JP4337745B2 - Image processing apparatus and method - Google Patents

Description

  The present invention relates to a technique for embedding digital data in a digital image such as a digital watermark, and more particularly to a method for reducing errors in digital data generated by embedding.

  Conventionally, as a technique for printing and recording digital data, a barcode and a two-dimensional barcode obtained by evolving it are widely known and used. These codes clearly recognize the printed part where the data is recorded and do not look good. In some cases, it is possible to tamper with a portion where digital data is printed. For these technologies, digital watermark technology that adds a format that cannot be recognized by human eyes at first glance has been researched and developed. Many of these techniques have the feature that the target image in which the digital data is embedded can be made into an arbitrary photograph or picture according to the purpose and preference of the user. However, when embedding digital data, the embedding printing of the original target image and the digital data interferes with each other, such as the density and color of the image of the target image, and a sudden change in density, and an error occurs in the recording and reproduction process of the digital data. There is a case.

For example, the present applicant has proposed a digital data embedding method in Patent Document 1. In this method, different pattern images are assigned to the codes “0” and “1” of the digital data to be embedded, and the embedded images are arranged by arranging the pattern images according to the code sequence and the arrangement rule of the pattern images. The data is embedded by superimposing the embedded image on the target image data. Each pattern image is
(A) The result of adding the corresponding pixels of both pattern images is the same predetermined value (for example, “0”).
(B) The result of adding all the pixels in each pattern image is the same predetermined value (for example, “0”).
(C) Each pattern image has a discontinuous line of pixel values (called an edge) that passes through the center of the image and has a different direction. The direction of the edge can be, for example, a direction along a vertical line and a horizontal line,
(D) The absolute value of the pixel value of each pattern image is the largest at the center and decreases as the distance from the center increases.
It has the characteristics.

  FIG. 1 shows an example of a pattern image having such characteristics and having the edge direction horizontal and vertical. In FIG. 1, for example, the pattern (A) indicates the code “0”, and the pattern (B) indicates the code “1”.

  In this way, by expressing the code by a pattern having an area, the resistance to each image quality deterioration factor is acquired, while the density of the image is prevented from changing greatly after composition (depending on the characteristics of (a) and (b)). ), The detection of the pattern image is easy and the decoding process is simplified (according to the characteristics of (b) and (c)), and the occurrence of an edge between the patterns is prevented (according to the characteristics of (d)). Its presence becomes visually inconspicuous. This edge is used for estimation of a pattern period at the time of decoding.

  When decoding an image obtained by synthesizing this pattern image, a sum of pixel values after synthesis corresponding to each quadrant divided by edges in the pattern image (R1 to R4 for the first to fourth quadrants) is calculated. For example, when R1> R2 and R1> R4 and R3> R2 and R3> R4, it is determined that the code is “1”. That is, decoding can be performed by comparing the sum of pixel value groups for each quadrant.

  In the case of a data embedding method in which an edge is formed in a pattern image of each code as in Patent Document 1 and this edge is used for decoding, the digital data of the printed digital data is overlapped with a portion where the density change of the image to be embedded overlaps abruptly Information is prone to errors. For example, when using a pattern image as shown in FIG. 1 in which the edge direction is horizontal and vertical, the pattern image has a characteristic along the diagonal direction. In some cases, the partially superimposed pattern image is difficult to decode.

  In this way, when digital data is embedded in a target image by digital watermark technology, the target image and digital data may interfere with each other and cause an error, so as to realize a highly reliable apparatus for recording and reproducing digital data. It is necessary to eliminate these errors.

JP 2004-140764 A

  The present invention provides a method of reducing interference between a pattern image and a target image in an embedding method of embedding information in a target image using a pattern image having a characteristic direction component inside.

