Encoded Signature Halftone Screen

Abstract

In an example, a method includes at least one processor determining a halftone screen in response to each of a plurality of requests. Determining the halftone screen includes encoding a signature pattern in the halftone screen, and the halftone screens for different requests may be encoded with different signature patterns. The halftone screen may be arranged so that when applied to image data to provide a printout, the pattern is visible in the printout to provide a signature for the printout.

Description

Technical Field

[0001] This disclosure relates generally to data processing. Background Art

[0002] A printing system can convert input data (e.g., data representing an image to be printed in two dimensions or data representing an object to be printed in three dimensions) into printing instructions that specify where printing material (e.g., colorants such as ink, toner, or other printable material) is to be placed during a printing operation.

[0003] Using techniques in converting data includes using a halftone screen. In some examples, the halftone screen is implemented as an array or matrix of threshold values ​​that correspond to pixels in the input data. A value associated with a pixel in the input data is compared to at least one threshold value for that pixel, and printing material may be deposited (or not deposited) based on the comparison. Examples of halftone screens include amplitude modulation halftone screens where the size of the applied dots or spots can be varied and frequency modulation halftone screens where the number of applied dots or spots can be varied. Summary of the invention

[0004] In one aspect, the present disclosure provides a method for data processing, comprising: determining, by at least one processor: a halftone screen in response to each of a plurality of requests, wherein determining the halftone screen comprises encoding a signature pattern into the halftone screen, and different signature patterns are encoded in halftone screens for different requests; and applying the halftone screen to image data, wherein the halftone screen is arranged so that when applied to the image data to provide a printout, the pattern can be seen in the printout so as to provide a signature for the printout, wherein the printout comprises one or more halftone blocks, the one or more halftone blocks comprising less than a complete pattern, the complete pattern corresponding to the encoded signature pattern of the halftone screen.

[0005] In one aspect, the present disclosure provides a method for data processing, comprising: obtaining, by a processing circuit, a digital sample of a printed image; determining, by the processing circuit, whether the printed image includes a halftone signature based on the digital sample; and verifying, by the processing circuit, a source of the image based on whether the printed image includes the halftone signature, wherein the digital sample includes one or more halftone blocks, the one or more halftone blocks include less than a complete pattern, and the complete pattern corresponds to the halftone signature. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] For a more complete understanding, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

[0007] Figure 1is a flow chart of an example of a method of determining a halftone screen for an encoded signature pattern;

[0008] Figure 2A An example of image data is shown;

[0009] Figure 2B An example of a printout including a signature pattern is shown;

[0010] Figure 2C , Figure 2D and Figure 2E are examples of halftone pattern representations encoding different signature patterns;

[0011] Figure 3 is a flow chart of an example of a method of assigning halftone screens;

[0012] Figure 4 and Figure 5 is an example method of determining whether a signature is included in a printed image; and

[0013] Figure 6 and Figure 7 is a simplified schematic diagram of an example processing circuit. DETAILED DESCRIPTION

[0014] In the case of two-dimensional printing, the print addressable location can include at least one pixel, and each print addressable location can be printed using at least one colorant such as ink (e.g., cyan, magenta, yellow, and black inks), paint, or other printing materials, as well as combinations of these printing materials.

[0015] In the case of three-dimensional printing (also known as additive manufacturing), three-dimensional space can be characterized by 'voxels', i.e., three-dimensional pixels, where each voxel occupies or represents a discrete volume. Thus, in the example of three-dimensional printing, an addressable area may include at least one voxel, and each voxel may be 'printed', i.e., generated or manufactured, using one or a combination of agents and / or build materials.

[0016] To briefly discuss three-dimensional printing in more detail, objects generated by an additive manufacturing process can be formed in a layer-by-layer manner. In one example, an object is generated by solidifying multiple portions of each building material layer. In examples, the building material can be in the form of a powder or powdered material, a fluid, or a thin sheet of material. In some examples, the desired solidification and / or physical properties can be achieved by printing an energy-absorbing agent onto the building material layer. Energy can be applied to the layer, and the building material to which the agent has been applied can coalesce and solidify when cooled. In other examples, directed energy can be used to selectively cause coalescence of the building material, or a binding agent can be used to selectively solidify the building material.

