JP2000032251A - Image processing unit and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make image quality of an output image compatible with decoding of added specific information by forming a visual image based on the image data with the specific information added thereto and generating the specific information as a code to ensure an inter-code distance. SOLUTION: Fixed information 121 is read from a ROM 120, variable information is added to the fixed information 121 to produce original added information. Pre-processing such as encryption is applied to the original added information and a code conversion section 140 applies redundant processing to the information and a detection specific pattern is imbedded in an image. The redundancy coding assigns codes with an inter-code distance by which the original information is decoded. When encryption is applied to the information for the coding, the original added information is reproduced by applying decoding processing to the information. A redundant code possible for error correction is used as a specific pattern denoting the specific information of the processing unit so as to imbed a pattern hardly perceived by people to the image in the case of image forming and the pattern is sufficiently detected while suppressing deterioration in the image quality due to the specific pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image processing apparatus and method, and more particularly, to an image processing apparatus and method for adding a specific pattern that is difficult to visually recognize to image data.

[0002]

2. Description of the Related Art Conventionally, color printers, color copiers, color facsimile machines and the like have been put into practical use as color image forming apparatuses for forming a color image and outputting it on a recording medium.

With the recent progress in circuit technology and image processing technology, such color image forming apparatuses have been provided at low cost.
In addition, the output image quality is significantly improved. However, with the development of such technology, for example, securities, bills, etc.
There is a fear that copy processing of a document (hereinafter referred to as a specific document) for which copying should be prohibited, that is, forgery is easily performed.

In order to prevent such illegal copying, the following measures have been taken in a conventional color image forming apparatus.

For example, an image pattern of a specific document is registered in advance in a color copying machine, a color printer, or the like, and an image recognition process is performed on the document at the time of copying to identify the specific document. Could be prevented.

As another example, in order to identify a device used for printing out a specific document and a person who has performed the illegal output, various types of information necessary for specifying the device are included in the copy result. The pattern was added in a visually inconspicuous format. For example, a color image forming apparatus performs a modulation to add a predetermined value to an image signal of a color component (for example, Y) which is most difficult for human eyes to recognize among output color components (for example, YMCK) in color image formation. Was added to the pattern indicating the serial number or the like. According to such a method, a color image forming apparatus can be specified by detecting a pattern recorded on a forged security or the like and restoring the embedded information.

[0007]

However, in the above-described conventional color image forming apparatus, since an extra color signal is simply superimposed on the output image, the original image is
There is a problem that the added signal acts as noise, and it is difficult to restore the embedded information.

In order to facilitate the restoration of the embedded information, the embedded information may be superimposed so that the pattern expressing the embedded information becomes clearer. In this way, the additional information can be easily recognized by the naked eye of the apparatus user. You can see it,
The image quality will be degraded. This is not preferable because the output image becomes an image with low fidelity deviating from the intention of the device user.

As a method of adding information to an output image,
Other more sophisticated methods also exist. However, even with advanced addition methods that are not simple data superposition,
The essence of the problem remains the same. That is, in the method of embedding information in a form that is difficult for human eyes to identify, it is an unavoidable problem that the image quality of the output image deteriorates due to the interference of the original image and the reversibility of the restoration of the embedded information.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and when outputting specific data to image data, the image quality of the output image and the resilience of the added specific information are improved. It is an object of the present invention to provide an image processing apparatus and a method thereof that are compatible with each other.

[0011]

As one means for achieving the above object, the image processing apparatus of the present invention has the following arrangement.

That is, input means for inputting image data,
Specific information generating means for generating the specific information to be added to the image data as a code having redundancy; adding means for adding the specific information to the image data; and, based on the image data to which the specific information has been added. And an image forming means for forming a visible image by using the specific information generating means, wherein the specific information generating means generates the specific information as a code having a secured inter-code distance.

For example, the inter-code distance is two or more.

For example, the inter-symbol distance is 3 or more.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below in detail with reference to the drawings.

<Outline Description> In the present embodiment, at the same time as using an embedding pattern at a level that is difficult to visually recognize (with little image disturbance), redundancy is added to code information in order to reliably restore additional information. By having
Even if a missing bit occurs in a unit word, word information can be restored.

