JP2003101760A - Image processing apparatus and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in a conventional constitution, where a same information filling method and the same information extracting method are used without taking a fact, that the image quality is not uniform over a paper and both superior printing regions and inferior printing regions exist on the paper according to a characteristic mechanical structure of a printer, into account. SOLUTION: This image processing apparatus has an input means which inputs an image, a filling means which fills the inputted image with prescribed information according to a prescribed method, an image forming means which forms the image filled with the prescribed information as an image on a recording medium, and a changeover means which changes the filling method used by the filling means according to the spatial coordinates of the recording medium.

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 Laid-Open Patent Publication 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 are visually insensitive.

However, the above-mentioned technique has the following problems. FIG. 16 is a diagram showing the embedding of general additional information of the digital watermark technique. The image information A and the additional information B are multiplexed via the adder 1601 and changed into the multiplexed information C. FIG. 16 shows an example in which additional information is multiplexed in the real space area of image information. If the multiplexed information C can be distributed without being subjected to image processing such as various kinds of filtering or encoding such as lossy compression, decoding of the additional information B from the multiplexed information C is possible even in the conventional technique. 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 watermarking technique of FIG. 16 is output to the printer, as shown in FIG. 17, the pseudo gradation processing section 1701 causes the multiplexing information C to be a quantum of D. The converted information is changed to the converted information and then printed on the paper by the printer output unit 1702, and changed to the extremely deteriorated on-paper information (printed matter) E. Therefore, decoding the additional information from the information on the paper for the purpose of preventing 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 1701 and 1702 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. 18 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. 18, the image information is transformed into the frequency domain by the orthogonal transformation processing 1801, and the adder 1802 adds the additional information to the specific frequency which is difficult to be visually discriminated. After being returned to the real space area again by the inverse orthogonal transform processing 1803, it is equivalent to passing through a filter having large changes such as a pseudo gradation processing unit and a printer output unit, as in the example of FIG.

FIG. 19 shows a process of separating the additional information from the paper. That is, the information on the printed matter is input to the scanner 190 via an image reading unit such as a scanner.
Do 1 Since the input information is an image whose gradation is expressed by the pseudo gradation processing unit, restoration processing 1902 which is an inverse pseudo gradation processing unit is performed. The restoration process generally uses an LPF (low-pass filter). After the restored information is subjected to orthogonal transform processing by 1903, separation processing 1904 separates the embedded additional information from the power of a specific frequency.

As is apparent from FIGS. 18 and 19, 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 range. 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, when the pseudo gradation process is a prerequisite,
It can be seen that the method of 8 is not suitable. 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 process are linked, there are special registration 2640939 and special registration 2777800.

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, unless the printer has a high resolution and is very excellent in mechanical accuracy, it is difficult to output a photographic-like high image quality. This is because a slight deviation in mechanical precision occurs as low-frequency noise such as horizontal stripes and is easily visible on paper. Also,
When the dither matrix is changed periodically, the band of the specific frequency generated by the regularly arranged dither is disturbed, which adversely affects the image quality.

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, on the decoding (separation) side, a decoding method that estimates which dither matrix has been binarized when the pixel value of the image information that is the original signal is unknown may cause incorrect decoding. Very big.

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.

According to this method, the shape of the texture only slightly changes microscopically, and therefore the image quality does not deteriorate visually. 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 color images, the method of multiplexing the color components with 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.

In order to solve the above-mentioned problems, the applicant of the present invention amplitude-modulates the quantization threshold value itself of the error diffusion method with a predetermined periodicity, and the periodicity of this threshold value modulation is divided into a plurality of regions. 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, relative power information in a plurality of predetermined frequency bands is a more important decoding factor than the phase information forming the code, as compared with the above-described method of determining the position and shape of the texture. Therefore, good decoding can be realized even on paper.

[0023]

However, the above-mentioned proposal has the following problems. That is, the mechanical precision may not be excellent depending on the printer that creates the printed matter.

In the case of an ink jet printer, ink is ejected and adhered to a recording medium.
Naturally, the flying ink drops often deviate from the expected landing point positions. When dots are misaligned on one line that conveys the recording paper, it becomes visually more noticeable, so recordings on the same line are thinned out.
A method of printing by scanning a plurality of times by a plurality of nozzles has become common.