[0017] Some processes for printing three-dimensional objects use control data or print instructions generated from a model of the three-dimensional object. Such control data may, for example, specify where agents are applied to build material, or where build material itself may be placed, and in what amounts. A halftone screen may be used to determine where droplets of agents (e.g., energy absorbing agents, binding agents, and / or colorants) are placed.

[0018] In the example of a halftone screen, it may be intended to avoid patterns associated with the screen appearing in the printout. For example, a 'moiré' pattern may be seen where clusters of dots repeat, or where multiple colours are printed (these colours would be printed in different layers, or 'separations'), dots of one colour may visually interfere with dots printed in another colour. Such patterns may be seen as reduced image quality. Halftone screens may be designed to avoid such patterns appearing in the printout, or to minimise their appearance or impact. However, in the examples herein, the halftone screen may be designed to intentionally include a pattern, for example so that a 'signature' pattern may be seen in the printout. In some examples, the pattern may be suitable for verifying the origin of the printout.

[0019] Figure 1 A flow chart of an example is shown, which may be a computer-implemented method and may be a method of determining a halftone screen encoding a signature pattern. This may, for example, provide a means of verifying the origin of a printout printed using print instructions generated using a particular halftone screen (i.e., a halftone screen encoding a particular pattern).

[0020] In block 102, the method includes determining, by at least one processor in response to a first request, a first halftone screen encoding a signature pattern.

[0021] Block 104 includes determining a second halftone screen that encodes a signature pattern in response to the second request, the signature pattern being different from the signature pattern encoded in the first halftone screen. The halftone screen is arranged, derived or configured so that when used to process image data to provide print instructions for generating a printout, the pattern can be seen in the printout so as to provide a signature for the printout. This can be achieved in practice by assigning thresholds to the screen based on the signature pattern. For example, the halftone screen can include areas that may cause gaps to appear in the printout. This can be achieved by having areas in the halftone screen have a consistently high threshold (assuming that in halftoning, printing agent is deposited when the pixel value in the image data exceeds the threshold of the corresponding pixel in the halftone screen).

[0022] For example, using such a screen, an image may be embedded with lines or dots or areas with more and lesser amounts of printing agent, which are added to the image data via the halftone screen to provide a visible pattern. In the image, the signature pattern may be seen, for example, by visual inspection (which may be visual inspection with the naked eye or magnified visual inspection in some examples). In some examples, the inspection may be performed with light that makes the pattern visible (e.g., UV light or IR light that causes the printing agent to fluoresce, etc.). In other examples, the inspection may be performed using an optical sensing device (e.g., an amplifying device) or an inspection outside the observable frequency range of human vision, which, for example, may be able to detect patterns that are not visible to the human eye.

[0023] In summary, halftone screens for different requests can be encoded with different signature patterns. In some examples, each request results in a halftone screen encoded with a signature pattern that is unique (or substantially unique) to the request. As described above, this means that the signature can be used to at least partially verify the source of the printout (or to increase the confidence that the printout originates from the source). For example, the printout can be checked to determine whether it includes a signature pattern corresponding to a signature pattern provided in response to a particular request. In such an example, there is a high degree of confidence that the printout originates from an entity that has access to the pattern. In some examples, this may be the entity that requested the halftone screen. The same halftone screen can be used to provide signatures for any number of printouts, which can be different from each other (e.g., showing different images), but can have the same signature.

[0024] Thus, the signature pattern may provide a security feature embedded in a printed output.In some examples, the signature pattern may be associated with a particular entity and / or printing device to which it is transmitted.

[0025] In some examples, the method may include preventing the same pattern from being encoded in screens sent in response to different requests. For example, determining the halftone screen may include selecting a predetermined halftone screen from a plurality of predetermined halftone screens or selecting a predetermined signature pattern from a plurality of predetermined signature patterns. In such an example, the method may further include preventing, using at least one processor, a previously selected halftone screen / signature pattern from being selected in response to a subsequent request. For example, the halftone screen / signature pattern may be deleted from a list, or its index may be changed so that it cannot be selected after being selected once.