In general, a Hamming code is known as one of the error correction codes that make it possible to make information redundant and to restore information even if bit information is lost. The Hamming code itself is a code sequence having a 1-bit error correction capability. This type of error correction code provides a bit string representing each information in one word at a distance from each other, so that even if an error occurs in a small number of bits, it is interpreted together with the information of the shortest distance to correct the error. Do.

In such a code sequence, the greater the distance between the bit strings, the greater the resilience of information. However, at the same time, the number of characters (meaning) assigned to one word decreases or the number of assigned characters increases. Means that the word length increases. Therefore, it is necessary to balance the correction ability and the word length according to the frequency of occurrence of errors.

Here, for example, in the case where one word has a correction capability of one bit in one word, a distance between codes of two or more is required. When performing code selection with an inter-code distance of 2 or more with an n-bit word length, there are n nearest neighbor codes for each element Xi of a certain code sequence. Since the nearest neighbor code and Xi do not overlap each other, the number of elements of Xi is smaller than 2 ^ n / (n + 1). Here, A ^ r indicates A to the power of r. That is, when n = 7, the number of elements that Xi can take is sixteen. Conversely, to secure 256 codes, a word length of 12 bits is required.

In the present embodiment, by performing such a word conversion, an embedding pattern with less image disorder is generated while restoring the embedding information is secured.

<Apparatus Configuration> An apparatus configuration in the present embodiment will be described below.

In the present embodiment, in an image processing apparatus in which an image generating section and an image forming section are integrated, at the time of image generation, specific information for specifying the apparatus is added at the time of image generation. In such a configuration, if necessary,
It is possible to change / add the content of the specific information to be added. For example, when variable information such as output date and time is added, or when a document image is highly likely to be a specific document such as securities, the amount of specific information to be added is increased. Becomes possible.

Further, since the image generating unit and the image forming unit are integrated, it is possible to use a method other than the simple superimposition method as a format for adding the specific information.
For example, it is possible to adopt an additional method of operating the output image expression, such as changing the position or shape of a halftone dot.

However, the feature of this embodiment is that a redundant code is employed. Therefore, a specific image operation method for adding specific information to image data, and a format and content of the specific information to be added. Details are not specified.

FIG. 1 shows a block configuration of an image processing apparatus according to the present embodiment. In FIG. 1, reference numeral 100 denotes an image forming unit, and 101 denotes an image generating unit. Both are connected by a predetermined interface, and transmit an image signal 200 generated by the image generating unit 101, various control signal groups 102 for the image forming unit 100, and the like. Reference numeral 201 denotes an input signal from an external device such as a host computer to the image generation unit 101, which is image generation information in a format such as a control code, character information, and an output image.

In the image generator 101, reference numeral 110 denotes a RAM, which temporarily stores various information. An output image area 115 exists in a part of the RAM 110, and an output image is formed according to the image generation information. Although it depends on the additional form of the specific information, each drawing command confirms the drawing area at the time of forming the output image, and the actual additional work is added at the time of drawing processing of the additional area of the specific information, so that the output is performed. Drawing processing of the entire image is performed.

Reference numeral 120 denotes a ROM, in addition to various control programs such as drawing generation and data exchange with an external device, etc., and fixed information 121 for generating a specific pattern in the present embodiment.
Is recorded. Here, the fixed information includes, for example, a serial number of the image forming unit 100 and the like.

Reference numeral 140 denotes a code conversion unit for making a specific pattern redundant which is a feature of the present embodiment; 150, a timer having a timekeeping function; 160, an input / output control unit for controlling input / output of a control signal 102 for printing. It is. 130 is a CPU, and RO
According to the control program stored in M120, the image generation unit
The processing in 101 is generally controlled.

In the image generation unit 101, after an image is completed on the output image area 115 in the RAM 110 based on the instruction of the input signal 201 from the external device, the image information is converted to an image signal 200 as an image signal 200. Output to At this time, under the control of the input / output control unit 160, various control signals 102 for printing are transmitted according to the timing of the printing mechanism of the image forming unit 100, so that the image output of the image forming unit 100 is printed. Done.

