Embedding data in halftone images

Patent metadata

Field	Value
Publication number	US-10027843-B2
Application number	US-201415114392-A
Country	US
Kind code	B2
Filing date	Jan 30, 2014
Priority date	Jan 30, 2014
Publication date	Jul 17, 2018
Grant date	Jul 17, 2018

Abstract

A data-bearing image (391) is created from a carrier image (371). The carrier image (371) is scaled to produce a scaled image. A clustered-dot halftone screen is applied to the scaled image to produce a halftone image. A resulting number of cells in the halftone image conforms to a cell count (372) that includes a horizontal cell value and a vertical cell value. Payload data is encoded into the halftone image to produce a data-bearing halftone image, including shifting pixel clusters within cells of the halftone image that include pixel clusters.

First claim

We claim:

1. A system that creates a data-bearing image, comprising:
a halftone image generator that receives a carrier image ( 371 ), the halftone image generator including:
an image scaler that scales the carrier image to produce a scaled image, and
a halftoner that applies a clustered-dot halftone screen to the scaled image to produce a halftone image so that a resulting number of cells in the halftone image conform to a cell count that includes a horizontal cell value and a vertical cell value;

an encoder that produces a data-bearing halftone image by encoding payload data into the halftone image, including shifting pixel clusters within cells of the halftone image that include pixel clusters; and,
an output device configured to output the data-bearing halftone image.

2. A system as in claim 1 wherein the output device is a printer that is configured to print a hard copy of the data-bearing halftone image.

3. A system as in claim 1 wherein the halftone image generator includes an image preprocessor that performs preprocessing on the carrier image before the carrier image is scaled.

4. A system as in claim 1 wherein the encoder includes a preprocessor that performs preprocessing on the payload data before encoding the payload data into the halftone image.

5. A system as in claim 1 wherein the encoder includes a preprocessor that performs preprocessing on the payload data before encoding the payload data into the halftone image, the preprocessing including at least one of the following:
error correction encoding;
encryption;
data compression.

6. A system as in claim 1 wherein the encoder encodes at most one bit of data in each cell.

7. A system as in claim 1 wherein every bit of data in the payload data is redundantly assigned to more than one cell in the cells of the scaled image.

8. A system as in claim 1 wherein the cell count is determined from physical size constraints associated with the data-bearing halftone image.

9. A system as in claim 1 wherein the system additional recovers the data payload from the data-bearing halftone image, and wherein the system additionally comprises:
a cell alignment block that receives the data-bearing halftone image and uses the cell count including the horizontal cell value and the vertical cell value to locate cells within the data-bearing halftone image; and,
raw payload recovery block that detects shifting of pixel clusters within the cells within the data-bearing halftone image to recover the payload data encoded within the data-bearing halftone image.

10. A system as in claim 9 additionally comprising:
a payload post processor that performs post processing on the recovered data to produce the payload data.

11. A system as in claim 9 additionally comprising:
an image capture device that captures a hard copy that includes the data bearing halftone image, the image capture device producing a digital version of the data-bearing halftone image that the image capture device forwards to the cell alignment block.

12. A system as in claim 9 , wherein an estimate of the scale of the image is combined with cell count to determine a boundary that, when correctly placed, delimits the captured data-bearing halftone image.

13. A system as in claim 12 , wherein the boundary is combined with iterative measurements to determine the location of the captured data-bearing halftone image.

14. A method for creating a data-bearing image, comprising;
receiving a carrier image;
scaling the carrier image to produce a scaled image;
applying a clustered-dot halftone screen to the scaled image to produce a halftone image,
encoding payload data into the halftone image to produce a data-bearing halftone image, including:
determining cell count including associated horizontal and vertical values from physical size constraint on the data-bearing halftone image; and,

using a hardware output device to produce the data-bearing halftone image with the determined cell count.

15. The method of claim 14 , further comprising:
receiving the data-bearing halftone image;
using the cell count including the horizontal cell value and the vertical cell value to locate cells within the data-bearing halftone image; and,
detecting shifting of pixel clusters within the cells within the data-bearing halftone image to recover the payload data encoded within the data-bearing halftone image.

16. A system to recover a data payload from a data-bearing halftone image, comprises:
a cell alignment block that receives the data-bearing halftone image and uses the cell count including the horizontal cell value and the vertical cell value to locate cells within the data-bearing halftone image; and,
raw payload recovery block that detects shifting of pixel clusters within the cells within the data-bearing halftone image to recover the payload data encoded within the data-bearing halftone image.

17. The system of claim 16 , further comprising:
a payload post processor that performs post processing on the recovered data to produce the payload data.

18. The system of claim 16 , further comprising:
an image capture device that captures a hard copy that includes the data-bearing halftone image, the image capture device producing a digital version of the data-bearing halftone image that the image capture device forwards to the cell alignment block.

19. The system of claim 16 , wherein an estimate of the scale of the image is combined with cell count to determine a boundary that, when correctly placed, delimits the captured data-bearing halftone image.

20. The system of claim 19 , wherein the boundary is combined with iterative measurements to determine the location of the captured data-bearing halftone image.

Assignees

• Hewlett Packard Development Co

Inventors

• Ulichney Robert
• Gaubatz Matthew D
• Pollard Stephen

Classifications

• H04N2201/3281

  Encryption; Ciphering · CPC title

• H04N1/4486

  using digital data encryption · CPC title

• H04N1/32277

  Compression · CPC title

• H04N2005/91335

  the copy protection signal being a watermark · CPC title

• H04N19/467

  characterised by the embedded information being invisible, e.g. watermarking · CPC title