On the other hand, due to the mechanical structure of the printer, in the process of conveying the recording paper, when the recording paper rushes into various rollers used for the conveyance or when the recording paper comes off the rollers, the recording during printing is performed. The image quality may be disturbed by the impact vibration of the paper. As described above, since the same line is often printed by being divided into a plurality of scans, the print disturbance also affects a plurality of lines and causes a predetermined width on the paper to deteriorate the image quality.

Further, at the left and right edges of the recording paper, the printing accuracy may be inferior to the central portion of the recording paper.

That is, the image quality is not uniform on the paper, and there are relatively good portions and poor portions due to the mechanical structure peculiar to the printer. The part with poor image quality can be considered to have a mechanical noise component superimposed on the image information.

When considering the separation of additional information from the printed matter proposed by the present applicant, decoding (extraction) may be difficult if the image quality is not uniform on the paper.
That is, even if the additional information can be easily separated in the portion with relatively good image quality, in the portion with poor image quality, the separation may fail due to the superimposed noise. .

However, in order to avoid the failure of the separation, if the whole is strongly multiplexed, the deterioration of the image quality due to the multiplexing becomes conspicuous. Also, on the decoding side, if a highly accurate decoding method is used over the entire surface of the paper in order to avoid separation failure, processing time will increase.

The present invention has been made to solve the above problems, and provides an image processing apparatus and an image processing method capable of realizing control of image quality in an information adding section and information extracting section and optimum design of extraction accuracy. The purpose is to provide.

[0031]

In order to achieve the above object, the image processing apparatus of the present invention comprises an input means for inputting an image and a predetermined embedding method for embedding predetermined information in the input image. Embedding means for embedding, image forming means for forming an image in which the predetermined information is embedded on a recording medium, and switching means for switching the embedding method by the embedding means based on the spatial coordinates of the recording medium. It is characterized by

In order to achieve the object, the image processing method of the present invention comprises an input step of inputting an image, and an embedding step of embedding predetermined information in the input image according to a predetermined embedding method. An image forming step of forming an image in which the predetermined information is embedded on a recording medium, and a switching step of switching the embedding method based on the spatial coordinates of the recording medium.

Further, in order to achieve the above object, the image image processing apparatus of the present invention has an input means for inputting an image in which predetermined information is embedded, and a predetermined information for the predetermined information from the input image. It has extraction means for extracting according to the extraction method, and switching means for switching the extraction method by the extraction means based on the spatial coordinates of the recording medium.

Further, in order to achieve the object, the image processing method of the present invention comprises an input step of inputting an image in which predetermined information is embedded, and a predetermined extraction method of the predetermined information from the input image. And an extraction step of switching the extraction method based on the spatial coordinates of the recording medium.

[0035]

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-gradation 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 page 102, in-page coordinate information indicating how an image image or a document is laid out is input within one page output from the image information. The layout within a page can be easily created by application software for freely arranging image images and documents. Of course, it is also possible to place only the image on the entire paper without including the document information such as characters in the page.

Reference numeral 103 denotes an additional information multiplexing apparatus, which is an apparatus for embedding additional information in image information so that it is difficult to visually discriminate. This additional information multiplexing device 103
Manages the multiplexing of the additional information and the quantization of the input multi-tone image information.

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

With respect to the output printed matter, the information on the printed matter is read by using the scanner 105, and the additional information separating device 10
6, the additional information embedded in the printed matter is separated and output to the output terminal 107.

FIG. 2 shows an additional information multiplexing device 103 of FIG.
3 is a block diagram showing the configuration of FIG.

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 the error diffusion method, and 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 is 201
Change and control the quantization condition for each block area. The quantization condition control unit 202 controls the quantization condition on a block-by-block basis based on the additional information input through the input terminal 101 and the in-page coordinate information of the image information input through 102.

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 the details of the error diffusion processing section 200. A general error diffusion process is described in Reference R. Floyd & L. Steinberg: "An A
daptive Alogorithm for Sp
atial Grayscale ”, SID Symp
osium Digest of Paper pp.
36-37 (1975) for further details.