<Specific Pattern Addition Processing> Hereinafter, the image forming processing including a specific pattern in the present embodiment will be described in detail.

In the present embodiment, an image operation type addition method is adopted as a method for adding specific information, instead of a simple superimposition type. FIG. 2 shows and describes a flowchart of a drawing process for adding specific information in the present embodiment.

The basis of the specific information adding algorithm in the present embodiment is to determine whether or not the drawing of the target object collides with the addition of the specific information at the time of drawing, and to switch the drawing algorithm according to the determination result. . However, when the target object is drawn, if it is checked for each pixel whether or not the area is the additional area of the specific information, the drawing speed is fatally reduced. Therefore, the determination is performed for each object.

Therefore, in step S201, the drawing area of the object to be drawn is compared with the n specific information added areas Kn. As a result of the comparison, if the two do not collide in step S202, the process proceeds to step S203 to perform a normal drawing process, and if the two collide, the process proceeds to step S204 to create the image as described later. Switching is performed to perform a drawing process for adding a pattern indicating the specified information. As described above, by performing the area comparison on an object basis, the processing efficiency can be improved.

Thereafter, when the comparison processing for all the objects is completed in step S205, the image data drawn in step S206 is output to the image forming unit 100 as the image signal 200. That is, a predetermined image operation is performed when drawing an area determined to be an area to which specific information is added.
(Step S204) is performed to perform drawing in which the original image data is modulated in a form that is difficult to visually recognize in accordance with the specific information.

In the algorithm shown in FIG. 2, an example in which rectangular collision detection is performed in only one stage has been described.
For example, a plurality of more detailed collision detections may be performed or the drawing object may be subdivided according to the processing speed of the apparatus.

<Specific Pattern Generation Processing> FIG. 3 is a flowchart of the specific pattern generation processing in the present embodiment. This processing is executed in the additional drawing processing shown in step S204 in FIG. 2 described above, and the generated specific pattern is added to the image.

In this embodiment, first, step S301
Reads the fixed data 121 from the ROM 120, and then proceeds to step S
At 302, variable information such as the current time is extracted from the timer 150 and added to the fixed data. Here, the variable information is not limited to the current time. As a result, the original additional information is generated first. Then, in step S303, preprocessing such as encryption is performed on the original additional information as necessary. Then, the process proceeds to step S304, where the original additional information is made redundant in the code conversion unit 140. The details of the redundant coding in the code conversion unit 140 will be described later. Step S305
Then, a pattern header for detection is added as necessary. Here, the pattern header has a specific pattern that is unlikely to occur in normal print image data. By adding the pattern header to the original additional information, the pattern header includes The additional information can be reliably detected.

As described above, in this embodiment, an arbitrary specific pattern is generated by adding variable information to fixed information to make it redundant and further adding a detection pattern. Then, the specific pattern is embedded in the image.

<Redundancy Coding Processing> The redundancy coding method according to the present embodiment will be described below.

In this embodiment, even if an error of one bit occurs in one word, the inter-code distance at which the original information can be restored
Assign code 2 FIG. 5 shows an example of a code assignment table (hereinafter, simply referred to as a code table) in the present embodiment. The code table is for associating a plurality of pieces of character information with codes, and is provided in the ROM 120. Alternatively, the code table may be provided in the RAM 110 so as to be updated. In the present embodiment, there are 32 types of characters to which codes are assigned, that is, 5-bit codes, and the codes are assigned within a 9-bit word length. By providing a code table for associating a character with a bit string as described above, it is possible to refer to a bit string from a character or vice versa. That is, in step S304 of FIG. 3, the code conversion unit 140 converts 32 types of characters into bit strings according to the code table.

In this embodiment, a code is assigned to a word having a 9-bit word length.
In the case of bits, the number of nearest neighbor code 9 plus the number itself 10
Dividing the total code number 512 by gives 51.2. Therefore, in the present embodiment, there is a margin for the number of codes 32 to which characters are actually assigned, that is, there is a margin for the distance between the used codes. For this reason, in the present embodiment, a code sequence has the ability to correct 1-bit errors in all codes and the ability to detect some 2-bit errors.

