Encoding dot patterns into printed images based on source pixel color

Patent metadata

Field	Value
Publication number	US-11089180-B2
Application number	US-201816971616-A
Country	US
Kind code	B2
Filing date	Mar 20, 2018
Priority date	Mar 20, 2018
Publication date	Aug 10, 2021
Grant date	Aug 10, 2021

Abstract

In an example method, a set of source pixels corresponding to an image to be printed and a dot pattern of pixels including information to be encoded across the image are received. The dot pattern of pixels is mapped to a corresponding subset of the source pixels. A value of a clipping channel color in the subset of the source pixels is modified based on an original value of the clipping channel color for each pixel in the subset. The clipping channel color is used to detect the dot pattern of pixels. The image including the subset of pixels with modified clipping channel colors is printed.

First claim

What is claimed is:

1. A method comprising:
receiving a set of source pixels corresponding to an image to be printed and a dot pattern of pixels comprising information to be encoded across the image;
mapping the dot pattern of pixels to a corresponding subset of the source pixels;
modifying a value of a clipping channel color in the subset of the source pixels based on an original value of the clipping channel color for each pixel in the subset, wherein the clipping channel color is used to detect the dot pattern of pixels; and
printing the image comprising the subset of pixels with modified clipping channel colors.

2. The method of claim 1 , wherein modifying the value of the clipping channel color comprises setting the value of the clipping channel color to a maximum value in response to detecting that the original value of the clipping channel color of a pixel in the subset of source pixels is less than a threshold or setting the value of the clipping channel color to zero in response to detecting that the value of the clipping channel color of a pixel in the subset of source pixels is greater than the threshold.

3. The method of claim 1 , wherein modifying the value of the clipping channel color comprises setting the value of the clipping channel color to a maximum value in response to detecting that a most significant bit of the original value of the clipping channel color of a pixel in the subset of source pixels is equal to zero or setting the value of the clipping channel color to zero in response to detecting that the most significant bit of the original value of the clipping channel color of a pixel in the subset of source pixels is equal to one.

4. The method of claim 1 , comprising modifying the value of at least one additional clipping channel color in the subset of source pixels based on an original value of the at least one additional clipping channel color, wherein the clipping channel color, the at least one additional clipping channel color, or any combination thereof, is used to detect the dot pattern of pixels.

5. The method of claim 1 , comprising receiving a scanned copy of the printed image, detecting the dot pattern of pixels using the clipping channel color, and extracting information from the detected dot pattern of pixels.

6. The method of claim 1 , wherein mapping the dot pattern of pixels to the corresponding subset of the source pixels comprises comparing a source page and a dot pattern image one region, such as one pixel, at a time to match the corresponding subset of the source pixels to the dot pattern of pixels.

7. The method of claim 1 , wherein modifying the value of the clipping channel color in the subset of the source pixels based on the original value of the clipping channel color for each pixel in the subset further comprises converting the original value for each pixel in the subset into a three-bit number including red, green, and blue (RGB) most significant bits (MSBs).

8. An apparatus comprising:
a receiver to receive a set of source pixels corresponding to an image to be printed and a dot pattern of pixels comprising information to be encoded across the image;
a pattern mapper to map the dot pattern of pixels to a corresponding subset of the source pixels;
a pixel modifier to generate a color component representation for each of the corresponding subset of the source pixels and modify the color of each of the subset of the source pixels based on a replacement color corresponding to the color component representation in a predefined lookup table; and
a printer to print the image comprising the subset of pixels with modified colors.

9. The apparatus of claim 8 , wherein a size of the dot pattern of pixels is the same size as a source document page of the set of source pixels.

10. The apparatus of claim 8 , wherein the color component representation comprises a three bit index corresponding to most significant bits of red, green, and blue color components of each of the subset of the source pixels, and the predefined lookup table comprises replacement colors comprising cyan, magenta, yellow, and black.

11. The apparatus of claim 8 , wherein the predefined lookup table comprises a replacement color for each of eight color component representations based on low visibility and high detectability in a color component channel to be used to detect the dot pattern of pixels.

12. The apparatus of claim 11 , wherein the replacement color for each of the eight color components representations is predefined based on a printed and scanned test chart comprising candidate replacement colors against various background colors.

13. The apparatus of claim 8 , wherein the pattern mapper maps the dot pattern of pixels to the corresponding subset of the source pixels by comparing a source page and a dot pattern image one region, such as one pixel, at a time to match the corresponding subset of the source pixels to the dot pattern of pixels.

14. A non-transitory machine-readable storage medium encoded with instructions executable by a processor, the machine-readable storage medium comprising instructions to:
receive a set of source pixels corresponding to an image to be printed and a dot pattern of pixels comprising information to be encoded across the image;
map the dot pattern of pixels to a corresponding subset of the source pixels;
modify a value of a clipping channel color in the subset of the source pixels based on an original value of the clipping channel color for each pixel in the subset, wherein the clipping channel color is to be used to detect the dot pattern of pixels; and
print the image comprising the subset of pixels with modified clipping channel colors.

15. The non-transitory machine-readable storage medium of claim 14 , comprising instructions to set the value of the clipping channel color to a maximum value in response to detecting that the original value of the clipping channel color of a pixel in the subset of source pixels is less than a threshold and set the value of the clipping channel color to zero in response to detecting that the value of the clipping channel color of a pixel in the subset of source pixels is greater than a threshold.

16. The non-transitory machine-readable storage medium of claim 14 , comprising instructions to set the value of the clipping channel color to a maximum value in response to detecting that a most significant bit of the original value of the clipping channel color of a pixel in the subset of source pixels is equal to zero and set the value of the clipping channel color to zero in response to detecting that the a most significant bit of the original value of the clipping channel color of a pixel in the subset of source pixels is equal to one.

17. The non-transitory machine-readable storage medium of claim 14 , comprising instructions to modify the value of at least one additional clipping channel color in the subset of source pixels based on an original value of the at least one additional clipping channel color, wherein the clipping channel color, the at least one additional clipping channel color, or any combination thereof, is to be used to detect the dot pattern of pixels.

18. The non-transitory machine-readable storage medium of claim 14 , comprising instructions to receive a copy of the printed image, detect the dot pattern of pixels using the clipping channel color, and extract information from the detected dot pattern of pixels.

19. The non-transitory machine-readable storage medium of claim 14 , wherein the machine-readable storage medium comprises inst

Assignees

• Hewlett Packard Development Co

Inventors

• Ulichney Robert
• Gaubatz Matthew D

Classifications

• H04N1/32219 Primary

  involving changing the position of selected pixels, e.g. word shifting, or involving modulating the size of image components, e.g. of characters (H04N1/32224 takes precedence) · CPC title

• H04N1/32309 Primary

  in colour image data · CPC title

• G06K15/1892

  adding a digitally readable background pattern · CPC title

• H04N1/32208

  involving changing the magnitude of selected pixels, e.g. overlay of information or super-imposition (H04N1/32219, H04N1/32224 take precedence) · CPC title

• H04N1/32256

  in halftone data · CPC title