JP2005026848A - Electronic watermark parameter setting device, electronic watermark parameter setting method and electronic watermark parameter setting program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic watermark parameter setting device by which an appropriate electronic watermark burying parameter is set in an analog picture, and to provide an electronic watermark parameter setting method and an electronic watermark parameter setting program. <P>SOLUTION: Quality is evaluated by burying an electronic watermark in a digital picture by specified electronic watermark burying strength and filter strength. When a poor quality evaluation result is found, a corresponding quality evaluation value is read from a parameter map storing the quality evaluation value of the analog picture. Setting is done by reading a combination of the burying strength and the filter strength weaker and stronger than a combination of a plurality of burying strength and filter strength having the same read quality evaluation value as the quality evaluation value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital watermark parameter setting apparatus, a digital watermark parameter setting method, and a digital watermark parameter setting program for acquiring appropriate digital watermark parameter settings in print-compatible digital watermarks.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, printing systems for accurately determining print quality exist as print quality management and print quality assurance techniques for printed matter.
For example, in the prior art document 1, not only when print data is received by communication and printed out on the spot, for example, there is a space between a place where the print data is provided and a place where the print data is printed out. Even when the print data is transmitted / received by transmission / reception via communication, even when the print data is printed, the subject matter portion of the print is printed with the print data. It is described that printing is controlled by a quality judgment chart printing control means for performing printing control, and measurement is performed by a quality judgment chart measuring means for measuring the printed quality judgment chart.
[0003]
[Patent Document 1]
JP 2002-166635 A
[0004]
[Problems to be solved by the invention]
On the other hand, in the case of digital watermarks for printing, it is necessary to be able to perform watermark detection processing even for analog images called printed matter. Digital watermark for printing is a digital watermark that embeds digital watermark information in a digital image and outputs it to a print medium such as paper, and uses an AD converter to convert the output print to a digital image and detect the digital watermark. It is.
However, as a characteristic of an analog image, depending on the printing process, the analog / digital conversion process, the printing method at the time of printing, and the characteristics of the printing paper / ink, the digital watermark may not be detected due to the deterioration of the analog image.
Further, when embedding a digital watermark in a digital image, the quality is deteriorated. Therefore, it is also necessary to keep this deterioration within a range that can withstand the required quality of the printed matter.
[0005]
In order to make it possible to detect a digital watermark from a printed matter, it is possible to cope with it by appropriately changing parameter settings when embedding a digital watermark in a digital image.
However, parameter setting at the time of embedding digital watermarks and quality evaluation of printed materials are the final parameter settings unless people with multiple specialized knowledge such as engineers familiar with digital watermark technology and designers familiar with print quality gather. I could not judge.
[0006]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide an electronic watermark parameter setting apparatus, an electronic watermark parameter setting method, and an electronic watermark parameter setting method capable of setting an appropriate electronic watermark embedding parameter in an analog image. It is to provide a digital watermark parameter setting program.
[0007]
[Means for Solving the Problems]
The present invention has been made to solve the above problems, and the invention according to claim 1 is characterized in that a storage means for storing a parameter map for storing a quality evaluation value of an analog image in which a digital watermark is embedded, and at least a predetermined The digital watermark embedding means for embedding the digital watermark in the digital image with the digital watermark embedding strength and the filter strength, and the image quality evaluation for evaluating the quality according to a predetermined standard for the digital image embedded with the digital watermark by the digital watermark embedding means And a parameter setting unit that reads a more appropriate parameter map from the storage unit and sets the digital watermark embedding unit when the quality evaluation result by the image quality evaluation unit is defective.
It is characterized by comprising.
[0008]
The invention according to claim 2 stores a parameter map for storing a quality evaluation value of an analog image in which a digital watermark is embedded based on the embedded strength and filter strength in a combination array of digital watermark embedding strength and filter strength. Storage means, digital watermark embedding means for embedding a digital watermark in a digital image with a predetermined digital watermark embedding strength and filter strength, and a digital image embedded with the digital watermark by the digital watermark embedding means according to a predetermined standard. When the quality evaluation result by the image quality evaluation means for evaluating the quality and the quality evaluation result by the image quality evaluation means is defective, the quality evaluation value corresponding to the embedding strength and filter strength of the predetermined digital watermark is read from the parameter map, and the read Multiple quality evaluation values and quality evaluation values are the same A combination of embedding strength and filter strength, the embedding strength is weak, or, a combination filter strength is stronger read from the parameter map, characterized by comprising a parameter setting means for setting said electronic watermark embedding means.
[0009]
According to a third aspect of the present invention, there is provided a parameter map for storing a quality evaluation value of an analog image in which a digital watermark is embedded based on the embedding strength and filter strength in a combination array of digital watermark embedding strength and filter strength. A digital watermark embedding means for embedding a digital watermark in the digital image with a predetermined digital watermark embedding strength and filter strength, and a digital image embedded with the digital watermark by the digital watermark embedding means. If the quality evaluation result by the image quality evaluation means and the quality evaluation result by the image quality evaluation means is bad, the quality evaluation value corresponding to the embedding strength and filter strength of the predetermined digital watermark is read from the parameter map, A set with a higher quality evaluation value than the read quality evaluation value The Align reads from the parameter map, characterized by comprising a parameter setting means for setting said electronic watermark embedding means.
