How To Make Visible Watermarks More Effective

The Google Research Team has been finding out how easy it is to remove watermarks from images which might seem like a weird thing to be doing but there is method in their madness. 

By finding out how easy watermarks are to remove, they have been able to come up with methods that make it much trickier for people, and algorithms, to remove the watermarks. 

Most people do use complicated watermarks that feature thin lines and shadows that make them harder to remove but most will use the same watermark and add them in the same way and place to all images. 

"A fact that has been overlooked so far is that watermarks are typically added in a consistent manner to many images," says Google. "We show that this consistency can be used to invert the watermarking process - that is, estimate the watermark image and its opacity, and recover the original, watermark-free image underneath."

Basically, as we are creatures of habit, a computer algorithm can quite easily remove the watermarks we use and it can even be done as a batch process, removing the watermark from several images in one go. 

You can see more on 'how it's done' over on the Google Blog but we're more interested in what can be done to stop this happening and Google do have a solution. 

"The vulnerability of current watermarking techniques lies in the consistency in watermarks across image collections. Therefore, to counter it, we need to introduce inconsistencies when embedding the watermark in each image," says Google. 

The research team tried various alterations, including changing the watermark’s position randomly per image and making small random changes in the watermark’s opacity, but these didn't stop watermarks from disappearing. However, the team did find that warping the watermark slightly before embedding it into each image made it harder for the algorithm to remove it. Plus, what's even better news about this is that warping a watermark is really easy to do. 

In the below examples you can see how visible artifacts remain when the algorithm attempted to remove the warped watermark. 

"While we cannot guarantee that there will not be a way to break such randomized watermarking schemes in the future, we believe (and our experiments show) that randomisation will make watermarked collection attacks fundamentally more difficult. We hope that these findings will be helpful for the photography and stock image communities, says Google.