[0026] In another example, determining the halftone screen includes generating a pattern on a deterministic basis. For example, the pattern can be a geometric pattern having at least one configurable parameter (e.g., spacing of pattern elements, size or relative size within the pattern, shape of at least one pattern element, etc.). In such an example, the method can further include preventing, using at least one processor, the halftone screen from being determined in response to a subsequent request. For example, parameter combinations can be prevented from being repeated.

[0027] In other examples, there may be a large number of possible patterns / screens so that the instances of selecting the same screen are rare enough to avoid security issues associated with selecting the same screen again.

[0028] In some examples, the signature may include 'errors' or inconsistencies in an otherwise regular pattern. For example, a pattern may include a concentric arrangement of rings consisting of pattern elements including smaller circles, and one of the rings - e.g., the nth largest ring - may be missing a circle in an otherwise regularly spaced circle. In other examples, features such as the number of rings / circles, the spacing of the rings / circles, the size of the rings / circles, etc. may provide a signature alone or in combination.

[0029] In some examples, the halftone screen / pattern can be stored and / or determined in a secure or tamper-proof manner. In some examples, the halftone screen determined in response to the request can be securely transmitted, such as after being encrypted, to the requesting entity or some other entity (e.g., an entity identified in the request).

[0030] In some examples, a halftone screen can be generated prior to a print job and provided to a printer (e.g., a printer of a requesting entity) as a 'ready to use' halftone screen. Since the printer uses this screen to convert image data into a format ready for printing, this does not result in a change in the printer's workflow. In some examples, a halftone screen can be defined at a resolution higher than the expected printing resolution. For example, when the printing resolution may be approximately 800dpi, a halftone screen can be defined at a resolution of approximately 2400dpi. This relatively high resolution can allow the halftone threshold to be defined to provide a reasonable number of lines per inch (Ipi), thereby allowing finer lines to be reproduced. In other examples, the relatively high resolution can allow amplitude and / or frequency modulation. Since the halftone screen can be tiled (i.e., composed of many copied or repeated tiles), this can provide a relatively compact image despite the higher resolution.

[0031] Figure 2A A representation of image data is shown, depicting a relatively simple image in this example, but could be, for example, a more complex image in other examples. Figure 2BA representation of an image, such as a printout of the image, is shown that has been halftoned using a halftone screen encoding a signature pattern. Figure 2C A representation of a portion (tile) of a halftone pattern used to generate the image is shown. The tile has an array of small circles, which are themselves arranged in concentric rings. In this example, the high threshold in the halftone screen indicates a light color, while the low threshold indicates a darker color. In practice, this will be an array of thresholds, which are, for example, distributed between 0 and 1 or have the same value distribution as the pixel values ​​in the image data. In use (in a simple case - although in other examples, the halftone screen can be an amplitude modulation screen or a frequency modulation screen), when the pixel value is compared to the threshold, if the pixel value is higher than the threshold, the printing agent can be applied to the position corresponding to the pixel, otherwise it is not applied. Therefore, the low threshold (black area) will usually be associated with the placement of the printing agent unless there is a gap in the image data (e.g., a blank portion of the image). The high threshold (white area) is usually associated with a gap in the printed image (regardless of whether the blank space is indicated in the image data). Therefore, the pattern can be encoded with a distribution of thresholds.

[0032] Figure 2D Figures showing different signature patterns. Figure 2C , but this one has discernible differences. In fact, it can be noted that the first ring starting from the center has twelve small circles, while Figure 2C The pattern in the figure has eleven small circles. This difference has an impact on how users perceive Figure 2B The half-toned image shown in FIG. 1 has minimal effect, but still provides an image similar to that shown as embedded in FIG. Figure 2B The 'signature' of the pattern may be different from the signature in the image of the image. Thus, in this example, the 'signature' of the pattern comprises at least the number of circles in the first ring starting from the center. The signature may also include other features or characteristics of the pattern, a combination of which may be associated with a particular halftone screen. For example, the number and / or spacing of concentric rings or circles may comprise all or part of the signature, as may the diameter or one or more rings, or irregularities in the rings or circles. This in turn may allow identification of the entity to which the halftone screen has been provided, and therefore it may be at least preliminarily assumed that the identified entity is the source of the printout comprising the signature pattern.