[0010]
According to a fourth aspect of the present invention, there is provided a parameter map for storing a quality evaluation value of an analog image in which a digital watermark is embedded based on the embedding strength and filter strength in a combination array of digital watermark embedding strength and filter strength. A digital watermark embedding means for embedding a digital watermark in a digital image with a predetermined digital watermark embedding strength and filter strength, and an output based on the digital image embedded with the digital watermark by the digital watermark embedding means In response to the input of the quality evaluation result for the analog image, if the quality evaluation result is defective, the quality evaluation value corresponding to the embedding strength and filter strength of the predetermined digital watermark is read from the parameter map, and the reading is performed. Multiple quality evaluation values are the same A combination of embedding strength and filter strength, the embedding strength is weak, or, a combination filter strength is stronger read from the parameter map, characterized by comprising a parameter setting means for setting said electronic watermark embedding means.
[0011]
According to a fifth aspect of the present invention, there is provided a parameter map for storing a quality evaluation value of an analog image in which a digital watermark is embedded based on the embedding strength and filter strength in a combination array of digital watermark embedding strength and filter strength. A digital watermark embedding means for embedding a digital watermark in a digital image with a predetermined digital watermark embedding strength and filter strength, and an output based on the digital image embedded with the digital watermark by the digital watermark embedding means A digital watermark detection means for detecting a digital watermark from the analog image to be detected, and a quality evaluation value corresponding to the embedding strength and filter strength of the predetermined digital watermark if the detection result by the digital watermark detection means is bad Read out, the read quality evaluation value and A parameter setting unit that reads a combination having a higher embedding strength or a lower filter strength than the combination of a plurality of embedding strengths and filter strengths having the same quality evaluation value from the parameter map and sets the combination in the digital watermark embedding unit It is characterized by comprising.
[0012]
The invention according to claim 6 embeds a digital watermark in a digital image with a predetermined digital watermark embedding strength and filter strength, and evaluates the quality of the digital image embedded with the digital watermark according to a predetermined standard, When the quality evaluation result is poor, in a combination array of digital watermark embedding strength and filter strength, from a parameter map that stores a quality evaluation value of an analog image in which the digital watermark is embedded based on the embedding strength and filter strength, A quality evaluation value corresponding to the embedding strength and filter strength of the predetermined digital watermark is read, and the embedding strength is weaker than a combination of a plurality of embedding strengths and filter strengths in which the read quality evaluation value and quality evaluation value are the same value. Or a combination with strong filter strength from the parameter map Out look, and sets the embedding strength and filter strength of the watermark.
[0013]
According to a seventh aspect of the present invention, a process for embedding a digital watermark in a digital image with a predetermined digital watermark embedding strength and filter strength, and a predetermined reference for the digital image in which the digital watermark is embedded. If the quality evaluation result is defective and the quality evaluation result is poor, the quality evaluation value of the analog image in which the digital watermark is embedded based on the embedded strength and the filter strength in the combination array of the embedded strength and the filter strength of the digital watermark A process of reading a quality evaluation value corresponding to the embedding strength and filter strength of the predetermined digital watermark from a parameter map for storing a plurality of embedding strengths and filters in which the read quality evaluation value and the quality evaluation value are the same value The embedding strength is weaker or the filter strength is stronger than the combination of strengths The combined viewed by reading from the parameter map is a watermarking parameter setting program for executing the processing of setting the electronic watermark embedding means.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a digital watermark parameter setting apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram illustrating a configuration of a digital watermark parameter setting apparatus 1 according to the present embodiment. The digital watermark parameter setting device 1 according to the present embodiment includes an input unit 10, a digital watermark embedding unit 11, a parameter setting unit 12, an image quality evaluation processing unit 13, a print layout processing unit 14, a digital watermark detection unit 15, and an output unit 16. And an original image database (hereinafter referred to as DB) 20, a parameter DB 21, and a digital watermark embedded image DB 22.
[0015]
The input unit 10 is an input interface of the digital watermark parameter setting device 1, and inputs a quality evaluation result (described later) by a user and a digital image AD-converted by the AD converter 2.
The digital watermark embedding unit 11 embeds the digital watermark in the digital image stored in the original image DB 20 using the digital watermark embedding strength and filter strength set in the parameter setting unit 12 and stores the digital watermark in the digital watermark embedded image DB 22.