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 pixel value of interest 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-mentioned 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 of FIG. 3 shows a distribution table for four surrounding pixels, but the distribution table 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. The variable i is a variable for counting addresses in the vertical direction.

S402 shows the initialization of the variable j. The variable j is a variable for counting addresses in the horizontal direction. Both the variables i and j are relative coordinates from the start point of image information (the upper left of the image).

Subsequently, step S403 is a determination step 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 multiplexed 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 additional information is multiplexed in this image. The upper left of the image is the origin,
Blocking is performed with N pixels horizontally and M pixels vertically. 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. When multiplexing the maximum amount of information in this image, N × M blocks 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.

[0058] W = INT (WIDTH / N) ... Formula 1 H = INT (HEIGHT / M) ... Equation 2 However, INT () indicates an integer part in ().

The number of surplus pixels that cannot be divided by 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
At 4, the quantization condition C is set. On the other hand, if it is determined to be within the multiplexing area, the additional information to be multiplexed is read. Now, in order to facilitate the explanation, additional information is coded.
An array of [] is used to represent each one bit.

In S405, the variable bit substitutes the information in the array code [] as follows.

Bit = code [INT (i / M) × W + INT (j / N)] Equation 3 Subsequently, it is determined whether or not the variable bit substituted in S406 is “1”. As described above, since the information in the array code [] is stored for each 1 bit, the variable bit
The value of 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 and S410, the target pixel position being processed is evaluated, but not in relative coordinates from the image image origin, but in absolute coordinates within the page.

The in-page layout will be described with reference to FIG.

In FIG. 6, the absolute distance from the page origin is (image_j) pixels in the horizontal direction and (i) in the vertical direction.
An example of a layout in which an image image used for multiplexing is arranged at the position of the image_i) pixel is shown.
The hatched portion in the figure shows the image image.

FIG. 7 shows an example in which one page of paper output by a printer is assumed and is classified into two types: a part where printing is good and a part where printing is poor. As described above, when the recording paper comes off the various rollers during printing, or when the recording paper rushes into the various rollers during printing, the impact vibration often causes poor printing. This will differ depending on the mechanical configuration of the printer.

In FIG. 7, the print area (hatched portion) when the recording paper is removed from the roller is indicated by the inferior area,
The other areas are set as good areas. Of course,
It is preferable to classify each paper size to be used.
Also, inferior area and good ar
Instead of the two types of ea, a larger number of classifications may be made according to the image quality level. Since these classifications are unique to the printer, it is preferable to obtain them experimentally.

In the examples of FIGS. 6 and 7, there is an inferior area in the image used for multiplexing, but this determination is made in S409 and S410.

In both S409 and S410, the absolute coordinates within the page of the current pixel of interest are set (image_i +
i, image_j + j) is within a good area.

If it is determined NO in S409,
In S411, the quantization condition is changed from the quantization condition A to the quantization condition A ′, and if it is determined NO in S410, the quantization condition is changed from the quantization condition B to the quantization condition B in S412. Change to '.

Subsequently, in S413, the quantization processing is performed based on the set quantization condition. This quantization processing corresponds to the error diffusion method described in FIG.

Subsequently, in S414, the horizontal variable j is counted up, and in S415, it is determined whether or not it is less than WIDTH which is the horizontal pixel number of the image, and the processed pixel number is WIDT.
The above-mentioned processing is repeated until it becomes H. When the horizontal processing is completed by the number of WIDTH pixels, the vertical variable i is incremented in S416, and it is determined in S417 whether the number is less than HEIGHT which is the vertical pixel number of the image, and the number of processed pixels is HEIGHT. The above-mentioned processing is repeated until.

With the above operation procedure, it becomes possible to change the quantization condition for each block consisting of N × M pixels.

Next, examples of the quantization conditions A, B, C and A ', B'will be described. Although there are various factors for the quantization condition in the error diffusion method, the quantization condition is the quantization threshold value in this embodiment. The use of quantization condition C is
Since it is outside the multiplexing area, any quantization threshold value is acceptable. As described above, when one pixel is a gradation expression with 8 bits and the quantization level is binary, the maximum value is “25”.
5 "and the minimum value" 0 "are the quantization representative values, but the intermediate value" 128 "is often set as the quantization threshold value. The condition is such that the threshold value is fixed at “128”.