  In the present invention, among the four regions divided by two intersecting edges, the difference in pixel values between regions adjacent to each other through the edge is larger than the difference in pixel values between regions not adjacent to each other. An additional image expressing the additional information is formed by arranging a plurality of set pattern images, and the additional image is combined with the embedding target image to generate an image in which the additional information is embedded. An image processing apparatus, comprising: a block dividing unit that divides the embedding target image into blocks of a predetermined size; and for each divided block, the block is divided into two by a dividing line parallel to one of the two edges of the pattern image. The contrast between the divided areas when divided and the contrast between the divided areas when divided into two by a dividing line parallel to the other edge are obtained. A filter processing unit that performs a filtering process so that each pixel value is uniform while maintaining the sum of the pixel values of each of the divided regions for each of the divided regions having a larger contrast, and the filter processing unit An image processing apparatus is provided that includes an embedding processing unit that generates an image in which the additional information is embedded by synthesizing the additional image with the processed embedding target image.

  The best mode for carrying out the present invention (hereinafter referred to as “embodiment”) will be described below with reference to the drawings.

  FIG. 2 shows an example of a digital watermark system to which the method of this embodiment is applied. As shown in this figure, in the present embodiment, a pattern used for expressing digital data to be embedded from an embedding target image by applying a predetermined filtering process to the embedding target image in the image processing apparatus 100. The direction component that interferes with the characteristic direction component of the image is removed or reduced. Details of this filtering process will be described later. Next, the digital watermark printing apparatus 200 encodes digital data to be embedded (hereinafter, also referred to as “additional information”), and replaces each code of the code string obtained as a result with the corresponding pattern image and arranges it. Additional image data is created, and the additional image data is combined with the filter-embedded image to be embedded output from the image processing apparatus 100. The creation of the additional image data and the synthesis with the embedding target image here are performed using, for example, the method disclosed in Patent Document 1. Here, since the component that interferes with the feature direction component of the pattern image has already been removed or reduced by the image processing apparatus 100 from the embedding target image to be synthesized, even if it is synthesized with the additional image data, The characteristic direction component of each pattern image is difficult to cancel. Then, the digital watermark printing apparatus 200 prints the composite image data obtained as a result of the synthesis, and outputs a paper 400 on which information is embedded. When detecting information embedded in the printed paper 400, the digital watermark scanning device 300 optically reads the paper 400, and from the resulting digital image, decoding corresponding to the algorithm of the embedding process is performed. Play back the embedded data using an algorithm. The reproduction data obtained as a result is provided to the application system and used for a predetermined purpose.

  In the above, an example of a system that prints and circulates composite image data in which additional information is embedded in an embedding target image, reads the printed matter, and reads the additional information therein, but as will be understood from the following description, The system according to the embodiment is also effective when the synthesized image data is distributed as electronic data without printing.

  As described above, in the present invention, before the additional image data obtained from the additional information is combined with the image to be embedded, the image to be embedded is added to the image in the additional image data by preprocessing in the image processing apparatus 100. The image is converted into an image having a good property in a form that does not interfere with the characteristics of the individual pattern image data.

  Hereinafter, before explaining the processing contents of the image processing apparatus 100, an example of an additional information embedding method used in the present embodiment will be described.

As shown in FIG. 3, the embedding method assumed as one of the application destinations of the preprocessing of the present embodiment is plane 1 of the target image that is an embedding destination of additional information and plane 2 of the additional image that represents additional information. The composite image data is obtained by performing multiplication, addition, or other operations for each pixel or for each block in which a plurality of pixels are collected. In the case of each pixel, the calculation is performed, for example, by setting the pixel value representing the density of each pixel of the target image plane 1 to X, the pixel value of the corresponding pixel in the additional image plane 2 to Y, and the pixel value of the corresponding pixel of the composite image data If Z is Z, for example, the calculation is as shown in equation (1).
Z = X + a * Y (1)

  Here, a is a constant indicating the embedding strength of the additional image plane 2. That is, in this example, the value of each pixel of the embedding target image is linearly corrected by the value of the corresponding pixel of the additional image.

