JP2003060887A - Image processor and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processor and an image processing method by which extraction precision and extraction time are optimized when prescribed information is extracted from the image. SOLUTION: The image processor is provided with an image inputting means for reading records with formed image where prescribed information is buried and inputting the image corresponding to the records, related information input means for inputting related information concerning an image forming situation with respect to the records, an extracting means for extracting prescribed information from the inputted image in response to a prescribed extracting method and a changeover means for changing-over the extracting method by the extracting means based on the inputted related information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and an image processing method, and in particular, in image information, information different from the image information, such as voice information or text document information,
The present invention relates to image processing for embedding in a visually inconspicuous manner by using various information relating to an image, completely different image information, and the like as additional information.

[0002]

2. Description of the Related Art Conventionally, much research has been conducted on multiplexing other information related to an image in the image information.
In recent years, it has been called digital watermarking technology, and in image information such as photographs and paintings, the author's name and additional information such as permission / prohibition of use are multiplexed so that it is difficult to visually distinguish, and the network such as the Internet is used. The technology distributed through is being standardized.

As another field of application, as the image output devices such as copying machines and printers have become higher in image quality, they are output on paper for the purpose of preventing unauthorized forgery of banknotes, stamps, securities and the like. There is a technique of embedding additional information in an image in order to specify the output device and its machine number from the image.

For example, Japanese Patent Laid-Open No. 7-123244 proposes a technique for multiplexing information by embedding additional information in the high frequency regions of the color difference component and the saturation component, which have low visual sensitivity.

However, the above-mentioned technique has the following problems. FIG. 14 is a diagram showing the embedding of general additional information in the digital watermark technique. The image information A and the additional information B are multiplexed via the adder 1401 and changed into multiplexed information C. FIG. 14 shows an example in which additional information is multiplexed in the real space area of image information. If it is possible to distribute this multiplexed information C without performing image processing such as various filtering or encoding such as lossy compression, it is possible to decode the additional information B from the multiplexed information C even with the conventional technology. It's easy. If the image information distributed on the Internet has some noise resistance, it can be decoded even through a digital filter for improving image quality such as edge enhancement and smoothing.

However, it is now assumed that the multiplexed image is printed by an output device such as a printer and the additional information is extracted from the printed matter. Moreover, it is assumed that the printer to be used has a printer output of only two to several gradations per single color. In recent years, inkjet printers have been put on the market, which have ink with a low dye concentration or can control the output dot diameter in a variable manner to express several gradations per single color. The gradation property of a photographic image cannot be expressed unless is used.

That is, under the above-mentioned assumption that the multiplexing method using the digital watermark technique of FIG. 14 is output to the printer, the multiplexed information C is quantized as D by the pseudo gradation processing 1501, as shown in FIG. Information, and then printed on paper at printer output 1502,
The information on the paper (printed matter), which is very deteriorated, changes. Therefore, decoding the additional information from the information on the paper for the purpose of preventing the forgery described above means that the additional information B is decoded from the on-paper information E after the series of processing in FIG. The amount of change in information due to both the processes 1501 and 1502 is very large, and it is very difficult to multiplex additional information so that it cannot be visually discriminated and to correctly decode the multiplexed additional information from the paper. become.

Further, FIG. 16 shows an example of a conventional digital watermarking technique in which image information is converted into a frequency domain using Fourier transform or the like and then combined into a high frequency domain or the like, instead of the real space domain. In FIG. 16, the image information is transformed into the frequency domain by the orthogonal transformation processing 1601, and the adder 1602 adds the additional information to a specific frequency that is difficult to be visually discriminated. After being returned to the real space area again by the 1603 inverse orthogonal transform processing, it corresponds to passing through a filter that undergoes large changes such as pseudo gradation processing and printer output, as in the example of FIG.

FIG. 17 shows a procedure for separating the additional information from the paper. That is, the information of the printed matter is input through the image reading device 1701 such as a scanner. Since the input information is an image in which gradation is expressed by pseudo gradation processing, restoration processing 1702 which is inverse pseudo gradation processing is performed. The restoration process generally uses an LPF (low-pass filter). Information after restoration 1
After the orthogonal transform processing by 703, in the separation processing of 1704, the embedded additional information is separated from the power of the specific frequency.

As is apparent from FIGS. 16 and 17, it is understood that a large number of complicated processing steps are passed from the multiplexing of the additional information to the separation thereof. In the case of a color image, a color conversion process for converting into a color peculiar to the printer is included in this series of processing steps. In order to achieve good separation even in such complicated processing steps,
You have to put in a very strong signal. It is difficult to insert a signal with high tolerance while maintaining good image quality. In addition, the large number of processing steps and the complexity make the processing time required for multiplexing and separation very long.