The parameter setting unit 12 sets, by default, predetermined standard parameters (standard digital watermark embedding strength and filter strength) that are different for each printing condition. The quality evaluation result by the image quality evaluation processing unit 13, the user's visual inspection, and the like Based on the quality evaluation result by, and the digital watermark detection result by the digital watermark detection unit 15, parameters (embedding strength and filter strength of the digital watermark) at the time of digital watermark embedding are examined, and based on the parameter map stored in the parameter DB 21. , Update the parameter.
[0016]
Here, printing conditions that affect the detection success rate of digital watermarks include printing methods (gravure, letterpress, intaglio, ink jet, laser, etc.), printing media (recycled paper, cardboard, PET, etc.), ink (CMYK ink, special color). Ink, etc.), the pattern of images used for printing, applications (documents, books, catalogs, flyers, photo collections, product packages, etc.), analog / digital conversion methods (types of AD converters, scanners, digital cameras, etc.) The predetermined standard parameters described above are set in advance for each of these printing conditions before the evaluation is started. The standard parameter is a combination of parameters that can maintain the quality and detect the digital watermark for each printing condition.
In this specification, this combination of parameters is defined as the accuracy of digital watermarking and is represented by Z (a). When the embedding strength of the digital watermark is X and the filter strength is Y, the accuracy of the digital watermark can be expressed as Z (a) = f (X, Y).
... Z (a-2) <Z (a-1) <Z (a) <Z (a + 1) <Z (a + 2) ...
Define the magnitude relationship. Here, Z (a), which is the center of the magnitude relationship, is set as a standard parameter for each printing condition.
[0017]
The parameter DB 21 stores a parameter map that stores a quality evaluation value of an analog image in which the digital watermark is embedded based on the embedded strength and the filter strength in the combination array of the digital watermark embedding strength and the filter strength.
FIG. 2 shows a parameter map made up of a combination of a plurality of intensities created by the above-described digital watermark embedding strength X and filter strength Y.
Here, the embedding strength X is an image processing strength when an electronic watermark is embedded in an original image. When the embedding strength is increased, the deterioration of the image becomes conspicuous. In the present specification, the degree of image deterioration (degree of reduction in image quality) in an image in which a digital watermark is embedded in the original image is defined as an image deterioration degree.
The filter strength Y is the strength of the filter for smoothing the image so that the deterioration of the image and the portion where the digital watermark is embedded are not noticeable after the digital watermark is embedded. When the filter strength is increased, the image becomes close to the original image before embedding the digital watermark, and deterioration of the image becomes inconspicuous. However, it is difficult to detect a digital watermark. On the contrary, if the filter strength is weakened, the deterioration of the image cannot be erased, but the digital watermark is easily detected.
[0018]
That is, as the embedding strength X increases, the detection probability of digital watermark increases and the degree of image degradation increases. Further, as the filter strength Y is weaker, the degree of image degradation increases and the detection probability of digital watermark increases. Further, as the embedding strength X becomes weaker, the detection probability of the digital watermark becomes lower and the degree of image degradation is smaller. In addition, the stronger the filter strength Y, the smaller the image deterioration level and the lower the detection probability of the digital watermark.
In the parameter map shown in FIG. 2, since the embedding strength X level is higher in the right direction of the X axis and the filter strength Y is higher in the lower direction of the Y axis, the image deterioration is more remarkable in the upper right region and the image deterioration is in the lower left region. Inconspicuous.
[0019]
Hereinafter, a method for determining the quality evaluation value of the analog image in which the digital watermark is embedded based on the embedding strength and the filter strength corresponding to the accuracy Z (a) of the digital watermark will be described.
In the present embodiment, the value of Z (a) = f (X, Y) is determined based on empirical rules. For example, the larger the value, the higher the detection probability of the digital watermark and the greater the degree of image degradation.
That is, first, P values of embedding strength X (5 will be described later in the parameter map of the present embodiment) and Q values of filter strength Y (5 will be described later in the parameter map of the present embodiment). Create a combination. The P × Q combinations (25 in this embodiment) embed a digital watermark, and points are assigned to each combination by subjective evaluation of the user. That is, this score is defined as the quality evaluation value described above.
That is, the quality evaluation value is a numerical value when subjective evaluation of an analog image is performed, and the quality evaluation value may be different even for the same parameter depending on the pattern, application, and situation of the image.
[0020]
As a specific example, for example, five levels of intensity are set with P = 5 and Q = 5. Then, a digital watermark is embedded in the digital image with a combination of the embedding strength and the filter strength, and printed on an analog medium such as paper. The user performs a subjective evaluation of the analog image (printed material) and assigns a quality evaluation value to each. Here, the best quality evaluation value is 100 points and the worst quality evaluation value is 10 points.
[0021]
Now, as shown in FIG. 2, it is assumed that quality evaluation values are given by subjective evaluation of analog images for all 25 f (X, Y). For example, assuming that Z (a) = f (3, 3) is the standard parameter as the center of the quality evaluation value, combinations with higher values (scores) are defined as Z (a + 1) and Z (a + 2). A combination with a low score is defined as Z (a-1) and Z (a-2).