[0033] Figure 2E Another different signature pattern based on a diamond spiral is shown. In this pattern, the signature can be based on any one or any combination of, for example, the tightness of the spiral, the length of the tail at the center of the spiral, the location of the break in the spiral, etc.

[0034] In other examples, shapes may be used to provide a signature. For example, an array of hearts, diamonds, spades and clubs may be formed, and the arrangement of these shapes (as well as other features such as size or distorted instances of one of the shapes) may provide a 'signature' for the pattern.

[0035] Figure 3 is an example of a method of determining a halftone screen that may be implemented, at least in part, by one or more processors.

[0036] In this example, block 302 includes determining a grayscale pattern. For example, a combination of one or more features of a pattern (e.g., an arrangement of a subset of points or lines) can be used, for example, to identify a pattern (in some examples, the pattern is substantially unique relative to other patterns generated according to the methods herein). For example, as described above, a pattern can include irregularities, unique geometric shapes, and / or unique shapes within the pattern, etc., to provide a signature of the pattern. For example, a signature pattern can include a relatively simple pattern, such as a geometric pattern. A signature pattern can have one or more repeating elements.

[0037] The pattern may be created in a deterministic manner, for example, based on an algorithm that may be seeded with a predetermined seed or the like.

[0038] Block 304 includes storing an indication of the pattern in a memory or the like (which may be, for example, a copy of the pattern, or an identifier from which the pattern may be recreated) for later verification of the signature. The pattern is associated with an identifier, which in turn may be associated with a requesting entity (and / or a particular request) so that the pattern may subsequently be identified. In some examples, the identifier may include a seed from which the pattern may be created (or may be algorithmically associated with the seed), so the indication of the pattern may include the identifier itself. The memory may be a secure memory, and / or the indication may be stored in an encrypted manner to keep the pattern secure. In other examples, the indication of the pattern may be a halftone screen generated from the pattern, as described below.

[0039] Block 306 provides an example of a method for determining, by at least one processor (which may be the same or a different processor than described with respect to block 302), a halftone screen from a pattern, the method being implemented by converting, by the at least one processor, the pattern into a halftone screen comprising a threshold matrix.

[0040] In examples, the grayscale values ​​of the pixel array of the grayscale image directly provide the halftone thresholds of the pixel array of the halftone screen, i.e., the grayscale values ​​within the grayscale are proportionally converted to the halftone thresholds within the halftone threshold range. In other examples, there may be some value jittering, etc., making the conversion less direct. In some examples, any parameters for converting grayscale values ​​to halftone thresholds may be stored.

[0041] Block 308 includes transmitting the halftone screen (e.g., via a network, etc.) to an entity, which may include a printer operator, and / or may be a sender of information about the halftone screen. Figure 1 The method may include encrypting the halftone screen prior to transmission. In other examples, the halftone screen may be securely distributed in some other manner (e.g., securely physically distributed on a tangible storage medium, etc.).

[0042] The printer operator can (in some examples, having decrypted data based on a shared key, etc.) apply a halftone screen to the image data to determine print instructions, and print the image based on the instructions. Applying the halftone screen to the image data can include associating at least one pixel of the screen with a pixel of the image data, comparing the image pixel value with a threshold value of the or each halftone screen pixel, and determining the print instructions for each image pixel accordingly (e.g., the print instructions can be binary and / or include the number or size of print reagent dots). Thus, the printed image can have a signature embedded therein. In some examples, the halftone screen includes multiple repeated 'tiles', or the printing device can use each halftone screen in a tiled manner.

[0043] In some examples, a halftone screen may be applied to multiple color planes (e.g., CMYK color planes). However, the signature may not be present in all color planes, although still detectable in some cases. It should be noted that in some examples, when a halftone screen is used for multiple color planes, a relative rotation may be applied to a particular halftone screen to avoid moire effects. In this case, if the pattern is such that a relative rotation would mean that the pattern is offset in different color planes (and it is expected that the pattern should be aligned in all planes), the digital image plane may be rotated before halftoning and then rotated back before printing.