Further, in the above-mentioned Japanese Patent Laid-Open No. 7-123244, the information is added to the high frequency region. However, when the error diffusion method is implemented in the pseudo gradation process in the subsequent stage, a high-pass filter peculiar to the error diffusion method is used. Due to the characteristic (1), the band of the additional information is buried in the band of the texture generated by the error diffusion, and there is a possibility that the decoding may fail. Further, a highly accurate scanner device is required for decoding.

That is, it is understood that the method of FIGS. 15 and 16 is not suitable when the pseudo gradation processing is premised.
In other words, a method of multiplexing additional information that makes the most of the characteristics of pseudo gradation processing is required.

As an example in which the multiplexing of the additional information and the redundancy of the pseudo gradation processing are linked, as a special registration 2640939 and a special registration 27778.
There is 00.

In the former method, when binarizing by the systematic dither method, data is mixed in the image signal by selecting one of the dither matrices representing the same gradation.

However, in the systematic dither method, high resolution
Moreover, unless it is a printer with excellent mechanical accuracy,
It is difficult to output photographic-quality high quality images. This is because a slight deviation in mechanical precision occurs as low-frequency noise such as horizontal stripes and is easily visible on paper. Further, when the dither matrix is changed periodically, the band of the specific frequency generated by the regularly arranged dither is disturbed,
The image quality is adversely affected. Further, the gradation expression capability greatly differs depending on the type of dither matrix. Particularly on paper, since the change in area ratio due to dot overlap and the like differs depending on the dither matrix, it is possible to cause a change in density even by switching the dither matrix even in a region where the density is uniform on the signal.

Further, in the decoding method for estimating what kind of dither matrix is binarized in the state where the pixel value of the image information which is the original signal is unknown to the decoding (separation) side,
There is a great possibility that the wrong decoding will be done.

The latter is a method of multiplexing the additional information by the arrangement using the color dither pattern method. With this method, similarly to the former method, deterioration of image quality cannot be avoided by switching. Further, as compared with the former, a larger amount of additional information can be multiplexed, but a change in color appearance is brought about by changing the arrangement of color components, and the image quality is deteriorated particularly in a flat portion. Further, it is expected that decoding on paper will become more difficult.

In any case, both of the methods of changing the dither matrix have a problem that the image quality is largely deteriorated but the decoding is difficult.

Therefore, the applicant of the present invention first uses a texture generated by the error diffusion method and artificially creates a combination of quantized values that cannot be generated by a normal pseudo gradation process. The method of embedding is proposed.

In this method, the shape of the texture is only slightly changed microscopically, and therefore the image quality is not visually deteriorated. Further, if the method of changing the quantization threshold of the error diffusion method is used, the density value of the area gradation can be visually maintained, so that the multiplexing of different signals can be realized very easily.

However, according to the above-mentioned proposal, the decoding side must determine whether or not the texture is artificial. In the printed matter output on the paper, the texture may not be reproduced well due to the deviation from the desired landing point position such as the dot deviation.

In the case of a color image, the method of multiplexing to the color component having the least visual sensitivity is the mainstream.
The determination of the texture in the real space area is easily affected by other color components, which makes it difficult to separate the multiplexed information.

Further, in order to solve the above-mentioned problems, the present applicant amplitude-modulates the quantization threshold value itself of the error diffusion method with a predetermined periodicity, and a plurality of types of the periodicity of this threshold value modulation are used for each region. We proposed a method to control the probability of occurrence of quantized values in pseudo grayscale processing by controlling, and to embed a code based on this periodicity. In this method, as compared with the method of determining the position or shape of the texture described above, the relative power information in a plurality of predetermined frequency bands becomes an important decoding factor rather than the phase information forming the code. Good decoding can be realized even on paper.

[0024]

However, the above-mentioned proposal has the following problems.

That is, when considering a decoding means for separating the additional information from the printed matter, the deterioration of the printed matter due to a change with time becomes a serious problem. If it is an electronic file,
Due to the longevity of digital data, it is not necessary to consider such deterioration factors at all, but when printing on printed matter, especially on paper with an inkjet printer, immediately after printing, days after printing, months after printing, After a year, fading or discoloration occurs due to the characteristics of the ink and the recorded printing medium and the robustness, and the degree of the change also changes.

Up to now, since the decoding method is independent and the printing situation cannot be understood, the same decoding method must be used for the printed matter immediately after printing and the printed matter after fading several years later. There was no way. Further, since there is no means for knowing not only the date and time when the printed matter was created but also the environment such as temperature and humidity at the time of creation, the same decoding method had to be used for printed matter printed in any environment.

That is, a decoding system which can realize the optimum design of the detection accuracy in decoding and the decoding processing time has not been proposed.

The present invention has been made in order to solve the above problems, and an image processing apparatus and an image processing which can realize optimization of extraction accuracy and extraction time when extracting predetermined information from an image. The purpose is to provide a method.

[0029]

In order to achieve the above object, an image processing apparatus of the present invention reads a recorded matter on which an image in which predetermined information is embedded is imaged and forms an image corresponding to the recorded matter. Image input means for inputting, related information inputting means for inputting related information relating to the image formation state on the recorded matter, extracting means for extracting the predetermined information from the input image according to a predetermined extracting method, and the inputting Switching means for switching the extraction method by the extraction means based on the related information thus obtained.