Since the use of the quantization condition A and the quantization condition B is a block in the multiplex area, it is necessary to cause a difference in image quality due to a difference in the quantization 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. 8 is an example showing the quantization conditions A and B. FIG. 8A 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. 8A, a matrix of 8 pixels in the horizontal direction and 4 pixels in the vertical direction is assembled, and the threshold value of only the threshold value of the gray cell is set as the threshold value.

Similarly, FIG. 8B is a diagram showing the cycle of change of the quantization threshold value under the quantization condition B. Figure 8
In the example of FIG. 8B, unlike the case of FIG. 8A, 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.

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 is set to“ 48. ”When the quantization threshold 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 occur in the arrangement of gray cells in FIG. 8A and a block in which dots occur in the rows of gray cells in FIG. 8B coexist. Naturally, in the same block of N × M pixels, as shown in FIG.
The matrix of (a) or FIG. 8 (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. This is because even if the quantization threshold changes, the error that is the difference between the signal value and the quantized value is diffused to the surrounding pixels, so that 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.

In the above example, the quantization condition A is simply switched when the value of the variable bit is "0", and the quantization condition B is switched when the value of the variable bit is "1". However, the present invention is not limited to this. It is also possible to represent the variable bit by combining the quantization conditions. For example, as shown in FIG.
The block of N × M pixels is further divided into four small blocks, and when the value of the variable bit is “0”, the arrangement of FIG. 9A is used, and when the value of the variable bit is “1”, the arrangement of FIG. 9A is used. Then, it is possible to make a difference by quantizing.

The quantizing conditions A ′ and B ′ have the same changing period as the quantizing conditions A and B. However,
The place where the quantization conditions A ′ and B ′ are used is a region where the image quality is deteriorated by the mechanical noise of the printer. For that reason,
It is necessary to apply strong multiplexing. Therefore, in order to firmly apply the multiplexing, in this embodiment, the amplitude for modulating the threshold value is set to be large. For example, in the modulation of the quantization threshold value under the quantization conditions A and B, the normal threshold value "128" is changed to "48", but the normal threshold value "128" is set in the quantization conditions A'and B '. Change and set "" to "16". As a matter of course, since the probability that a desired dot is generated increases, the separation process becomes easy, but the image quality due to the multiplexing process deteriorates. However,
Originally, in the inferior area, since the image quality is disturbed by the occurrence of mechanical noise, even if the strong multiplexing is executed, there is almost no visual effect.

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

FIG. 10 is a block diagram showing the structure of the additional information separation device 106.

Reference numeral 1000 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, the printer resolution and the scanner resolution are assumed to be the same resolution for ease of explanation.

A geometrical correction unit 1001 corrects the rotation and expansion / contraction of the printed matter read by the scanner. Various well-known methods can be considered for the geometric correction unit 1001.

Reference numeral 1002 denotes a blocking unit, which is P × Q.
Blocking is done for each pixel. 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 ... Equation 4 holds.

Further, in the block formation in P × Q pixel units, the block formation is carried out by skipping every certain fixed interval. 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 1003 and 1004 denote spatial filters A and B having different characteristics, and reference numeral 1005 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 using the two types of periodicity shown in FIGS. 8A and 8B for changing the quantization condition in the additional information multiplexer 103. Spatial filter A100 used in the separation device at that time
3 and an example of the spatial filter B1004 are shown in FIGS. 11 (a) and 11 (b). In the figure, the central portion of 5 × 5 pixels is the target pixel, and the other 24 pixels are peripheral pixels. In the figure, the blank pixels represent that the filter coefficient is "0". As is clear from the figure, FIG.
(B) is a filter for edge enhancement. 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. 11A is created so as to match FIG. 8A, and FIG. 11B is created so as to match FIG. 8B.

Reference numeral 1106 denotes a feature amount detecting unit, which detects some feature amount based on the converted value after filtering from the filtering unit 1005 by the spatial filter A1003 and the spatial filter B1004. 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 1007 denotes a judging section, which compares the respective dispersion values and judges that 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 estimated that the quantization value is 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 (b in equation 3).
Since it is linked to it, it is possible to identify the quantization condition, which means that the multiplexed code can be specified. That is, when the quantization condition A is estimated, b
If it is estimated that it = 0 and the quantization condition B, bit
It can be judged that = 1.

