US 8,275,168 B2Granted

Orientation free watermarking message decoding from document scans

AssigneeSeiko Epson Corporation

InventorsChunyu Gao, Jing Xiao

Life of this patent

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Abstract

Bit data is encoded into characters in an input image by providing different darkness levels for pixels in either half of a text character. To determine if the input image is of a right-side up document, or an upside-down document, multiple scans of the input image at 90° rotations between scans may be made. Each scan result is searched for occurrences of a indicator prefix bit-sequence. The scan that contains the indicator prefix bit-sequence is elected as the right-side up orientation for the input image. If multiple scans show occurrences of the indicator prefix bit-sequence, then the scan that has the highest number of occurrences is elected as the correct orientation. Alternatively, the number of data bits between repeated occurrences of the indicator prefix bit-sequence is compared with a predefined message bit size, and the scan that matches most closely is elected as the correct orientation.

Claims14

Dependent claims

A processing unit for recovering an embedded message within an input image, comprising:

(i) an input for receiving said input image having logic data bit information encoded into characters within said input image;
(ii) a site detection unit for identifying characters within said input image;
(iii) a bit extraction unit for extracting logic data bit information from said characters to define a working set of logic bits;
(iv) a detect bitstring unit for:
(1) conducting a first search operation on said working set of logic bits for occurrences of a predefined indicator prefix bit-sequence;
(2) reversing the bit order of said working set of logic bits and logically inverting each bit to create an inverse set of logic bits;
(3) conducting a second search operation on said inverse set of logic bits for occurrences of said predefined indicator prefix bit-sequence;
and
(4) identifying a true set of logic bits based on the results of said first and second search operations;
and
(v) a decoding unit for converting said true set of logic bits to characters according to a predefined decoding scheme.

8 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/549,842Filed 28 Aug 2009
Published: US 2011/0051989 A13 Mar 2011
Granted: 25 Sep 2012
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

H04N 1/32208
Spatial or amplitude domain methods: involving changing the magnitude of selected pixels, e.g. overlay of information or super-imposition
G06T 1/0021
General purpose image data processing: image watermarking
G06T 1/005
Image watermarking: robust watermarking, e.g. average attack or collusion attack resistant
H04N 1/32144
Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title: embedded in the image data, i.e.…