KR102564641B1 - Method for embedding and extraction of watermarking data - Google Patents

Abstract

A technical problem to be solved through an embodiment of the present invention is to provide a method and a device to which the method is applied, in which the recognition rate and security are improved during extraction by embedding data using a random number sequence. In order to solve the above technical problem, an embedding method according to an embodiment of the present invention comprises constructing a noise base image in units of blocks having M x M pixels, each of the blocks, pixels of all pixels belonging to the block and converting the noise-based image by modifying pixel values of some pixels of each block using the watermark data while traversing each block, The converting may include sequentially selecting random numbers from a pre-stored random number sequence while traversing each block using the watermark data, and correcting pixel values of some pixels according to a rule corresponding to the selected random numbers. can

Description

Embedding and extracting method of watermark data {METHOD FOR EMBEDDING AND EXTRACTION OF WATERMARKING DATA}

The present invention relates to a method for embedding and extracting watermark data. More specifically, it relates to a method of embedding watermark data in an image in a manner that is not recognized by human eyes but can be extracted through image processing, and extracts the watermark data so embedded from the image.

Using watermarking technology, it is possible to insert watermark data or watermarking texture, which is invisible to the eye in the original image, but is revealed in the case of unauthorized copying, to the original image. This watermarking technology is widely used for purposes such as authenticity authentication or authenticity authentication. However, a watermarking technology that is invisible to humans and can be extracted through image processing through a computing device, but cannot be extracted in the case of unauthorized copying, is not provided.

In the conventional watermark technology, by embedding data as a rule of one method, a synchronization signal is damaged, causing a problem in that the recognition rate is lowered during extraction. Furthermore, since a certain pattern is formed by embedding data according to a rule of one method, security concerns arise due to leakage of a noise-based image in which data is embedded.

Korean Patent Registration No. 10-1877372

Another technical problem to be solved through an embodiment of the present invention is to provide a method and a device to which the method is applied, in which the recognition rate and security are improved during extraction by embedding data using a random number sequence.

Another technical problem to be solved by an embodiment of the present invention is to provide a method for providing a watermark in a form suitable for an original image by changing the form of a noise-based image, and an apparatus to which the method is applied.

A technical problem to be solved by the present invention is to provide an extraction method that reduces the time and computing power required for determining whether watermark data exists from an image and extracting the watermark data.

The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below.

In order to solve the above technical problem, an embedding method according to an embodiment of the present invention comprises constructing a noise base image in units of blocks having M x M pixels, each of the blocks, pixels of all pixels belonging to the block and converting the noise-based image by modifying pixel values of some pixels of each block using the watermark data while traversing each block, The converting may include sequentially selecting random numbers from a pre-stored random number sequence while traversing each block using the watermark data, and correcting pixel values of some pixels according to a rule corresponding to the selected random numbers. can

In one embodiment, the M x M pixels are 2 x 2 pixels, and the stored random number sequence is:

It is an array of random numbers corresponding to any one of six cases, and the step of modifying the pixel value of the M x M pixels is a rule corresponding to the selected random number while traversing each 2 x 2 pixel. A step of modifying a pixel value of the 2x2 pixel may be included.

In an embodiment, the method may further include obtaining an aspect ratio of the original image, and when the aspect ratio corresponds to a reference range, the noise base image may be a rectangular image having a shape corresponding to the aspect ratio.

In one embodiment, a rectangle having a shape corresponding to the aspect ratio may correspond to a rectangle having a fixed aspect ratio.

In one embodiment, the rectangle having a shape corresponding to the aspect ratio may correspond to a rectangle having the same aspect ratio as that of the original image.

In an embodiment, the method may further include obtaining a horizontal and vertical pattern of the pattern of the original image as a numerical value, and when the numerical value corresponds to a reference value or less, the noise base image may be a rectangular image having a shape corresponding to the numerical value.

In an embodiment, the obtaining of the tendency as a numerical value may include obtaining a minimum distance from an axis having a most adjacent peak coordinate in a magnitude spectrum of a Fourier transform frequency domain of the original image.

In one embodiment, the rectangle may be a rectangle in which a vertical length of the rectangle is greater than a horizontal length when the axis closest to the peak coordinate corresponds to the x-axis.

In one embodiment, when the axis adjacent to the peak coordinates corresponds to the y-axis, the rectangle may have a horizontal length greater than a vertical length.

In an embodiment, the method may further include replacing the selected random number with a number other than the selected random number when the random number of the random number sequence is continuously selected a reference number of times or more.

In order to solve the above technical problem, a data extraction method according to an embodiment of the present invention blocks an image in units of blocks consisting of M x M pixels and blocks a noise base in units of blocks consisting of M x M pixels. and extracting data while traversing each block of the image, wherein the step of extracting data while traversing each block of the image determines a data extraction rule for each block using a stored random number sequence. and extracting the watermark data for each block using the determined rule.

In one embodiment, the step of obtaining a random number sequence identifier from the image may further include, and the step of extracting the watermark data while traversing each block of the image may include: among the stored random number sequences, the random number sequence identifier indicates and determining the watermark data extraction rule for each block by referring to the random number sequence.

In one embodiment, the apparatus for extracting watermark data includes an image capturing unit, a similarity determining unit, and a data extracting unit, wherein the data extracting unit traverses each block in the captured image obtained from the image capturing unit and stores the A data extraction rule may be determined for each block using a sequence, the watermark data may be extracted for each block using the determined rule, and the extracted data may be output.