[0044] The printing device may, for example, include printing device components such as (multiple) print heads, at least one printing reagent supply, etc. In the case where the printing device is a 'two-dimensional' printer, the printing device may, for example, include a laser printer or an inkjet printer, etc., and may include a print head, a substrate delivery system, an ink or toner source, etc. In the case where the printer is a 'three-dimensional' printer, the printing device may include a print bed, a manufacturing chamber, a print head, at least one energy source, a source of build material, etc., or be associated with these components.

[0045] Figure 4 is an example of a method that may include a computer-implemented method for verifying a signature within a printed image. In some examples, Figure 4The method may be performed by a processing device having access to a storage database of patterns associated with an identifier associated with the requesting entity. The database may be a secure database, for example to which access is restricted.

[0046] Block 402 includes obtaining, by processing circuitry, a digital sample of a printout. For example, the printout may be scanned or digitally photographed to provide a digital sample. In some examples, the image may be captured using a camera of a mobile phone. This may include imaging an image area corresponding to a plurality of halftone 'tiles', since each tile itself may not provide a complete pattern, for example due to light portions or gaps in the halftone image data. The number of tiles in the digital sample may depend on a number of factors, including the content of the printout and the convenience of capturing that number of tiles.

[0047] Block 404 includes identifying, by the processing circuit, a signature in the digital sample. For example, this may include determining whether the printed image includes a halftone signature. A halftone signature may be a signature introduced using a halftone screen having a signature pattern. For example, this may include comparing one or more stored signatures to the image to identify a matching signature. In some examples, an indication of an expected matching signature may be provided (e.g., the purported origin of the image). In some examples, the pattern may be extracted from the digital sample. In some examples, the extraction may be performed using input from a user. In other examples, machine learning techniques may be used to derive a model for extracting patterns from digital samples, such as a model that has been 'trained' using a plurality of printed halftone images and their corresponding signature patterns to see how features of the pattern may be represented in a printed output. In some examples, the extraction method may take into account random variations introduced during the printing process, for example, the exact location of printed dots may vary systematically (e.g., due to the printing device, print head, or software used) and randomly (e.g., due to environmental conditions and tolerances of the printing device). Thus, when extracting the pattern, the extraction may allow for small variations in the expected location of the ink dots. For example, an estimate of where the printing instructions indicate that an ink dot should be placed may be obtained, but the estimate may be associated with uncertainty based on random variations that may be encountered during printing.

[0048] Block 406 includes determining whether the signature is a stored signature associated with the entity. In some examples, the match may be a 'fuzzy' match, for example to account for random variations introduced during the printing process as described above. In some examples, therefore, random variations may be accounted for in blocks 404 and / or 408. For example, the expected signature may be compared to the digital sample, and if the digital sample corresponds closely enough to the expected signature, it may be determined that the digital sample includes the expected signature. In some examples, a model trained using the machine learning techniques described above may be employed to determine whether the match is close enough.

[0049] Depending on the context, the determination may then have different conclusions. For example, in the case of a negative determination, it may be indicated that the printed image is a fraudulent image, or that further verification is required. In some examples, if the comparison result is inconclusive, a new digital sample may be requested. In the case of a match with a stored signature, this in turn means confirmation of the content of the printed page, which may include, for example, valuable items (e.g., vouchers, or bills, etc., with monetary value) or technical content that can be trusted.

[0050] Figure 5 is an example of a method that may include another computer-implemented method of verifying a signature within a printed image.

[0051] In this example, in block 502 , a digital sample of a printed image is obtained by processing circuitry, eg, as described above with respect to block 402 .

[0052] Additionally, in this example, the claimed origin of the image is also obtained by the processing circuitry in block 504. For example, this may include an entity claiming to have printed the image (e.g., HP Indigo), and / or may include an indication of a particular printing device.

[0053] In block 506, the claimed provenance is used to look up the expected pattern(s) for the entity / AM device. In some examples, this may include accessing a stored grayscale image of the pattern, accessing an algorithmic representation of the pattern, or accessing a halftone screen. In other examples, the method may include looking for an indication of a 'signature' rather than the pattern itself. For example, a 'signature' may include some combination of features (e.g., spacing of pattern features, irregularities, combinations of shapes within the pattern, etc.).

[0054] Box 508 includes comparing the expected pattern with the digital sample. For example, this may include looking for matching features and / or inconsistencies between the printed image and the pattern. As noted, the match may be a 'fuzzy' match.

