JP2000078387A - Printing method and device, pattern read method and device and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To embed copyright information and the management information of merchandise, etc., invisibly to the eyes of a human in a printed matter. SOLUTION: RGB image data S0 are obtained by reading a photographic original G in an image read means 1. A bit pattern P to be embedded in the image data S0 is generated in a pattern generation means 2, and they are inputted to a pattern burying conversion means 3. In the pattern burying conversion means 3, the image data S0 are converted into image data S1 (CMYK) for printing, so as to almost conditionally color-equalize a part for burying the pattern P and the other part in the image data S0. The image data S1 are printed in a printing means 4 on a paper sheet as visible images. In the printed matter, although the embedded pattern can not be recognized visually under a normal light source, the embedded pattern can be recognized visually under a special light source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing method and apparatus for embedding a predetermined pattern in color printing data for printing, a method and apparatus for reading an embedded pattern from an image obtained by this printing method, and The present invention relates to a computer-readable recording medium on which a program for causing a computer to execute these methods is recorded.

[0002]

2. Description of the Related Art When a photographic original is used as a printing original, the photographic original is read by a scanner or the like to read RGB images.
Digital data consisting of three color components is obtained, and color separation data for printing is created based on the digital data. As color components of the separation data, in addition to C (cyan), M (magenta), and Y (yellow), which are the three primary colors of normal printing, K is added to reproduce a shadow portion of a character or a subject. In some cases, four color components are used. Further, when the color reproduction range is wide, or when printing is performed so that a vivid image is obtained, six or more color components including G (green) and O (orange) inks are used. is there. Here, when converting digital data composed of RGB color components into CMYK (or CMYGOK) color components, conversion parameters are set so as to reproduce a color faithful to a document. At this time, in consideration of printing stability, ink cost, and the like, various parameters for optimizing the method of inserting K in particular are used.

[0003] On the other hand, since photo manuscripts and printed materials themselves are copyrighted because they are valuable as creations, it is necessary to prevent their unauthorized duplication. In addition, some printed materials, such as banknotes, securities, and various types of tickets, can themselves be exchanged for money. In particular, such printed materials need to completely prevent unauthorized duplication.
However, with the spread of color scanners and printers that can obtain high-quality images at low cost, an environment in which color prints can be easily reproduced is rapidly being formed.

[0004] In order to prevent the above-mentioned illegal duplication, a method of embedding a watermark in paper, a method of embedding a UV ink or a metal belt, and various special printing methods for the purpose of preventing forgery of micro-characters and the like, especially banknotes Has been done.

[0005]

However, these methods require very special techniques due to their characteristics, so that the number of printing companies is limited, and the printing cost is high. At present, these methods cannot be used in terms of profitability with relatively inexpensive tickets and the like, and there is almost no protection against unauthorized duplication.

On the other hand, in printing a product package or the like, it is necessary to print product management information for quality and distribution, such as a manufacturing date, a lot number, or a price, and these are usually printed using characters and bar codes. Is done. However, if the merchandise management information is printed as characters or barcodes, the degree of freedom of the package design is limited. Therefore, it is desired to print the merchandise management information as inconspicuously as possible.

The present invention has been made in view of the above circumstances, and a printing method capable of embedding various information such as information for preventing unauthorized duplication and merchandise management information by a simple method and performing printing. Provided are a reading method and apparatus for reading information embedded from printed matter obtained by the printing method and apparatus, and a computer-readable recording medium on which a program for causing a computer to execute these methods is recorded. It is intended for.

[0008]

A printing method according to the present invention is a printing method for embedding pattern data composed of a predetermined pattern in color printing data and printing an image in which the pattern is embedded. Modulating the data of the pattern portion in which the pattern is embedded in the printing data with substantially the same color as the data of the other portion to obtain modulated printing data, and performing the printing based on the modulated printing data. It is characterized by the following.