In the present embodiment, since there is a portion where the inter-code distance has a margin as described above, several arrangements are possible as a code sequence. In the present embodiment, a code sequence that can be recognized in 3-bit units as shown in the code table of FIG. 5 is adopted so as to be easily grasped visually.

For example, for characters 1 to 8, a code is created using a 3-bit string "000" and its inverted value "111", and the distance between the mutual codes is always a multiple of three. Also, characters 9 to 16 are 3
A code is created using the bit string "001" and its inverted value "110", the inter-code distance is also always a multiple of 3, and for characters 1-8, always 1 for every 3 bit strings. Since the values for ~ 2 bits are different, the distance between codes is 3 or more.
Similarly, characters 17 to 24 are composed of a 3-bit string “010” and its inverted value “1”.
01 "to create the sign, the system of characters 1-8, and the characters 9
The inter-symbol distance is 3 or more for the systems of ~ 16. The same applies to characters 25 to 32.

As described above, according to the code bit string of the code table shown in FIG. 5, it can be easily confirmed that the mutual code distance in the present embodiment is always 3 or more.

As described above, in the present embodiment, after performing pre-processing such as encryption, a 5-bit value is converted into a 9-bit pattern according to the code table shown in FIG. Do.

<Specific Pattern Detection Process> In this embodiment, the specific pattern embedded in the image as described above is read out by the following process.

First, image data to be printed is read, and the image data is scanned to detect an embedding position of a specific pattern. As described above, in the present embodiment, the specific pattern is added to the specific pattern which is unlikely to occur on normal image data, so that the embedding position can be reliably detected.

Then, the embedded specific pattern is read out, and the bit string of the redundant code of the original additional information is restored based on the specific pattern. The redundant code bit string restored in this way is restored to the original additional information next. Hereinafter, a method of restoring the original additional information will be described.

FIG. 4 is a flowchart of the restoration processing of the original additional information in the present embodiment. First, in step S401, the redundant coded bit string is compared with each code in the code table shown in FIG. As a result of the comparison, if the redundant coded bit string matches any of the codes in the code table in step S402, the process proceeds to step S407, where it is determined that the redundant coded bit string indicates a character corresponding to the matched code. I do.

On the other hand, if the redundant code bit string does not match any code in the code table, step S4
Proceeding to 03, first, an exclusive OR of each code in the code table with the redundant code bit string is calculated. Then, for each of the bit strings obtained as the operation result, the step
In S404, the number of bits that are "1" is counted. Then, in step S405, if there is only one bit “1” in the bit string obtained as a result of the exclusive OR, it is determined that an error has occurred in only one bit of the redundant code bit string. Proceeding to step S407, it is determined that the redundant code bit string indicates a character corresponding to the code to be calculated in the code table.

For example, if the redundant code bit string is "001,001,10"
If "0", the result of the exclusive OR with the code "001,001,110" corresponding to "character 10" in the code table is "000,
000,010 ", and only one bit is different. In addition, as for the exclusive OR with other codes, all bits are two or more".
Thus, the redundant code bit string is considered to be located at the shortest distance from the code of "character 10", and thus is determined to indicate "character 10".

In step S405, if there is no code having a difference of only one bit, that is, it is determined that the restoration of the redundant code bit string has failed, and the flow advances to step S406 to perform appropriate error processing.

As described above, the redundant code bit string is restored, but if encryption has been performed at the time of encoding, the original additional information is reproduced by performing a further decryption process. In this way, similar restoration processing is performed for a plurality of embedded areas of an image, and it is confirmed that the restored original additional information does not contradict each other.

As described above, according to this embodiment,
By using a redundant code capable of error correction as a specific pattern indicating specific information of the apparatus, when forming an image,
It becomes possible to embed patterns that are more difficult for humans to perceive. Therefore, pattern detection can be sufficiently performed while suppressing image quality deterioration due to the specific pattern. That is, it is possible to achieve both the image quality of the output image and the resilience of the specific pattern.

