Halftone screens encoding signatures
View Patent ↗In an example, a method includes, at least one processor, in response to each of a plurality of requests, determining a halftone screen. Determining the halftone screen comprises encoding a signature pattern in the halftone screen, and halftone screens for different requests may be encoded with a different signature pattern. The halftone screen may be arranged such that, when applied to image data to provide a printed output, the pattern is discernible therein to provide a signature for the printed output.
1 . A method comprising, by at least one processor:
in response to each of a plurality of requests, determining a halftone screen, wherein determining the halftone screen comprises encoding one unpartitioned signature pattern into the halftone screen, and halftone screens for different requests are encoded with a different one unpartitioned signature pattern; and
applying the halftone screen to image data, the halftone screen being arranged such that, when applied to the image data to provide a printed output, the one unpartitioned signature pattern is discernible therein to provide a signature for the printed output, wherein applying the halftone screen to the image data includes:
associating a pixel of the halftone screen with a pixel of the image data, comparing a pixel value of the image data with a threshold value of the pixel of the halftone screen, and
determining print instructions for the pixel of image data based on a result of the comparison.
2 . A method according to claim 1 further comprising transmitting the halftone screen to an entity identified in the request.
3 . A method according to claim 2 further comprising encrypting the halftone screen and transmitting the encrypted halftone screen.
4 . A method according to claim 2 further comprising: storing an indication of each one unpartitioned signature pattern in association with an identity of each entity to which the halftone screen was transmitted.
5 . A method according to claim 4 wherein storing the indication of each one unpartitioned signature pattern comprises securely storing the indication.
6 . A method according to claim 4 further comprising:
obtaining a digital sample of the printed output;
identifying the one unpartitioned signature pattern in the digital sample; and
determining that the one unpartitioned signature pattern is a stored signature associated with an entity.
7 . A method according to claim 1 , wherein the halftone screen includes a matrix of threshold values that corresponds to the one unpartitioned signature pattern.
8 . The method of claim 1 , wherein the one unpartitioned signature pattern includes an encoded pattern of dots or lines.
9 . The method of claim 1 , wherein the one unpartitioned signature pattern includes one or more predetermined shapes.
10 . The method of claim 1 , wherein the one unpartitioned signature pattern includes an inconsistency in an otherwise regular pattern.
11 . The method of claim 1 , wherein the one unpartitioned signature pattern includes a predetermined grayscale pattern.
12 . The method of claim 1 , wherein the one unpartitioned signature pattern includes an irregular pattern.
13 . The method of claim 1 , wherein the one unpartitioned signature pattern includes a geometric pattern.
14 . A method comprising, by at least one processor:
in response to each of a plurality of requests, determining a halftone screen, wherein determining the halftone screen comprises encoding a signature pattern into the halftone screen, and halftone screens for different requests are encoded with a different signature pattern; and
applying the halftone screen to image data, the halftone screen arranged such that, when applied to the image data to provide a printed output, the pattern is discernible therein to provide a signature for the printed output; and
preventing selection of the halftone screen or signature pattern in response to a subsequent request.
15 . The method of claim 14 , wherein determining the halftone screen comprises:
selecting the halftone screen from a plurality of predetermined halftone screens; and
selecting the signature pattern from a plurality of predetermined signature patterns.
16 . The method of claim 14 , wherein determining the halftone screen comprises generating a pattern on a deterministic basis.
17 . The method of claim 14 , further comprising: storing an indication of the signature in association with an identity of an entity to which the halftone screen was transmitted.
18 . The method of claim 14 , wherein applying the halftone screen to the image data includes:
associating a pixel of the halftone screen with a pixel of the image data,
comparing a pixel value of the image data with a threshold value of the pixel of the halftone screen, and
determining print instructions for the pixel of image data based on a result of the comparison.