1 is a conceptual diagram for explaining a situation in which a method of embedding watermark data according to an embodiment of the present invention and a method of extracting watermark data according to another embodiment of the present invention are utilized.
2 is a diagram for comparison between an image in which watermark data is embedded according to a method of embedding watermark data according to some embodiments of the present invention and an original image.
3 is a flowchart of a method of embedding watermark data according to an embodiment of the present invention.
FIG. 4 is a flowchart for explaining in detail some operations of a method of embedding watermark data that can be understood with reference to FIG. 3 .
FIG. 5 is a diagram for explaining a result of blocking a noise base as a result of some operations that can be understood with reference to FIG. 4 .
FIG. 6 is a flowchart for explaining in detail some operations of a method of embedding watermark data that can be understood with reference to FIG. 4 .
FIG. 7 is a flowchart for explaining in detail some operations of a method of embedding watermark data that can be understood with reference to FIG. 6 .
FIG. 8 is an exemplary view illustrating rules corresponding to random numbers that may be referred to in FIG. 7 .
9 is a diagram for explaining block traversal for watermark data embedding, which may be referred to in some embodiments of the present invention.
10 to 13 are exemplary diagrams for illustrating in detail a method of embedding watermark data, which can be understood with reference to FIG. 7 .
14 is a conceptual diagram illustrating a method of embedding watermark data according to an embodiment of the present invention.
15 and 16 are views for explaining synchronization signals that may be referred to in some embodiments of the present invention.
17 is a diagram for explaining in detail a method of embedding watermark data according to an embodiment of the present invention.
18 to 20 are exemplary diagrams specifically illustrating a method of embedding watermark data, which can be understood with reference to FIG. 17 .
21 is a flowchart of a watermark data extraction method according to another embodiment of the present invention.
22 is a diagram for explaining why pre-processing of a captured image is necessary in the watermark data extraction method according to an embodiment of the present invention.
23A to 23C are diagrams for explaining an operation of identifying a plurality of image blocks from a captured image in the method of extracting watermark data that can be understood with reference to FIG. 21 .
FIG. 24 is a detailed flowchart for explaining in detail an operation of determining a first similarity and obtaining a rotation angle and a scale for each image block in the method of extracting watermark data, which can be understood with reference to FIG. 21 .
25 is a diagram for explaining a preprocessing result of a photographed image.
FIG. 26 is a detailed flowchart for explaining in detail an operation of determining a second similarity and obtaining a reference point with respect to a selected image block in the method of extracting watermark data, which can be understood with reference to FIG. 21 .
FIG. 27 is a detailed flowchart for explaining in detail an operation related to data extraction of the watermark data extraction method, which can be understood with reference to FIG. 21 .
28 is a block diagram of a watermark data embedding device according to another embodiment of the present invention.
29 is a block diagram of a watermark data extraction apparatus according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Advantages and features of the present invention, and methods of achieving them, will become clear with reference to the detailed description of the following embodiments taken in conjunction with the accompanying drawings. However, the technical idea of the present invention is not limited to the following embodiments and can be implemented in various different forms, only the following embodiments complete the technical idea of the present invention, and in the technical field to which the present invention belongs It is provided to fully inform those skilled in the art of the scope of the present invention, and the technical spirit of the present invention is only defined by the scope of the claims.

In adding reference numerals to components of each drawing, it should be noted that the same components have the same numerals as much as possible even if they are displayed on different drawings. In addition, in describing the present invention, if it is determined that a detailed description of a related known configuration and/or function may obscure the gist of the present invention, the detailed description will be omitted.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used in a meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in commonly used dictionaries are not interpreted ideally or excessively unless explicitly specifically defined. Terminology used herein is for describing the embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms unless specifically stated otherwise in a phrase.

In addition, in describing the components of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the nature, order, or order of the corresponding component is not limited by the term. When a component is described as being "connected" or "coupled" to another component, the component may be directly connected to the other component, but between each component another component may be "connected" or "coupled". “It should be understood that it could be.

As used herein, "comprises" and/or "comprising" means that a stated component, step, operation, and/or element is one or more other components, steps, operations, and/or elements. Existence or additions are not excluded.

Hereinafter, some embodiments of the present invention will be described in detail with reference to the accompanying drawings.

outline

1 is a conceptual diagram for explaining a situation in which a method of embedding watermark data 10 according to an embodiment of the present invention and a method of extracting watermark data 10 according to another embodiment of the present invention are utilized. First, the resulting image 30 created as a result of embedding the watermark data 10 in the original image 20 can be distributed through various channels. The resulting image 30 may be, for example, a business card or a label attached to a surface of a product. Also, the resulting image 30 may be printed on the outer surface of a vehicle such as a box.

As shown in FIG. 1 , it is difficult to visually recognize whether the watermark data 10 is embedded by looking at the resulting image 30 . In the watermark data embedding method according to the present embodiment, unlike conventional barcode and QR code technologies, it is difficult to visually recognize whether or not the watermark data 10 is embedded, so that the original image 20 is not damaged. There is an advantage of being able to contain the mark data 10 . In addition, the size of watermark data 10 according to an embodiment is 144 bits, and among them, body data that can actually be used is 54 bits. As a result, the number of cases of 254 can be expressed using the watermark data. Therefore, if the present technology is applied to a label attached to the surface of a product, even if the label appears to be the same to the naked eye, it is possible to assign a unique ID to each product and embed the ID as watermark data in the label. Furthermore, more usable data is increased than the existing 248, and more variable data can be created.

Although it is difficult to visually recognize whether the watermark data is embedded by looking at the result image 30, using the user terminal 900 executing the watermark data extraction method according to some embodiments of the present invention, the result image 30 ), watermark data 10 can be extracted. For example, it is possible to extract the watermark data 10 by photographing the resulting image 30 using a camera provided in the user terminal 900 and executing watermark data extraction logic on the photographed result. .

In some embodiments of the present invention, the watermark data 10 that can be embedded may have the format of Table 1, for example.

4 bits 3 bits 8 bits 54 bits 7 bit 68 bit control parameter body data CRC8 Body data error correction bit version code CRC4 Control parameter error correction bit

The watermark data 10 may include a 15-bit control parameter, 54-bit body data, 7-bit verification code (CRC 8), and 68-bit error correction code. can A control parameter of Table 1 may indicate a type of body data. For example, the user terminal 900 may extract the watermark data 10, recognize 54-bit body data, and transmit a content request containing the body data and control parameters to the content server. The content server may store a content DB that manages each type of content assigned a unique ID. The content server may provide the user terminal 900 with the content of the type corresponding to the control parameter among the content whose ID matches the body data. In one embodiment, the control parameter is a 4-bit version code ( Version Code), a 3-bit verification code (CRC4) for the corresponding area, and an 8-bit error correction code. By dividing the watermark data 10 into 24 versions and managing them according to the version code, the versions can be updated and managed or multiple versions can be operated at the same time.

A 68-bit Error Correction Bit may include an error correction code to compensate for the possibility that the watermark data 10 may be incorrectly extracted. For example, the error correction code may be a Bose-Chaudhuri-Hocquenghem (BCH) code.

2 is a diagram for comparison between an original image and an image in which watermark data is embedded according to a method of embedding watermark data according to some embodiments of the present invention. As shown in FIG. 2 , the resulting image 30 is not significantly different from the original image 20 visually. However, the resulting image 30a converted to monochrome has more noise compared to the monochrome version 20a of the original image. This is because watermark data according to an embodiment of the present invention is embedded in the original image in the form of noise. In this regard, it will be described in more detail with reference to some drawings.

Embedding of watermark data

Hereinafter, a method of embedding watermark data according to an embodiment of the present invention will be generally described with reference to FIG. 3 . The embedding method of watermark data according to the present embodiment may be executed by, for example, a computing device.

The computing device loads watermark data (S100) and loads a noise base image (S120). Also, an original image containing watermark data is loaded (S160). A noise base can be understood as a kind of data container containing watermark data. The noise base may be loaded from an image file or may be loaded in the form of data indicating a two-dimensional matrix in the frequency domain. Also, in one embodiment, it may be loaded in the form of a magnitude spectrum and a phase spectrum in the frequency domain.

The noise base image is converted according to a pattern determined using the stored watermark data and the stored random number sequence (S140), and the original image is adjusted using the converted noise base image to generate an image in which the watermark data is embedded. and output (S180, S200). For example, the image in which the watermark data is embedded may be output in the form of an image file or may be printed on a printing object such as paper by a printing device. According to one embodiment, the output may be made in the form of painting the outer surface of the printing result by a 3D printer.