Further, the image processing method of the present invention comprises an image input step of reading a recorded matter on which an image in which predetermined information is embedded is formed and inputting an image corresponding to the recorded matter, and an image for the recorded matter. A related information inputting step of inputting related information relating to the formation state; an extraction step of extracting the predetermined information from the input image according to a predetermined extraction method;
And a switching step of switching the extraction method in the extraction step based on the input related information.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings. It is efficient that the image processing apparatus according to the present embodiment is built in mainly as printer driver software in a computer that creates image information to be output to the printer engine, or as application software. It is also effective to incorporate it as hardware and software in the printer body or the like.

(First Embodiment) FIG. 1 is a block diagram showing the arrangement of an image processing system according to the first embodiment.

Reference numerals 100, 101, and 102 denote input terminals, in which multi-tone image information is input from 100, and necessary additional information to be embedded in the image information is input from 101. This additional information is information different from the image information input through the input terminal 100, such as voice information, text document information, copyright relating to the image input through the input terminal 100, shooting date, shooting location, and shooting. Various applications are conceivable such as various information of the person or the like or completely different image information.

From 102, information relating to the date and time when a printed matter is created is input from the printer. In the present embodiment, in addition to the above-mentioned additional information, the print date and time is embedded in the image information as header information. The printing date and time may be input by a user with a keyboard, a mouse, or the like, or may be a date and time in a clock managed on a connected computer or other system.

Reference numeral 103 denotes an embedded information multiplexing device, which embeds date and time information and additional information (hereinafter, these two types are collectively referred to as embedded information) in the image information so that it is difficult to discriminate visually. Is. This embedded information multiplexing device 103 multiplexes embedded information and
It also controls the quantization of input multi-tone image information.

Reference numeral 104 denotes a printer, and the printer engine outputs the information created by the embedded information multiplexing apparatus 103. The printer is assumed to be a printer that realizes gradation expression by using pseudo gradation processing, such as an inkjet printer or a laser printer.

The output printed matter is read by the scanner 105 to read the information on the printed matter, and the embedded information separating device 106 separates (extracts) the embedded information embedded in the printed matter and outputs it to the output terminal 107. Output.

FIG. 2 shows an embedded information multiplexing device 1 of FIG.
It is a block diagram which shows the structure of 03.

Reference numeral 200 denotes an error diffusion processing unit, which converts the input image information into a quantization level smaller than the number of input gradations by performing pseudo gradation processing using an error diffusion method, and converts the quantization of a plurality of pixels. The gradation value is expressed in the area by the conversion value. Details of the error diffusion processing will be described later.

Reference numeral 201 denotes a blocking unit, which divides the input image information into predetermined area units. This blocking may be rectangular or may be divided into areas other than rectangular.

Reference numeral 202 denotes a quantization condition control unit, which changes and controls the quantization condition in units of regions blocked by the blocking unit 201. The quantization condition control unit 202 controls the quantization condition on a block-by-block basis based on the embedded information input at the input terminal 101.

210 is a CPU 211, a ROM 212,
The control unit includes a RAM 213 and the like. CPU211
Controls the operation and processing of the above-described components according to the control program stored in the ROM 212. RA
The M213 is used as a work area of the CPU 211.

FIG. 3 is a block diagram showing details of the error diffusion processing section 200. For general error diffusion processing, see R.
Floyd & L. Steinberg: “An Adaptive Alogorithm for
Spatial Grayscale ”, SID Symposium Digest of Paper
Details are described in pp.36-37 (1975). Now, an error diffusion process in which the quantized value is binary will be described as an example.
The quantized value is not limited to binary, but may be multi-valued, for example, ternary or quaternary.

Reference numeral 300 denotes an adder, which adds the target pixel value of the input image information and the distributed quantization error of the already binarized peripheral pixels. The comparison unit 301 compares the quantization threshold value from the quantization condition control unit 202 and the addition result in which the error is added, and if it is larger than a predetermined threshold value, "1" is set, and otherwise, "0" is set. Output. For example, 8
When expressing the gradation of a pixel with bit precision, it is general to express it with the maximum value "255" and the minimum value "0". Now, it is assumed that dots (ink, toner, etc.) are printed on the paper when the quantized value is "1".

Reference numeral 302 denotes a subtracter, which calculates an error between the quantization result and the above addition result, and the error distribution calculation unit 303.
Based on, the error is distributed to the peripheral pixels to be subjected to the quantization process in the future. As the error distribution ratio, an error distribution table 304 that is experimentally set based on the relative distance to the target pixel is owned in advance, and the error is distributed based on the distribution ratio written in the distribution table.

The distribution table 304 in FIG. 3 shows a distribution table for four surrounding pixels, but it is not limited to this.

