JP2003110839A - Device and method for processing image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that optimal multiplexing cannot be performed since multiplexing can be performed only on fixed multiplexing conditions. SOLUTION: In the image processor for embedding prescribed information in an image, this device has an image input means for inputting the image, an information input means for inputting the prescribed information to be embedded in the image, a setting information input means for inputting condition setting information on embedding conditions, a quantizing means for quantizing the image by an error diffusing method, and a control means for controlling the quantizing conditions of the error diffusing method corresponding to the prescribed information for each image area of a size determined on the basis of the condition setting 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, photography,
A technique is being standardized in which image information such as a picture is multiplexed with additional information such as the author's name and permission / prohibition of use so that it is difficult to visually discriminate, and is distributed through a network such as the Internet.

As another application field, with the improvement in image quality of image output devices such as copying machines and printers, paper has been 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 Application Laid-Open No. 7-123244 proposes a technique for multiplexing information by embedding additional information in the high frequency region of a color difference component and a saturation component which are visually insensitive.

However, the above-mentioned technique has the following problems. FIG. 17 is a diagram showing the embedding of general additional information of a digital watermark technique. The image information A and the additional information B are multiplexed via the adder 1701 and changed into the multiplexed information C.

FIG. 17 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 a multiplexed image is printed by an output device such as a printer and additional information is taken out 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 shown in FIG. 17 is output to the printer, the multiplexed information C is quantized as D by the pseudo gradation process 1801, as shown in FIG. Change to information, then
By being printed on the paper by the printer output 1802, the information E on the paper (printed matter), which is extremely deteriorated, is changed. 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 1801 and 1802 processing 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. 19 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. 19, the image information is transformed into the frequency domain by the orthogonal transformation processing 1901, and the adder 1902 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 1903 inverse orthogonal transform processing, it corresponds to passing through a filter which undergoes large changes such as pseudo gradation processing and printer output, as in the example of FIG.

FIG. 20 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 2001 such as a scanner. Since the input information is an image in which gradation is expressed by pseudo gradation processing, restoration processing 2002 that is inverse pseudo gradation processing is performed. The restoration process generally uses an LPF (low-pass filter). After performing the orthogonal transformation process 2003 on the restored information, in the separation process 2004, the embedded additional information is separated from the power of the specific frequency.

As is apparent from FIGS. 19 and 20, 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 executed 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, in the case where the pseudo gradation process is a prerequisite, FIG.
It turns out that the method of 9 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 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, one of the dither matrices representing the same gradation is selected to mix the data in the image signal. 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. With 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. Also, in color images, the method of multiplexing to the color component with the least visual sensitivity is the mainstream, but the determination of texture in the real space area is
It is easily affected by other color components, which makes it difficult to separate 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 of the prior art with a predetermined periodicity, and the periodicity of this threshold value modulation is used as a region unit. We proposed a method to control the probability of quantized values in pseudo-tone processing by controlling multiple types 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.

[0022]

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

That is, in the above-mentioned method, the multiplexed image quality and the amount of multiplexed information have a trade-off relationship.
That is, in order to improve the image quality of the printed matter, only a small capacity can be multiplexed, and conversely, when a large amount of capacity is desired to be multiplexed, the image quality of the printed matter deteriorates. In the conventional method, the optimum conditions of the multiplexed image quality and the multiplexed information amount are experimentally set based on this trade-off relationship.

For the purpose of preventing forgery of banknotes and the like, all printed matter output from a printer or a copying machine should have a maker name,
In applications where model names are multiplexed, it is necessary to design so that image quality degradation is not generated as much as possible. Since the multiplexing process is automatically performed regardless of the user's (printer's intention) use, considering both the multiplexing effect and the image quality deterioration due to the multiplexing, the user benefit of the multiplexing process is extremely small. .