The example in which the multiplexing method considering the characteristics of the local image quality deterioration of the printer is realized by setting the strength of the multiplexing has been described above.
Other than the modulation amplitude of the quantization threshold value, it can be considered. For example, for a color image, there is a method of changing the ink color used for multiplexing. That is, a method of multiplexing “inferior area” by using an ink color that is strong against noise can be considered.

As described above, according to the first embodiment, the moment when the recording medium is removed from the various rollers or the recording medium is determined based on the absolute coordinates within the page, not the relative coordinates from the image image origin. , The area where the printing becomes poor, which is the printing area at the moment when it rushes into various rollers, and the area where the printing becomes good, which is the other printing area,
For areas where printing is poor, an information embedding method that emphasizes ease of extraction rather than image quality is used. For areas where printing is good, information embedding that emphasizes image quality rather than ease of extraction is used. By using, it is possible to realize the extraction precision at the time of extracting information, the optimization of the extraction time, and the optimum design of the image quality.

(Second Embodiment) FIG. 12 shows the arrangement of an image processing system according to the second embodiment. In the present embodiment, in the configuration shown in FIG. 1, the decoding (extraction) method is switched according to the absolute coordinates in the page.

In the present embodiment, the additional information multiplexing device is
Since it is assumed that the flow chart of FIG. 4 is followed, the minimum unit for switching the decoding method is the block unit.

In FIG. 12, a terminal 1200 indicates an input terminal to which the image information for one page read by the scanner is input. A geometrical correction unit 1001 corrects rotation and expansion / contraction of the printed matter read by the scanner. A block forming unit 1002 forms blocks in P × Q pixel units.

Reference numeral 1201 denotes an in-page coordinate detecting section,
By counting the coordinates of one page as the decoding process proceeds, the in-page coordinate information currently being processed is acquired.

Reference numerals 1202 and 1203 respectively denote an additional information decoding unit A and an additional information decoding unit B, which have two types of decoding units.

Reference numeral 1204 denotes a selection unit, which makes the following selections via the switch 1205 in accordance with the in-page coordinates.

1) When the processing block is good area ... The additional information decoding unit A is selected. 2) When the processing block is the inferior area ... The additional information decoding unit B is selected. 13 shows. A block surrounded by a chain line indicates the additional information decoding unit A. This additional information decoding unit A is the same as the in-block processing of the method shown in FIG.

FIG. 14 is a block diagram showing the additional information decoding unit B. Similarly, a block surrounded by a chain line indicates the additional information decoding unit B.

In the figure, reference numeral 1401 denotes an orthogonal transform unit, which orthogonally transforms the blocked P × Q pixels. 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 composed of P × P pixels
The conversion factor of T is

[Outer 1]

[0108]     However, C (x) = 1 / √2 (x = 0),           C (x) = 1 (x ≠ 0) ... Equation 5 Given in.

Reference numeral 1402 denotes a class classification section, which classifies each band of orthogonal transform coefficients.

FIG. 15 shows an example of class classification when P = Q = 16. FIG. 15 shows the orthogonal transform coefficient F (u, v) in one block, where the upper left is a DC component and the remaining 255 components are AC components. Now F (4,8)
Two classes are created: a class A centered at and a class B centered at F (8,4). The two classes are indicated by bold lines in the figure. This class classification means does not need to classify all 256 components, and only needs to classify the desired components into a plurality of classes. 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 1403 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 shown in FIGS. 8A and 8B 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, if orthogonal transformation processing is performed, class B in FIG.
Generates a large amount of power. That is, it is determined whether the quantization condition at the time of multiplexing the corresponding block is the quantization condition A or the quantization condition B by relatively comparing the magnitude relation between the powers of the class A and the class B. it can.

The quantization condition is the sign of the additional information (b in equation 3).
Since it is linked to it, it is possible to identify the quantization condition, which means that the multiplexed code can be specified. In the example of the flowchart shown in FIG. 4, bit = 0
Is set to the quantization condition A, and bit = 1 is set to the quantization condition B. Therefore, when the power of class A is larger, the bit
= 0, when the power of class B is higher, bit =
It can be judged as 1.