Next, the entire operation procedure including the quantization condition control unit 202 will be described with reference to the flowchart of FIG. Now, an example in which the quantized value is binary will be described.
The quantized value is not limited to binary, but may be multi-valued, for example, ternary or quaternary.

S401 shows the initialization of the variable i. Variable i
Is a variable that counts vertical addresses.

S402 shows the initialization of the variable j. The variable j is a variable for counting addresses in the horizontal direction.

Subsequently, step S403 is a determination process based on the address values of i and j, i, j which is the current processing address.
It is determined whether or not the coordinates of belong to the area where the multiplexing process should be executed.

The multiplexing area will be described with reference to FIG.
FIG. 5 shows one image image in which the number of horizontal pixels is WIDTH and the number of vertical pixels is HEIGHT.

Now, assume that embedded information is multiplexed in this image. The upper left of the image is used as the origin, and blocks are formed with N horizontal pixels and M vertical pixels. In this embodiment, the block is formed with the origin as the reference point, but a point distant from the origin may be set as the reference point. If the maximum amount of information is to be multiplexed in this image, N ×
The blocks of M are arranged from the reference point. That is, assuming that the number of blocks that can be arranged in the horizontal direction is W and the number of blocks that can be arranged in the vertical direction is H, the following relationship is established. W = INT (WIDTH / N) ... Equation 1 H = INT (HEIGHT / M) ... Equation 2 However, INT () shows the integer part in ().

The number of surplus pixels that cannot be divided in the equations (1) and (2) corresponds to the end when a plurality of N × M blocks are arranged, and is outside the code multiplexing area.

In FIG. 4, if it is determined in S403 that the pixel of interest currently being processed is outside the multiplexing area, S40 is executed.
At 4, the quantization condition C is set.

On the other hand, when it is determined that the information is within the multiplexing area, the embedded information to be multiplexed is read. For ease of explanation, it is assumed that the embedded information is represented by each 1 bit using an array called code []. For example, assuming that the print date / time related information is 32 bits and the additional information is 200 bits, the embedded information is 232 bits obtained by adding two types, and the array code [] is code [0] to code [231]. Up to this, each one bit is stored.

In S405, the information in the array code [] is substituted for the variable bit as follows. bit = code [INT (i / M) × W + INT (j / N)] Equation 3 Next, it is determined whether the variable bit substituted in S406 is “1”. As described above, since the information in the array code [] is stored for each one bit, the value of the variable bit also indicates either "0" or "1".

If it is determined to be "0" in S406, the quantization condition A is set in S407, and if it is determined to be "1", the quantization condition B is set in S408.

Subsequently, in S409, a quantization process is performed based on the set quantization condition. This quantization processing corresponds to the error diffusion method described in FIG.

Subsequently, in S410, the horizontal direction variable j is counted up, and in S411, it is the number of horizontal pixels of the image.
It is determined whether or not it is less than WIDTH, and the above processing is repeated until the number of processed pixels reaches WIDTH. In addition, the horizontal processing is WI
When the number of DTH pixels is completed, the vertical direction variable i is determined in S412.
Is counted up, and in S413, it is determined whether the number of pixels is less than HEIGHT which is the vertical pixel number of the image.
The above-mentioned processing is repeated until. With the above operation procedure, it becomes possible to change the quantization condition for each block composed of N × M pixels.

Next, examples of the quantization conditions A, B and C will be described.

Although there are various factors for the quantization condition in the error diffusion method, the quantization condition is the quantization threshold in this embodiment. Since the use of the quantization condition C is outside the multiplexing area, any quantization threshold may be used. As described above, when one pixel is represented by a gradation of 8 bits and the quantization level is binary, the maximum value “255” and the minimum value “0” are the quantization representative value. However, it becomes an intermediate value of "1".
In many cases, 28 "is set as the quantization threshold. That is, in the quantization condition C, the quantization threshold is fixed to" 128 ".

Since the use of the quantizing condition A and the quantizing condition B is a block in the multiplexing area, it is necessary to cause a difference in image quality due to a difference in the quantizing condition. However, the difference in image quality must be expressed so that it is difficult to distinguish visually and can be easily identified from the paper.

FIG. 6 is an example showing the quantization conditions A and B. FIG. 6A is a diagram showing a cycle of change of the quantization threshold value under the quantization condition A. 1 square in the figure
Assuming pixels, the white cells have a fixed threshold and the gray cells have a variable threshold.

That is, in the example of FIG. 6A, a matrix of 8 horizontal pixels and 4 vertical pixels is assembled, and the threshold value of only the gray threshold value is set as the threshold value.

Similarly, FIG. 6B is a diagram showing the cycle of change of the quantization threshold value under the quantization condition B. Figure 6
In the example of (b), unlike the case of FIG. 6A, a matrix of 4 pixels in the horizontal direction and 8 pixels in the vertical direction is combined, and only the threshold value of the gray square is set as the threshold value.