Further, in the case of the same score, the higher embedding strength X level (value) is defined as the upper level, and when the embedding strength is the same, the higher filter strength Y level is defined as the upper level.
As a specific example, the digital watermark accuracy Z (a) having a quality evaluation value of 70 points is represented by f (2, 2), f (3,4), f (3, 5) in the parameter map shown in FIG. These magnitude relationships are based on the level of embedding strength X and the level of filter strength Y.
f (2,2) <(f (3,4) <(f (3,5)
It is defined as follows.
[0022]
The user creates a parameter map for storing these quality evaluation values for each image pattern, application, and situation. As a classification of the pattern, use, and situation, for example, the following classification is used.
Pattern: Landscape, person, food, CG, continuous pattern, etc.
Application: Packaging, flyers, catalogs, WEB, etc.
Situation: Printing machine, paper, ink, printing method (gravure, letterpress ink jet, laser ... etc), etc.
At the same time, for each printing condition and image condition, a parameter that can stably maintain quality and that can detect a digital watermark is acquired and set as a standard parameter.
[0023]
The image quality evaluation processing unit 13 evaluates the quality of the digital image embedded with the digital watermark by the digital watermark embedding unit 11 according to a predetermined standard.
Evaluation of the quality of an image after embedding a digital watermark refers to evaluating the quality of an image used for printed matter with respect to a digital image after embedding a digital watermark.
Although the quality evaluation criteria of a digital image differ depending on the design of the image, usage, printing method, and the like, the following cases can be considered as examples.
(Pattern)
・ Images with little color change such as sky, sea, and animation (solid, gradation, etc.)
→ Degradation of quality is conspicuous
・ Images with many color changes, such as trees and crowded images
→ Quality degradation is not noticeable
(Use)
・ Images used for catalogs of cars and jewelry, photo collections, product packaging, etc.
→ High quality images are required
・ Images used for newspaper inserts, in-house documents, etc.
→ Although some quality is acceptable, it is acceptable.
(Printing method)
・ Differences in printing methods such as letterpress, intaglio, lithographic ink jet and laser
・ Difference in ink type
・ Differences depending on the type of paper
That is, the image quality evaluation processing unit 13 sets a quality evaluation reference level in advance for each of these patterns, uses, and printing methods, and determines which quality evaluation reference level the digital image to be subjected to quality evaluation belongs to. To do. If the determination result of the quality evaluation reference level (= quality evaluation result) does not reach a predetermined threshold (or the quality evaluation reference level or lower, the same), it is determined that the quality evaluation result is defective, and the parameter setting unit 12 On the other hand, a parameter review / update request is output. On the other hand, if the determination result of the quality evaluation reference level has reached a predetermined threshold value, it is determined that the quality evaluation result is good, and a digital image that is the quality evaluation target is output to the printing layout processing unit 14.
[0024]
The print layout processing unit 14 determines a print layout for printing on one or a plurality of digital images output from the image quality evaluation processing unit 13 on paper as an analog medium. In the present embodiment, as shown in FIG. 3, a digital watermark is embedded with a digital watermark accuracy Z (a-4) to Z (a + 4) around a digital watermark accuracy Z (a) defined as a standard parameter. The nine digital images are laid out on one printing sheet and output to the printing machine 3 via the output unit 16.
[0025]
The digital watermark detection unit 15 detects a digital watermark from an analog image output based on the digital image in which the digital watermark is embedded by the digital watermark embedding unit 11. Specifically, an analog image converted from digital data to analog data by printing with the printer 3 (DA converter) is converted again into a digital image by the AD converter 2 such as a scanner or a digital camera. After that, it is input to the digital watermark detection unit 15 via the input unit 10 and it is determined whether or not digital watermark detection is possible.
[0026]
Next, the operation of the digital watermark parameter setting apparatus 1 of the present embodiment will be described with reference to the drawings. FIG. 4 is a flowchart showing a parameter setting process performed by the digital watermark parameter setting apparatus 1 according to this embodiment.
Now, in the digital watermark parameter setting device 1, when a user wants to embed a digital watermark when printing a digital image stored in the original image DB 20, the user selects the digital image to be embedded as a digital watermark. A selection is made from the image DB 20, and pre-processing such as necessary trimming processing and color correction processing is performed (see step S1 in FIG. 4). Further, the user sets which of the printing conditions described above is used. By setting the printing conditions, the parameter setting unit 12 determines the standard parameters and parameter map to be used, and the pre-processed digital image is read into the digital watermark embedding unit 11 (step S2).
[0027]
The digital watermark embedding unit 11 receives the input of the preprocessed digital image, embeds the digital watermark in the digital image with the digital watermark embedding strength and filter strength set in the parameter setting unit 12, and the digital watermark embedded image DB 22 To store.
The image quality evaluation processing unit 13 performs quality evaluation (referred to as quality evaluation 1) of the digital image in which the digital watermark is embedded (step S4).
FIG. 5 is a flowchart showing the flow of processing in quality evaluation 1.