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, with respect to a good print area, it is determined that the decoding is easy, and the decoding unit A having a fast decoding (extracting) time decodes. On the other hand, for the print area on which the noise component is superimposed, the decoding detection rate is given priority over the decoding (extraction) time, and a more accurate decoding method is used.

As described above, by using the absolute coordinates of the recorded printed matter as the evaluation factor, the printing quality can be predicted and a more optimal decoding unit can be selected.

In the present embodiment, two types of decoding units, A and B, have been described, but 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. In other words, iterative decoding with high redundancy is effective in a decoding unit that requires higher accuracy. For example, in the method using the above-mentioned orthogonal transformation using P × Q pixels (decoding means B), P × Q
A method is conceivable in which a block of pixels is spatially shifted by several pixels, orthogonal transformation is performed a plurality of times, and determination accuracy is improved through a plurality of class comparisons. At that time, it is also an effective method to empirically rank the physical characteristics of the recording medium and set them as evaluation factors, and control the number of repetitions to gradually increase according to the rank.

Of course, if the judgment is made by using the orthogonal transformation a plurality of times, the decoding accuracy is improved, but the processing time becomes extra. The optimization is preferably designed empirically.

In addition, since the present embodiment is premised on the multiplexing according to the flowchart of FIG. 4, at the time of multiplexing and at the time of decoding, robust multiplexing and high accuracy are achieved for the print area where the image quality deteriorates. Although decoding is performed, it is naturally effective to perform uniform multiplexing without distinction at the time of multiplexing and change the accuracy only at the time of decoding.

When the method is changed based on the absolute coordinates on the paper for both multiplexing and decoding, the block size with the periodicity of the modulation of the quantization threshold is good.
A change such as setting the area small and the area area large may be considered.

Further, the inferior area can be considered in addition to the impact vibration when the roller rushes into or out of the roller. For example, in the case of a mechanical configuration that realizes full-face printing without paper margins, the accuracy of the edge of the paper is likely to deteriorate, and there is a high possibility that the area will become inferior area.

Although the decoding method and the switching of the multiplexing method have been described above, the multiplexing method and the method of separating the additional information are not limited to the methods described above. In any multiplexing method and separation method, a configuration for controlling the separation method and the multiplexing method based on the absolute coordinates on the paper is effective.

As described above, according to the second embodiment, the moment when the recording medium is removed from the various rollers or the recording medium is determined based on the absolute coordinate within the page, not the relative coordinate from the image image origin. , The area where the printing becomes poor, which is the printing area at the moment when it rushes into various rollers, and the area where the printing becomes good, which is the other printing area,
For areas where printing is poor, use an information extraction method that emphasizes extraction accuracy over extraction time, and for areas that print well, use an information extraction method that emphasizes extraction time over extraction accuracy. With this, it is possible to realize the extraction accuracy when extracting information, the optimization of the extraction time, and the optimum design of the image quality.

Even when the present invention is applied to a system composed of a plurality of devices (eg, host computer, interface device, reader, printer, etc.), a device composed of one device (eg, copier, facsimile). Device).

Further, an object of the present invention is to supply a storage medium (or a recording medium) recording a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and a computer of the system or the 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.

[0128]

As described above, according to the present invention,
Since the separation method and the multiplexing method are controlled based on the absolute position of the recording paper to be printed, it is possible to realize the detection accuracy at the time of decoding, the optimization of the decoding time, and the optimum design of the image quality.

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 principal block diagram showing a configuration of an image processing apparatus according to a first embodiment.

FIG. 2 is a block diagram of a main part showing a configuration of an additional information multiplexing device in FIG.

FIG. 3 is a block diagram of essential parts showing an error diffusion unit in 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] Example of image layout

FIG. 7 is an explanatory diagram of an image deterioration area on a recording sheet.

FIG. 8 shows an example of a change in quantization threshold under a quantization condition.

FIG. 9 is an arrangement example of a combination of quantization conditions.

10 is a block diagram of a main part showing the configuration of the additional information separation device of FIG.

FIG. 11 is an example of a spatial filter.

FIG. 12 is a principal block diagram showing the configuration of an additional information separation device according to the second embodiment.

