8. An apparatus comprising: one or more processors and a memory; an input module adapted to receive, from a user interface, an annotation associated with a background image; a control module adapted to add the annotation to a queue of pending annotations; an output module adapted to transmit the annotation from the apparatus to a server; wherein the control module removes the annotation from the queue of pending annotations, and adds the annotation to a list of acknowledged annotations, when an acknowledgment of the annotation is received by the apparatus from the server; wherein the output module generates a display image comprising the background image, annotations in the list of acknowledged annotations, and annotations in the queue of pending annotations; and wherein the one or more processors and the memory cooperate to implement at least in part the input, output and control modules.
14. The apparatus of claim 8 : wherein the output module generates an acknowledged annotation image comprising the background image, and the annotations in the list of acknowledged annotations; and wherein the output module generates the display image based on the acknowledged annotation image and the annotations in the queue of pending annotations.