Now, as described above, when one pixel has a gradation value of 8 bits, as an example, the fixed threshold value is "12".
8 "and the protruding threshold value is set to" 48. "When the quantization threshold value becomes low, the quantized value of the pixel of interest easily becomes" 1 "(quantized representative value" 255 "), that is, FIG.
In both (a) and (b), the quantized value “1” is likely to occur in the arrangement of gray cells in the figure. In other words, N × M
For each block of pixels, a block in which dots are generated in the arrangement of gray cells in FIG. 6A and a block in which dots are generated in the arrangement of gray cells in FIG. 6B are mixed. Naturally, in the same block of N × M pixels, as shown in FIG.
The matrix of (a) or FIG. 6 (b) is repeated.

A slight change in the quantization threshold value in the error diffusion method does not significantly affect the image quality. In the systematic dither method, the image quality of gradation expression greatly depends on the dither pattern used. However, in the error diffusion method in which the quantization threshold value is regularly changed as described above, since the gradation expression that determines the image quality is the error diffusion method, the dot arrangement may be slightly changed or the texture may be changed. For example, the occurrence will change, and the image quality of gradation expression will not be affected.

Even if the quantization threshold changes,
Since the error, which is the difference between the signal value and the quantized value, is diffused to the surrounding pixels, the input signal value is stored macroscopically. That is, the redundancy of dot arrangement and texture generation in the error diffusion method is very large.

Further, in the above-mentioned example, the quantizing condition A is simply switched when the value of the variable bit is "0", and the quantizing condition B is switched when the value of the variable bit is "1", but the present invention is not limited to this. The variable bit can also be expressed by a combination of quantization conditions. For example, as shown in FIG. 7, N × M
Divide the pixel block into four smaller blocks
It is possible to make a difference by quantizing the arrangement of FIG. 7A when the bit value is “0” and using the arrangement of FIG. 7A when the bit value is “1”.

Next, the embedded information separating device 106 will be described.

FIG. 8 is a block diagram showing the structure of the embedded information separation device 106.

Reference numeral 800 denotes an input terminal to which the image information read by the scanner is input. The resolution of the scanner used is preferably equal to or higher than the resolution of the printer that creates the printed matter. As a matter of course, in order to accurately read the dot information of dots on the printed matter, the resolution on the scanner side is more than double that on the printer side, due to the sampling theorem. However, if they are equal to or more than equal, it is possible to determine that dots are scattered to some extent even if they are not accurate.

In the present embodiment, it is assumed that the printer resolution and the scanner resolution are the same in order to facilitate the explanation.

Reference numeral 801 denotes a printed matter creation related information decoding unit, which first decodes the printing date and time information, which is the header information, of the embedded additional information. It is preferable that the printed matter creation related information decoding unit 801 uses an additional information decoding unit B described later, but the present invention is not limited to this. First, decoding is performed from the header information.

Reference numeral 802 denotes a selection unit, which calculates the following variable D from the decoded print date / time information. D = (decoding date / time) − (printing date / time) Equation 4 That is, the variable D is for calculating how much time has passed since the printed matter was created. In this case, the decryption date and time may be input by the user with the keyboard or the mouse, or may be the date and time in the clock managed on the connected computer and other systems, like the print date and time. .

Reference numerals 803 and 804 denote the additional information decoding unit A and the additional information decoding unit B, respectively, one of which is selected based on the value of D calculated by the selection unit 802.

Reference numeral 805 denotes a switch, and the following selections are made. 1) In the case of D <TH: ... Select the additional information decoding unit A 2) In other cases: Select the additional information decoding unit B Here, TH is a threshold value that is experimentally and empirically obtained in advance. .
That is, when it is determined that the date has not been printed too much, the additional information decoding unit A is selected, and the decoding unit B is selected in other cases.

FIG. 9 is a block diagram showing the structure of the decoding unit A.

Reference numeral 901 denotes a blocking unit, which blocks in units of P × Q pixels. This block must be smaller than the N × M pixels that were blocked when multiplexing. That is, the relation of P ≦ N and Q ≦ M ...

Further, the block formation in P × Q pixel units is as follows.
Blocking is performed by skipping at regular intervals. That is, it is divided into blocks so that one block of P × Q pixel units is included in a region assumed to be a block of N × M pixels at the time of multiplexing. The number of skip pixels is basically N horizontal pixels and M vertical pixels.

Reference numerals 902 and 903 denote spatial filters A and B having different characteristics, and reference numeral 904 denotes a digital filtering unit for calculating the sum of products with peripheral pixels. Each coefficient of this spatial filter is created by adapting to the cycle of the variation threshold of the quantization condition at the time of multiplexing.

Now, it is assumed that the additional information is multiplexed by changing the quantization condition in the embedded information multiplexer 106 by using the two types of periodicity shown in FIGS. 6 (a) and 6 (b).