[0009] Here, "modulation with equal color conditions" means that color printing is perceived as the same color under a certain observation light source, but as a different color under a specific observation light source. Modulating the application data. Therefore, it is not possible to perceive the color difference between the pattern and the other part under the observation light source that is usually used, but to perceive the color difference between the two under the special observation light source. By setting to, the pattern cannot be visually recognized when the printed matter is observed under a normal light source, but the pattern can be visually recognized only when observed under a special light source.

In the printing method according to the present invention,
The color printing data is composed of four color component data of CMYK, and by changing at least the value of the K data of the four color component data, the data of the pattern portion and the data of the other portion are substantially adjusted. It is preferable to make the colors match.

A pattern reading method according to the present invention is a method for reading the pattern from an image obtained by the printing method according to the present invention, wherein the pattern is detected by detecting means having spectral sensitivity characteristics different from those of human eyes. It is characterized by reading.

A printing apparatus according to the present invention is a printing apparatus that embeds pattern data of a predetermined pattern in color printing data and prints an image in which the pattern is embedded, wherein the pattern in the color printing data is printed. A modulating unit that modulates the data of the pattern portion in which is embedded with substantially the same color as the data of the other portion to obtain modulated printing data, and a printing unit that performs the printing based on the modulated printing data. It is characterized by having.

In the printing apparatus according to the present invention,
The color printing data is composed of CMYK four-color component data, and the modulating unit changes at least the value of the K data of the four-color component data to thereby obtain the data of the pattern portion and the other portion. It is preferable that the data is a means for substantially equalizing colors with data.

A pattern reading apparatus according to the present invention is an apparatus for reading the pattern from an image obtained by the printing apparatus according to the present invention, wherein the apparatus has a detecting means having spectral sensitivity characteristics different from those of human eyes. It is a feature.

The printing method and the pattern reading method according to the present invention may be provided by being recorded on a computer-readable recording medium as a program for causing a computer to execute the method.

[0016]

According to the present invention, since the data of the pattern portion in the color printing data is modulated so as to be substantially equal in color to the data of the other portions, it is possible to observe the printed material under a certain observation light source. The color of the pattern part and the color of the other part will be perceived as the same color, but the color of the pattern part will be perceived as a color different from the color of the other part under a specific observation light source Becomes Therefore, under the observation light source that is normally used, the color difference between the pattern and the other part cannot be visually recognized under the condition for color matching, but the color difference between the two can be visually recognized under the special observation light source. The information for preventing the above-mentioned unauthorized duplication and the management information of the product can be embedded in the printed matter so that the information cannot be easily visually recognized. As a result, when the pattern is the copyright information of the printed matter, the copyright information can be embedded in the printed matter without being known to an unauthorized user, and the pattern can be read by reading the pattern under a special observation light source. Since the copyright information of the printed matter can be obtained, the source of the printed matter can be confirmed. In addition, since product management information such as a bar code cannot be visually recognized under a normal light source, there are no restrictions on the design of a product package or the like, thereby enabling free design.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic block diagram showing the configuration of a printing apparatus according to an embodiment of the present invention. As shown in FIG.
The printing apparatus according to the present embodiment includes an image reading unit 1 such as a scanner that reads an image from a photographic original G to obtain image data S0 of three colors of RGB, and a pattern that generates a pattern to be embedded in a printed matter as a bit pattern P. The generating means 2 embeds the bit pattern P in the image data S0 and converts the image data S0 into CMYK to
It comprises a pattern embedding conversion unit 3 for obtaining image data S1 for printing which is composed of four colors of YK and in which a bit pattern P is embedded, and a printing unit 4 for printing the image data S1 on paper.

The pattern generation means 2 generates a pattern to be embedded in the image data S0 as a bit pattern P, and inputs this to the pattern embedding conversion means 3 as a modulation signal. Here, examples of the pattern to be embedded include a character pattern and a logo representing the copyright of the photo document G, and the character pattern may be an encrypted pattern. When the printed material is a product package, the bit pattern P is product management information such as characters and bar codes.

The pattern embedding / conversion means 3 converts the RGB image data S0 into CMYK print image data S1. The conversion characteristic at the time of this conversion is modulated by the bit pattern P, thereby converting the image data S1. The bit pattern P is embedded. Here, the pattern embedding conversion means 3
2 is shown in FIG. Here, a case where the binary bit pattern P is embedded will be described.

