Anyone has any good idea to save data on image that is hard to see by human but recognizable by device with camera? Number on licence plate can be recognized by computer; QR code can be recognized by our smart phone. They are all visible to human also. What if I had no space to show my QR code beside my ad picture? Visualead has developed something like http://www.visualead.com/css/design-v4/images/row_2.jpg, which saves space of the QR code.
Can we do it deeper, making the QR code nearly invisible? Use something like special color?