  On the other hand, the case where the calculation is performed in units of blocks is a case where the resolution is different between the target image plane 1 and the additional image plane 2. For example, when the target image plane 1 has a higher resolution, a collection of a plurality of pixels of the target image plane 1 corresponding to a region of one pixel (temporarily called pixel A) in the additional image plane 2 becomes a block in this case. . The value Y of the corresponding pixel A in the additional image plane 2 is caused to act on the value X of each pixel of the target image plane 1 belonging to this block according to the above equation (1), whereby the pixel of each pixel of the composite image data The value Z is calculated. The resolution of the composite image data is the same as that of the target image plane 1. The block referred to here is different from the rectangular block 3 of the additional image plane 2 described below.

  The additional image plane 2 includes a plurality of rectangular blocks 3 having a predetermined size. The additional information to be embedded is encoded by, for example, an error correction code, and each code (“0” or “1”) of the code string obtained as a result is recorded in association with each block 3 of the additional image plane 2. The That is, the above-described pattern image (see FIG. 1) corresponding to the code corresponding to the block 3 is arranged in each block 3 of the additional image plane 2.

  In creating individual pattern images according to codes, as shown in FIG. 4, first, with respect to the basic block pattern 4 set in advance by the system, a block information mask pattern 5 (code) corresponding to the code to be embedded therein. Is multiplied by “1”) or the block information mask pattern 6 (when the code is “0”).

For example, in Patent Document 1, when the center point of the block is the origin, and the horizontal and vertical lines passing through the origin are the x axis and the y axis, respectively, the value of the pixel (x, y) is exp (−α (x A pattern such as ² + y ² )) is used as the basic block pattern 4. As can be seen from this equation, the basic block pattern 4 is a radial pattern centered on the origin. Of course, this is an example, and the basic block pattern 4 may be generated by another function. Instead of generating based on the function, the system (digital watermark printing apparatus 200 in the example of FIG. 1) may have a pattern map indicating the value of each pixel of the basic block pattern 4.

  On the other hand, the mask patterns 5 and 6 have the same shape and the same size as the basic block pattern 4 (that is, the same number of vertical and horizontal pixels). The value of each pixel of the mask pattern 5 is “+1” in the first and third quadrants, “+1” in the second and fourth quadrants, and vice versa in the mask pattern 6.

  A pattern image 7 formed by multiplying the basic block pattern 4 by the mask pattern 5 or 6 has the above-described properties (a) to (d) as shown in FIG. The additional image plane 2 is obtained by arranging the pattern images generated in this way according to the code string.

  When the digital additional information embedded from the image scanned by the digital watermark scanning apparatus 300 is reproduced, each block 4 (pattern image) is detected from the entire image by the method disclosed in Patent Document 1. As shown in FIG. 5, the block 4 is further divided into four quadrants on the top, bottom, left and right from the center. Assuming that the divided quadrant areas are Q1, Q2, Q3, and Q4, the digital watermark scanning apparatus 300 uses the values of the pixels included in the respective areas Q1, Q2, Q3, and Q4 (this pixel value is a reflected reflection value). The total sum of the light amount, that is, the brightness) is obtained, and “1” or “0” is recorded in the target block according to the determination method disclosed in Patent Document 1 depending on the magnitude relationship between the sums of the respective areas. Judge whether it has been.

  In such a digital watermark method, each code embedded in an image is represented by a pattern image (block). This pattern image is derived from the mask patterns 5 and 6 in FIG. 4, and has boundary lines in the vertical and horizontal directions that pass through the center point of the pattern image itself. The shading changes in the diagonal direction of the two quadrants. For this reason, if there is a sharply changing portion of the image density in the oblique direction in the embedding target image, the portion itself has the property of being easily discriminated as “0” or “1” in the first place. In that case, even if a pattern image showing a code opposite to the code that is easily discriminated due to the nature of the image of the part itself is embedded in the part, the property of the original part is won, and the code reading result is It may be the opposite of the original value. This is a read error.