The switch 6 selects which of the two color conversion LUTs 1 and 2 converts the pixel value of a certain pixel in the image data S0 from RGB to CMYK. This selection is performed by switching the switch 6 depending on whether the value of the bit pattern P corresponding to the pixel to be converted is 1 or 0. When the value of the bit pattern P is 0, the color conversion L
The switch 6 is switched so that UT1 is selected, and when it is 1, the color conversion LUT2 is selected.

The color conversion LUTs 1 and 2 are CMYK conversion LUTs.
It is created by the creating means 7. Here, the color conversion LUT
Data S2 obtained by conversion by 1, 2
(CMYK) and data S2 '(C'M'Y'K)
Has the relationship shown in the following equation (1).

Lab {CMYK (RGB)} = Lab {C′M′Y′K ′ (RGB)} (1) where Lab {} is a function that gives a CIE colorimetric value of a printed color for CMYK data. And CMYK ()
Is a conversion formula for RGB data to CMYK data.

Here, CMYK and C'M'Y'K '
Is a data pair having the same colorimetric value calculated from the same print color reproduction characteristic description data K by the CMYK conversion LUT creating means 7, that is, a condition-matching color pair. Therefore, although the two data S2 and S2 'obtained by the color conversion LUTs 1 and 2 are different, the printing means 4
Are perceived as the same color on the printed material obtained by the above. Therefore, the pixel value corresponding to the bit pattern P portion on the image represented by the image data S0 is converted by the color conversion LUT2, and the bit pattern P
The pixel values corresponding to the other parts are converted by the color conversion LUT 1 to obtain data S 2 ′ and data S 2, which constitute the image data S 1, and the printing unit 4 performs printing based on the image data S 1. In the resulting printed matter, the embedded pattern is usually invisible to the human eye.

CMYK having such a condition-equal color relationship
Table 1 below shows an example in which data combinations are obtained from the color reproduction characteristics of a four-color offset printing press. The combinations shown in Table 1 were obtained so as to achieve color matching under a standard observation light source having a color temperature of 5000 K, and the values of Lab in Table 1 were obtained under this light source. It should be noted that not only the combinations of the CMYK data for the conditionally equal colors shown in Table 1 but also various other combinations can be used.

[0026]

[Table 1]

When the LUT is created by the CMYK conversion LUT creating means 7, the modulation intensity of the bit pattern P to be embedded can be changed by specifying the parameter H of the modulation intensity. For example, if data A shown in Table 1 above is used as CMYK data and data B is used as C'M'Y'K 'data, the modulation intensity of the bit pattern P becomes relatively small. Therefore, under these conditions, the bit pattern P is not easily visually recognized even if the observation light source slightly changes, which is suitable for applications where emphasis is placed on invisibility. On the other hand, data A shown in Table 1 above is used as CMYK data, and C′M′Y ′
If data C is used as the K 'data, the modulation intensity of the bit pattern P becomes relatively large. Therefore,
Under these conditions, the embedded bit pattern P cannot be visually recognized under a standard light source, but the pattern P can be easily detected under a different light source. Therefore, it is suitable for applications where importance is placed on detectability.

When the bit pattern P is multi-valued, the bit value may be used as the modulation intensity. In this case, the bit pattern P is input to the CMYK conversion LUT creating means 7 as the modulation intensity parameter H, and if the value is large, data with a large K value is selected from the group of conditional color matching, and if the value is small, the data is proportional to it. By selecting data with a small K value, a pattern having a gradation corresponding to the bit pattern P can be embedded.