However, in a highly entertaining application such as creating a card in which character information and voice information are invisible in a printed matter and passing them to a friend or acquaintance, the card is multiplexed in accordance with the intention of the user. As a result of the digitization process, some deterioration in image quality can be tolerated. Moreover, the permissible range depends on the image information to be multiplexed, and also on the preference (preference) of the user (printer).

However, in the above-mentioned conventional method, there is no setting means suitable for the purpose of the user, and it is difficult to prepare the multiplexed printed matter desired by the user.

In addition to user preferences and preferences, it is necessary to set conditions for multiplexing processing. In the above-mentioned conventional method, only fixed multiplexing processing conditions exist even with respect to changes in the type, resolution, etc. of input image information, and it is not possible to create an optimal multiplexed print.

In order to create a printed matter, various image processing steps are performed by application software, a printer driver, a printer engine, etc., from the image input to the output on paper. In the above-mentioned conventional method, there is no interlocking with image processing other than the multiplexing processing and the printing process of the printer. Therefore, there is a drawback that various settings become complicated for the user. Further, since the condition setting of the multiplexing process and the various settings in other image processing are independent of each other, the image quality on paper cannot be estimated, and the optimum condition setting of the multiplexing process cannot be performed.

An object of the present invention is to provide an image processing device and an image processing method capable of solving at least one of the above problems.

[0030]

In order to achieve the above object, an image processing apparatus of the present invention is an image processing apparatus for embedding predetermined information in an image, the image inputting means for inputting an image, and the image Information input means for inputting predetermined information to be embedded in, a setting information input means for inputting condition setting information regarding an embedding condition, a quantizing means for quantizing the image by an error diffusion method, and a condition setting information based on the condition setting information. And a control unit for controlling the quantization condition of the error diffusion method according to the predetermined information for each image area of the determined size.

In order to achieve the object, the image processing method of the present invention is an image processing method for embedding predetermined information in an image, which comprises an image input step of inputting an image and a predetermined image to be embedded in the image. An information input step of inputting information,
A setting information input step of inputting condition setting information regarding an embedding condition, a quantization step of quantizing the image by an error diffusion method, and the predetermined information for each image area of a size determined based on the condition setting information. And a control step of controlling the quantization condition of the error diffusion method according to the above.

In order to achieve the above object, the image image processing apparatus of the present invention is an image processing apparatus for embedding predetermined information in an image, and image input means for inputting the image,
Information input means for inputting predetermined information to be embedded in the image, setting information input means for inputting condition setting information regarding embedding conditions, quantizing means for quantizing the image by an error diffusion method, and the predetermined information. Amplitude modulation of the quantization threshold of the error diffusion method according to the above, the periodicity of the amplitude modulation is controlled for each of the image regions according to the predetermined information, and the amplitude of the amplitude modulation according to the condition setting information. And a control means for controlling.

In order to achieve the object, the image processing method of the present invention is an image processing method for embedding predetermined information in an image, which comprises an image input step of inputting an image and a predetermined image to be embedded in the image. An information input step of inputting information,
A setting information input step of inputting condition setting information regarding an embedding condition, a quantization step of quantizing the image by an error diffusion method, and an amplitude modulation of a quantization threshold of the error diffusion method according to the predetermined information, A control step of controlling the periodicity of the amplitude modulation for each of the image regions according to the predetermined information and controlling the amplitude of the amplitude modulation according to the condition setting information.

In order to achieve the object, the image processing apparatus of the present invention is an image processing apparatus for embedding predetermined information in an image, which comprises image input means for inputting an image and a predetermined image to be embedded in the image. Information input means for inputting information,
Setting information input means for inputting condition setting information regarding embedding conditions, quantizing means for quantizing the image by an error diffusion method, and amplitude modulation of a quantization threshold of the error diffusion method according to the predetermined information, Control means for controlling the periodicity of the amplitude modulation for each image area of a size determined based on the condition setting information according to the predetermined information, and controlling the amplitude of the amplitude modulation according to the condition setting information; It is characterized by having.

