JP2001069335A - Image processor, image processing method and storing medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To add information while suppressing the deterioration of a picture quality of an image to be formed by adding the prescribed information to the image expressed with a picture signal as frequency components obtained from the quantized picture signal. SOLUTION: Prescribed information is added to an image expressed with a picture signal as frequency components obtained from the quantized picture signal. In an inexpensive printer, e.g. original image data is delivered to a printer driver as RGB image data 101, converted to the RGB image data 102 of a device corresponding to the characteristic of each printer, decomposed to the CMYK image data 103, and binarized to the CMYK binary image data 104, which is delivered to a printer engine to be printed on paper. In this case, a tracking pattern can be added to an image featured value by binarize- processing through the use of two kinds of dither patterns where a main component vector of a covariance of the image featured values is orthogonal with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image processing device, an image processing method, and a storage medium.

[0002]

2. Description of the Related Art In digital color image forming apparatuses such as printers and copiers, image quality has been remarkably improved.
It has become possible to easily obtain high-quality full-color prints. That is, anyone can obtain the required printed matter by image processing using a high-performance scanner, printer, copier, and computer. For this reason, problems such as counterfeiting of bills and securities occur, and some devices have a forgery prevention function.

This function generally has both a counterfeit tracking function and a bill recognition function. The forgery tracking function, as a general realization method, is to print a regular pattern representing the model code of the recording device at the time of printing, and when a forged bill is discovered, the dot pattern struck on the bill This is a so-called tracking pattern method in which a model number is determined and a recording model from which the model number is output is specified. Also, since this dot pattern is printed on all output images,
It is common to strike in yellow.

FIG. 14 shows a printing example of a tracking pattern hit in yellow. Here, 1401 is called a dot. The dots are composed of a plurality of pixels on the digital data. The dot pattern is determined by calculating the position of each dot from the printed image.

FIG. 15 shows an example of an image in which a tracking pattern is hit. Reference numeral 1501 denotes a dot of the tracking pattern.
Reference numeral 2 denotes a picture dot.

[0006]

However, when the above-described conventional tracking pattern method is applied to a low-cost color printer in which the landing positions of dots are unstable, the accuracy of dot pattern discrimination is improved in copiers and laser beam printers. It is much lower than that. Further, in this method, it is difficult to discriminate a dot pattern from a portion having a picture of a bill or a securities.

Further, in the above-mentioned method, since the tracking pattern is hit on a portion having no picture, the pattern is conspicuous and image quality is deteriorated.

An object of the present invention is to provide an image processing apparatus, an image processing method, and a storage medium for solving at least one of the above problems.

Further, according to the present invention, tracking information and other predetermined information are added as frequency components obtained from a quantized image signal, so that the information is added while suppressing deterioration of the image quality of a formed image. The purpose is to:

A further object of the present invention is to improve the discrimination accuracy of the information by calculating a frequency component from an image signal obtained from an image and extracting predetermined information based on the frequency component.

[0011]

In order to achieve the above object, the present invention provides an adding means for adding predetermined information to an image represented by an image signal as a frequency component obtained from a quantized image signal. And output means for outputting an image signal to which the predetermined information has been added to the outside.

In order to further achieve the above object, the present invention provides
It is characterized by comprising a means for calculating a frequency component from a quantized image signal, and an extracting means for extracting predetermined information added based on the calculated frequency component.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Hereinafter, a preferred embodiment according to the present invention will be described with reference to the accompanying drawings.

In the following embodiment, a low-cost color printer (hereinafter, referred to as a low-cost printer) having an unstable dot landing position will be described as an example.