Examples of the spatial filter A 902 and the spatial filter B 903 used in the embedded information separating apparatus 106 at that time are shown in FIGS. 10 (a) and 10 (b). 5x in the figure
The central portion of the five pixels becomes the target pixel, and the other 24 pixels become the peripheral pixels. In the figure, the blank pixels represent that the filter coefficient is "0". As is clear from the figure, FIGS. 10A and 10B are edge emphasis filters. Moreover, the directionality of the edge to be emphasized and the directionality of the variation threshold value when multiplexed are the same. That is, FIG. 10 (a) corresponds to FIG. 6 (a), and FIG.
Are created so as to correspond to FIG.

Reference numeral 905 denotes a feature quantity detection unit, which is based on the converted value after filtering from the filtering unit 904 by the spatial filter A 902 and the spatial filter B 903.
Detect some feature amount. The following can be considered as examples of the detected feature amount. 1. Maximum value of conversion value in block after digital filter 2. 2. Difference between the maximum value and the minimum value of the converted values in the block after digital filtering Variance value of conversion value in block after digital filter In the present embodiment, the variance value shown in the above 3 is used as a feature amount.

Reference numeral 906 denotes a judging unit, which compares the respective dispersion values and judges that the one having the larger dispersion value is the code. That is, if the variance value of the filtering by the spatial filter A is large, it is assumed that it was quantized by the quantization condition A at the time of printing, and conversely, if the variance value of the filtering by the spatial filter B is large, the quantization condition B at the time of printing is determined.
It is supposed to be quantized by.

The quantization condition is the sign of the additional information (bi in equation 3).
Since it is linked to t), the fact that the quantization condition can be identified corresponds to the fact that the multiplexed code can be specified. That is, when the quantization condition A is estimated,
When it is estimated that t = 0 and the quantization condition B, it can be determined that bit = 1.

FIG. 11 is a block diagram showing the additional information decoding unit B.

FIG. 1101 shows the blocking unit, and FIG.
The same as 902 of No. 902 of FIG.

Reference numeral 1102 denotes an orthogonal transform unit, which orthogonally transforms the P × Q pixels in blocks. However, when performing a two-dimensional orthogonal transformation, it is necessary to form a block with a square block of Q = P. In this embodiment, DCT (discrete cosine transform) is taken as an example.

Two-dimensional DC of a block consisting of P × P pixels
The conversion coefficient of T is, however, given by C (x) = 1 / √2 (x = 0), C (x) = 1 (x ≠ 0) ...

Reference numeral 1103 denotes a class classification unit, which classifies each band of orthogonal transform coefficients.

FIG. 12 shows an example of class classification when P = Q = 16. FIG. 12 shows the orthogonal transform coefficient F (u, v) in one block, where the upper left is the DC component and the remaining 2
55 components become AC components.

Now, class A centering on F (4,8) and F
Create two classes of class B centered on (8,4). Two
Classes are indicated by bold lines in the figure. This class classification unit 1103
Does not need to classify all 256 components, but only needs to classify them into a plurality of classes centered on a desired component.
The required number of classes corresponds to the number of conditions under which the quantization control is performed at the time of multiplexing. That is, the number of classes does not become larger than the number of conditions under quantization control.

Reference numeral 1104 denotes a power comparison unit, which compares the total power of each class. In order to speed up the calculation, the absolute value of the generated conversion coefficient may be used as a substitute for electric power. The signal of the additional information is determined by comparing the total power of each class.

Now, an example in which the quantization conditions A and B of FIGS. 6A and 6B are applied at the time of multiplexing will be described. As described above, in the quantization using the quantization conditions A and B, a texture in which dots are arranged in diagonal directions with different angles is likely to occur. That is, when the block quantized under the quantization condition A is subjected to the orthogonal transformation process, the class A in FIG.
Generates a large amount of power.

On the other hand, in the block quantized under the quantization condition B, when orthogonal transformation processing is performed, the class B in FIG.
Generates a large amount of power.

That is, by comparing the magnitude relationships between the powers of the class A and the class B relatively, the quantization condition at the time of multiplexing the corresponding block is either the quantization condition A or the quantization condition B. Can judge. Since the quantization condition is linked to the code of the additional information (bit of Expression 3), the fact that the quantization condition can be identified means that the multiplexed code can be specified.

In the example of the flow chart shown in FIG.
Since t = 0 is set as the quantization condition A and bit = 1 is set as the quantization condition B, when the power of class A is larger,
= 0, when the power of class B is higher, bit = 1
Can be judged.

Although two types of decoding units have been described above, switching of the decoding units of this embodiment is necessary for optimum design of the decoding detection rate and the decoding time.

That is, it is judged that the discoloration or fading has not progressed with respect to the printed matter which has not been printed for a long time, and the decoding section A having a high decoding time decodes it. On the other hand, for a long time after printing, it is determined that discoloration and fading have progressed, and the decoding detection rate is prioritized over the decoding time, and a more accurate decoding method is used.

As described above, by using the elapsed time from the printing date and time as the evaluation factor, discoloration and fading can be predicted, and a more optimal decoding unit can be selected.