Next, the operation of the first embodiment will be described. FIG. 3 is a flowchart showing the processing performed in the first embodiment. First, the photo original G is read by the image reading means 1, and RGB image data S0 is obtained (step S1). On the other hand, the pattern generating means 2
, A bit pattern P to be embedded is generated (step S2). Then, the image data S0 and the bit pattern P are input to the pattern embedding conversion means 3 (step S3). In the pattern embedding conversion means 3, the CM
The YK conversion LUT creating means 7 performs color conversion LUT1, LUT based on the bit pattern P and the modulation intensity parameter H.
UT2 is created (step S4). Then, the image data S0 is converted into the bit pattern P according to the bit pattern P.
Are converted to image data S2 '(C'M'Y'K') by the color conversion LUT2, and the pixels not corresponding to the bit pattern P are converted to image data S2 (CMYK) by the color conversion LUT1. (Step S5). Then, the image data S1 (CMY) in which the bit pattern P is embedded by the image data S2 and S2 '.
K) is created (step S6). The image data S1 created in this way is input to the printing means 4, where it is printed as a visible image on paper (step S7).

In the printed matter obtained in this way, the embedded pattern cannot be visually recognized under a normal light source, but the embedded pattern is read by a reader having a spectral sensitivity characteristic different from that of human eyes. The bit pattern P can be detected. As such a reader, for example, a three-wavelength fluorescent lamp is used as a reading light source,
Various devices can be used, such as a device using D, a device using an LED light source, or a scanner using a sensor having sensitivity in the infrared region.

As described above, according to the present embodiment, the image data S0 (RGB) is converted to the image data S1 (CMY) for printing.
At the time of conversion to K), the pixels corresponding to the bit pattern P to be embedded are modulated so as to be conditionally equal in color to the pixels in the other portions. Is perceived as the same color as the color of the pattern portion, but under a specific observation light source, the color of the pattern portion is perceived as a color different from the colors of the other portions. Therefore, the embedded bit pattern P cannot be visually recognized under a normal light source, but the bit pattern P can be visually recognized only under a special light source. As a result, in order to prevent unauthorized duplication. Information and product management information can be embedded in printed matter so as not to be easily perceived. As a result, when the pattern P is used as the copyright information of the printed matter, the copyright information can be embedded in the printed matter without being known to an unauthorized user, and the pattern P can be read under a special observation light source. As a result, the copyright information of the printed matter can be obtained, so that the source of the printed matter can be confirmed. In addition, since product management information such as a bar code cannot be visually recognized under a normal light source, there is no restriction on the design of a product package or the like, thereby enabling free design.

Next, a second embodiment of the present invention will be described. The second embodiment obtains image data S0 'in which information is embedded by deeply encrypting the additional information F such as copyright information and image management information into the image data S0 and embedding it as a so-called digital watermark. When printing based on the image data S0 ', the image data S0'
, The additional information F is read from the image data S0 'as a bit pattern,
By performing K conversion, image data S1 '(CMYK) for printing is obtained.

FIG. 4 is a schematic block diagram showing the configuration of an apparatus for embedding supplementary information in image data used in the second embodiment of the present invention. As shown in FIG. 4, this apparatus generates image reading means 1 for obtaining image data S0 (RGB) in the same manner as in the first embodiment by reading a photographic original G, and generates additional information F embedded in the image data S0. And an embedding unit 11 that obtains image data S0 'in which the incidental information F is embedded by embedding the incidental information F in the image data S0 by deep encryption.

Here, as a method of embedding the supplementary information F in the image data S0 by deep encryption in the embedding means 11, for example, JP-A-8-289159,
Methods described in Japanese Patent Application Nos. 0-108180 and 9-214636 are known. In this method, by embedding authentication information and copyright information in a redundant part of the data, it is not possible to confirm the embedded information only by reproducing the image data, but a device or software for reading the information is used. By using software, information embedded in data can be read and displayed. Details of this deep encryption are described in various documents (for example, “Digital Watermark, Koshio Matsui, Oplus E No. 213, August 1997”).