Image data to be binarized are C (cyan), M (magenta), Y (yellow), BK (black)
8 bits each. The dither pattern used for the binarization includes tracking information (0,
According to 1), the distribution of image feature quantity (spatial frequency, etc.) of a certain number of dimensions is composed of middle and high band components without low frequency components, and the absolute value of the covariance is large enough to prevent image quality degradation. And two kinds of dither patterns in which the second principal component vector is orthogonal to each other (hereinafter, the one corresponding to information '0' is referred to as the first dither pattern,
The information corresponding to the information '1' is referred to as a second dither pattern) and a dither pattern (hereinafter, referred to as a third dither pattern) which includes low-frequency components and middle-high band components, and has an absolute value of covariance smaller than the above two dither patterns. Dither pattern)
And Tracking information is added only to Y.

Further, a scanner for reading a binary image uses a low-cost scanner.

FIG. 1 is a diagram showing a flow of image data conversion of a low-cost printer according to the first embodiment of the present invention. In this figure, the original image data is RGB image data 101
As passed to the printer driver for low cost printers. Next, the RGB image data 101 is converted into RGB image data 102 of a device that matches the characteristics of each printer, and the RGB image data 102 of the device is further decomposed into CMYK image data 103, and the CMYK image data 103 is converted into a CMYK binary image. The data is binarized into data 104.

The CMYK binary image data 104 is passed to a printer engine and printed on paper.

Next, a first dither pattern, a second dither pattern, and a third dither pattern according to the present embodiment will be described.

FIG. 2 is a diagram showing a distribution of threshold values of an MxM-dimensional first dither pattern. The threshold value is 0 to 255, and a black portion indicates the threshold value 0.

FIG. 3 is a diagram showing the spectrum distribution of the amplitude of the DFT (discrete Fourier transform) of the first dither pattern of the MxM dimension. The dimension of this figure is MxM and the center is D
The higher the frequency of the C component, the closer to the periphery. Also,
It is assumed that the darker the part, the weaker the spectrum.

Similarly, FIG. 4 is a diagram showing a distribution of threshold values of the second dither pattern of MxM dimension, and FIG. 5 is a diagram showing a spectrum distribution of DFT amplitude of the second dither pattern of MxM dimension. FIG. 6 is a diagram showing a distribution of threshold values of an MxM-dimensional third dither pattern, and FIG. 7 is a diagram showing a spectrum distribution of DFT amplitudes of the MxM-dimensional third dither pattern.

3 and 5, the absolute value of the covariance is larger than that of FIG. 7, and the first principal component vectors are orthogonal to the second principal component vectors.

In this embodiment, M = 64.

Next, a procedure for adding tracking information (for example, a signal indicating the model code of the recording apparatus) to Y will be described.

FIG. 8 is a diagram showing an example of a bit sequence of the tracking information. Here, 801 indicates bit '0' and 802 indicates bit '1'. In this example, 8-bit information can be represented.

FIG. 9 shows a flowchart for adding tracking information to Y. Description will be made with reference to this figure.

First, the image data of Y is read (90
1).

Next, as shown in FIG. 10, Y is divided into M × M blocks. Here, 1001 indicates an MxM block, 1002 indicates a row number index, and 1003 indicates a column number index. In the figure, the index numbers are nxn matrices. From this index matrix, nxn
Generate a dimensional index vector (90
2). At this time, the element number of the index vector becomes the index number of each block.

Next, a random number from 1 to nxn is generated without duplication of numerical values based on predetermined or input key information (903). This random number is generated to prevent the tracking information added to the image data from being read maliciously. At this time, the generated random number is the index generated in 902
Corresponds to the element number of the vector. That is, each random value is an index number of each block.

Then, the bit sequence of the tracking information information (FIG. 8) is associated with the index number of the block (9).
04). At this time, when the association reaches the end of the bit sequence, the next association starts from the head of the bit sequence. Since the repetitive bit sequence is used as described above, the tracking information can be reproduced even if a part of the image is missing.

FIG. 11 shows an example of correspondence between a bit sequence, a random number sequence, and a block index number. Bit sequence 110
The number of 1s and the number of 1102, which is a random number sequence and also a block index number, are both nxn.

Further, the index number and the bit of the block corresponding to X = 1st in the random number sequence are obtained (90).
5).