Although the present embodiment has been described with respect to an example in which the redundant encoding is performed by the code conversion unit 140, the present invention can be realized by software. That is, the present invention can also be realized by mounting a code conversion program on the ROM 120 and executing the program by the CPU 130.

[0056]

[Other Embodiments] Even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus (for example, a copying machine) Machine, facsimile machine, etc.).

An object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or apparatus, and to provide a computer (or CPU) of the system or apparatus.
And MPU) read and execute the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

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

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. ) May perform some or all of the actual processing, and the processing may realize the functions of the above-described embodiments.

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

[0062]

As described above, according to the present invention, when specific information is added to image data and output, the image quality of the output image and the resilience of the added specific information can be made compatible. Becomes

[0063]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a device configuration according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a drawing process according to the embodiment.

FIG. 3 is a flowchart illustrating a specific pattern generation process according to the embodiment.

FIG. 4 is a flowchart illustrating restoration processing of additional information according to the embodiment.

FIG. 5 is a diagram showing a code table for redundant coding in the embodiment.

[Explanation of symbols]

 100 Image forming unit 101 Image generating unit 110 RAM 120 ROM 130 CPU 140 Code conversion unit 150 Timer

Claims (18)

[Claims] An input unit for inputting image data; a specific information generating unit for generating specific information to be added to the image data as a code having redundancy; and an adding unit for adding the specific information to the image data. Means, and an image forming means for forming a visible image based on the image data to which the specific information has been added, wherein the specific information generating means generates the specific information as a code having a secured inter-code distance. An image processing apparatus comprising: 2. The image processing apparatus according to claim 1, wherein the inter-code distance is two or more. 3. The image processing apparatus according to claim 1, wherein the inter-code distance is three or more. 4. The image processing apparatus according to claim 1, further comprising a table that is referred to by said specific information generating means at the time of encoding. 5. The image processing apparatus according to claim 4, wherein the table is a table for associating a character to be encoded with its code. 6. The distance between the respective codes held in the table is all two or more.
The image processing apparatus according to any one of the preceding claims. 7. The image processing apparatus according to claim 6, wherein all of the exclusive ORs between the respective codes held in the table have 2 bits or more as 1. 8. The apparatus according to claim 5, wherein the distances between the respective codes held in the table are all three or more.
The image processing apparatus according to any one of the preceding claims. 9. The image processing apparatus according to claim 8, wherein each code held in said table is constituted by a predetermined 3-bit string and its inverted bit string. 10. The image processing apparatus according to claim 1, further comprising a holding unit that holds the specific information as fixed information. 11. The image processing apparatus according to claim 10, further comprising variable information generating means for generating variable information to be added to said specific information. 12. The image processing apparatus according to claim 11, wherein said variable information generating means is a timer, and generates the current time as variable information. 13. The image processing apparatus according to claim 1, wherein the specific information is information capable of specifying the image processing apparatus. 14. An input step of inputting image data, a specific information generating step of generating specific information to be added to the image data as a code having redundancy, and an adding step of adding the specific information to the image data. And an image forming step of forming a visible image based on the image data to which the specific information has been added. In the specific information generating step, the specific information is a code that secures an inter-code distance. An image processing method characterized by generating. 15. The specific information generating step: an obtaining step of obtaining predetermined fixed information; an original additional information generating step of adding variable information to the fixed information to generate original additional information; And a header adding step of adding a header to the encoded data encoded in the encoding step. 15. The image processing step according to 14. 16. The image processing method according to claim 14, wherein the distance between codes is two or more. 17. The image processing method according to claim 14, wherein the inter-code distance is 3 or more. 18. A recording medium on which a program code for image processing is recorded, wherein the program code includes a code for an input step of inputting image data, and a code having redundancy, which is a specific information added to the image data. A code of a specific information generating step generated as a code of an adding step of adding the specific information to the image data; and an image forming step of forming a visible image based on the image data to which the specific information is added. The recording medium, comprising: in the adding step, the specific information is added as a code that secures an inter-code distance.