In the present embodiment, the decoding unit has been described as two kinds of A and B, but naturally more decoding units may be used. Also, the decoding unit is not limited to this.

It is also possible to use the same decoding unit and change only the detection accuracy. That is, iterative decoding with high redundancy is effective in a decoding unit that requires higher accuracy.

For example, in the above-described method using the orthogonal transformation by P × Q pixels (decoding section B), the block of P × Q pixels is spatially shifted by several pixels to perform the orthogonal transformation a plurality of times, and the class of a plurality of times A method of improving the accuracy of judgment through comparison can be considered. At this time, it is also an effective method to use the elapsed time from the printing date and time as an evaluation factor and to control the number of repetitions to gradually increase with the elapsed time.

Of course, if the determination is performed using a plurality of orthogonal transformations, the decoding accuracy will be improved, but the processing time will be extra. The optimization is preferably designed empirically.

Further, a method of predicting the degree of fading and correcting it is also conceivable. That is, since the density of the printed matter decreases due to fading, the elapsed time from the printing date and time is used as an evaluation factor,
A decoding method including empirical correction values and density correction can also be considered.

At this time, a density correction curve depending on the elapsed time is prepared in advance as a plurality of types of tables and is corrected at the time of decoding.

Further, when the degree of fading differs depending on the color material (ink), a method of changing the color used for the decoding process can be considered. For example, if magenta tends to fade more easily than other colors (cyan, yellow, black), the elapsed time is used as an evaluation factor and the degree of decoding influence from the G component, which is the complementary color of magenta, of RGB is determined. It is also effective to change.

That is, when the elapsed time has not elapsed, the determination is made mainly on the decoding of the G component, and the influence of the decoding of the G component is reduced as the elapsed time elapses.

As described above, according to the first embodiment, the extraction method at the time of extraction is switched by switching the extraction method for extracting the predetermined information embedded in the image based on the elapsed time from the print date and time. The accuracy and the extraction time can be optimized.

(Second Embodiment) FIG. 13 shows the arrangement of an image processing system according to the second embodiment.

Since FIG. 13 is partially different from the configuration shown in FIG. 1, only different points will be described. That is, in the present embodiment, the printing environment information is embedded as header information from the terminal 1301 instead of the printing date and time information of the first embodiment described above.

The printing environment information may be temperature, humidity, atmospheric pressure (altitude), etc. when the printed matter is prepared, but in the present embodiment, only the temperature is targeted. The temperature at the time of printing may be input by a user with a keyboard, a mouse, or the like, or may be a signal from a temperature detection unit built in the printer. For example, if the temperature information is 16 bits and the additional information is 200 bits, a total of 216 bits of embedded information will be multiplexed.

The decoding unit is the same as in the first embodiment described above. In this embodiment, the variables of the first embodiment described above are used.
Instead of D, temperature information is used as a variable T to switch decoding units or control decoding accuracy.

The temperature at the time of printing becomes a factor for changing the dot diameter for an ink jet printer or an electrophotographic printer. That is, a dot printed at a high temperature has a large dot diameter, which may make decoding more difficult than at a normal temperature. On the contrary, when printed at a low temperature, the dot diameter becomes smaller, and similarly, there is a possibility that the decoding becomes more difficult than that at a normal temperature. Therefore, it is necessary to control the variable T so as to improve the decoding accuracy as the temperature changes to a high temperature or a low temperature around the normal temperature. As described above, the improvement of the decoding accuracy is a trade-off with the decoding time, so it is necessary to experimentally set the optimum method.

Although the printing environment has been described by taking the temperature as an example, the same control can be realized with the other environment information described above.

A method is also conceivable in which the print date / time information and various print environment information are combined into a header and embedded information is multiplexed.

The multiplexing method and the additional information separating method are not limited. In any multiplexing method or separation method, a configuration in which the separation method is controlled based on the elapsed time from the printing date or time or the environmental information at the time of printing is effective.

As described above, according to the second embodiment, by changing the extraction method for extracting the predetermined information embedded in the image based on the environmental information at the time of printing, the extraction accuracy at the time of extraction, The extraction time can be optimized.

(Other Embodiments) Further, even when 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 device (a device composed of one device). For example, a copier,
It may be applied to a facsimile machine).

Further, an object of the present invention is to supply a storage medium (or recording medium) recording a program code of software for realizing the functions of the above-described embodiments to a system or apparatus, and to supply the computer of the system or apparatus. (Or CPU or MPU) reads and executes the program code stored in the storage medium,
It goes without saying that it will be achieved. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.
Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also based on the instruction of the program code,
An operating system (OS) running on the computer does some or all of the actual processing,
It goes without saying that the processing includes the case where the functions of the above-described embodiments are realized.

Further, after the program code read from the storage medium is written in the memory provided in the function expansion card inserted into the computer or the function expansion unit connected to the computer, based on the instruction of the program code, It goes without saying that a case where the CPU included in the function expansion card or the function expansion unit performs a part or all of the actual processing and the processing realizes the functions of the above-described embodiments is also included.