Then, MxM image data corresponding to the obtained block index number is obtained (906).
If the bit of the corresponding bit sequence is '0', it is binarized by the first dither pattern (907), and if the bit is '1', it is binarized by the second dither pattern (908).

The same processing is performed up to the nxn-th random number sequence (909).

Next, binarization of C, M and BK is performed.

FIG. 12 shows a flowchart. Description will be made with reference to this figure.

First, the image data of C is read (120).
1).

Next, as shown in FIG.
It is divided into MxM blocks (1202).

Then, each block is binarized by the third dither pattern (1203).

The same processing is performed for M and BK.

The CMYK binary image data thus obtained is passed to the printer engine as 104 in FIG. 1 and printed on paper.

A means for extracting tracking information from the print image created by the above means will be described.

FIG. 13 shows a flowchart. Description will be made with reference to this figure.

First, a print image is read by a scanner in 8 bits for each of the RGB modes (1301).

Next, conversion from the RGB mode to the CMYK mode is performed (1302).

Then, the image data of Y is converted to the size when the tracking information is added (1303).

The following processing is performed on the converted Y.

First, as shown in FIG. 10, Y is divided into M × M blocks. Here, 1001 indicates an MxM block, 1002 indicates a row number index, and 1003 indicates a column number index. In the figure, the index numbers are nxn matrices. From this index matrix, nxn
Generate a dimensional index vector (130
4). At this time, the element number of the index vector becomes the index number of each block.

Next, a random number from 1 to nxn is generated based on predetermined key information or input key information (1305). At this time, the generated random number is 13
04 corresponds to the element number of the index vector generated. That is, each random value is an index number of each block.

Further, the index number and the index of the block corresponding to X = 1st in the random number sequence are obtained (1306).

Then, MxM image data corresponding to the obtained block index number is obtained (130).
7).

The MxM image data, the first dither pattern, the second dither pattern, and the amplitude spectrum distribution of each DFT are calculated (1308). Further, a threshold is calculated from the amplitude spectrum distribution of each DFT calculated in 1308. A distribution below S0 is generated (1309).

The first principal component vectors of the two-variable distribution below the threshold value S0 are obtained (1310). At this time, the first principal component vector obtained from the first dither pattern is the first vector, the first principal component vector obtained from the second dither pattern is the second vector, and the second principal vector is obtained from MxM image data. The first principal component vector will be referred to as an observation image vector.

The similarity is calculated from the inner product of the vector of the observation image thus obtained and the first vector (131).
1). At this time, the obtained similarity is set to m1. Also,
The similarity is calculated from the inner product of the vector of the observation image and the second vector (1312). At this time, the obtained similarity is set to m2.

By comparing the magnitudes of the similarities m1 and m2, if m1> m2 (1313), it is determined that the embedded bit is “0” (1314).
It is determined that the embedded bit is “1” (131
5).

The same process is performed up to the nxn-th random number sequence (1316).

The bit sequence extracted in this way is subjected to majority decision to make the bit length at the time of embedding.

As described above, according to the first embodiment, in order to prevent counterfeiting of bills and securities as in the prior art, the regular pattern representing the model code of the recording apparatus is a yellow dot pattern. Rather than driving in, image components (spatial frequency, etc.) are tracked by performing binarization processing using two types of dither patterns in which principal component vectors of the covariance of image features (spatial frequencies, etc.) are orthogonal to each other. Since a pattern can be added, a tracking pattern can be added without deteriorating the image quality of an image.

In order to extract the tracking information added to the image as in the prior art, the position of each dot representing the tracking information is not calculated and the tracking information is extracted. Improve the reading accuracy of tracking information by calculating the similarity based on the inner product of the principal component vector of the covariance of the image feature amount (such as spatial frequency) and the principal component vector of the dither pattern and extracting the tracking information. Can be.