13 is a block diagram of an additional information decoding unit A of FIG.

14 is a block diagram of an additional information decoding unit B of FIG.

FIG. 15 is an explanatory diagram of class classification in the two-dimensional frequency domain.

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

FIG. 17 is a block diagram showing an example of conventional multiplexing.

FIG. 18 is a block diagram showing an example of conventional multiplexing.

FIG. 19 is a block diagram showing an example of separation according to a conventional method.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kiyoshi Umeda             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation F term (reference) 2C087 AA03 AA09 AA13 AA15 AB05                       AC07 AC08 BA03 BA06 BD07                       CA05 CB07                 2H134 NA21 NA24 NA42                 5B057 AA11 CA08 CB07 CB19 CE08                       CE09 CE13 CG07 CH18 DA07                       DA08                 5C076 AA14 BA05 BA06 CA10

Claims (18)

[Claims] 1. An input unit for inputting an image, an embedding unit for embedding predetermined information in the input image according to a predetermined embedding method, and an image in which the predetermined information is embedded on a recording medium. An image processing apparatus, comprising: 2. The switching means determines, on the basis of the spatial coordinates of the recording medium, an area where printing is good and an area where printing is bad in the recording medium. The image processing apparatus according to claim 1, wherein an embedding method by the embedding unit is switched depending on whether the printing is in a poor area. 3. The area where the printing becomes poor is a printing area when the recording medium enters a roller that conveys the recording medium, or a printing area when the recording medium comes off the roller. The image processing device according to claim 2. 4. The image processing apparatus according to claim 2, wherein the area where the printing is poor is an end portion of the recording medium. 5. The region where the printing is poor is different depending on the mechanical configuration of the apparatus.
The image processing device described. 6. The image processing apparatus according to claim 1, wherein the switching unit switches between an embedding method that emphasizes ease of extracting predetermined information and an embedding method that emphasizes image quality. 7. Input means for inputting an image in which predetermined information is embedded, extraction means for extracting the predetermined information from the input image according to a predetermined extracting method, and spatial coordinates of the recording medium. An image processing apparatus comprising: a switching unit that switches the extraction method by the extraction unit based on the above. 8. The switching means determines, based on the spatial coordinates of the recording medium, an area where printing is good and an area where printing is bad in the recording medium. The image processing apparatus according to claim 7, wherein the extraction method by the extraction unit is switched depending on whether the printing is in a bad area. 9. The area where the printing becomes poor is a printing area when the recording medium is thrust into a roller that conveys the recording medium, or a printing area when the recording medium is removed from the roller. 9. The image processing apparatus according to claim 8, wherein: 10. The image processing apparatus according to claim 8, wherein the area where the printing is poor is an end portion of the recording medium. 11. The image processing apparatus according to claim 8, wherein the area where the printing becomes poor differs depending on the mechanical configuration of the apparatus. 12. The image processing apparatus according to claim 8, wherein the switching unit switches between an extraction method that emphasizes extraction time and an extraction method that emphasizes extraction accuracy. 13. An input step of inputting an image, an embedding step of embedding predetermined information in the input image according to a predetermined embedding method, and an image in which the predetermined information is embedded is formed on a recording medium. And an image forming step, and a switching step of switching the embedding method based on the spatial coordinates of the recording medium. 14. An input step of inputting an image in which predetermined information is embedded, an extraction step of extracting the predetermined information from the input image according to a predetermined extraction method, and spatial coordinates of the recording medium. An image processing method including a switching step of switching an extraction method based on the extraction method. 15. A program code of an input step of inputting an image, a program code of an embedding step of embedding predetermined information in the input image according to a predetermined embedding method, and an image in which the predetermined information is embedded. A computer program comprising: a program code of an image forming step of forming an image on a recording medium; and a program code of a switching step of switching the embedding method based on spatial coordinates of the recording medium. 16. A program code of an input step of inputting an image in which predetermined information is embedded, a program code of an extraction step of extracting the predetermined information from the input image according to a predetermined extraction method, and the recording. A computer program comprising: a program code of a switching step of switching an extraction method based on spatial coordinates of a medium. 17. A recording medium on which the computer program according to claim 15 is stored. 18. A recording medium on which the computer program according to claim 16 is stored.