The image quality evaluation processing unit 13 performs quality evaluation based on a predetermined quality evaluation standard (step S20 in FIG. 5). For example, when it is determined that the color difference of the digital image in which the digital watermark is embedded is equal to or less than a threshold value and the necessary quality is maintained when the digital image is printed (step S21), the digital image in which the digital watermark is embedded It is determined whether a digital watermark can be detected from the image (step S22).
On the other hand, when it is determined that the color difference of the digital image in which the digital watermark is embedded is equal to or greater than the threshold value or that the quality required when the digital image is printed is not maintained (defect in step S21), the image quality evaluation processing unit 13 It is determined that the quality is poor (step S23).
[0028]
When the digital watermark is successfully detected from the digital image in which the digital watermark is embedded (detection is successful in step S24), the image quality evaluation processing unit 13 determines that the quality is good (step S25).
On the other hand, when the detection of the digital watermark from the digital image in which the digital watermark is embedded fails (detection failure in step S24), the image quality evaluation processing unit 13 determines that the quality is poor (step S23).
Through the above processing, the image quality evaluation processing unit 13 outputs a quality determination result (good or bad) (step S26).
[0029]
If the quality evaluation result output by the image quality evaluation processing unit 13 is defective (NG in step S5), the parameter setting unit 12 examines the standard parameters for embedding the digital watermark as follows (step S6).
The parameters to consider at this time are
・ Digital watermark embedding strength X
-Filter strength Y after embedding digital watermark
These are two. The parameter setting unit 12 prioritizes parameter change in the order of embedding strength and filter strength.
[0030]
It is necessary to set the balance between the filter strength and the embedding strength to an appropriate place, and the parameters are changed according to the following cases.
(1) When the quality evaluation of a digital watermark embedded image is bad
If it is determined that the color difference of the digital image in which the digital watermark is embedded is equal to or greater than the threshold value, or that the digital image and the printed material do not maintain the quality of the printed material, the parameters are changed so that the image becomes closer to the original image. In particular,
・ Decrease the embedding strength (lower the embedding strength X level)
-Increase the filter strength (increase the filter strength Y level)
Change the parameters in the order.
Specifically, the parameter setting unit 12 reads the quality evaluation value corresponding to the standard parameter from the parameter map, and the read quality evaluation value and the quality evaluation value are the same value, from a combination of a plurality of embedding strengths and filter strengths, A combination having a low embedding strength or a low filter strength is read from the parameter map and set in the digital watermark embedding unit 11.
When there are not a plurality of digital watermark accuracies Z having the same quality evaluation value, the parameter setting unit 12 reads out the quality evaluation value corresponding to the embedding strength and filter strength of the predetermined digital watermark from the parameter map, and reads the read quality A combination having a higher quality evaluation value than the evaluation value is read from the parameter map and set in the digital watermark embedding unit 11.
[0031]
(2) When a digital watermark cannot be detected from a digital image
To make it easier to detect a digital watermark from a digital image immediately after embedding the digital watermark,
-Increase embedding strength (increase embedding strength X level)
-Decrease the filter strength (lower the filter strength Y level)
Change the parameters in the order.
Specifically, when the detection result is defective, the parameter setting unit 12 reads a quality evaluation value corresponding to the standard parameter from the parameter map, and the plurality of embedding strengths that have the same value as the read quality evaluation value Then, a combination having a higher embedding strength or a lower filter strength than the combination of the filter strengths is read from the parameter map and set in the digital watermark embedding unit 11.
[0032]
As a result of the above parameter examination, when the combination of the embedding strength and the filter strength to be read is registered in the parameter map (when the parameter can be determined in step S7), the parameter setting unit 12 determines the parameter change (step S9). .
On the other hand, when the combination of the embedding strength and the filter strength to be read is not registered in the parameter map (when the parameter cannot be determined in step S7), the parameter setting unit 12 stops the parameter changing process (step S8).
[0033]
When the quality evaluation result is good (OK in step S5), the print layout processing unit 14 prints one or more digital images output from the image quality evaluation processing unit 13 on paper or the like that is an analog medium. Is determined (step S10).
That is, as shown in FIG. 3, nine digital watermarks embedded with digital watermark accuracy Z (a−4) to Z (a + 4) centering on the digital watermark accuracy Z (a) defined as the standard parameter. If the quality evaluation result is good for the image (OK in step S5), the printing layout processing unit 14 lays it out on one printing sheet and outputs it to the printing machine 3 via the output unit 16. .
On the other hand, if all the quality evaluation results for these nine digital images are bad (NG in step S5), the parameters are changed (step S9), for example, as shown in FIG. Quality evaluation of nine digital images embedded with digital watermark accuracy Z (a-13) to Z (a-5) with digital watermark accuracy Z (a-9) down by 9 If the result is good (OK in step S5), the printing layout processing unit 14 lays out this on one sheet of printing paper and outputs it to the printing press 3 via the output unit 16.