  FIG. 6 is an enlarged view of an example of a portion (block having a size of 8 × 8 pixels in the illustrated example) that easily induces such an error in the embedding target image. FIG. 7 shows pixel values that take values from 0 to 255 in the block shown in FIG. Note that the pixel value indicates brightness, and a larger value looks white. Further, FIG. 6 does not accurately show the brightness of the pixel value, but is added to explain the shade of the pixels in the block.

  6 and 7 are similar to the block information mask pattern 5 representing the embedding code “1” illustrated in FIG. 4, and the embedding code “0” is represented in such a block. Even if the pattern image block corresponding to the block information mask pattern 6 is superimposed, even if an attempt is made to read the embedded code from the superimposed image, “1” is detected due to the influence of the original embedding target image. There are many.

  The image processing apparatus 100 according to the present embodiment executes filter processing so as to reduce a portion having such a property that an error is likely to be induced from an embedding target image that is an embedding destination of additional information. A mechanism for such filter processing will be described below with reference to FIG.

  As illustrated in FIG. 8, the image processing apparatus 100 includes a block dividing unit 102, a filter processing unit 104, and a block combining unit 106. The contents of processing performed by each of the units 102, 104, and 106 will be described below. As can be understood from the description, these units can be realized in software or configured as a hardware circuit. it can.

  The block dividing unit 102 divides the given embedding target image into blocks of a predetermined size. This block preferably has the same shape and size as the pattern image corresponding to the code to be embedded. In the block division in this case, it is preferable that the position of each resulting block is the same position as each pattern image included in the additional image plane 2. As a result, each block of the embedding target image after the filter processing and each pattern image constituting the additional image plane 2 are exactly overlapped, so that the interference suppression effect is high. For each block of the embedding target image generated in this way, the filter processing unit 104 performs filter processing on the block according to the procedure shown in FIG.

  In the filtering process, first, the target block is divided into four quadrants Q1, Q2, Q3, and Q4 (upper and lower, left and right) by horizontal and vertical dividing lines passing through the center point (the dividing method shown in FIG. 7). The sum of the pixel values included in each of the regions Q1, Q2, Q3, and Q4 (referred to as S1, S2, S3, and S4, respectively) is calculated (S10). Here, when the vertical or horizontal block size or both are set to odd numbers, the pixel value of the pixel crossed by the dividing line is halved, and the corresponding pixel value Include in area. If the number of pixels in both the vertical and horizontal directions is odd, the pixel value of the pixel located at the center point of the block is divided into four and distributed to each of the four areas.

Next, the filter processing unit 104 obtains the values V and H indicated by the expressions (2) and (3) (S12).
V = | (S1 + S2) − (S3 + S4) | (2)
H = | (S1 + S4) − (S2 + S3) | (3)
Here, V is a scale indicating the contrast in the vertical direction in the block, and H is a scale indicating the contrast in the horizontal direction.

Next, V and H thus obtained are compared (S14). If H ≦ V, that is, if the vertical contrast is larger than the horizontal contrast, the first and second quadrants are compared. The pixel values X12 of all the pixels in the regions Q1 and Q2 are replaced with the average of the pixel values in both the regions Q1 and Q2, and the values X34 of the respective pixels in the regions Q3 and Q4 in the third and fourth quadrants are similarly changed. It replaces with the average of the pixel value of area | region Q3, Q4 (S16). That is,
X12 = (S1 + S2) / (N1 + N2)
X34 = (S3 + S4) / (N3 + N4)
And Here, N1, N2, N3, and N4 are the numbers of pixels in the regions Q1, Q2, Q3, and Q4, respectively. It should be noted that the number of pixels N1 to N4 in each quadrant area is 0 when either the vertical or horizontal size of the block is odd or both, and the dividing line of the area crosses the pixel, or when the pixel is divided into two. Add 5 to the number of pixels in each area. When the number of vertical and horizontal pixels is odd, the central pixel of the block is divided into four. In this case, 0.25 is distributed to the number of pixels in each region.

