A method of printing a digital photo including transmitting instructions for printing the photo to a printer, printing the photo onto a surface using the printer; also printing on the surface coded data indicative of an identity of the photo and a plurality of reference points on the photo, wherein the coded data is printed on the surface in a form which can be read by an optical sensing device to identify a location of the sensing device relative to the photo, thereby enabling a function to be invoked in relation to the photo.