[0123]

As described above, according to the present invention,
To optimize the extraction accuracy and extraction time at the time of extraction by switching the extraction method that extracts the predetermined information embedded in the image based on the elapsed time from the printing date and time or the environmental information at the time of printing You can

Further, according to the present invention, since the additional information can be easily multiplexed with the image information, it is possible to provide a service or application for embedding voice information or secret information in the image information. In addition, it is possible to prevent illegal forgery of bills, stamps, securities, and the like, and prevent copyright infringement of image information.

[Brief description of drawings]

FIG. 1 is a block diagram of essential parts showing an image processing system according to an embodiment.

FIG. 2 is a block diagram of essential parts showing the embedded information multiplexing apparatus of FIG.

3 is a principal block diagram showing an error diffusion processing unit of FIG.

FIG. 4 is a flowchart showing an operation procedure of a multiplexing process including a quantization control unit.

FIG. 5: Example of blocking

FIG. 6 shows an example of a change in quantization threshold under a quantization condition.

FIG. 7: Example of arrangement of combinations of quantization conditions

8 is a principal block diagram showing the embedded information separation device of FIG. 1. FIG.

9 is a block diagram showing a configuration of an additional information decoding unit A of FIG.

FIG. 10 is an example of a spatial filter

11 is a block diagram showing the configuration of an additional information decoding unit B of FIG.

FIG. 12 is an explanatory diagram of frequency vectors in a two-dimensional frequency domain.

FIG. 13 is a block diagram of essential parts showing an embedded information separating device according to a second embodiment.

FIG. 14 is a block diagram showing an example of conventional multiplexing.

FIG. 15 is a block diagram showing an example of conventional multiplexing.

FIG. 16 is a block diagram showing an example of conventional multiplexing.

FIG. 17 is a block diagram showing an example of separation according to a conventional method.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 1/40 H04N 1/40 Z 5C077 // H04N 7/08 7/08 Z 7/081 (72) Invention Kiyoshi Umeda 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term within Canon Co., Ltd. (reference) 2C087 AA03 AA09 AC07 AC08 BA03 BA06 BA12 BA14 BB10 5B021 AA01 LG07 LG08 5B057 AA11 BA02 BA29 BA30 CC03 CE08 CE09 CE13 CG07 CH07 CH07 CH07 CH07 CH07 CH07 CH07 CH07 CH07 CH07 CH07 CH07 CH07 CH07 CH07 CH07 CH07 CH07 CH07 CH07 CH18 5C063 AA01 AB03 AB05 AC01 AC10 CA23 CA36 DA02 DA05 DA07 DA13 DB09 5C076 AA14 AA16 BA06 5C077 LL14 NN11 PP21 PP23 PP27 PP43 PP47 PP65 PP68 PP74 PP77 PP78 PP80 PQ08 PQ20 RR08 RR11

Claims (12)

[Claims] 1. An image input unit for reading a recorded matter on which an image having predetermined information embedded therein is formed and inputting an image corresponding to the recorded matter, and related information relating to an image formation state of the recorded matter. It has a related information input means, an extraction means for extracting the predetermined information from the input image according to a predetermined extraction method, and a switching means for switching the extraction method by the extraction means based on the input related information. Image processing device. 2. The image processing apparatus according to claim 1, wherein the related information is a creation date and time when a recorded material is created. 3. The switching means estimates the elapsed time of the recorded material based on the creation date and time and the extraction date and time when the predetermined information is extracted from the recorded material, and based on the estimated elapsed time. The image processing apparatus according to claim 2, wherein the extraction method by the extraction means is switched. 4. The image processing apparatus according to claim 1, wherein the related information is recorded matter creation environment information. 5. The image processing apparatus according to claim 4, wherein the environmental information is temperature information at the time of making a printed matter. 6. The image processing apparatus according to claim 4, wherein the environmental information is humidity information at the time of making a recorded matter. 7. The image processing apparatus according to claim 4, wherein the environmental information is atmospheric pressure information at the time of creating a recorded material. 8. The switching means switches the extraction method by selecting an optimum extraction means from a plurality of extraction means each having a different extraction method and performing extraction by the selected extraction means. The image processing apparatus according to claim 1. 9. The image processing apparatus according to claim 1, wherein the switching unit switches the extraction method by switching the extraction accuracy when performing extraction by the extraction unit. 10. An image input step of reading a recorded matter on which an image in which predetermined information is embedded is formed and inputting an image corresponding to the recorded matter, and inputting relevant information on an image formation state of the recorded matter. A related information input step, an extraction step of extracting the predetermined information from the input image according to a predetermined extraction method, and a switching step of switching the extraction method by the extraction step based on the input related information. Image processing method. 11. A program for executing the image processing method according to claim 10, when the program is executed on a computer. 12. A recording medium on which the program according to claim 11 is recorded.