In order to achieve the object, the image processing method of the present invention is an image processing method for embedding predetermined information in an image, which comprises an image input step of inputting an image and a predetermined image to be embedded in the image. An information input step of inputting information,
A setting information input step of inputting condition setting information regarding an embedding condition, a quantization step of quantizing the image by an error diffusion method, and an amplitude modulation of a quantization threshold of the error diffusion method according to the predetermined information, A control step of controlling the periodicity of the amplitude modulation according to the predetermined information for each image area of a size determined based on the condition setting information, and controlling the amplitude of the amplitude modulation according to the condition setting information; It is characterized by having.

[0036]

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 all denote input terminals. From 100, multi-gradation image information is input, and from 101, necessary additional information to be embedded in the image information is input. 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, condition setting information relating to condition setting of the multiplexing process is input according to a user's instruction. Details of this condition setting information will be described later. The user's instruction method may be input from a printer driver on a computer on which multiplexing processing operates, or input from a keyboard, mouse, etc. in application software, or by setting from a device other than the computer such as a copying machine or a facsimile. Alternatively, the input may be performed using buttons on an operation panel such as a touch panel.

Reference numeral 103 denotes an additional information multiplexing device, which is a device 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 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 optically by using the scanner 105, and the additional information separating device 106 separates (extracts) the additional information embedded in the printed matter and outputs it. Output to the terminal 107.

FIG. 2 shows an additional information information multiplexing apparatus 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 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 changes and controls the quantization condition in units of regions blocked by the blocking unit 201.

The quantization condition control unit 202 has the input terminal 10
Quantization conditions are controlled in block units based on the additional information and condition setting information input at 1 and 102.

Reference numeral 210 is a CPU 211 and a ROM 21.
2, a RAM 213 and the like. CP
The U211 controls the operation and processing of the above-described components according to the control program stored in the ROM 212. The RAM 213 is used as a work area of the CPU 211.

FIG. 3 is a block diagram showing details of the error diffusion processing 200. A general error diffusion process is described in Reference R.
Floyd & L.F. Steinberg: "An A
daptive Alogorithm for Sp
atial Grayscale ”, SID Symp
osium Digest of Paper pp.
36-37 (1975) for further details.

Now, the error diffusion processing 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 represents 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 and the addition result with the error added.
, And if it is larger than the predetermined threshold, “1”
Otherwise, "0" is output. For example, when expressing the gradation of a pixel with an accuracy of 8 bits, it is general to express it with a maximum value of "255" and a minimum value of "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 subtractor, which calculates an error between the quantization result and the above addition result, and the error distribution calculation unit 303.
Based on the result of the calculation by, 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 the distribution table is not limited to this.

Next, the operation procedure of the entire multiplexing process 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. Note that the quantized value is not limited to binary, but is multivalued, for example, 3
Value or 4 may be used.

First, in S401, the condition setting information by the user is input. There are a plurality of condition settings, and the multiplexed image quality related to the image quality due to multiplexing and the multiplexed information amount related to the amount of information to be multiplexed are linked.

FIG. 5 shows an example of the setting user interface.

Although FIG. 5 shows an example in which there are four types of settings, the number of settings is not limited. Further, in the present embodiment, an example in which the multiplexed image quality and the amount of multiplexed information are linked will be described, but each may be independent.

As the condition setting information by the user, a number (hereinafter referred to as No) corresponding to the set value is assigned and managed.
In the example of FIG. 5, the setting with the largest amount of multiplexed information (the leftmost setting) is No = 0, and the setting with the best image quality (the rightmost setting) is No = 3.

Next, in S402, the set No
Based on the above, the number N of horizontal pixels and the number M of vertical pixels in one block when dividing into blocks during multiplexing are determined. The values of N and M increase as No increases. That is, the better the image quality, the larger the block size of one block required for multiplexing.

Subsequently, in S403, the condition setting No. is added to the image margin by a dot code pattern. This pattern addition may be performed by using a conventionally used method and is not limited here. It is preferable that the texture is composed of a combination of a plurality of pixels of at least two pixels in a visually inconspicuous ink color.