[0055] Block 510 includes verifying the origin of the image if the printed image includes an expected halftone signature, where the halftone signature may be a signature introduced using a halftone screen having a signature pattern. In other words, an assessment may be made as to whether the pattern matches, indicating that the claimed origin is authentic if so, or incorrect if not. In other examples, instead of comparing the patterns, an image processing algorithm may be used to identify a 'signature' in the digital sample. In some examples, if the signature is not represented in the printed image, it may be determined that the pattern does not match.

[0056] Although in this example, the claimed origin is obtained, this may not be the case in all examples. In some examples, the digital sample may be processed by the image processing circuit to determine the characteristics of the pattern and thereby identify possible signatures within the pattern. This may include evaluating a digital sample area corresponding to multiple halftone tiles, since each tile itself may not provide a complete pattern, for example due to light portions or gaps in the image data.

[0057] Figure 6 is an example of a processing circuit 600 including a matrix module 602 and a security module 604 .

[0058] In use of the processing circuit 600, the matrix module 602 is used to determine a halftone threshold matrix for the encoded signature pattern in response to a request from a requesting entity, wherein the determined halftone threshold matrix will be provided to the requesting entity. The threshold matrix may have any of the properties of the halftone screen described above.

[0059] In use of the processing circuit 600, the security module 604 is used to prevent the same signature pattern from being encoded into multiple threshold matrices and provided to another (different) requesting entity. This allows the signature to provide a security feature in the printout, for example, for verifying and / or authenticating the source of the printout. In some examples, the security module 604 can securely store an indication of the pattern, and / or can encrypt it, for example, before distributing the halftone screen.

[0060] Figure 7 It includes about Figure 6 An example of a processing circuit 700 of a matrix module 602 and a security module 604 is depicted. In this example, the matrix module 602 further includes a pattern module 702, a conversion module 704, and the processing circuit 700 further includes a verification module 706.

[0061] In use of the processing circuit 700, the pattern module 702 is used to determine a grayscale pattern, such as a repeating (eg, tiled) pattern having dots or lines, etc. For example, the pattern module 702 may perform Figure 3 Frame 302.

[0062] In the use of the processing circuit 700, the conversion module 704 is used to convert the grayscale value into a threshold value in the halftone screen. For example, the conversion module 704 can perform Figure 3 Frame 304.

[0063] In use of the processing circuit 700, the verification module 706 is used to verify the digital sample of the printed image. For example, the verification module 706 may execute Figure 4 or Figure 5 , or any combination thereof.

[0064] While in this example, the same processing circuitry that provides the halftone screen also provides verification, it will be appreciated that in some examples these processes may be separate from one another.

[0065] Examples in the present disclosure may be provided as methods, systems, or machine-readable instructions (such as any combination of software, hardware, firmware, etc.). Such machine-readable instructions may be included on a non-transitory machine (e.g., computer) readable storage medium (including but not limited to disk storage devices, CD-ROMs, optical storage devices, etc.) having computer-readable program code therein or thereon.

[0066] The present disclosure is described with reference to the flowcharts and block diagrams of the methods, devices and systems according to the examples of the present disclosure. Although the flowcharts described above show a specific execution order, the execution order may be different from the depicted order. The boxes described in one flowchart may be combined with the boxes of another flowchart. It should be understood that each box in the flowchart and / or block diagram and the combination of boxes in the flowchart and / or block diagram may be implemented by machine-readable instructions.

[0067] The functions described in the specification and the drawings can be implemented, for example, by executing machine-readable instructions by a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device. In fact, a processor or a processing device or a module thereof can execute machine-readable instructions. Therefore, the functional modules (for example, any one of the matrix module 602, the security module 604, the pattern module 702, the conversion module 704, and the verification module 706) and the device of the processing circuit 600, 700 can be implemented by a processor that executes machine-readable instructions stored in a memory or a processor that operates according to instructions embedded in a logic circuit. The term 'processor' should be broadly interpreted as including a CPU, a processing unit, an ASIC, a logic unit, or a programmable gate array, etc. The method and the functional module can all be executed by a single processor, or divided between several processors.