As described with reference to FIG. 3 , in this embodiment, the noise base plays a key role. The noise-based image generated through the frequency domain is configured to maintain the characteristics of a synchronization signal even if the image is partially damaged according to the characteristics of the frequency, thereby increasing the success rate of watermark data extraction. In addition, after the original noise-based image is blocked, conversion is performed by watermark data, so the original noise-based image is not easily leaked through analysis of the resulting image.

In the conventional watermark technology, by embedding data according to a rule of one method, a synchronization signal is damaged, resulting in a problem of deterioration in recognition rate during extraction. Furthermore, since a certain pattern is formed by embedding data according to a rule of one method, a security concern arises due to leakage of a noise-based image in which data is embedded. A method of embedding watermark data to solve the above problem will be described in detail with reference to FIGS. 4 to 16 below.

FIG. 4 is a flowchart illustrating the noise-based image conversion step (S140) shown in FIG. 3 in more detail.

The noise base image is segmented in block units of M x M pixels (S141). It is preferable that one block is formed in a rectangular shape composed of an even number of pixels in horizontal and vertical directions. For example, one block may have a size of 2 x 2 pixels. Since a block of 2x2 pixels is a block with a minimum size that can be configured, an effect that can correspond to images of various sizes is obtained by configuring one block with a size of 2x2. However, it is not limited thereto and one block may be formed in a square shape composed of an even number of pixels in horizontal and vertical directions.

In some embodiments, the size of a block may be adjusted according to embedding settings. When the size of the block increases, there is an effect of reducing the required embedding time. When the block size is reduced, there is an effect of embedding more data in small pixels.

Next, for each block, the average of pixel values belonging to the block is calculated, and if the average value is greater than or equal to a reference value (for example, a value between a pixel value indicating white and a pixel value indicating black), all values of the corresponding block are calculated. The color is unified into a first color (eg, black) (S143). If the average value is less than the reference value, all colors of the corresponding block are unified into a second color (eg, white) (S143).

FIG. 5 shows a blocked noise base image 41 as a result of segmentation and unification of the noise base image 40 described with reference to FIG. 4 . Referring to a picture in which the blocked noise base image 41 is enlarged in pixel units, all square unit blocks having a size of 2x2 pixels are unified with the same pixel value. The current block 41a is assigned a pixel value of 0 and corresponds to white.

Blocking described with reference to FIGS. 4 and 5 prevents the formation of a repetitive pattern that occurs by inserting only watermark data into a noise-based image, and the recognition rate during extraction that occurs by inserting watermark data only in units of one pixel. degradation can be prevented. Furthermore, by performing blocking, a synchronization signal corresponding to a frequency characteristic of the original noise-base image may be maintained.

Referring back to FIG. 4 , the blocky noise base image 41 is converted (S145) by modifying some pixel values of the block according to a pattern determined by the stored random number sequence by reflecting the watermark data. Transformation of the blocked noise base image 41 is embodied by some embodiments to be described later.

FIG. 6 is a flowchart for specifically explaining the transformation (S145) of the noise-based image 41 described in FIG. 4 . The embedding method of watermark data according to the present embodiment may be executed by, for example, a computing device.

The computing device loads a pre-stored random number sequence to convert the noise-based image (S1451). The pre-stored random number sequence may be a sequence of repeatedly generated random numbers stored in the order of occurrence. However, it is not limited thereto. In one embodiment, the number of random numbers in the random number sequence required to embed 144-bit watermark data is 144. For example, the random number may correspond to any one number selected from among natural numbers from 1 to 6.

In the example described above, since one block is partitioned into 2 x 2 pixels, a total of 6 rules for selecting 2 pixels out of 4 pixels must be assigned to represent 1 bit. However, it is not limited thereto, and the number of random number cases may be changed according to the scale of the block.

Meanwhile, in the process of embedding and extracting watermark data, one of two or more random number sequence sets may be selectively used. A plurality of sets of random numbers are shared in advance between a device embedding watermark data and a device extracting watermark data.

In another embodiment, the generated random numbers may be stored as a sequence of random numbers according to the order in which they are generated. When embedding, it is stored as a random number sequence, and when extracting, the stored random number sequence is used to perform extraction according to a corresponding rule. In another embodiment, the sequence of random numbers may be stored in encrypted form. As it is stored in an encrypted form, security concerns due to leakage may be reduced.

In one embodiment, when the random number of the stored random number sequence is continuously selected a reference number of times or more, a step of replacing the random number with a number other than the selected number may be included. By embedding watermark data by applying multiple rules rather than one rule, synchronization signals can be maintained and security can be enhanced. It may include a step of substituting with a number other than the consecutively adopted number.

Next, the pixel value of the block is modified according to a rule corresponding to the random number using the loaded watermark data and the selected random number (S1453). Referring to FIG. 8 , in the case of the 2×2 pixels exemplified above, a total of six rules correspond to preset random numbers.

Referring to FIG. 7 , a step ( S1453 ) of correcting a pixel value of a block according to a rule corresponding to the random number described in FIG. 8 will be described in more detail. The embedding method of watermark data according to the present embodiment may be executed by, for example, a computing device.

If the current block is white (S1453-1), a rule corresponding to the n-th random number is loaded (S1453-2). Referring to FIG. 8 , in the case of 2x2 pixels, rules corresponding to the number of 6 cases can be confirmed. Next, some pixels of the current block are converted to black to match the corresponding rule (S1453-3).

If the current block is black (S1453-1), a rule corresponding to the n-th random number is loaded (S1453-5). Referring to FIG. 8 , in the case of 2x2 pixels, rules corresponding to the number of 6 cases can be confirmed. However, since the corresponding rule is shown based on the case where the current block is white, the rule in which black and white are inverted corresponds to the rule when the current block is black. Next, some pixels of the current block are converted to white to match the corresponding rule (S1453-6).

Next, when all watermark data processing is not completed (S1453-7), the same process is repeated using the watermark data and random numbers while traversing each block (S1453-4).

9 illustrates a process of embedding watermark data while traversing each block described above (S1453-4). In order to embed 144-bit watermark data, 144 blocks are composed, and at least 576 pixels are required. In some embodiments to be described later, the noise base image may consist of a rectangle rather than a square.

A specific example of the embedding method described in FIG. 7 will be described with reference to FIGS. 10 to 14 below. For convenience of description below, it is assumed that a block corresponds to 2 x 2 pixels, and a selected random number corresponds to any one of natural numbers from 1 to 6.

Referring to FIG. 10, the first watermark data is 0, and the selected random number corresponds to 1. Since the conversion target block 43a is blocked in white, the pixel value of the conversion target block 43a is modified according to the 0 of Case 1 corresponding to the random number with reference to FIG. 8 .