S404 shows the initialization of the variable i. The variable i is a variable for counting addresses in the vertical direction.

S405 shows the initialization of the variable j. The variable j is a variable for counting addresses in the horizontal direction. Then, S406 is a determination unit based on the address values of i and j, and determines whether or not the coordinates of the current processing address i and j belong to the area in which the multiplexing process is to be executed.

The multiplexed area will be described with reference to FIG.
In FIG. 6, the horizontal pixel number is WIDTH and the vertical pixel number is HEI.
One picture image which consists of GHT is shown.
Now, assume that additional 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. The values determined in S402 are used as the values of N and M. In the present embodiment, the origin is used as the reference point for blocking, 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. W = INT (WIDTH / N) ... Equation 1 H = INT (HEIGHT / M) ... Equation 2 where INT () indicates the 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 S406 that the pixel of interest currently being processed is outside the multiplexing area, S40
At 7, 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. For example, assuming that the additional information is 8000 bits worth of information, the array code [] stores 1 bit each from code [0] to code [7999]. In S408, 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 the variable bit substituted in S409 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". S
If it is determined to be “0” in 409, the quantization condition A [No] is set in S410, and if it is determined to be “1”, the quantization condition B [No] is set in S411. To do. The quantization condition A [] and the quantization condition B [] are represented by an array of condition setting variables No. Some elements of the quantization condition differ depending on the variable No. A detailed description of setting the quantization condition will be described later.

Subsequently, in S412, 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 S413, the horizontal variable j is counted up, and in S414, it is determined whether or not it is less than WIDTH which is the number of horizontal pixels of the image, and the number of processed pixels 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 direction variable i is counted up in S415, and it is determined in S413 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 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 value 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 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. 7 is an example showing the quantization conditions A and B. FIG. 7A is a diagram showing the modulation cycle 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. 7A, a matrix of 8 pixels in the horizontal direction and 4 pixels in the vertical direction is combined, and the threshold value of only the threshold value of the gray cell is set as the threshold value.

Similarly, FIG. 7B is a diagram showing the modulation cycle of the quantization threshold value under the quantization condition B. Figure 7
In the example of FIG. 7B, unlike the case of FIG. 7A, 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 is set to“ 48. ”When the quantization threshold is low, the quantized value of the pixel of interest is likely to be“ 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. 7A and a block in which dots are generated in the arrangement of gray cells in FIG. 7B are mixed. Naturally, in the same block of N × M pixels, as shown in FIG.
The matrix of (a) or FIG. 7 (b) is repeated.

A slight change in the quantization threshold value in the error diffusion method does not have a great influence on 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 amplitude modulation of the quantization threshold value is regularly applied 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. That is, the image quality of the gradation expression is hardly affected, such as the occurrence of noise. 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.

Next, switching of the quantization condition according to the condition setting number will be described. The condition setting number is a factor that controls the multiplexed image quality and the amount of multiplexed information. Condition setting N
As described above, the block size of one block is switched based on o. However, in the present embodiment, the image quality is controlled by switching the amplitude when the quantization threshold is amplitude-modulated.

FIG. 8 shows an example. FIG. 8 shows a state in which the amplitudes of the four types of quantization thresholds having condition setting Nos. 0 to 3 are changed. As is clear from FIG.
The larger the setting number, the smaller the amplitude for modulating the quantization threshold. That is, as the amplitude of the quantization threshold increases, the quantization result at the desired pixel position that has been modulated can be controlled. However, on the contrary, the regularity of the modulation causes the deterioration of the image quality on the paper. Therefore, in the image quality priority setting, the regularity due to modulation is weakened instead of increasing the block size, and the occurrence of multiplexing noise is reduced.

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

FIG. 9 is a block diagram showing the structure of the additional information separation device 106.

Reference numeral 900 denotes an input terminal to which the image information obtained by optically reading the multiplexed printed matter with a scanner is inputted. 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.