As such a deep encryption method, various methods such as a pixel space use type, a quantization error use type, and a frequency domain use type are known. The pixel space utilization type extracts a plane of, for example, 3 × 3 pixels near the target pixel, and
This is a method of embedding supplementary information in bits. The quantization error utilization type focuses on a quantization error generated in the process of compressing image data, and controls the quantization output to an even number and an odd number with 0 and 1 of the bit sequence of the incidental information, so that an apparent quantization noise is generated. Embedded in the image data.
For this quantization error utilization type, see "Image deep encryption".
(Koshio Matsui, Morikita Publishing, 1993) describes the details. The frequency domain utilization type is a method of embedding supplementary information in a visually insensitive frequency domain on an image domain. For example, since the high-frequency component in the image is a visually insensitive area, the image data is decomposed into a plurality of frequency bands, the additional information is embedded in the high-frequency band, and the additional information is embedded by reconstructing the image data. be able to. As for human visual characteristics, color difference and saturation information generally have lower gradation discrimination ability than luminance information, and there is an area where recording that is invisible to the difference between luminance and color difference or saturation information is possible. Exists. Therefore, additional information can be embedded in this area.

Other methods include embedding incidental information in a bit plane with a poor S / N ratio as noise by adding noise as redundancy, and embedding information into information blocks in a certain range of pixel blocks (spaces). A method of embedding a quantization error in the case where the amount of data information is reduced due to encoding when performing data compression is exemplified.

FIG. 5 is a schematic block diagram showing the configuration of a printing apparatus according to the second embodiment. As shown in FIG.
The printing apparatus according to the second embodiment reads the additional information F from the image data S0 'obtained by the apparatus shown in FIG. 4, and obtains the additional information F and the additional information F from which the additional information F is separated. Readout unit 12 and image data S
Pattern embedding conversion means for embedding the additional information F as a bit pattern in 0 "and converting the image data S0" into CMYK to obtain image data S1 'for printing consisting of four colors of CMYK and having the additional information F embedded therein. 3 and printing means 4 for printing the image data S1 'on paper.

The pattern embedding and converting means 3 embeds the incidental information F as a bit pattern in the image data S0 'in the same manner as described in the first embodiment.

Next, the operation of the second embodiment will be described. FIG. 6 is a flowchart showing processing performed in the second embodiment. First, the photo original G is read by the image reading means 1 to obtain RGB image data S0 (step S11). On the other hand, the additional information generating means 10 generates additional information F for deep encryption and embedding in the image data S0 (step S12).
Then, the additional information F is deeply encrypted by the embedding means 11 and embedded in the image data S0, and the image data S0 'in which the additional information F is embedded is obtained (step S1).
3).

Next, in the printing apparatus, the image data S
0 'is input to the supplementary information reading means 12, and the image data S
0 'is read out of the additional information F embedded and embedded in the image data S from which the additional information F is separated.
0 "is obtained (step S14). The supplementary information F and the image data S0" are input to the pattern embedding conversion unit 3 (step S15). In the pattern embedding conversion unit 3, the CMYK conversion LUT creation unit 7 uses the color conversion LUT based on the supplementary information F and the modulation intensity parameter H.
1. LUT2 is created (step S16). Then, for the pixel whose image data S0 "corresponds to the supplementary information F, the image data S2 '(C'
M′Y′K ′), and for pixels that do not correspond to the supplementary information F, the image data S2 (C
MYK) (step S17). Then, image data S1 '(CMYK) in which the supplementary information F is embedded is created by the image data S2 and S2' (step S18). The image data S1 'thus created is input to the printing means 4, where it is printed as a visible image on paper (step S19).

As described above, also in the second embodiment, image data S0 '(RGB) is converted to image data S1' for printing.
At the time of conversion to (CMYK), the pixels corresponding to the additional information F to be embedded are modulated in such a manner that the pixels corresponding to the other parts are color-matched with the other parts, so that the additional information part can be obtained even when the printed matter is observed under a certain observation light source. And the color of the other part will be perceived as the same color, but the color of the incidental information part will be perceived as a color different from the color of the other part under a specific observation light source. Become. Therefore, the embedded additional information F cannot be visually recognized under a normal light source, but the additional information F can be visually recognized only under a special light source. As a result, in order to prevent unauthorized duplication. Information and product management information can be embedded in printed matter so as not to be easily perceived.