Referring to FIG. 11, the second watermark data is 1, and the selected random number corresponds to 3. Since the conversion target block 43b is black, the pixel value of the conversion target block 43b is modified according to the inverted form of Case 3 1 corresponding to the random number with reference to FIG. 8 .

Referring to FIG. 12, the third watermark data is 1, and the selected random number corresponds to 4. Since the transformation object block 43c is blocked in white, the pixel value of the transformation object block 43c is modified according to Case 4 of 1 corresponding to the random number with reference to FIG. 8 .

Referring to FIG. 13, the fourth watermark data is 0, and the selected random number corresponds to 5. Since the conversion target block 43d is black, the pixel value of the conversion target block 43d is modified according to the inverted form of case 5 corresponding to the random number with reference to FIG. 8 .

Referring to FIGS. 7 to 13 , a specific method of embedding watermark data on a block-blocked noise base image 41 using random numbers and rules corresponding to the random numbers has been described. Unlike the conventional watermark technology embedding with one rule, an embodiment according to the present invention can improve the recognition rate during extraction without damaging the synchronization signal. Furthermore, since a certain pattern is formed by embedding data according to a rule of one method, security concerns due to leakage of a noise-based image in which data is embedded may also disappear.

Hereinafter, a method of embedding watermark data according to an embodiment of the present invention described in detail with reference to FIGS. 6 to 13 will be described with a conceptual diagram shown in FIG. 14 . In one embodiment, in embedding the watermark data 10 in the blocked noise base image 41, a pre-stored random number sequence is used, and some pixel values of the block are used as a rule corresponding to the random number selected while traversing each block to obtain a transformed noise base image 50 by modifying .

In some embodiments, the converted noise base image 50 that can be referenced maintains synchronization signal characteristics better than a conventional noise base image converted according to one rule, and security is enhanced because a constant pattern is not formed.

Referring to FIGS. 15 and 16 , synchronization signals that may be referenced in some embodiments will be described. In the noise-based image generated through the frequency domain, synchronization signal characteristics are maintained even if the image is partially damaged according to the characteristics of the frequency. Therefore, in the extraction process, geometric distortion can be corrected by using the similarity between the synchronization signal and the captured image.

As shown in FIG. 15 , when the noise base image 40 is subjected to Fourier transform, a magnitude spectrum 45 and a phase spectrum 47 in the frequency domain can be obtained. The illustrated noise base image 45 corresponds to images generated by synchronization signals 45a, 45b, 45c, and 45d. As shown in FIG. 16, synchronization signals 51aa, 51ab, 51ac, and 51ad are maintained in the magnitude spectrum 51a in the frequency domain according to the Fourier transform of the transformed noise base image 50. As described above, a synchronization signal is maintained even after the steps of blocking and embedding watermark data, so that a noise-based image corresponding to a container containing data can be recognized in the extraction step.

Returning to FIG. 3 again, an image in which watermark data is embedded is created by adjusting the original image using the converted noise base image (S180). The adjusting includes adjusting the first pixel only when the R channel value, the G channel value, and the B channel value of the first pixel of the original image exceed the threshold value or fall below the threshold value. In this case, adjusting the current pixel of the original image is to first adjust the first pixel when the second pixel of the converted noise-base image is white, and to first adjust the first pixel when the second pixel is black. and performing a second adjustment according to a different rule from the first adjustment. For example, the first adjustment is to decrease the R channel value of the first pixel, increase the G channel value, and decrease the B channel value, and the second adjustment is to adjust the R channel value of the first pixel. increase, decrease the G channel value, and increase the B channel value.

In the above adjustment, the values of three constants α, β, and γ are utilized. The values of the above three constants are ratios to be used for monochromeization in order to maximize noise in the image in the watermark data extraction process.

Assuming (R, G, B = pixel values of each of the original R, G, and B channels before updating, R, G, B' = pixel values of each of the R, G, and B channels after updating), The following adjustment rules may be considered.

Case 1: When the pixel value of the noise is 0 and the pixel value of the original image is greater than 250 for all three channels R, G, and B, R' = R(1 - α), G'= G(1 + β), B' = B(1 - γ)

Case 2: When the pixel value of the noise is 0 and the pixel value of the original image is less than 250 for all three channels R, G, and B, R' = R(1 - α), G'= G(1 + β), B' = B(1 - γ)

Case 3: When the pixel value of the noise is 255 and the pixel value of the original image is greater than 250 for all three channels R, G, and B, R' = R(1 + α), G'= G(1 - β), B' = B(1 + γ)

Case 4: When the pixel value of the noise is 255 and the pixel value of the original image is less than 250 for all three channels R, G, and B, R' = R(1 + α), G'= G(1 - β), B' = B(1 + γ)

The three constants α, β, and γ used to insert noise into the original image depend on the original image. This technology has a characteristic that it is difficult to identify with the human eye. In order to satisfy this, the values of α, β, and γ must vary according to pixel values of the original image where noise is to be inserted.

Hereinafter, specific examples in which a noise base image corresponds to a rectangle rather than a square in a watermark data embedding method according to an embodiment of the present invention will be described with reference to FIGS. 17 to 20 .

A method of embedding watermark data based on an aspect ratio of an original image will be described with reference to FIGS. 17 and 18 below.

In one embodiment, the step of obtaining the aspect ratio of the original image may be further included, and if the aspect ratio of the original image corresponds to the reference range, the watermark data is obtained by using a noise base image of a non-square rectangular image corresponding to the aspect ratio of the original image. can be embedded. In response to the design characteristics of the original image, the watermark can be flexibly modified and embedded. Since the design characteristics of the original image are reflected, recognition performance can be improved when watermark data is extracted. For example, when the aspect ratio (= width/length) is 4 or more or 0.25 or less, watermark data may be embedded using a noise base image of a rectangular image.

In one embodiment, when the aspect ratio of the original image corresponds to the reference range, watermark data may be embedded using a rectangular noise base image having a fixed aspect ratio.

In one embodiment, when the aspect ratio of the original image corresponds to the reference range, watermark data may be embedded using a rectangular noise base image having the same aspect ratio as that of the original image. For example, referring to FIG. 9, if a conventional square watermark is composed of 12 x 12 blocks and is composed of 24 x 24 pixel units, the unit watermark corresponding to the aspect ratio of 4 may be composed of 48 x 12 pixels. . A unit watermark corresponding to the aspect ratio of 0.25 may be composed of 12 x 48 pixels.

17 shows the rectangular watermark described above. The square watermark 70 is created by the 24x24 pixel square unit watermark 60. A rectangular watermark 70a having a width greater than a height is generated by a 48 x 12 pixel rectangular unit watermark 60a having a width longer than a height. A rectangular watermark 70b having a vertical dimension longer than a horizontal one is generated by a 12x48 pixel rectangular unit watermark 60b having a vertical dimension longer than a horizontal one. As described above, since the watermark is generated by reflecting the design characteristics of the original image, recognition performance can be improved when watermark data is extracted.