Reference numeral 901 denotes a block size estimating unit,
The condition setting information multiplexed by the dot code in the image margin is decoded, and the values of the block sizes N and M at the time of multiplexing are estimated.

Reference numeral 902 denotes a block forming unit for separation, which forms blocks in P × Q pixel units.

FIG. 10 shows a state of blocking in units of N × M pixels and P × Q pixels. The rectangular area surrounded by each solid line is divided into blocks in N × M pixel units,
The rectangular area surrounded by the dotted line is a block in P × Q pixel units.

The block of P × Q pixels must be smaller than the N × M pixels that are divided into blocks at the time of multiplexing. That is, the relation of P ≦ N and Q ≦ M ... Equation 4 holds.

As shown in FIG. 10, the block formation in P × Q pixel units is performed by skipping at regular intervals. That is, each block start position is controlled so that one block of P × Q pixel unit 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 N horizontal pixels and M vertical pixels.
Pixels are the basis.

FIG. 11 shows the size relationship between blocks in N × M pixel units and blocks in P × Q pixel units. Since the values of N and M change depending on the condition setting at the time of multiplexing, the values of P and Q are set to increase as the values of N and M increase (FIG. 11A). , (B)).

Here, it is preferable that P and Q are prepared in advance in correspondence with the estimated values of N and M, such as a value obtained by subtracting a predetermined fixed value from N and M, respectively.

Reference numerals 903 and 904 denote spatial filters A and B having different characteristics, and reference numeral 905 denotes a digital filtering unit for calculating the sum of products with surrounding 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, the change of the quantization condition in the multiplexer will be described with reference to FIG.
It is assumed that the additional information is multiplexed by using the two types of periodicity of (b).

An example of the spatial filter A903 and the spatial filter B904 used in the separating apparatus at that time is shown in FIG.
12 (a) and 12 (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 pixel in the blank area has a filter coefficient of "0".
It means that. As is clear from FIG.
(A) and (b) are filters 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.
7A is shown in FIG. 7A, and FIG.
Create to match (b).

Reference numeral 906 denotes a feature amount detecting section, which is based on the converted value after filtering from the filtering section 905 by the spatial filter A 903 and the spatial filter B 904.
It is a means for detecting some characteristic 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 907 denotes a determination unit that compares the respective dispersion values and determines 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 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.

Although the multiplexing process and the demultiplexing process have been described above, the feature of the present embodiment is that the image quality and the amount of information can be freely set according to the user's intention and intention of creation. When the image quality is emphasized, the amplitude of regularity addition is reduced, and instead, the block size expressing one bit is increased to maintain the decoding detection accuracy. At the time of decoding, the larger the block size, the more averaging will be performed irrespective of the local image characteristics such as the edge part and the dark part, so the regularity added at the time of multiplexing will be easier to extract, and the decoding accuracy will be improved. To do.

The multiplexing method and the separating method described above are examples, and the present invention is not limited to these. In the separation method,
Alternatively, a method using orthogonal transform may be considered.

Although one bit is represented in one block, it is not limited to this. A configuration may be used in which a plurality of bits are expressed per block by switching more modulation cycles of the quantization threshold of the error diffusion method.

Also, an example has been shown in which the condition setting information is multiplexed by embedding the dot code in the image margin, but the invention is not limited to this. For example, the condition setting information may use the same multiplexing method as the additional information. At that time, at least the block size in which the condition setting information is multiplexed is
It is preferable to make uniform regardless of the condition setting.

(Second Embodiment) FIG. 13 is a block diagram showing the structure of an additional information multiplexing device according to the second embodiment. The present embodiment is characterized in that the setting mode in multiplexing is linked to other image processing and printing process processing.

Since FIG. 13 is only partially different from the additional information multiplexing processing shown in FIG. 2, the same parts will be denoted by the same reference numerals and only different points will be described.