(Other Embodiments) In the first embodiment, two types of dither patterns are used in which principal component vectors of covariances of image feature amounts (such as spatial frequencies) are orthogonal to each other in accordance with tracking information. By performing the binarization process, tracking information was added to the image features (such as spatial frequency). To add the tracking information to the image features (such as spatial frequency),
The execution may be performed by another method without using the above two types of dither patterns.

For example, to an image signal to which tracking information is added,
By adding an image signal of an amount corresponding to the tracking information and performing binarization processing with one type of dither pattern, a result similar to that obtained by binarization processing with two types of dither patterns may be obtained. .

In addition to the binarization processing, tracking information may be added by quantizing using multi-level dither.

Further, instead of embedding the tracking information in the entire screen as described above, the tracking information may be embedded in a part of the image.

The information to be added includes information unique to the apparatus on which the image processing is performed and the apparatus for forming the image-processed image, for example, a product number, and other information such as creator information of the image. You may.

In the first embodiment, the tracking information is added to the yellow image signal of yellow, magenta, and cyan.
Tracking information may be added to an image signal of another color such as blue among green and blue.

In order to realize the functions of the above-described embodiment, even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), a single device may be used. (For example, a copying machine, a facsimile machine, etc.).

In order to operate various devices so as to realize the functions of the above-described embodiments, an apparatus connected to the various devices or a computer in the system includes:
A program code of software for realizing the functions of the embodiment (for example, functions realized by the flowcharts of FIGS. 9, 10, and 13) is supplied, and a computer (CPU or MPU) of the system or apparatus is stored. The present invention also includes those implemented by operating the various devices according to a program.

In this case, the program code itself of the software realizes the functions of the above-described embodiment, and the program code itself and means for supplying the program code to the computer, for example, the program code Is provided.

As a storage medium for storing such a program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, magnetic tape, nonvolatile memory card, ROM or the like can be used.

When the computer executes the supplied program code, not only the functions of the above-described embodiment are realized, but also the OS (operating system) running on the computer or another program. Needless to say, the program code is included in the present embodiment even when the functions of the above-described embodiment are realized in cooperation with application software and the like.

Further, the supplied program code is stored in a memory provided in a function expansion board of a computer or a function expansion unit connected to the computer, and then stored in the function expansion board or the function storage unit based on the instruction of the program code. It is needless to say that the present embodiment also includes a case where a provided CPU or the like performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0073]

According to the first aspect, as described above,
Since predetermined information can be added as a frequency component obtained from a quantized image signal, for example, when forming an image using an image signal to which predetermined information has been added, a predetermined Information can be added.

The image processing method according to claim 20,
Similar effects can be obtained with the storage medium according to claim 39.

According to the present invention, when an image is formed using an image signal added as a frequency component, predetermined information can be added without deteriorating the image quality.

According to claims 4 and 23, predetermined information can be added as a frequency component by performing quantization processing using a plurality of patterns, so that predetermined information can be added without deteriorating the image quality of an image. Can be added.

According to the fifth and twenty-fourth aspects, the frequency component and predetermined information are added by performing quantization processing using two kinds of dither patterns in which the main component vectors of the covariance of the frequency component are orthogonal to each other. Therefore, predetermined information can be added without deteriorating the image quality of the image.

According to the eighth and 27th aspects, predetermined information can be added by using a random number, so that it is possible to prevent malicious reading.

According to the tenth aspect, the frequency component is calculated from the image signal obtained from the image, and the predetermined information is extracted based on the frequency component, so that the accuracy of determining the predetermined information can be improved. .

An image processing method according to claim 29,
A similar effect can be obtained in the storage medium according to the present invention.

According to Claims 11, 13, 30, and 32,
The predetermined information added can be extracted by quantizing the image signal using a plurality of patterns having different frequency components.

Claims 12, 14, 15, 30, 32, and 3
According to No. 3, it is possible to extract predetermined information added by quantizing the image signal using patterns in which the main component vectors of the covariance of the frequency components are different from each other.

[Brief description of the drawings]

FIG. 1 is a diagram showing a flow of image data conversion of a low-cost printer.