18 corresponds to an exemplary diagram illustrating a specific example in which the above-described rectangular watermark is utilized. Since the watermark is not recognized by the human eye, it can be used together by locating the CI or QR code of the company in the middle (60c). In particular, when used with a QR code, it can be used to strengthen the security of commercial transactions using QR codes in the future. Rectangular unit watermarks 60a with a width longer than the vertical may be positioned at the top and bottom, and rectangular unit watermarks 60b with a vertical length longer than the width may be positioned at the left and right ends to constitute watermarks that are not recognized by the human eye. there is.

Referring to FIGS. 19 and 20, a method of embedding watermark data based on pattern tendency of an original image will be described.

In one embodiment, the step of obtaining the vertical and horizontal trend of the pattern of the original image as a numerical value may be further included, and if the numerical value corresponds to a reference value or less, the watermark data is embedded using a rectangular noise base image having a shape corresponding to the numerical value. It can be.

In one embodiment, the step of obtaining the pattern aspect ratio as a numerical value may include obtaining a minimum distance from an axis to which peak coordinates are most adjacent in a magnitude spectrum of a Fourier transform frequency domain of the original image. Referring to FIG. 19 , as a result of Fourier transformation of the original image 53 in which vertical patterns are continuous, a magnitude spectrum 53a showing peak points on the x-axis can be obtained. As a result of Fourier transformation of the original image 55 in which the horizontal patterns are continuous, a magnitude spectrum 55a showing peak points on the y-axis can be obtained. In the case of this example, since it corresponds to the peak point located on the axis, the minimum distance from the adjacent axis corresponds to 0.

In one embodiment, when the minimum distance between the peak coordinates and an adjacent axis corresponds to a reference value or less, when the adjacent axis corresponds to the x-axis, watermark data is generated by using a noise base image in which the vertical side of the rectangle is longer than the horizontal side. can be embedded. In one embodiment, when the minimum distance between the peak coordinate and the adjacent axis corresponds to a reference value or less, when the adjacent axis corresponds to the y-axis, the watermark data is generated by using a noise base image with a rectangle whose width is longer than the vertical can be embedded. Referring to FIG. 19 , as a result of step 53a , a watermark having a height longer than a width may be embedded in the original image 53 . As a result of step 55a, a watermark longer in width than in height can be embedded in the original image 55. By adjusting the size of the unit watermark corresponding to the pattern tendency of the original image, there is an effect of improving the recognition rate during extraction by maintaining a strong synchronization signal.

20 shows a specific example of arranging a watermark corresponding to the pattern of the original image described above. A unit watermark 60a, the width of which is longer than the height, is disposed on the horizontal pattern original image 20b. A unit watermark 60b whose length is longer than its width is disposed on the vertical pattern original image 20c. As described above, by adjusting the size of the unit watermark corresponding to the pattern tendency of the original image, there is an effect of improving the recognition rate and reducing the recognition speed during extraction by maintaining a strong synchronization signal.

Extraction of watermark data

Hereinafter, a method of extracting watermark data according to another embodiment of the present invention will be described with reference to FIGS. 21 to 27. The watermark data extraction method according to the present embodiment is applicable only to watermark data embedded by the watermark data embedding method according to the above-described embodiment of the present invention. First, it will be described with reference to FIG. 21 .

The watermark data extraction method according to the present embodiment starts by receiving a captured image and identifying a plurality of image blocks from it (S200).

If a watermark is extracted on a PC with a digital image file in which a watermark is inserted, as in the existing digital watermarking technology, the watermark can be extracted by performing the embedding process exactly in reverse. However, since the technology of the present invention supports recognizing a watermark using a camera of a mobile terminal such as a smartphone camera, many image preprocessing steps are required before extracting the watermark. Referring to FIG. 22 , a user of a smart phone 900 can take a picture of a medium 30 ′ on which an image embedded with watermarking data is printed without paying special attention to extracting the watermarking data. The watermark data extraction method according to the present embodiment has been developed to enable extraction of watermark data even in this case.

The pre-processing process makes it possible to maintain a high recognition rate in many variables such as the location, size, rotation, brightness, and damage of objects to determine whether or not there is a watermark in a photo taken by the camera. In this process, the presence or absence of a watermark is determined using the synchronization signal inserted during the embedding process, and the image is transformed into optimal conditions for extracting data.

Prior to performing the preprocessing process in earnest, pre-calibration may be performed. For example, when an object to determine whether a watermark is to be determined is illuminated using a smartphone camera, a preview entering the smartphone screen is captured in a size of 1920x1080. After this, all pixel values of the captured image are converted into RGB format. This is because the embodiments of the present invention perform operations based on RGB.

Next, the captured 1920x1080 image (hereinafter, referred to as “photographed image”) is partitioned into a plurality of image blocks. Here, each of the plurality of image blocks is an image unit to be processed for the first similarity determination in step S210 to be described later, and whether or not watermark data exists for any one image block selected as a result of the first similarity determination. is determined and watermark data extraction is attempted.

23A is a diagram showing an example in which a captured image 90 is partitioned into a total of nine image blocks 91 to 99 having the same size. If the captured image is an image 90 having a size of 1920x1080, the image blocks 91 to 99 may be a part of the captured image, each having a size of 256x256 pixels or 512x512 pixels, respectively. The size of each of the image blocks may be set to an arbitrary size so that watermark existence determination and watermark data extraction can be smoothly performed in steps (S210 to S250) to be described later, but at least watermark embedding It should be set larger than the size of the noise base image used for . At this time, the size of the noise base image is selected as an appropriate size in consideration of the size (number of bits) of watermark data to be embedded.

In this case, the plurality of image blocks 91 to 99 may partially overlap each other. In the example shown in FIG. 23A, the image blocks 1, 2, and 3 each have an overlapping region (region marked with a dark shade) with the image blocks 4, 5, and 6, and the image blocks 7 and 8 , 9) each has an overlapping region (region marked with a dark shade) with the image blocks 4, 5, and 6.

The first similarity determination step (S210), which will be described later, is a process of finding an image block having the highest possibility of having watermark data in a state where it is not known in which region of the captured image 90 the watermark data exists. Therefore, as many image blocks as possible are overlapped with each other in the captured image 90 , the possibility of not being able to recognize the watermark existing in the captured image 90 is reduced. However, as the number of image blocks increases, computing power and time consumed in the first similarity determination performed on each image block increase. Conversely, as fewer image blocks are set in the captured image 90, the computing power and time consumed in step S210 to be described later are reduced, but the possibility of not recognizing the watermark existing in the captured image 90 increases. do. If the watermark is not recognized even though it exists in the captured image 90, eventually, the watermark recognition process must be performed again for the new captured image, so the final consumed computing power and delay time can further increase. there is.

Meanwhile, it is preferable that all regions of the captured image 90 are covered by at least one of the plurality of image blocks 91 to 99, but this is not necessarily the case. Since it is very likely that the user illuminates an object with a camera so that the object comes to the center of the screen, some of the outer regions of the captured image 90 are not covered by the plurality of image blocks 91 to 99 described above. Even if it is not present, the effect on the watermark recognition result may be relatively low.