In the figure, reference numeral 1300 denotes an input terminal for inputting image quality setting information according to a user's instruction. This image quality setting information is also transmitted to the color conversion unit 1301, the quantization condition control unit 202, and the printer engine 1302. The printer engine 1302 is assumed to be a color inkjet printer. There are multiple levels of image quality settings, from the image quality priority mode where the image quality of the printed matter is best output to the speed priority mode where the image quality is slightly degraded but the processing speed and printing speed can be output at high speed. There is.

For ease of explanation, it is assumed that the image quality priority mode and the speed priority mode described above are provided. FIG. 14 shows an example of the processing contents of the color conversion unit, the quantization condition control unit, and the printer engine for the two types of modes.

The color conversion unit 1301 converts the brightness signal (RGB) of the input image information into each ink color output by the ink jet printer. Now, the inkjet printer can print in 6 colors: cyan, magenta, yellow, black, light cyan (diluted dye concentration of cyan ink), and light magenta (diluted dye concentration of magenta ink). Assuming various engines. From the table of FIG. 14, in the image quality priority mode, R
Conversion from GB to the above-described 6-color ink is performed. In the speed priority mode, conversion to four-color ink excluding light cyan and light magenta is performed.

Next, in the image quality priority mode, the quantization controller increases the block size and decreases the amplitude of amplitude modulation of the quantization threshold. Conversely, in speed priority mode,
The block size is reduced and the amplitude of the amplitude modulation of the quantization threshold is increased. As a matter of course, in the image quality priority mode, the quantization processing is performed for each color on the ink color information for six colors, and for the ink color information for four colors in the speed priority mode.

In the ink jet printer, in order to eliminate the non-uniformity of the nozzles ejecting ink, a technique of printing one line by a plurality of head scans using a plurality of nozzles arranged in the sub-scanning direction has been conventionally used. Has been done.
Naturally, increasing the number of scans will cause the nozzle to twist,
The image quality deterioration due to non-ejection is evenly distributed over a plurality of lines, so that the image quality is visually improved. In the setting of FIG. 14, four scans (referred to as four passes) are performed in the image quality priority mode, and two scans (referred to as two passes) are performed in the speed priority mode.

The example in which the setting mode in multiplexing is linked to other image processing and printing process processing according to the user's setting has been described above. However, the user can specify the desired setting only once. Since the mode can be set, there is an advantage in terms of ease of use.

Further, the table of FIG. 14 is an example, and the setting contents, types of items to be set, and the number are not limited to these.

Further, interlocking a series of image processing and printing process processing is also advantageous in terms of stabilizing the image quality on paper. For example, if the image quality on paper can be predicted from the aspects of image processing related to printing and the printing process,
It is possible to experimentally obtain the modulation amplitude of the quantization threshold of the quantization control unit that can be decoded with the predicted on-paper image quality.
In other words, it is possible to realize not only the configuration in which the block size at the time of multiplexing is changed as in FIG. 14 but also the configuration in which only the condition of the modulation amplitude of the quantization threshold is changed.

(Third Embodiment) FIG. 15 is a block diagram showing the arrangement of an additional information multiplexing device according to the third embodiment. In the present embodiment, the condition setting of the multiplexing process is set not according to the user's designation as described above but according to the input image.

In other words, even the input image information, various images such as a natural image photographed by a digital camera or the like, an illustration or a CG image artificially created by a computer, a halftone image of a printed matter optically read by a scanner, etc. There is a seed.

In FIG. 15, the terminal 1500 inputs image type information indicating what kind of image the input image is. This input may be automatically determined from the extension of the image file or the like, or may be input by the user from the keyboard, mouse or the like. Based on this input, the processing condition of the quantization controller is set. The setting item may be the above-described block size and the modulation amplitude of the quantization threshold, or either one of them. Although the setting conditions are not limited, in a natural image, since the modulated regularity is visually unnoticeable, the amplitude may be increased, and in the halftone original image, the periodicity of halftone dots may interfere with decoding. Therefore, the amplitude is similarly increased, and in a graphic image such as CG, since there are many flat portions, regularity due to multiplexing is easily noticeable, and decoding is easy. It is possible to set conditions that match the image type, such as making it smaller.