If it is determined in step S14 that H ≦ V is not satisfied, it can be said that the contrast in the horizontal direction is larger than the contrast in the vertical direction. In this case, the pixel values X14 of all the pixels in the first and fourth quadrants Q1 and Q4 are replaced with the average of the pixel values in both the regions Q1 and Q4, and similarly the second and third quadrants Q2 and Q3. The value X23 of each pixel is replaced with the average of the pixel values of both regions Q2 and Q3 (S18). That is,
X14 = (S1 + S4) / (N1 + N4)
X23 = (S2 + S3) / (N2 + N3)
And

  The above is an example of the processing of the filter processing unit 104.

  When the above-described filter processing is performed on the image portion illustrated in FIG. 7, an image having a pixel value distribution as shown in FIG. 10 is obtained. In the example of FIG. 7, S1 = 563, S2 = 923, S3 = 2596, S4 = 1267, and from these, V = 2377 and H = 1690. Therefore, since H ≦ V is established, the calculation of S14 is performed, and the value of each pixel in the first and second quadrant areas Q1 and Q2 is X12 = 46.438, the third and fourth quadrant areas Q3 and Q3. The value of each pixel of Q4 is X34 = 120.719.

  If the pixel value of the embedding target image can only be an integer, each value of X12 and X34, X23 and X14 may be obtained by rounding the calculated result value below the decimal point (may be rounded off or rounded down). FIG. 10 shows a value rounded by truncation. FIG. 11 is a diagram showing the shade of FIG.

  As described above, according to the processing in FIG. 9, each block of the original embedding target image changes in contrast in the direction in which the contrast in the block is strong in the vertical or horizontal direction, and in the direction in which the contrast is strong. In the orthogonal direction, the image has a uniform density. Therefore, the change in shading in the diagonal (diagonal) direction that easily induces an error is eliminated from the block. For this reason, even if a pattern image having characteristic direction components in the diagonal direction as shown in FIG. 1 is synthesized with the block after the filter processing, the grayscale components in the diagonal direction, which are the basis for the discrimination of the codes, are exclusively used. Since it comes from the pattern image, the possibility of occurrence of an error during decoding of the code is reduced. In addition, when viewed in individual blocks, the density of the entire block does not change, and the direction in which the contrast is strong does not change greatly. Therefore, the change in the appearance of the entire embedding target image due to the filter processing is relatively small. Such an image of the filter processing result can be said to be suitable as an image to be embedded in the digital watermark system.

  When an image in which information is actually embedded by an electronic watermarking system is printed on a sheet of paper, the pixel spacing on the sheet is generally about 40 μm to 100 μm. For this reason, if the block size is about several pixels to several tens of pixels, even if the above-described filter processing is performed, it is difficult to distinguish between the case where the processing is applied to the embedding target image and the case where the processing is not performed on the naked eye. It can be said that it is difficult to deteriorate.

  For example, the 16 × 16 pixel embedding target image shown in FIG. 12 has a strong image component in the diagonal direction. On the other hand, when the above filter processing is applied with a block size of 8 × 8 pixels, the density shown in FIG. An image of the distribution is obtained. Here, if the size of the pattern image indicating the code to be embedded is, for example, 8 × 8 pixels, there is no diagonal component in the 8 × 8 pixel block of the embedding target image after the filter processing. Hard to interfere.

  Returning to the description of FIG. 8 again, each block filtered as described above is arranged at the position of the block in the original embedding target image by the block synthesizing unit 106, and the filtering process corresponding to the entire embedding target image is performed. The resulting image is determined.