Meanwhile, in some embodiments, deblur processing is performed on each of the plurality of image blocks 91 to 99 previously identified from the captured image 90, thereby image blocks to be used in steps S210 to S250 to be described later. can make them clearer.

An example of identifying a total of 9 image blocks 91 to 99 from a captured image 90 has been described in FIG. 23A, but the present invention is not limited to such an example. Considering various factors such as the purpose for which the present invention will be used, the performance of the device to which the watermark data extraction function will be implemented, the time and computing power required for watermark recognition and extraction of watermark data, You can choose to use image blocks.

23B and 23C show other examples in which a plurality of image blocks are identified from the captured image 90. As described above, since it is highly likely that the user illuminates an object with a camera so that the object comes to the center of the screen, it is preferable to set the image blocks so that there is a high possibility of finding watermark data in the center of the captured image 90. can do. FIG. 23B is a diagram showing an example in which a plurality of image blocks are arranged around the center of a captured image 90, and FIG. 23C is a diagram in which a plurality of image blocks are arranged to overlap each other in the vicinity of the center of the captured image 90. This is a drawing showing an example.

Meanwhile, in some embodiments in which one of two or more random number sequence sets is selectively used in the process of embedding and extracting watermark data, a watermark from the captured image 90 in step S250 to be described later. An identifier for determining a random number sequence to be referred to when extracting data may be identified from the captured image 90 . Note that the identifier is not a random number sequence itself, but an identifier that distinguishes a plurality of random number sequences from each other. A plurality of sets of random numbers are shared in advance between a device embedding watermark data and a device extracting watermark data. Meanwhile, the identifier may be identified from the captured image 90 using various conventional methods for identifying data from an image.

As described above, a photographed image is obtained and a plurality of image blocks are identified therefrom (S200).

Next, a first similarity with the noise base image is determined for each of the plurality of image blocks 91 to 99 (S210). In step S210, a first similarity, a rotation angle, and a scale of each image block 91 to 99 are determined by comparing each image block 91 to 99 with a noise base image through frequency domain processing. . This operation will be described in more detail with reference to FIG. 24 .

First, one image block among the plurality of image blocks 91 to 99 is converted into a frequency domain (S211), and a 2D magnitude spectrum image MS2 of the image block is generated (S212). In addition, an image MS1 of a 2D magnitude spectrum of a noise base to be compared with the image block is also prepared (S213). The image MS1 of the 2D magnitude spectrum of the noise base may be generated from a pre-stored image of the noise base or simply retrieved from pre-stored data.

Next, the 2D magnitude spectrum image MS1 of the noise base and the 2D magnitude spectrum image MS2 of the image block are subjected to LogPolar transformation (S215). Since LogPolar transformation has invariant characteristics in two-dimensional rotation and size transformation, by using LogPolar transformation, it is possible to obtain an effect of repairing flaws in a photographed image that are reliable in terms of rotation and size.

Next, each image created as a result of LogPolar transformation is converted into the frequency domain (S215), the result of transformation into the frequency domain is multiplied (S216), and the result of transformation into the frequency domain (f_LP2) of the captured image is converted into a magnitude matrix. By dividing, a first result matrix for the image block is generated (S217). The first result matrix may be understood as a matrix indicating how much noise base is included in the image block and a ratio thereof. Also, the first result matrix may be understood as a matrix indicating a degree of similarity between the image block and the image of the noise base.

Next, a first reference image for the image block is generated by transforming the first result matrix of the image block into a spatial domain (S218). A first similarity of the image block is calculated using the first reference image (S219). The first similarity is a maximum value among pixel values of the first reference image with respect to the image block. Further, the rotation angle is the X coordinate of the pixel having the maximum pixel value, and the scale is the Y coordinate of the pixel (S219).

The above steps S211 to S219 are performed for each of the plurality of image blocks 91 to 99 in the captured image 90, and as a result, a first similarity for each image block is calculated.

It will be described with reference to FIG. 21 again.

In step S220, a first image block is selected from among the plurality of image blocks 91 to 99 based on the result of the first similarity calculation in step S210, and the rotation angle and scale are reflected to the first image block. to pre-process

In step S220, the first similarities calculated for each of the plurality of image blocks 91 to 99 in step S210 are compared with each other. An image block having the largest first similarity is selected as the first image block. An image block having the highest first similarity in the captured image 90 may be understood as an area in which the watermark is most likely to exist in the captured image 90 . In step S220, a first region having the highest possibility of having a watermark is selected from among the plurality of image blocks 91 to 99, thereby precisely recognizing the watermark and watermark data in steps S230 to S250 to be described later. An object of processing related to extraction is limited to a partial area within the captured image 90 rather than the entire captured image 90 . As a result, computing power and processing time consumed in performing steps S230 to S250 to be described later may be reduced.

In some embodiments, when the first similarities calculated for each of the plurality of image blocks 91 to 99 are all less than a threshold value, watermark data does not exist in any of the plurality of image blocks 91 to 99. may be implying that Therefore, when the first similarity of the first image block is less than the threshold value, the watermark data extraction operation targeting the captured image 90 is stopped, and a new captured image can be automatically obtained by returning to step S200. there is. For example, an image shown as a preview on a screen of a smartphone camera capturing an object to be determined whether or not a watermark is present may be automatically acquired as a new captured image. Subsequently, a plurality of image blocks in the new captured image are identified, and operations after step S210 may be repeated.

In step S220, pre-processing is performed on the selected first image block.

As described above in relation to step S210, in the process of calculating the first similarity for each of the plurality of image blocks 91 to 99, the rotation angle of each image block (the maximum value among pixels of the first reference image) X coordinate of the pixel) and scale (Y coordinate of the pixel) are obtained together. In operation S220, pre-processing is performed on the first image block using the acquired rotation angle and scale of the first image block.

The results of the preprocessing may be understood with reference to FIG. 25 . As a result of the preprocessing, the orientation of the captured image 90 is matched, and the size is also corrected to match the comparison with the noise base.

It will be described with reference to FIG. 21 again.

In step S230, operations for calculating a second similarity with respect to the first image block (hereinafter, referred to as “corrected image”) of which the rotation angle and scale are corrected and determining a watermark extraction reference point are performed. In step S230, a second similarity of the corrected image is calculated by comparing the corrected image and the noise base image through processing in a frequency domain, and a reference point serving as a criterion for extracting a watermark from the corrected image is determined. This operation will be described in more detail with reference to FIG. 26 .

The second similarity calculation operation targeting the corrected image in step S230 compares the first similarity calculation operation targeting each of the plurality of image blocks 91 to 99 in step S210 with the image block. Similar except that it does not perform a LogPolar transform on .