[0034]
When nine analog images are printed on one sheet of printing paper in the printing machine 3 (step S11), the user visually determines the quality of the printed material (step S12).
When it is determined by visual determination that all or a part of the nine analog images have a large degree of image degradation and a problem in quality (NG in step S13), the user inputs the result of the determination to the input unit 10 The parameter is examined again (step S6). In particular,
(3) When the quality evaluation of printed matter is bad
If it is determined that the printed material does not maintain the quality of the printed material, the parameters are changed so that the image becomes close to the original image. In particular,
・ Decrease the embedding strength (lower the embedding strength X level)
-Increase the filter strength (increase the filter strength Y level)
Change the parameters in the order.
Note that, when the parameter examination is performed again, the digital watermark detection process after the step may be selected to be performed or not performed depending on the implementation.
[0035]
On the other hand, if it is determined by visual judgment that there is no problem in quality for all or at least a part of the nine analog images (OK in step S13), the user prints on the AD converter 2. The resolution or the like is set (step S14), the printed matter is AD converted (step S15), and is input to the digital watermark detection unit 15 via the input unit 10.
[0036]
When the AD-converted digital image is input, the digital watermark detection unit 15 tries to detect the digital watermark for the digital image (step S16). And the parameter setting part 12 performs the following processes by the result obtained by these evaluations.
That is, when the detection result output by the digital watermark detection unit 15 fails (detection failure in step S17), the parameter setting unit 12 examines the standard parameters for digital watermark embedding as follows (step S6).
The parameters to be examined at this time are the same as in the case of NG in steps S5 and S13.
・ Digital watermark embedding strength X
-Filter strength Y after embedding digital watermark
These are two. The parameter setting unit 12 prioritizes parameter change in the order of embedding strength and filter strength.
[0037]
It is necessary to set the balance between the filter strength and the embedding strength to an appropriate place.
(4) When a digital watermark cannot be detected from a digital image
To make it easier to detect digital watermarks from digital images obtained by scanning printed materials,
-Increase embedding strength (increase embedding strength X level)
-Decrease the filter strength (lower the filter strength Y level)
Change the parameters in the order.
[0038]
As described above, the digital watermark parameter setting apparatus 1 according to the present embodiment performs the following parameter selection based on whether the image quality is good and whether digital watermark detection is possible.
(A) When it is determined that all images have a large degree of image degradation and a problem with quality. However, it is assumed that a digital watermark is detected.
For all nine digital images, digital watermarks have been detected, but if it is determined that there is a problem with quality, the parameter setting unit 12 sets the digital watermark accuracy to 9 more than the digital watermark accuracy used for the previous evaluation. Only one order is lowered (NG, S6, S7, S9 in step S13). Then, as shown in FIG. 6, the same processing is performed using nine digital images in which digital watermarks are embedded with digital watermark accuracy Z (a-13) to Z (a-5).
[0039]
(B) When the digital watermark detection fails for all images. However, it is assumed that there is no problem in image quality.
All nine digital images have no problem in image quality. However, when the digital watermark is not detected, the accuracy of the digital watermark used for the previous evaluation is increased only by nine (detection failure in step S17, S6, S7, S9). Then, as shown in FIG. 7, the same processing is performed using nine digital images in which digital watermarks are embedded with digital watermark accuracy Z (a + 5) to Z (a + 13).
(C) When digital watermark detection fails and there is a problem with image quality.
For all nine digital images, there is a problem with the quality of the image, and when the digital watermark is not detected, the conditions used for the evaluation (depending on the printing press, printing paper, ink, image, etc.) The change of the filter strength cannot be handled (when the parameter cannot be determined in step S7), and the process ends (step S8).
In this case, the problem is not solved by the parameters that can be determined by the present system, but is solved by changing the parameters related to embedding of the digital watermark, such as changing the used printing paper, changing the used ink, or the like.
[0040]
On the other hand, among the nine digital images, there is no problem in quality for some of the digital images, and when a digital watermark is detected, the parameters set for the part of the digital images are set as optimum parameters. In the present specification, an image in which there is no problem in quality and a digital watermark is detected is regarded as a print-compatible digital watermark detection successful image.
At this time, if the printable digital watermark detection success image is one (Z (a + 13)) (see FIG. 8), this is set as the optimum parameter. On the other hand, when there are a plurality of print-compatible digital watermark detection successful images (see FIG. 9), the parameter closest to the standard parameter is set as the optimum parameter.
For example, in the example illustrated in FIG. 9, Z (a + 10), Z (a + 11), Z (a + 12), and Z (a + 13) are the print-compatible digital watermark detection success images, but Z (a + 10) to Z (a + 13) Among them, the embedding strength filter strength corresponding to Z (a + 10) closest to the standard parameter Z (0) is set as the optimum parameter (step S9).
