Topic areas


  The Active Print project





  The Active Print project



Q: What is the Active Print project?



A: The Active Print project is a collaboration between companies investigating how to bring about a new ecosystem. That ecosystem is the "printed internet", in which everyday printed and displayed items become links to content, retrieved with camera phones.




Q: Is Active Print a new idea?



A: The idea of reading codes with a camera and using the data in them to retrieve relevant content has been around for a long time. The companies participating in Active Print represent significant experience with that technology. However, an important shift in the past two years or so is that camera phones have become capable of reading codes. Since camera phones are becoming prevalent, there is a new opportunity to make this a mass phenomenon. It is already big in Japan. What is novel about the Active Print project (apart from some of the specifics of the technologies we are developing) is that we represent an ecosystem-wide look at how to link printed matter to online content, including understanding the user and authoring experiences, and developing business models.




Q: When and how did the Active Print project begin?



A: Active Print began life as the "Active Posters" research project at HP Labs in Bristol, in Autumn 2004. External partners joined and external projects took place from Spring 2005. The initial focus was on posters because they have the interesting property that they are situated, often in places where people dwell; for example, there are posters at bus stops and inside transportation. Since then, the project has expanded its remit to all forms of printed matter, as well as displays.





Q: What is popup text for?



A: The popup text provides an immediate way of engaging the user "beyond the paper", without any need for network communication. Indeed, some codes contain only popup text, needing no links to network content. The popup text can be used, for example, to tell the user more about what is printed, or to tease the user into activating the code.




Q: What types of connection can Glass make from codes?



A: Activating a code can cause a download, or send a text (SMS) message, or make a call, or.... The idea is for codes to be extensible to various types of interaction. An important research goal of Active Print is to understand in which types of situation these different interaction models are appropriate, and to support them accordingly.




Q: What is the purpose of the History, and how big can it grow?



A: The History is for "after the fact" code review and activation. Activated codes are automatically saved, but users can also save coded links if they are too busy to activate them in the moment. Users can use the saved codes to revisit content themselves, and to show their friends what they experienced. They can also "give" the code to their friends, by displaying it on their camera phone for reading. The History can hold up to 100 codes. If that limit is reached, the oldest items are deleted as new ones are added. But the user can delete individual items of their choosing or clear the entire history list.





Q: What types of codes are supported?



A: At the moment, we support only QR codes and Datamatrix codes (for examples, look here). Many other types of code exist, and we may go on to support others. In particular, as phone capabilities improve, the standard linear barcodes on products in the supermarket will be supported. QR and Datamatrix codes are our initial choice because they represent a good balance between important factors such as readability, robustness to errors, data density and aesthetics. They are also widely used standards.




Q: How much data can QR and Datamatrix codes hold?



A: The answer depends on the target phone's optics and the resolution of its imaging device. The more data a code holds, the closer the phone needs to be held. That is because the code needs to occupy as many pixels as possible, so that the code's cell size is sufficiently larger than the pixel size. A code with too much data for the phone's capabilities tends either to get out of focus, or to be too big for the screen. That is because ordinary camera phones (without a macro lens) are designed for taking pictures of subjects such as people, from a distance of about a metre or more. We expect camera phones to evolve so as to be better suited to the Active Print paradigm.

A rule of thumb is that codes of 2-5cm on a side can contain up to about 100 bytes and still be readable at video rate using a camera phone with VGA resolution. It's a good idea to mininimise the length of URLs in codes using a service such as




Q: How large should a code be printed?.



A: This depends on such factors as the capabilities of the target phones, the amount of data in the code, the symbology used (QR or Datamatrix - the latter is denser), and the distance from which the user is expected to read the code.

A rule of thumb is that codes smaller than about 2-3cm on a side are too difficult to read with most camera phones currently available.




Q: Should I use Datamatrix or QR codes?.



A: It's up to you. Datamatrix codes are somewhat denser and faster to read but have different aesthetics.