Since the additional information F is embedded in the image data S0 ', when the image data S0' is reproduced, the additional information F appears as noise in image quality.
The image quality is degraded. On the other hand, in the second embodiment, the additional information F is separated from the image data S0 ', and the image data S
Since the supplementary information F is embedded in 0 "as a bit pattern and converted into image data S1 'for printing, the supplementary information F does not appear as noise, thereby obtaining a high-quality print image. it can.

In the first and second embodiments, the case where printing is performed in four colors of CMYK has been described. However, in the six colors of CMYGOK to which orange (O) and green (G) are added. Even when printing is performed, the bit pattern P can be embedded as described above. In this case, for example, the ratio between CY and G is changed, or M
By changing the ratio between Y and O, it is possible to embed the bit pattern P in a conditionally uniform color.
By changing the K value as shown in FIG.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram illustrating a configuration of a printing apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic block diagram showing a detailed configuration of a pattern embedding conversion unit.

FIG. 3 is a flowchart illustrating processing performed in the first embodiment;

FIG. 4 is a schematic block diagram showing a configuration of an auxiliary information embedding device for obtaining image data used in a second embodiment of the present invention.

FIG. 5 is a schematic block diagram illustrating a configuration of a printing apparatus according to a second embodiment of the present invention.

FIG. 6 is a flowchart illustrating processing performed in a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image reading means 2 Pattern generation means 3 Pattern embedding conversion means 4 Printing means 6 Switch 7 CMYK conversion LUT creation means 10 Additional information generation means 11 Embedding means 12 Additional information reading means

Claims (9)

[Claims] 1. A printing method for embedding pattern data composed of a predetermined pattern in color print data and printing an image in which the pattern is embedded, wherein a pattern portion in the color print data in which the pattern is embedded. And modulating said data with substantially equal colors to data of other parts to obtain modulated printing data, and performing said printing based on said modulated printing data. 2. The color printing data comprises four color component data of CMYK, and by changing at least the value of K data among the four color component data, the data of the pattern portion and the data of the other portion are changed. 2. The printing method according to claim 1, wherein the data and the data are made substantially equal in color. 3. A method of reading the pattern from an image obtained by the printing method according to claim 1 or 2, wherein the pattern is read by a detection unit having spectral sensitivity characteristics different from human eyes. A pattern reading method characterized by the following. 4. A printing apparatus for embedding pattern data consisting of a predetermined pattern in color print data and printing an image in which the pattern is embedded, wherein the pattern portion in the color print data in which the pattern is embedded. And a modulating means for modulating the data of the other part with substantially the same color as the data of the other part to obtain modulated printing data, and a printing means for performing the printing based on the modulated printing data. Printing device. 5. The color printing data comprises four color component data of CMYK, and the modulating means changes at least the value of K data of the four color component data to thereby obtain data of the pattern portion. 5. The printing apparatus according to claim 4, wherein the printing unit is means for making the data of the other portion substantially equal in color. 6. An apparatus for reading the pattern from an image obtained by the printing apparatus according to claim 4 or 5, further comprising a detecting means having a spectral sensitivity characteristic different from that of human eyes. Pattern reading device. 7. A computer-readable recording medium storing a program for causing a computer to execute a printing method of embedding pattern data consisting of a predetermined pattern in color printing data and printing an image in which the pattern is embedded. A step of obtaining modulated print data by modulating the data of the pattern portion in which the pattern is embedded in the color print data with substantially the same color as the data of the other portions to obtain modulated print data; Performing the printing based on the modulated printing data. 8. The color printing data includes CMYK four-color component data. The step of obtaining the modulated printing data includes changing at least the value of K data of the four-color component data.
8. The procedure according to claim 7, wherein the data of the pattern portion and the data of the other portion are substantially equal in color.
The computer-readable recording medium according to claim 1. 9. A computer-readable recording medium in which a program for causing a computer to execute the method of reading the pattern from an image obtained by the printing method according to claim 1 or 2 is recorded, wherein the program is A computer-readable recording medium having a procedure of reading the pattern by detecting means having spectral sensitivity characteristics different from human eyes.