# US 2019/0378235 A1 · Generating signal bearing art using stipple, voronoi and delaunay methods and reading same

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- Number: US 2019/0378235 A1
- Document ID: US20190378235A1
- Status: Published application
- Kind: A1
- Application number: 16/435,164
- Filed: 2019-06-07
- Published: 2019-12-12
- Earliest claimed: 2018-06-08
- Assignees: Digimarc Corporation
- Applicants: Digimarc Corporation
- Inventors: Ajith M. Kamath
- Web page: https://patentgrep.com/patent/US20190378235A1

## CPC

- G06T 1/005: {Robust watermarking, e.g. average attack or collusion attack resistant}
- G06T 1/0028: {Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking}
- G06T 1/0064: {Geometric transfor invariant watermarking, e.g. affine transform invariant}
- H04N 1/32309: {in colour image data}
- H04N 1/3232: {Robust embedding or watermarking}
- G06T 2201/0061: Embedding of the watermark in each block of the image, e.g. segmented watermarking
- G06T 2201/0062: Embedding of the watermark in text images, e.g. watermarking text documents using letter skew, letter distance or row distance
- G06T 2201/0202: whereby the quality of watermarked images is measured; Measuring quality or performance of watermarking methods; Balancing between quality and robustness
- G06T 2201/0601: whereby calibration information is embedded in the watermark, e.g. a grid, a scale, a list of transformations
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

Optical code signal components are generated and then transformed into signal bearing art that conveys machine readable data. The components of an optical code are optimized to achieve improved signal robustness, reliability, capacity and/or visual quality. An optimization program can determine spatial density, dot distance, dot size and signal component priority to optimize robustness. An optical code generator transforms tiles of an optical code or image embedded with the optical code into signal-bearing art using stipple, Voronoi, Delaunay or other graphic drawing methods so as to retain prioritized components of the optical code. The optical code is merged into a host image, such as imagery, text and graphics of a package or label, or it may be printed by itself, e.g., on an otherwise blank label or carton. A great number of other features and arrangements are also detailed.

## Claims

### Claim 1 (depends on 14)

The method of claim 14 comprising:
generating optical code signal components, comprising a variable payload;
constructing a tile of a two-dimensional optical code, the tile comprising optical code elements located at coordinates within the tile at a spatial density;
drawing line art based on the coordinates, the line art conveying the variable digital payload; and
inserting the line art comprising plural tiles in an output image, the optical code being machine readable from an optical scan of the output image.

### Claim 2 (depends on 1)

The method of claim 1 wherein the optical code signal components comprise a reference signal for geometric synchronization.

### Claim 3 (depends on 1)

The method of claim 1 wherein the constructing comprises:
transforming the variable payload into a first optical code signal at a first spatial density, the first optical code signal comprising a two-dimensional array of pixel values that includes a reference signal for geometric synchronization; and
converting the first optical code signal to a second optical code signal at a second spatial density lower than the first spatial density, the second optical code signal comprising parts of the first optical code signal at the coordinates such that the spatial density of non-zero-pixel values of the second optical code signal is less than the first optical code signal.

### Claim 4 (depends on 1)

The method of claim 1 wherein drawing line art comprises drawing line segments according to a traveling sales person method.

### Claim 5 (depends on 1)

The method of claim 1 wherein drawing line art comprises drawing a contour plot.

### Claim 6 (depends on 1)

The method of claim 1 wherein drawing line art comprises drawing line segments that intersect at luminance minima of the two-dimensional optical code.

### Claim 7 (depends on 6)

The method of claim 6 wherein drawing line segments that intersect at luminance minima comprises generating a Delaunay triangulation of coordinates at the luminance minima.

### Claim 8 (depends on 1)

The method of claim 1 wherein drawing line segments comprises drawing a Voronoi diagram around luminance maxima of the two-dimensional optical code.

### Claim 9 (depends on 1)

The method of claim 1 wherein drawing line segments comprise placing graphic line art shapes around luminance maxima of the two-dimensional optical code.

### Claim 10 (depends on 14)

The method of claim 14 comprising:
a step for generating a dense optical code signal;
a step for generating a sparse optical code signal from the dense optical code signal;
a step for creating artwork carrying the sparse optical code signal; and
a step for inserting the artwork in a printed object design file.

### Claim 11 (depends on 10)

The method of claim 10 wherein the step for generating a dense optical code signal comprises generating an encoded payload, mapping the encoded payload to cells in a two-dimensional array, and combining the encoded payload with a reference signal.

### Claim 12 (depends on 10)

The method of claim 10 wherein the step for generating a sparse optical code signal comprises sorting elements of the dense optical code signal, and selecting elements based on amplitude and a minimum spacing constraint.

### Claim 13 (depends on 10)

The method of claim 10 wherein the step for generating the sparse optical code signal comprises filtering the dense optical code signal with a prediction filter and selecting elements of the optical code signal based on the filtering and a minimum spacing constraint.

### Claim 14

A method of generating a machine-readable optical code, the method comprising:
transforming a plural bit, variable payload into a pattern of spaced apart elements according to a keep-out distance between the elements, the elements being located at coordinates in a two-dimensional area; and
drawing a stipple, Voronoi, or Delaunay pattern based on the coordinates, the pattern conveying the variable digital payload.

### Claim 15 (depends on 14)

The method of claim 14 wherein transforming comprises:
transforming the plural bit, variable payload into a dense optical code signal tile at a first spatial density;
converting the dense optical code signal tile to a sparse optical code signal at a second spatial density lower than the first spatial density, the sparse optical code signal tile comprising parts of the dense optical code signal at the coordinates.

### Claim 16 (depends on 14)

The method of claim 14 comprising:
transforming a plural bit, variable payload into an optical code signal;
combining the optical code signal with host artwork; and
drawing a stipple, Voronoi or Delaunay pattern based on grayscale values of the combined optical code signal and host artwork.

### Claim 17

A method of generating a machine-readable optical code, the method comprising:
generating an optical code signal from a variable digital payload, the optical code signal comprising pixels carrying the variable digital payload and a reference signal for geometric registration;
generating a centroidal Voronoi diagram of the optical code signal based on pixel values of the optical code signal values and seed point locations;
forming an optical code carrying image by placing stipples, lines representing a Voronoi pattern or lines representing a Delaunay pattern at locations determined within Voronoi regions of the centroidal Voronoi diagram; and
inserting the optical code carrying image in an output image, the variable payload being machine readable from an optical scan of the output image applied to a physical object.

### Claim 18 (depends on 17)

The method of claim 17 wherein generating comprises combining host artwork according to values of error correction encoded signal elements of the variable payload and the reference signal, the modifying being performed by altering luminance of the host artwork.

### Claim 19 (depends on 17)

The method of claim 17 wherein generating comprises combining host artwork according to values of error correction encoded signal elements of the variable payload and the reference signal, the modifying being performed by altering chrominance of the host artwork.

### Claim 20

A system comprising:
means for generating an image comprising an optical code, the optical code comprising an encoded variable digital payload and a geometric registration pattern;
means for generating an optical code from the image, the optical code having elements at a predetermined spacing and size; wherein the means for generating the optical code comprises a programmed computer configured to compute a centroidal Voronoi diagram of the image and place stipples at coordinates of the optical code based on Voroinoi regions in the Voronoi diagram; and
means for inserting the optical code in a printed object design file.

### Claim 21

(canceled)