FIG. 2 is a diagram illustrating a distribution of threshold values of an MxM-dimensional first dither pattern;

FIG. 3 is a diagram illustrating a distribution of an amplitude spectrum of a DFT of an MxM-dimensional first dither pattern.

FIG. 4 is a diagram illustrating a distribution of threshold values of an MxM-dimensional second dither pattern;

FIG. 5 is a diagram illustrating a distribution of an amplitude spectrum of a DFT of an MxM-dimensional second dither pattern.

FIG. 6 is a diagram illustrating a distribution of threshold values of an MxM-dimensional third dither pattern.

FIG. 7 is a diagram showing a distribution of an amplitude spectrum of a DFT of an MxM-dimensional third dither pattern.

FIG. 8 is a diagram showing a bit sequence of tracking information.

FIG. 9 is a diagram showing a flowchart for adding tracking information to Y.

FIG. 10 is a diagram when image data is divided into MxM blocks.

FIG. 11 is a diagram illustrating a correspondence example of a tracking information bit sequence, a random number sequence, and a block index number.

FIG. 12 is a flowchart of a binarization process of C, M, and Bk.

FIG. 13 is a flowchart for extracting tracking information from a print image.

FIG. 14 is a diagram illustrating a print example of a tracking pattern hit in yellow.

FIG. 15 is a diagram illustrating an example of an image in which a tracking pattern is hit.

[Explanation of symbols]

 101 RGB image data, each 8 bits 102 RGB image data of device, each 8 bits 103 CMYK image data, each 8 bits 104 CMYK binary image data 801 Tracking information bit '0' 802 Tracking information bit '1' 1001 MxM Block 1002 row number index 1003 column number index 1101 bit sequence of tracking information 1102 random number sequence and block index number sequence 1401 dot of tracking pattern 1501 dot of tracking pattern 1502 dot of picture

Claims (40)