[0041]
As described above, in the digital watermark parameter setting device 1 of the present embodiment, the digital watermark information is embedded in the digital image with the embedding strength that maintains the quality of the printed material, and the digital watermark is detected from the printed material. When the detection fails, the digital watermark embedding parameters are changed, and the digital watermark information is embedded again in the digital image, thereby making it possible to systematize processing for obtaining appropriate digital watermark parameter settings.
Therefore, according to the digital watermark parameter setting device 1 of the present embodiment, an effect of detecting a digital watermark from a printed matter under various printing conditions can be obtained.
In addition, the quality of the printed product can be maintained based on the detection result of the embedded digital watermark, and an optimal digital watermark embedding parameter can be acquired and re-embedding can be obtained.
In the present embodiment, among the parameters set at the time of embedding digital watermark information, the parameters that can be changed by the system are embodied as two, namely, the embedding strength of the digital watermark and the filter strength for suppressing image degradation. It is assumed that parameters related to the efficiency of detection of other digital watermarks can be handled in the same manner.
[0042]
In this way, by automating the quality evaluation of digital data after embedding a digital watermark, it becomes possible to maintain the quality of an image that could only be judged by a person familiar with printing until now.
In addition, parameters can be changed automatically based on image quality and digital watermark detection results, enabling parameter changes that could only be done by people with knowledge of print-ready digital watermark technology. Become.
Therefore, there is an effect that it is possible to embed a print-compatible digital watermark that can be accurately detected with a quality that can be tolerated as a printed matter, even if there is not much knowledge of the digital watermark technology for printing and knowledge of quality evaluation of printed matter can get.
[0043]
The above-described digital watermark parameter setting apparatus 1 has a computer system therein.
A series of processes relating to the above-described digital watermark parameter setting process is stored in a computer-readable recording medium in the form of a program, and the above process is performed by the computer reading and executing this program. .
That is, each processing means and processing unit in the digital watermark parameter setting device 1 is such that a central processing unit such as a CPU reads the above program into a main storage device such as a ROM or RAM, and executes information processing / calculation processing. This is realized.
Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.
[0044]
【The invention's effect】
As described above, the present invention embeds a digital watermark in a digital image with a predetermined digital watermark embedding strength and filter strength, and evaluates the quality of the digital image embedded with the digital watermark according to a predetermined standard. When the result is bad, a predetermined digital watermark is obtained from a parameter map that stores a quality evaluation value of an analog image in which the digital watermark is embedded based on the embedded strength and the filter strength in the combination array of the digital watermark embedding strength and the filter strength. The quality evaluation values corresponding to the embedding strength and filter strength of the image are read out, and the read quality evaluation value and the quality evaluation value are the same value. Read strong combinations from the parameter map and Since set to lend embedding means, it is possible to obtain the analog image, the effect capable of setting an appropriate electronic watermark embedding parameter.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a digital watermark parameter setting apparatus according to an embodiment.
FIG. 2 is an explanatory diagram of a parameter map.
FIG. 3 is an explanatory diagram showing a state in which nine digital images in which digital watermarks are embedded with digital watermark accuracy Z (a-4) to Z (a + 4) are laid out on one print sheet.
FIG. 4 is a flowchart showing the operation of the digital watermark parameter setting apparatus of the present embodiment.
FIG. 5 is a flowchart showing a flow of quality evaluation 1;
FIG. 6 is an explanatory diagram showing a state in which nine digital images embedded with digital watermarks are laid out on a single print sheet with the digital watermark accuracy lowered by nine ranks.
FIG. 7 is an explanatory diagram illustrating a state in which nine digital images embedded with digital watermarks are laid out on a single print sheet by increasing the digital watermark accuracy by nine ranks.
FIG. 8 is an explanatory diagram showing a state where there is one printable digital watermark detection success image.
FIG. 9 is an explanatory diagram showing a state when there are a plurality of print-compatible digital watermark detection successful images.