(Fourth Embodiment) FIG. 16 is a block diagram showing the arrangement of an additional information multiplexing device according to the fourth embodiment.

In this embodiment, unlike the third embodiment, the multiplexing condition is set according to the resolution of the input image.

In FIG. 16, resolution information of an input image is input from a terminal 1600. If the resolution information is unknown, the enlargement ratio may be estimated based on the number of pixels of the input image and the ratio of the number of pixels that can be output. In this case, it is assumed that the smaller the number of input pixels, the rougher the resolution.
The condition of the quantization control means is set based on the input of the resolution information or the pixel number information.

The setting items are the above-mentioned block size and
Two items of the modulation amplitude of the quantization threshold value or either one may be used. Although the setting condition is not limited, as the input resolution becomes lower resolution, the higher frequency component does not exist, which is advantageous for decoding, and the amplitude can be set smaller. Conversely, the lower the input resolution is, the worse the image quality on paper is, and therefore, it may be possible to set the mode in which the information amount is prioritized.

(Other Embodiments) The condition setting of the multiplexing process has been described above. However, the present invention is applicable to a system including a plurality of devices (eg, host computer, interface device, reader, printer, etc.). Alternatively, it may be applied to an apparatus composed of one device (for example, a copying machine, a facsimile apparatus, etc.).

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 a 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.

Furthermore, 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.

[0115]

As described above, according to the present invention,
To control the conditions for embedding predetermined information in the image according to the user's selection, the type and resolution of the input image, etc., to realize the optimum information embedding process according to the intended use, purpose, and characteristics of the input image. You can Further, by linking with the printing characteristics of the printer and the condition setting of image processing other than the information embedding processing, it is possible to estimate the image quality on paper, and it is possible to realize better information embedding processing.

Further, according to the present invention, since the embedding process for embedding predetermined information in an image can be easily realized, a service or application for embedding voice information or secret information in an image can be provided. 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 showing a configuration of an image processing system according to a first embodiment.

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

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

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

FIG. 5 is a diagram illustrating display of condition settings.

FIG. 6 is an example of blocking.

FIG. 7 shows an example of a quantization threshold modulation period under a quantization condition.

FIG. 8 is a diagram illustrating quantization threshold modulation.

9 is a block diagram showing the configuration of the additional information separation device of FIG.

FIG. 10 is a diagram illustrating a blocking unit in FIG.

FIG. 11 is a diagram illustrating a blocking unit in FIG. 9.

FIG. 12 is an example of a spatial filter.

FIG. 13 is a block diagram showing a configuration of an additional information multiplexing device according to a second embodiment.

[Fig. 14] Example of condition setting

FIG. 15 is a block diagram showing a configuration of an additional information multiplexing device according to a third embodiment.

FIG. 16 is a block diagram showing a configuration of an additional information multiplexing device of a fourth exemplary embodiment.

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 conventional multiplexing.

FIG. 20 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) 5B057 BA30 CE08 CH01 CH11                 5C076 AA14 BA06                 5C077 LL14 PP23 PQ12 PQ22 RR08                       RR11

Claims (24)