  On the other hand, in the digital watermark printing apparatus 200, the additional image generation unit 202 generates additional image data corresponding to the additional information by the method of Patent Document 1, and the embedding processing unit 204 sends the additional image data from the block synthesis unit 106. It synthesizes the supplied filter target embedded data.

  As described above, the information-embedded image obtained in this way is less likely to cause a code reading error.

  The embodiment described above is merely an example, and various modifications are possible within the scope of the technical idea of the present invention.

  For example, in the above embodiment, in S16 and S18, the pixel value of each region obtained by dividing the block into two is converted into the average value of each region, but this is only an example. In principle, a certain degree of effect can be obtained if the distribution of the pixel values inside each of the two divided regions is made to approach evenly without strictly averaging. For example, when H ≦ V is established, the pixel value sum S1 of the region Q1 and the pixel value sum S2 of the region Q2 are made substantially equal, and the sum of the pixels included in the region Q1 and the region Q2 is the region before processing The sum S1 + S2 of the pixel values included in the region Q3 and the sum S1 + S2 of the pixel values included in the region Q3 and the sum S1 + S2 of the pixels included in the region Q3 are included in the region Q4. Pixels included in the region Q4 such that the sum of the pixel values of the pixels is substantially equal and the sum of the pixels included in the region Q3 and the region Q4 is the sum of the pixel values S3 of the pixels included in the region Q3 before processing If the sum S3 + S4 of the sum S4 of the pixel values is substantially equal, an effect close to the averaging process performed in S16 can be obtained. Similarly, when H ≦ V does not hold, the sum of the pixel values of the pixels included in the region Q1 and the sum of the pixel values of the pixels included in the region Q4 are substantially equal, and the regions Q1 and Q4 The sum of the pixels included in the pixel Q is approximately equal to the sum S1 + S4 of the sum S4 of the pixel values of the pixels included in the region Q4 with the sum S1 of the pixel values of the pixels included in the region Q1 before processing, and the pixels included in the region Q2 And the sum of the pixel values of the pixels included in the region Q3 are substantially equal, and the sum of the pixels included in the region Q2 and the region Q3 is the pixel value of the pixels included in the region Q2 before processing. The sum S2 and the sum S3 of the sum S3 of the pixel values of the pixels included in the region Q3 may be substantially equal.

  In the above embodiment, the block size when the block dividing unit 102 divides the embedding target image is made to match the size of the pattern image representing the embedding code, but this is not essential. For example, the block size may be an integer multiple of the size of the pattern image.In this case, the embedding target image after filtering is coarse, but the block size is the same size as the pattern image as an effect of reducing interference with the pattern image. The same effect as that obtained can be obtained. Also, the block size may be smaller than the size of the pattern image. In this case, the effect of reducing interference with the pattern image is lower than when the block size is the same size as the pattern image, but it is embedded before and after filtering. The change in the appearance of the target image is reduced.

  In the above description, the case where a pattern image having a horizontal and vertical edge is used as the pattern image expressing the code of the additional information has been described as an example. However, the present invention is not limited to such a pattern image. In principle, according to the present invention, among the four regions divided by the two edges that intersect each other, the difference in pixel values between regions adjacent to each other through the edge is greater than the difference in pixel values between regions that are not adjacent to each other. This is applicable when using a pattern image set so as to be large. For each block divided by the block dividing unit 102, the filter processing unit 104 divides the block by two dividing lines in a similar relationship to that the pattern image is divided by two edges. The contrast between the divided areas when divided into two by the dividing line parallel to one side and the contrast between the divided areas when divided into two by the dividing line parallel to the other edge are obtained. Then, for each of the divided regions obtained by division with a larger contrast, a filtering process may be performed so that each pixel value is uniform while maintaining the sum of the pixel values of the divided region.

