JPH1141445A - Device and method for processing image and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently decipher additional information by outputting an image to which the prescribed additional information is added while making 1st additional information hard to visual identification through a 1st method and making 2nd additional information hard to visual identification through a 2nd method, and enabling the 1st additional information to specify the 2nd additional in formation. SOLUTION: Corresponding to an instruction for an image processor to print color images, the additional information such as the product name, production number and maker name of the device is inputted to an enciphering circuit 405, enciphered and checked by a parity check circuit 406 and corresponding to its code output, a signal to add addon dots is sent out of a main operation counter 407 and a sub operation counter 408. Based on that signal, an addon dot generating circuit 409 converts image data to addon dots and sends them out. The image data measure the phase difference of addon dots at a host computer, the code is found and a maker ID is acquired. The module of a maker is activated and the additional information such as the product name and the production number is provided.

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 capable of adding additional information to an input image and a storage medium storing the method.

[0002]

2. Description of the Related Art In recent years, image processing apparatuses such as color printers and color copiers have been able to form high-quality images by improving performance. Under such circumstances, it is becoming possible to form an image similar to securities such as banknotes, and a technique for suppressing such an act is known.

For example, there is known an addition method in which a dot pattern indicating a serial number of an image processing apparatus is additionally printed together with a color image to be printed.

This dot pattern is periodically printed on the entire screen, and is added only to the yellow plane.

[0005] The method of adding dot patterns (additional information) as described above differs for each maker that manufactures each image processing apparatus, and is used to decode additional information such as a serial number based on a certain formed image. It is necessary to sequentially use a decoding method according to the additional method of each manufacturer.

[0006]

However, when the number of manufacturers that manufacture the apparatus is large, there is a problem that the load for sequentially using the decoding method is large as described above. In particular, when the above-described decoding is performed by software processing or the like, this problem becomes conspicuous.

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional example, and efficiently decodes additional information from an image in which additional information is hardly recognized by human eyes and may be added by a plurality of methods. It is an object of the present invention to provide an information adding technology that can perform the information.

It is another object of the present invention to provide a technique capable of reliably decoding additional information from an image to which additional information has been added.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, an image processing apparatus according to the present invention adds first additional information to an input image by a first method so as to be difficult for human eyes to recognize. An adding means for adding the second additional information to the human eye by the second method so as to be hardly distinguishable by human eyes, and an output means for outputting an image to which predetermined additional information has been added by the adding means to the image forming section. The first additional information is information that can specify the second method.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In this embodiment, an image processing apparatus using color electrophotography will be described. However, the present invention is not limited to this, and can also be applied to an image processing apparatus using a technique such as an inkjet method or a thermal transfer method. Further, the present invention is not limited to the device invention, but also includes a method of performing the processing described below, software for performing the method, and the like.

In this embodiment, input image data is 8-bit multi-valued image data of each of M (magenta), C (cyan), Y (yellow), and K (black). It is assumed that image data is input in a frame sequential manner.

The image processing apparatus (laser beam printer) of the present embodiment has a resolution of 600 dpi, and a dot pattern indicating additional information for forgery tracking is added only to the Y plane. By doing so, it becomes possible to make it difficult for human eyes to recognize as much as possible, and even if a color image to which additional information is added is used in the same manner as the original color image before adding the additional information. Becomes possible. The present invention is not limited to the case where additional information for tracking forgery is added. That is, the case where the name of the author who created the original image, the name of the work of the image, or the like is used as the additional information is also included in the present invention.

FIG. 1 shows the configuration of an image processing apparatus used in the following embodiments.

An image processing unit 1000 includes M, C,
After sequentially inputting multi-valued image data of Y and K from an external device or another device inside the device, and adding additional information to be described later, the image data of each color is output to the laser emitting unit 100.
The laser light emitting unit 1001 that outputs a laser beam L, which will be described later, is modulated according to the input image data.
Emits light.

The photosensitive drum 100 is charged by the charger 101.
Are uniformly charged to a predetermined polarity, and a first latent image of magenta, for example, is formed on the photosensitive drum 100 by exposure with the laser beam L. Next, in this case, a required developing bias voltage is applied only to the magenta developing device Dm to develop a magenta latent image, and a first magenta toner image is formed on the photosensitive drum 100.

On the other hand, immediately before the transfer paper P is fed at a predetermined timing and its leading end reaches the transfer start position, a transfer bias voltage (+1.8 KV) of the opposite polarity (for example, positive polarity) to the toner is applied to the transfer drum. The first toner image on the photosensitive drum 100 is transferred to the transfer paper P, and the transfer paper P is electrostatically attracted to the surface of the transfer drum 102. Thereafter, the magenta toner remaining on the photosensitive drum 100 is removed by the cleaner 103, and the photosensitive drum 100 is ready for the next color latent image forming and developing process.

Next, as in the case of the above-mentioned magenta, a second latent image of cyan is formed on the photosensitive drum 100 by the laser beam L, and then a cyan developing unit D is formed.
The second latent image on the photosensitive drum 100 is developed by c to form a second cyan toner image. Then, the cyan second toner image is transferred to the transfer sheet P in accordance with the position of the magenta first toner image previously transferred to the transfer sheet P. In the transfer of the second color toner image, a bias voltage of +2.1 KV is applied to the transfer drum 102 immediately before the transfer paper reaches the transfer portion.