[Claims] 1. An image processing apparatus for embedding predetermined information in an image, comprising image input means for inputting an image, information input means for inputting predetermined information to be embedded in the image, and condition setting information regarding embedding conditions. Setting information inputting means for inputting, the quantizing means for quantizing the image by an error diffusion method, and the error diffusion according to the predetermined information for each image area of a size determined based on the condition setting information. An image processing apparatus, comprising: a control unit that controls the quantization condition of the method. 2. The condition setting information is set based on a condition of image quality due to embedding.
The image processing device described. 3. The image processing apparatus according to claim 1, wherein the condition setting information is set based on an information amount of predetermined information to be embedded. 4. The image processing apparatus according to claim 1, wherein the condition setting information is set based on a type of the image. 5. The image processing apparatus according to claim 1, wherein the condition setting information is set based on a resolution of the image. 6. The image processing apparatus according to claim 1, wherein the condition setting information is set based on the number of pixels of the image. 7. The image processing apparatus according to claim 1, wherein the condition setting information is set based on a printing condition for printing the image. 8. An image processing apparatus for embedding predetermined information in an image, comprising image input means for inputting an image, information input means for inputting predetermined information to be embedded in the image, and condition setting information relating to embedding conditions. Setting information input means for inputting, a quantizing means for quantizing the image by an error diffusion method, amplitude modulation of a quantization threshold of the error diffusion method according to the predetermined information, and according to the predetermined information. And a control unit that controls the periodicity of the amplitude modulation for each image area and controls the amplitude of the amplitude modulation according to the condition setting information. 9. The condition setting information is set based on a condition of image quality due to embedding.
The image processing device described. 10. The image processing apparatus according to claim 8, wherein the condition setting information is set based on an information amount of predetermined information to be embedded. 11. The image processing apparatus according to claim 8, wherein the condition setting information is set based on a type of the image. 12. The image processing apparatus according to claim 8, wherein the condition setting information is set based on a resolution of the image. 13. The image processing apparatus according to claim 18, wherein the condition setting information is set based on the number of pixels of the image. 14. The image processing apparatus according to claim 8, wherein the condition setting information is set based on a printing condition for printing the image. 15. An image processing apparatus for embedding predetermined information in an image, comprising image input means for inputting an image, information input means for inputting predetermined information to be embedded in the image, and condition setting information regarding embedding conditions. Setting information input means for inputting, a quantizing means for quantizing the image by an error diffusion method, amplitude modulation of a quantization threshold of the error diffusion method according to the predetermined information, and according to the predetermined information. Controlling the periodicity of the amplitude modulation for each image area of a size determined based on the condition setting information, and controlling the amplitude of the amplitude modulation according to the condition setting information. Image processing device. 16. An image processing method for embedding predetermined information in an image, comprising an image input step of inputting an image, an information input step of inputting predetermined information to be embedded in the image, and condition setting information relating to embedding conditions. A setting information input step of inputting, a quantization step of quantizing the image by an error diffusion method, and an error diffusion according to the predetermined information for each image area of a size determined based on the condition setting information. And a control step of controlling the quantization condition of the method. 17. An image processing method for embedding predetermined information in an image, comprising an image input step of inputting an image, an information input step of inputting predetermined information to be embedded in the image, and condition setting information relating to embedding conditions. Setting information input step of inputting, a quantization step of quantizing the image by an error diffusion method, amplitude modulation of a quantization threshold of the error diffusion method according to the predetermined information, and according to the predetermined information. Controlling the periodicity of the amplitude modulation for each of the image areas, and controlling the amplitude of the amplitude modulation according to the condition setting information. 18. An image processing method for embedding predetermined information in an image, comprising an image input step of inputting an image, an information input step of inputting predetermined information to be embedded in the image, and condition setting information regarding embedding conditions. Setting information input step of inputting, a quantization step of quantizing the image by an error diffusion method, amplitude modulation of a quantization threshold of the error diffusion method according to the predetermined information, and according to the predetermined information. Controlling the periodicity of the amplitude modulation for each image area of a size determined based on the condition setting information, and controlling the amplitude of the amplitude modulation according to the condition setting information. Image processing method. 19. A program for executing the image processing method according to claim 16, when the program is executed on a computer. 20. A program for executing the image processing method according to claim 17, when the program is executed on a computer. 21. A program for executing the image processing method according to claim 18, when the program is executed on a computer. 22. A recording medium recording the program according to claim 19. 23. A recording medium recording the program according to claim 20. 24. A recording medium on which the program according to claim 21 is recorded.