It is a figure which shows the example of the pattern image showing each code | symbol. 1 is a diagram illustrating an example of a digital watermark system to which image processing according to an embodiment is applied. It is a figure for demonstrating the outline of the digital watermark system to which the image processing of embodiment is applied. It is a figure for demonstrating the production | generation process of the pattern image which shows each code | symbol. It is a figure for demonstrating the block 4 division process at the time of reading. It is a figure which shows typically the example of the image part which is easy to induce a reading error. It is a figure which shows the value of each pixel of the example of the image part which is easy to induce a reading error. It is a functional block diagram for demonstrating the internal structure of an image processing apparatus. It is a figure which shows the example of the process sequence of a filter process part. It is a figure which shows pixel value distribution as a result of performing the filter process of this embodiment with respect to the image part shown in FIG. FIG. 11 is a diagram schematically illustrating the density distribution of the pixel value distribution of FIG. 10. It is a figure which shows typically an example of the embedding target image with a strong shading change of a diagonal direction. It is a figure which shows typically the example of the filter processing result of the image of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 Image processing apparatus, 102 Block division part, 104 Filter process part, 106 Block composition part, 200 Digital watermark printing apparatus, 202 Additional image generation part, 204 Embedding process part, 300 Digital watermark scanning apparatus

Claims (4)

Among the four areas divided by two edges that intersect each other, a plurality of pixels that are set such that the difference in pixel values between areas adjacent to each other through the edges is larger than the difference in pixel values between areas that are not adjacent to each other An image processing apparatus that forms an additional image representing additional information by arranging various types of pattern images, and synthesizes the additional image with an embedding target image to generate an image in which the additional information is embedded. There,
A block dividing unit that divides the embedding target image into blocks of a predetermined size;
For each divided block, when the block is divided into two by a dividing line parallel to one of the two edges of the pattern image, the contrast between the divided areas is divided into two by a dividing line parallel to the other edge. In this case, for each divided region having a higher contrast, the pixel value is uniformized while maintaining the sum of the pixel values of the divided region. A filter processing unit for applying
An embedding processing unit that generates an image in which the additional information is embedded by combining the additional image with an embedding target image processed by the filter processing unit;
An image processing apparatus comprising:   2. The image according to claim 1, wherein the block dividing unit performs block division so that a position and a size of each block generated by the division are the same as a size and a position of each pattern image in the additional image. Processing equipment. Among the four areas divided by two edges that intersect each other, a plurality of pixels that are set such that the difference in pixel values between areas adjacent to each other through the edges is larger than the difference in pixel values between areas that are not adjacent to each other An image processing method for generating an image in which additional information is embedded by forming an additional image expressing additional information by arranging different types of pattern images and synthesizing the additional image with an image to be embedded. There,
Dividing the embedding target image into blocks of a predetermined size;
For each divided block, when the block is divided into two by a dividing line parallel to one of the two edges of the pattern image, the contrast between the divided areas is divided into two by a dividing line parallel to the other edge. In this case, for each divided region having a higher contrast, the pixel value is uniformized while maintaining the sum of the pixel values of the divided region. Applying steps,
Generating an image in which the additional information is embedded by synthesizing the additional image with the embedding target image subjected to the filtering process;
An image processing method. Among the four areas divided by two edges that intersect each other, a plurality of pixels that are set such that the difference in pixel values between areas adjacent to each other through the edges is larger than the difference in pixel values between areas that are not adjacent to each other An image processing device that forms an additional image representing additional information by arranging different types of pattern images and generates an image in which the additional information is embedded by synthesizing the additional image with an embedding target image. As a program for causing a computer system to function as a computer system,
Dividing the embedding target image into blocks of a predetermined size;
For each divided block, when the block is divided into two by a dividing line parallel to one of the two edges of the pattern image, the contrast between the divided areas is divided into two by a dividing line parallel to the other edge. In this case, for each divided region having a higher contrast, the pixel value is uniformized while maintaining the sum of the pixel values of the divided region. Applying steps,
Generating an image in which the additional information is embedded by synthesizing the additional image with the embedding target image subjected to the filtering process;
A program that executes

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