Two dimensional information symbol

摘要

Disclosed is a method (500) of encoding a message (501) into a target area of an original image by determining a set of data items into which the message can be partitioned, partitioning the message into the data items, encoding (580) a first mark into the target area at a location determined by applying (550) a hash function (505) to a first data item, and encoding (580) a second mark into the target area at a location dependent upon (a) a hash value determined by applying (550) the hash function (505) to the first data item and a second data item, (b) the location of the encoded first mark, and (c) a predetermined constraint (504), wherein the first and second marks form at least part of a pattern of marks in the target area of the encoded image, the pattern having a visual characteristic defined by the predetermined constraint.

主权项

1. A method of decoding a pattern of marks satisfying a predetermined constraint in an encoded image, to reconstruct a recovered message, the method comprising the steps of:
(a) determining a set of data items into which candidate messages can be partitioned; (b) determining a set of candidate messages; (c) selecting a current candidate message from the determined set of candidate messages; (d) applying an encoding method to said current candidate message to generate a current pattern of marks by;
(da) partitioning the selected current candidate message into said data items;(db) encoding a first mark into a target area of an original image to form the encoded image, at a location determined by applying a hash function to a first data item of the selected current candidate message;(dc) encoding a second mark into the target area at a location dependent upon (i) a hash value determined by applying the hash function to the first data item and a second data item of the selected current candidate message, (ii) the location of the encoded first mark, and (iii) a predetermined constraint; wherein the first and second marks form at least part of a pattern of marks in the target area of the encoded image, said pattern having a visual characteristic defined by the predetermined constraint; (e) if the current pattern of marks does not permit addition of a further mark without violating the predetermined constraint, then the current candidate message is one of said recovered message and a null set; (f) if the current pattern of marks does permit addition of a further mark without violating the predetermined constraint, then the method comprises the further steps of:
(fa) creating a set of new candidate messages by appending each possible data item from the step (a) to the current candidate message;(fb) adding the new set of candidate messages to the set determined in the step (b); and(fc) repeating the steps (c) to (f).