Two-dimensional bar codes that are both intensity-modulated and orientation-modulated for transmitting sensitive information along with non-sensitive information
A dual-modulated QR code (DMQR code) is in the format of a conventional QR code but uses elongated markers instead of black squares in the code modules. The positions of the markers within the DMQR code represent a nonconfidential primary message, and the orientations of the markers within the modules of the DMQR code represent a confidential secondary message.
1. A method of producing a two-dimensional barcode in which primary message data and secondary message data are encoded using a geometric layout having conventional synchronization patterns, conventional alignment patterns, and conventional data carrying modules, comprising:
a. encoding binary digit values of the primary message data by rendering the data carrying modules either as blank or as containing an elongated colored marker; and
b. encoding the secondary message data by varying only the orientations of said markers between at least two of
i. a vertical orientation,
ii. a horizontal orientation,
iii. a first inclined orientation, and
iv. a second inclined orientation.
2. The method of claim 1 , wherein the markers are elliptical.
3. The method of claim 1 , wherein the markers are all of identical size.
4. The method of claim 1 , wherein vertically and horizontally oriented markers have a first size and markers having inclined orientations have a larger size.
5. A method of extracting primary message data and secondary message data from a video image of a two-dimensional barcode produced using the method of claim 1 , comprising:
a. decoding the primary message data from the image using a conventional two-dimensional barcode decoding method; and
b. decoding the secondary message data from the orientations of the markers in the image.
6. The method of claim 5 , wherein the two-dimensional barcode decoding method is a QR barcode decoding method.
7. The method of claim 1 , wherein the conventional synchronization patterns, conventional alignment patterns, and encoding of binary digit values of the primary message data are used in conventional QR code encoding.