web works - it is almost impossible to prevent someone from copying or saving your images.
However there’s one little trick that may discourage the less-technical people from casually copying, or even hot-linking, to your web images. To give you an example, try saving the following image to your computer using the standard “save as” option.
The “save picture” option under right-click is still available for the above image but instead of downloading the actual photograph, all it would save is a blank image. Also, the URL for the image (under Properties) would appear as some junk characters (it’s called a data URI) and thus would deter the non-techies from hotlinking to that image.
Here’s how you may implement something similar for your own images:
The standard embed code for an image looks something like this:
<img src="photograph.jpg" width="500" height="250">
What you need to do is change the value of the src attribute to point to a blank image and then add a new style attribute to render the actual image. Also make sure that the value of the height and the width parameters are exactly the same as the actual image.
<img style="background-image:url(photograph.jpg);" src="data:image/gif;base64, R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==" width="500" height="250">
This is like overlaying a completely transparent screen over your photograph and anyone trying to save the image will end up downloading that screen instead of the image.
Obviously, there are simple workarounds to get around the above method. For instance, a copy of the full image will still be available in your browser’s cache. You may look at the HTML source or may even save the image using screen capture but again, these techniques may not always be known to the non-technical users of your website.