[0068] Such machine-readable instructions may also be stored in a computer-readable storage device, which may direct a computer or other programmable data processing apparatus to operate in a particular mode.

[0069] Such machine-readable instructions may also be loaded onto a computer or other programmable data processing device so that the computer or other programmable data processing device performs a series of operations to produce a computer-implemented process. Thus, the instructions executed on the computer or other programmable device implement the functions specified by the (multiple) processes in the flowchart and / or the (multiple) boxes in the block diagram.

[0070] Furthermore, the teachings herein may be implemented in the form of a computer software product that is stored in a storage medium and includes a plurality of instructions for causing a computer device to implement the methods recited in the examples of the present disclosure.

[0071] Although the methods, apparatus and related aspects have been described with reference to certain examples, various modifications, changes, omissions and substitutions may be made without departing from the spirit of the present disclosure. Therefore, the methods, apparatus and related aspects are intended to be limited by the scope of the claims and their equivalents. It should be noted that the examples mentioned above illustrate rather than limit what is described herein, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. Features described with respect to one example may be combined with features of another example.

[0072] The word “comprising” does not exclude the presence of elements other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfill the functions of several units listed in a claim.

[0073] Features from any dependent claim may be combined with features from any independent claim or from other dependent claims.

Claims

1. A method for data processing, comprising: A halftone screen is determined in response to each of the plurality of requests, wherein: The halftone screen includes a plurality of repeated halftone tiles, and Wherein, determining the halftone screen includes encoding a signature pattern into the halftone screen, and different signature patterns are encoded for halftone screens of different requests; and applying the halftone screen to image data, wherein the halftone screen is arranged such that when applied to the image data to provide a printed output, the pattern is visible in the printed output so as to provide a signature for the printed output, Wherein the printout includes a region corresponding to a halftone tile of the plurality of repeating halftone tiles, the region including less than a complete pattern, the complete pattern corresponding to the encoded signature pattern of the halftone screen. 2 . The method of claim 1 , further comprising transmitting each halftone screen to an entity identified in the request.

3. The method of claim 2, further comprising encrypting each halftone screen and transmitting the encrypted halftone screen. 4 . The method of claim 2 , further comprising storing an indication of each signature associated with an identity of each entity to which the halftone screen is transmitted.

5. The method according to claim 4, wherein: Storing the indication of each signature includes securely storing the indication.

6. The method according to claim 4, further comprising: obtaining, by at least one processor, a digital sample of the printout; identifying a signature in the digital sample; as well as A determination is made as to whether the signature is a stored signature associated with an entity.

7. The method according to claim 1, wherein: Determining the halftone screen in response to the request includes at least one of: selecting a predetermined halftone screen from a plurality of predetermined halftone screens and selecting a predetermined signature pattern from a plurality of predetermined signature patterns; And the method further comprises: Preventing selection of the halftone screen or the signature pattern using at least one processor in response to a subsequent request.

8. The method according to claim 1, wherein: Determining the halftone screen includes generating a pattern on a deterministic basis, and the method further includes preventing, using at least one processor, determining the halftone screen in response to a subsequent request.

9. A method for data processing, comprising: Acquiring, by processing circuitry, a digital sample of a printed image, wherein the digital sample includes a region corresponding to a halftone tile of a plurality of repeating halftone tiles included in a halftone screen, the region including less than a complete pattern, the complete pattern corresponding to a halftone signature; determining, by processing circuitry based on the digital sample, whether the printed image includes an expected halftone signature; and The origin of the image is authenticated by processing circuitry based on whether the printed image includes an expected halftone signature.

10. The method according to claim 9, further comprising: obtaining, by processing circuitry, the purported origin of the printed image; accessing a halftone signature associated with said purported origin; determining, by processing circuitry based on the digital sample, whether the printed image includes the halftone signature; as well as When the printed image includes the halftone signature, the purported origin of the printed image is verified.

11. The method according to claim 10, wherein: Accessing the halftone signature includes accessing a pattern encoding the signature, and determining whether the printed image includes the pattern based on the digital sample.

12. The method according to claim 9, wherein: Determining whether the printed image contains the halftone signature includes determining a fuzzy match that allows for random variations introduced by the printing process.

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