Encoding invisible electronic information in a printed document
AssigneeXerox Corporation
InventorSteven J Harrington
Life of this patent
Estimating the term…
Abstract
A printed image can be redundantly encoded by printing a visible image using a colorant with a luminance that contrasts with that of the output sheet and printing a redundant image using a colorant with a luminance that varies only slightly from that of the output sheet. Accordingly, the visible image can be easily read by a user while the redundant image is substantially invisible to the human eye at normal-reading distances, yet capable of being captured by a conventional digital scanner. In one aspect, redundantly encoded images may be printed on a white background, with visible images printed in black text and redundant images printed in blue in content regions of the visible image and in yellow in its background regions.
Claims11
A digital printing system, comprising:
- an image processor configured to generate binary printer signals that represent an encoded image inside a scan image, wherein said encoded image includes a visible representation of a presented image and has a substantially invisible representation of an original image printed among said presented image;
- a print channel configured to receive said binary printer signals from said image processor as a plurality of separations;
- an encoded image analyzer configured to obtain an encoding transformation function used to position pixels corresponding to said substantially invisible original image representation among said original image;
- an original image location identifier that identifies pixels in said scan image that correspond to locations of said substantially invisible original image representation and applies a decoding transformation function to said substantially invisible original image representation corresponding pixels;
- an original image recovery device configured to assign a selected grayscale value to each pixel of said substantially invisible original image representation identified by said decoding transformation function;
- and
- an output generator configured to generate a visible representation of said original image.
A method, comprising:
- digitally capturing grayscale pixels that represent an encoded image inside a scan image, wherein said encoded image includes a visible representation of a presented image and has a substantially invisible representation of an original image printed among said presented image;
- identifying an encoding transformation function used to position pixels corresponding to said substantially invisible original image representation among said original image;
- locating pixels in said scan image that correspond to locations of said substantially invisible original image representation;
- applying a decoding transformation function to said substantially invisible original image representation corresponding pixels to locate pixels corresponding to said original image;
- and
- assigning a selected grayscale value to each of said original image corresponding pixels.
Dependencies are inferred from the claim text.