The project was developed around "the CybSticker", which is an adhesive but removable vinyl sticker containing two elements:

1. A matrix code for unique identification and
2. An image called the hint, which, if properly selected by the user, conveys a hint of the contents, and thus serves as a teasing wrapping for the real contents.

Brief explanation of the concept

• User generates normal MMS (image, video, sound and text in addition to an image of the CybSticker matrix code) 
• The sticker is placed, for instance on a wall or a parkbench and the MMS is
  sent to the CybSticker server
• Readers who localize the sticker can read it’s content (image, video, sound
  and text) by photographing the matrix code and sending it to the CybSticker
  server.

Challenges

In the project we had a lot of Image Analysis challenges, mainly due to the wide range of different mobile phones used. The cameras often had poor optics and no macro focus, giving highly distorted, blurry and low resolution images. In addition the images was captured in varying lighting conditions, such as shadows and low lighting.

To cope with the problems we created a custom matrix code, specifically designed for robustness and simple decoding on mobile phones. The data was encoded as a square binary matrix pattern which gave rapid estimation of perspective-planar transform parameters (using four corners). 

The system was implemented and successfully tested with a exceptionally high readrate at the Kosmorama International Film Festival together with our partner  Mobiletech. 

Related article

Using mobile phones as matrix bar code readers for creating and accessing "digital grafitti" Schumann-Olsen, H.; Thielemann, J.T.; Rahlff, O-W.; Ødegård, H.
9th European Conference on Computer Vision (ECCV), Graz, Austria, May 2006, Demonstation Sessions

The image shows a step by step example decoding of an actual code.