Specifically, converting the corrected image into a frequency domain to obtain a frequency domain matrix f2 (S231), querying or generating a noise-based frequency domain matrix f1 (S232), f1 and f2 Generating a multiplied matrix R' (S233), dividing R' by the magnitude matrix of f2 to create a second result matrix (S234), converting the second result matrix into the spatial domain to obtain a second reference image The generating step (S235) is performed. In this case, the second result matrix may be understood as a matrix indicating a ratio of how much noise base is included in the corrected image.

In step S236, the second reference image generated in step S235 is analyzed to obtain information about a second similarity between the corrected image and the noise base image and the position of the noise base in the corrected image. Specifically, the coordinates of the reference pixel having the largest pixel value among the pixel values of the second reference image are determined as a reference point, which is a watermark data extraction location. Also, a pixel value of the reference pixel is determined as a second similarity of the corrected image.

It will be described with reference to FIG. 21 again.

In step S240, the second similarity calculated for the corrected image in step S236 is compared with a threshold value.

If the second degree of similarity is less than the threshold, this may imply that the watermark does not exist in the calibrated image or that watermark data cannot be extracted from the calibrated image. In this case, the operation of extracting watermark data for the corrected image (the image obtained by correcting the first image block, which is a partial area selected from the captured image 90 in step S200) is stopped.

In some embodiments, when the second similarity is less than the threshold value, a new captured image may be automatically obtained by returning to step S200. For example, an image shown as a preview on a screen of a smartphone camera capturing an object to be determined whether or not a watermark is present may be automatically acquired as a new captured image. Subsequently, a plurality of image blocks in the new captured image are identified, and operations after step S210 may be repeated.

In some other embodiments, when the second similarity is less than the threshold value, operations after step S220 may be repeated for an image block other than the first image block selected in step S210. As described above, in the previous step (S210), based on the result of calculating the first similarity between the plurality of image blocks 91 to 99 and the noise base image, the image block having the highest first similarity is designated as the first image block. is selected, and subsequent steps S220 to S230 are performed based on the first image block. If the second similarity calculated based on the first image block is less than the threshold value, the image block having the second highest first similarity calculated in step S210 is identified as the second image block, and the second image block Subsequent steps (S220 to S230) may be performed for the target.

As in the above-described embodiment, in the embodiment of performing some operations (steps S220 to S250) of the watermark data extraction process targeting the second image block in the existing captured image 90, a new captured image is obtained and Compared to the embodiment in which all processes (steps S200 to S250) of extracting watermark data are performed, computing power and processing time may be reduced. This is because the process of partitioning a new captured image into a plurality of image blocks and calculating the first similarity for each block (steps S200 to S210) can be omitted.

It will be described with reference to FIG. 21 again.

In step S240, if the second similarity is greater than or equal to the threshold value, the process proceeds to step S250.

In step S250, watermark data is extracted based on the watermark data extraction reference point obtained in step 240. This will be described with reference to FIG. 27 .

First, the correction image is monochromeized (S251). At this time, the same three constants α, β, and γ used to insert noise into the original image are used. As a result, the representation of noise in the calibration image will be maximized.

Then, the monochromeized corrected image is partitioned into 2x2 pixel block units (S252).

In subsequent steps S253 to S256, watermark data is extracted while traversing each block (2 x 2 pixels) of the monochrome correction image.

First, in step S253, the data extraction rule of the current block of the monochrome correction image is determined. The data extraction rules correspond to data embedding patterns of six cases described as an example with reference to FIG. 8 . In other words, a rule used when embedding watermark data in each block is a data extraction rule for each block.

A data extraction rule for each block may be determined by referring to a previously generated random number sequence. For example, the data extraction rule indicated by the first number of the random number sequence (for example, any one of the 6 patterns illustrated in FIG. 8) is applied to the first block of the monochromeized corrected image, and to the second block, the data extraction rule indicated by the second number of the random number sequence is applied. Data extraction rules apply. It will be appreciated that the random number sequence exactly matches the random number sequence referenced to determine the data embedding rule in the process of embedding watermark data in the image. In some embodiments, the random number sequence may be previously shared between a device for embedding watermark data in an image and a device for extracting watermark data from an image.

Meanwhile, in some embodiments in which one of two or more random number sequence sets is selectively used in the process of embedding and extracting watermark data, among a plurality of random number sequence sets, in the above-described step (S200), the The random number sequence indicated by the random number sequence identifier identified from the photographed image 90 is identified and can be used to determine a rule for extracting watermark data from the monochromeized corrected image.

Next, in step S254, watermark data of the current block is extracted according to the data extraction rule determined in step S253 with reference to the noise base image blocked in units of 2 x 2 pixels. The operation of extracting watermark data from the current block by referring to the blocked noise base image can be understood in the reverse order of the embedding process described with reference to FIGS. 7 to 13 .

In step S255, it is determined whether extraction of watermark data has been completed for all blocks of the monochromeized corrected image. is created All watermark data generated can be displayed, transmitted, or output.

In step S255, if extraction of all blocks of the monochromeized corrected image has not been completed, the next block is moved (S256). The order of traversing the monochrome correction image blocks is the same as the block traversal order of the embedding process. Subsequently, in step S253, a process of determining a data extraction rule for the next block of the monochromeized corrected image by referring to the random number sequence, and proceeding to step S254 to extract watermark data embedded in the next block. Repeat.

In the method for extracting watermark data according to some embodiments of the present invention described with reference to FIGS. 21 to 27, the entire process of determining whether a watermark exists and attempting to extract watermark data from a captured image 90 (S200 to S200 to Instead of performing S250), after calculating the first similarity of each of a plurality of image blocks that are parts of the captured image 90 (S210), a subsequent operation is performed targeting only one image block having the highest first similarity. (S220 to S250) are performed. As a result, computing power consumed in the operations S220 to S250 is reduced and processing delay time caused by the execution of the operations S220 to S250 is reduced. In addition, it is possible to meet the needs of users who wish to complete the recognition at the same time as the watermark recognizing device is directed to the image in which the watermark is embedded.

In the method for extracting watermark data according to some embodiments of the present invention, in embedding each bit of watermark data in a noise-based image or extracting each bit of watermark data from an image in which a watermark is embedded, each bit of watermark data is extracted. Instead of using one and the same embedding/extraction rule for bits, one of a plurality of embedding/extraction rules indicated by each random number in a pre-generated and shared random number sequence is used. In this way, even if the original noise-based image 40 is leaked, a third party may not use the data embedded in the watermark image without permission unless the random number sequence used when embedding each bit of the watermark data in the noise-based image is leaked. cannot be extracted. That is, the security of the watermark data embedding/extraction algorithm is greatly improved. In addition, a problem in which a pattern such as a wave pattern is generated in an image as a result of embedding a watermark is solved.

A watermark data extraction method according to some embodiments of the present invention uses a different random number sequence set for each different watermark and identifies an appropriate random number sequence set when extracting watermark data so that it can be used for data extraction. Even if one set of random number sequences is leaked, a third party cannot extract data embedded in a watermark image generated using another random number sequence without permission. That is, the security of the watermark data embedding/extraction algorithm can be further improved.