[Explanation of symbols]
1 ... Digital watermark parameter setting device 1
2 ... AD converter
3 ... Printer
10 ... Input section
11 ... Digital watermark embedding part
12 ... Parameter setting section
13. Image quality evaluation processing unit
14 ... Layout processing unit for printing
15 ... Digital watermark detection unit
16 ... Output section
20 ... Original image DB
21 ... Parameter DB
22 ... Digital watermark embedded image DB

Claims (7)

Storage means for storing a parameter map for storing a quality evaluation value of an analog image embedded with a digital watermark;
A digital watermark embedding means for embedding a digital watermark in a digital image with at least a predetermined digital watermark embedding strength and filter strength;
Image quality evaluation means for evaluating the quality of the digital image embedded with the digital watermark by the digital watermark embedding means according to a predetermined standard;
A digital watermark parameter setting device comprising: a parameter setting unit that reads a predetermined parameter map from the storage unit and sets the result in the digital watermark embedding unit when the quality evaluation result by the image quality evaluation unit is defective . Storage means for storing a parameter map for storing a quality evaluation value of an analog image embedded with a digital watermark based on the embedded strength and filter strength in a combination of the embedded strength and filter strength of the digital watermark;
A digital watermark embedding means for embedding a digital watermark in a digital image with at least a predetermined digital watermark embedding strength and filter strength;
Image quality evaluation means for evaluating the quality of the digital image embedded with the digital watermark by the digital watermark embedding means according to a predetermined standard;
If the quality evaluation result by the image quality evaluation means is defective, the quality evaluation value corresponding to the embedding strength and filter strength of the predetermined digital watermark is read from the parameter map, and the read quality evaluation value and the quality evaluation value are the same value. A parameter setting unit that reads a combination having a lower embedding strength or a stronger filter strength from the parameter map than the combination of a plurality of embedding strengths and filter strengths and sets the combination in the digital watermark embedding unit. An electronic watermark parameter setting device characterized by the above. A storage means for storing a parameter map for storing a quality evaluation value of an analog image in which the digital watermark is embedded based on the embedded strength and the filter strength in a combination of the digital watermark embedding strength and the filter strength; and at least a predetermined digital watermark A digital watermark embedding means for embedding a digital watermark in a digital image with an embedding strength and a filter strength of
Image quality evaluation means for evaluating the quality of the digital image embedded with the digital watermark by the digital watermark embedding means according to a predetermined standard;
When the quality evaluation result by the image quality evaluation means is bad, the quality evaluation value corresponding to the embedding strength and filter strength of the predetermined digital watermark is read from the parameter map, and the quality evaluation value is higher than the read quality evaluation value A digital watermark parameter setting apparatus comprising: parameter setting means for reading a combination from the parameter map and setting the combination in the digital watermark embedding means. Storage means for storing a parameter map for storing a quality evaluation value of an analog image in which the digital watermark is embedded based on the embedded strength and the filter strength in a combination array of the embedded strength and the filter strength of the digital watermark;
Digital watermark embedding means for embedding a digital watermark in a digital image with a predetermined digital watermark embedding strength and filter strength;
In response to the input of the quality evaluation result for the analog image output based on the digital image embedded with the digital watermark by the digital watermark embedding means, and the quality evaluation result is bad, the embedding strength of the predetermined digital watermark And the quality evaluation value corresponding to the filter strength is read from the parameter map, and the read quality evaluation value and the quality evaluation value are the same value. The embedding strength is weaker than the combination of a plurality of embedding strengths and filter strengths, or the filter. A digital watermark parameter setting apparatus comprising: parameter setting means for reading a combination having a high strength from the parameter map and setting the combination in the digital watermark embedding means. Storage means for storing a parameter map for storing a quality evaluation value of an analog image in which the digital watermark is embedded based on the embedded strength and the filter strength in a combination array of the embedded strength and the filter strength of the digital watermark;
Digital watermark embedding means for embedding a digital watermark in a digital image with a predetermined digital watermark embedding strength and filter strength;
Digital watermark detection means for detecting a digital watermark from an analog image output based on the digital image embedded with the digital watermark by the digital watermark embedding means;
If the detection result by the digital watermark detection means is bad, the quality evaluation value corresponding to the embedding strength and filter strength of the predetermined digital watermark is read from the parameter map, and the read quality evaluation value and the quality evaluation value are the same value. A parameter setting unit that reads a combination having a higher embedding strength or a lower filter strength than the combination of a plurality of embedding strengths and filter strengths from the parameter map and sets the combination in the digital watermark embedding unit. A digital watermark parameter setting device. Embed a digital watermark in a digital image with a predetermined watermark embedding strength and filter strength,
The digital image in which the digital watermark is embedded is evaluated based on a predetermined standard,
When the quality evaluation result is poor, in a combination array of digital watermark embedding strength and filter strength, from a parameter map that stores a quality evaluation value of an analog image in which the digital watermark is embedded based on the embedding strength and filter strength, Read a quality evaluation value corresponding to the embedding strength and filter strength of the predetermined digital watermark,
A combination of a plurality of embedding strengths and filter strengths having the same quality evaluation value and the quality evaluation value is read from the parameter map, and a combination having a weaker embedding strength or a higher filter strength is read from the parameter map, and the digital watermark is embedded. A digital watermark parameter setting method characterized by setting an intensity and a filter intensity. On the computer,
A process of embedding a digital watermark in a digital image with a predetermined digital watermark embedding strength and filter strength;
A process for evaluating the quality of the digital image embedded with the digital watermark according to a predetermined standard;
When the quality evaluation result is poor, in a combination array of digital watermark embedding strength and filter strength, from a parameter map that stores a quality evaluation value of an analog image in which the digital watermark is embedded based on the embedding strength and filter strength, A process of reading a quality evaluation value corresponding to the embedding strength and filter strength of the predetermined digital watermark;
A combination of a plurality of embedding strengths and filter strengths having the same quality evaluation value and the quality evaluation value is read out from the parameter map, and a combination of the embedding of the digital watermark is read out from the parameter map. A digital watermark parameter setting program for executing processing to be set in the means.

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