A technology that can "hide" information in plain sight on printed images has begun to see the first commercial applications.
Japanese firm Fujitsu is pushing a technology that can encode data into a picture that is invisible to the human eye but can be decoded by a mobile phone with a camera.
The company believes the technology will have spin off implications for the publishing industry.
"The concept is to be able to link the printed page into the digital domain," said Mike Nelson, general manager for sales operations at Fujitsu Europe.
The technique stems from a 2,500-year-old practice called steganography, which saw the Greeks sending warnings of attacks on wooden tablets and then covering them in wax and tattooing messages on shaved heads that were then covered by the regrowth of hair.
Fujitsu's technique works by taking advantage of the sensitivities of the human eye, which struggles to see the colour yellow.
"The key is to take the yellow hue in the picture and we skew that ever so slightly to create a pattern," said Mr Nelson.
"A camera is perfectly sensitive to that yellow hue but the human eye doesn't see it very well.
"Any camera, even those in mobile phones, can decode it very easily."
Pictures printed with the technique look perfectly normal but a camera can see the code printed into the image.
The technique can currently store just 12 bytes of information - soon to rise to 24 - the equivalent amount of data in a barcode.
That data could be a phone number, a message or a website link.
Printed materials can then connect to the online world by storing information which tells the phone to connect the web.
Almost any mobile phone can be used but a small java application must be downloaded before it can be used to decode the information. Other devices such as PDAs with a camera could also be used.