The methods according to the embodiments of the present invention described so far can be performed by executing a computer program implemented as a computer readable code. The computer program may be transmitted from the first computing device to the second computing device through a network such as the Internet, installed in the second computing device, and thus used in the second computing device. The first computing device and the second computing device include both a server device, a physical server belonging to a server pool for a cloud service, and a fixed computing device such as a desktop PC.

The computer program may be stored in a recording medium such as a DVD-ROM or a flash memory device.

The method of embedding and extracting watermark data according to an embodiment of the present invention may be modified and implemented in a form in which different noises are recognized according to the viewing direction, as shown in FIG. 25 .

Hereinafter, the configuration and operation of a data embedding device according to another embodiment of the present invention will be described with reference to FIG. 28 . As shown in FIG. 28, the data embedding apparatus 300 according to the present embodiment includes a memory (RAM) 330, an image processor 320 executing a data embedding software operation loaded into the memory 330, and a storage ( 340). In one embodiment, the embedding device 300 may further include an image sensor 310 , a network interface 370 , a system bus 350 and a printer interface 360 .

The storage 340 stores an execution file (binary file) 342 of data embedding software implementing the data embedding method described with reference to FIGS. 1 to 20 in software form. The executable file 342 of the data embedding software may be loaded into the memory 330 through the bus 350 . 28 shows operation 332 of the data embedding software loaded into memory 330.

The storage 340 may further store noise base data 341 . In one embodiment, the storage 340 may store the noise base data 341 in an encrypted form to prevent the original noise base from being leaked to the outside. In one embodiment, the storage 340 may include noise base data in the form of a resource in a data embedding software executable file to prevent leakage of the original noise base to the outside.

Storage 340 may further store one or more sets of random number sequences indicating rules for embedding watermark data. In one embodiment, the storage 440 may store the random number sequence in an encrypted form and store it in the form of a resource in a data embedding software executable file.

The data embedding device 300 receives watermarking data from an external device through the network interface 370, directly receives input from a user through an input unit (not shown) such as a keyboard or mouse, or watermarking data stored in the storage 340. (not shown) can be read. The data embedding device 300 obtains an original image, which is a target to embed the watermarking data, from the image sensor 310 that captures the target object, receives it from an external device through a network interface 370, or stores the original image 340. Watermarking data (not shown) stored in may be read.

The data embedding device 300 transmits the resulting image calculated by inputting the watermarking data and the original image into the data embedding software to an external device through the network interface 370, displays it on a display device (not shown), Printing may be performed through a printing device connected through the printer interface 360 .

The data embedding device 300 according to this embodiment may be, for example, a computing device or a printing device. When the data embedding device 300 is a printing device, the data embedding device 300 may include components for performing a printing function instead of the printer interface 360 .

Hereinafter, the configuration and operation of a data decoding apparatus according to another embodiment of the present invention will be described with reference to FIG. 29. In this specification, decoding of watermarking data and extraction of watermarking data refer to substantially the same operation. As shown in FIG. 29, the data decoding apparatus 400 according to the present embodiment includes a memory (RAM) 430, an image processor 420 executing a data decoding software operation loaded into the memory 430, and a storage ( 440). In one embodiment, the decoding device 400 may further include an image sensor 410, a network interface 470, a system bus 350, and a watermarking data interpretation processor 460.

The storage 440 stores an execution file (binary file) 442 of data decoding software implementing the data extraction method described with reference to FIGS. 21 to 27 in software form. An executable file 442 of data decoding software may be loaded into memory 430 through bus 450 . 29 shows operation 432 of the data decoding software loaded into memory 430.

The storage 440 may further store noise base data 441 . In one embodiment, the storage 440 stores the noise base data 441 in an encrypted form or includes the noise base data in the form of a resource in a data decoding software executable file to externally generate noise. It is possible to prevent the base original from leaking.

The storage 440 may further store one or more sets of random number sequences indicating rules for extracting watermark data. In one embodiment, the storage 440 may store the random number sequence in an encrypted form and store it in the form of a resource in a data decoding software executable file.

The data decoding device 400 obtains data of a photographed image from the image sensor 410 for photographing a target object on which an image in which watermarking data is embedded is printed, receives data from an external device through a network interface 470, or stores Data of the captured image stored in 440 can be obtained. Data of the photographed image is loaded into the memory 430 through the system bus 450 and referred to when the data decoding software operation 432 is executed.

The data decoding device 400 displays the watermark data extracted as a result of the execution of the data decoding software operation 432 on a display (not shown), transmits it to an external device through the network interface 470, or stores the watermark data 440. , or output in some other way.

In one embodiment, the data decoding device 400 may include a watermarking data interpretation processor 460 that performs a process using the extracted watermark data. For example, body data of the watermark data is extracted (see Table 1), and a content request containing the body data and control parameters (see Table 1) is sent to a content server (not shown) through the network interface 470. can be sent to A display device (not shown) of the data decoding device 400 may display content received as a response to the content request from the content server.

The data decoding apparatus 400 according to this embodiment may be, for example, a mobile terminal equipped with a camera.

Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art to which the present invention pertains can be implemented in other specific forms without changing the technical spirit or essential features of the present invention. can understand that Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting.

Claims (7)

In the method of embedding watermark data in an original image,
Transforming the noise base image by modifying pixel values of some pixels of each block using the watermark data while traversing each block of the noise base image configured in units of blocks having a plurality of pixels, ,
Further comprising obtaining a pattern tendency of the original image,
The noise base image,
Which is a form corresponding to the pattern tendency of the original image,
Data embedding method. According to claim 1,
The step of obtaining the pattern tendency of the original image,
Including the step of obtaining numerically the horizontal and vertical trend of the pattern of the original image,
When the numerical value is less than or equal to the reference value, the noise base image is a rectangular image having a shape corresponding to the numerical value.
Data embedding method. According to claim 2,
The step of obtaining the tendency as a numerical value,
Obtaining a minimum distance from an axis to which peak coordinates are most adjacent in a magnitude spectrum of a Fourier transform frequency domain of the original image,
The minimum distance is less than a predefined value,
Data embedding method. According to claim 3,
The rectangular image,
When the axis closest to the peak coordinate corresponds to the x-axis, a rectangular image in which the vertical length of the rectangle is longer than the horizontal length,
Data embedding method. According to claim 3,
The rectangular image,
When the axis adjacent to the peak coordinate corresponds to the y-axis, a rectangular image in which the horizontal length of the rectangle is longer than the vertical length,
Data embedding method. According to claim 1,
Further comprising adjusting the original image using the converted noise base image,
The adjustment step is
If the original image is a vertical pattern original image,
Disposing the converted noise base image, which is longer than the horizontal, in the original image.
Data embedding method. According to claim 1,
Further comprising adjusting the original image using the converted noise base image,
The adjustment step is
If the original image is a horizontal pattern original image,
Disposing the converted noise base image, which is longer than the vertical one, in the original image.
Data embedding method.

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