[Claims] An adding unit for adding predetermined information to an image represented by the image signal as a frequency component obtained from the quantized image signal; and outputting the image signal added with the predetermined information to the outside. An image processing apparatus comprising: 2. An image processing apparatus according to claim 1, wherein said output means outputs an image signal to which said predetermined signal is added to an image forming apparatus. 3. The image processing apparatus according to claim 2, wherein the adding unit adds the predetermined information to an image formed by the image forming apparatus so that the predetermined information is hardly seen by human eyes. 4. The method according to claim 1, wherein the adding unit adds the predetermined information by performing a quantization process on the image signal using a plurality of patterns having different frequency components according to the predetermined information. The image processing device according to claim 1. 5. A method according to claim 1, wherein said plurality of patterns include first and second principal component vectors of covariance of said frequency components orthogonal to each other.
5. The image processing apparatus according to claim 4, comprising a dither pattern of: 6. The image processing apparatus according to claim 1, wherein the predetermined information is information unique to the apparatus. 7. The image processing apparatus according to claim 1, wherein the image signal is yellow. 8. The image processing apparatus according to claim 1, wherein the predetermined information is added to the image signal according to a generated random number. 9. The method according to claim 4, wherein the plurality of patterns are used in accordance with bits of the predetermined information.
An image processing apparatus as described in the above. 10. A system comprising: means for calculating a frequency component from a quantized image signal; and extracting means for extracting predetermined information added based on the calculated frequency component. Image processing device. 11. The image processing apparatus according to claim 10, wherein the predetermined information is added by performing a quantization process on the image signal using a plurality of patterns having different frequency components. apparatus. 12. The method according to claim 1, wherein the plurality of patterns are composed of first and second dither patterns in which principal component vectors of the covariance of the frequency components are orthogonal to each other.
2. The image processing device according to 1. 13. The image processing apparatus according to claim 11, wherein the predetermined information is extracted based on a frequency component calculated by the calculation unit and a frequency component obtained from the plurality of patterns. 14. The method according to claim 1, wherein the predetermined principal component vector of the covariance of the frequency component calculated by the calculating means and the main component vector of the covariance of the frequency component obtained from the first and second dither patterns are used. 13. The image processing apparatus according to claim 12, wherein the information is extracted. 15. The method according to claim 15, wherein the extracting unit calculates a main component vector of the calculated covariance of the frequency component and a main component vector of the covariance of the frequency component obtained from the first and second dither patterns. The image processing apparatus according to claim 14, wherein the predetermined information is extracted based on a degree of similarity of the inner product. 16. The image processing apparatus according to claim 10, wherein the predetermined information is information unique to the apparatus. 17. The image processing apparatus according to claim 10, wherein the image signal is yellow. 18. The image processing apparatus according to claim 10, wherein the predetermined information is added to the image signal according to a generated random number. 19. The image processing apparatus according to claim 11, wherein the plurality of patterns are used according to bits of the predetermined information. 20. An adding step of adding predetermined information to an image represented by the image signal as a frequency component obtained from the quantized image signal, and outputting the image signal added with the predetermined information to the outside An image processing method comprising: 21. The image processing method according to claim 20, wherein said output step outputs an image signal to which said predetermined signal has been added to an image forming apparatus. 22. The image processing method according to claim 21, wherein the adding unit adds the predetermined information to an image formed by the image forming apparatus so that the predetermined information is hardly visible to human eyes. 23. The adding step, using a plurality of patterns having different frequency components according to the predetermined information,
21. The image processing method according to claim 20, wherein the predetermined information is added by performing a quantization process on the image signal. 24. The method according to claim 2, wherein the plurality of patterns are composed of first and second dither patterns in which principal component vectors of the covariance of the frequency components are orthogonal to each other.
3. The image processing method according to 3. 25. The image processing method according to claim 20, wherein the predetermined information is information unique to the device. 26. The image processing method according to claim 20, wherein the image signal is yellow. 27. The image processing method according to claim 20, wherein the predetermined information is added to the image signal according to a generated random number. 28. The image processing method according to claim 23, wherein the plurality of patterns are used according to bits of the predetermined information. 29. A method comprising: calculating a frequency component from a quantized image signal; and extracting the added predetermined information based on the calculated frequency component. Image processing method. 30. The image processing apparatus according to claim 29, wherein the predetermined information is added by performing a quantization process on the image signal using a plurality of patterns having different frequency components. Method. 31. The plurality of patterns are formed of first and second dither patterns in which principal component vectors of the covariance of the frequency components are orthogonal to each other.
0. The image processing method according to item 1. 32. The image processing method according to claim 30, wherein the predetermined information is extracted based on a frequency component calculated in the calculation step and a frequency component obtained from the plurality of patterns. 33. The method according to claim 32, further comprising: determining the predetermined principal component vector based on the covariance principal component vector of the frequency component calculated in the calculating step and the covariance principal component vector of the frequency component obtained from the first and second dither patterns. 32. The image processing method according to claim 31, wherein the information is extracted. 34. The extracting step includes: calculating a principal component vector of a covariance of the calculated frequency component and a principal component vector of a covariance of the frequency component obtained from the first and second dither patterns. The image processing method according to claim 33, wherein the predetermined information is extracted based on a similarity of the inner product. 35. The image processing method according to claim 29, wherein the predetermined information is information unique to the device. 36. The image processing method according to claim 29, wherein the image signal is yellow. 37. The image processing method according to claim 29, wherein the predetermined information is added to the image signal according to a generated random number. 38. The image processing method according to claim 30, wherein the plurality of patterns are used according to bits of the predetermined information. 39. A code for adding predetermined information to an image represented by the image signal as a frequency component obtained from the quantized image signal, and an image signal to which the predetermined information is added is output to the outside. And a computer readable storage medium having a code. 40. A computer comprising: a code for calculating a frequency component from a quantized image signal; and a code for extracting added predetermined information based on the calculated frequency component. A readable storage medium.