Similarly, third of yellow and black,
Fourth latent images are sequentially formed on the photosensitive drum 100,
Each of the toner images is sequentially developed by the developing units Dy and Db, and the third and fourth toner images of yellow and black are sequentially transferred while being aligned with the toner image previously transferred to the transfer paper P. Thus, a full-color image in which four color toner images are superimposed on each other is formed.

Next, additional information for forgery tracking added by the image processing apparatus of the present embodiment will be described.

FIG. 2 shows a state in which additional information is added to an image represented by input image data in the present embodiment. As described above, in the present embodiment, since the additional information is added only to the Y plane, FIG. 2 shows the image indicated by the Y plane of the color image composed of the Y, M, C, and K planes. Is shown.

Each dot 201 scattered in FIG. 2 is a small area dot composed of a plurality of pixels. This dot is hereinafter referred to as an AddOn dot.

In the figure, a shaded area 202 is a unit area indicating additional information added to this color image (yellow plane) in the present embodiment. The unit area 202 periodically exists in the original color image (yellow plane). By doing so, the additional information can be analyzed with respect to any area of the color image finally formed after the additional information is added.

In this unit area 202, there are a plurality of lines 203 called AddOn lines, and in this embodiment, there are 16 lines 203 in the main running difference direction. Note that the above-described AddOn dot corresponds to each AddOn dot in the unit area 202.
It is assumed that one is placed on the On line. As will be described later,
The additional information can indicate various types of information depending on the position (phase) of the AddOn dot on each AddOn line. It is possible to assign a product name, a serial number, a manufacturer name, and the like of the image processing apparatus to the various information.

In the unit area 202, a reference dot 204 for preventing the arrangement direction of AddOn dots for indicating additional information from being erroneously identified is added. The position of this reference dot is always fixed. In the present embodiment, the reference dot 204 is added to the 0th and 7th AddOn lines together with the AddOn dot. By doing so, the AddOn line at the beginning of the unit area can be determined, and the AddOn line 0
The direction of the ~ 15 array can be determined.

FIG. 4 is a block diagram of the AddOn dot addition processing unit included in the image processing unit 1000 of FIG. EEPROM
Additional information (product name, serial number, manufacturer name, etc. of the apparatus) stored in 401 is automatically loaded into the register 402 in the CPU when the power of the image processing apparatus is turned on.

FIG. 3 shows the internal structure of the register 402. In the register 402, F000 to F0
Codes are stored up to address 0A. 8 bits of address F000 and upper 4 bits of address F0001 represented by oblique lines in the figure.
The total of 12 bits is an area dedicated to the above-mentioned maker name (manufacturer ID), and stores a unique ID number assigned to each maker that manufactures the image processing apparatus. In other areas (lower 4 addresses of address F0001)
In the bits and F002 to F00A), codes indicating the product name, serial number, and the like of the image processing apparatus uniquely determined by each manufacturer are entered.

Note that, in addition to the above-described additional information, the register 402 also stores a fixed bit in which a fixed value is entered and a parity bit for parity check.

When the image processing apparatus receives a command to print a color image, the additional information (product name of the apparatus,
The serial number, manufacturer name, etc.) are input to the encryption circuit 405 and encrypted.

The encrypted additional information is input to a parity check circuit 406, where the parity and fixed bits are checked. If an error occurs here, it is determined that the additional information has been remodeled, and control is performed to stop the printing operation.

The main scanning counter 407 performs a counting operation in accordance with a clock signal PCLK in the main scanning direction of image data, and sends ON at a position where an AddOn dot is to be added in accordance with a code loaded from the parity check 406. The sub-scanning counter 408 performs a counting operation according to the clock signal BD in the sub-scanning direction, and is turned on by the AddOn line.
Is sent.

The AddOn dot generation circuit 409 has a CP
U and the main scanning counter 4 receive the AddOn dot shape parameter stored in the ROM 403 in the U and turn ON only when the yellow plane of the image data is transmitted.
07, AddOn dots are generated only when all the sub-scanning counters 408 are ON, and the AddOn signal is turned ON and transmitted.

The AddOn addition circuit 404 sends the input image data as it is if the AddOn signal is OFF,
If the AddOn signal is ON, it is converted to an AddOn dot and transmitted.
Thus, additional information (AddOn dots) is formed as shown in FIG.

Next, a method for analyzing the additional information added to the image data in the present embodiment, that is, a method for representing the additional information by using AddOn dots will be described.

FIG. 5 shows n in the unit area 202 of FIG.
It is an enlarged view of the nth and (n + 1) th AddOn lines. Describing the (n + 1) th AddOn line, a phase difference based on the AddOn dot on the nth AddOn line is assigned to 0 to 7 (3 bits) as shown in the figure.
Then, an AddOn dot is added at a position corresponding to the 3-bit information to be added in the (n + 1) th AddOn line. This makes one AddOn line (AddOn dot)
Can represent three bits of information. Therefore,
In the present embodiment, there are 16 AddOn lines, so that a total of 48 bits of additional information can be added.

However, the present invention is not limited to this, and additional information may be added by another method. For example, by adding a plurality of AddOn dots on each AddOn line, more additional information may be added.

In the analysis of the above-mentioned phase difference, for example, a color image to which additional information is added is read by a scanner, and only the image of the Y (yellow) plane is extracted by a host computer. It can be measured by measuring the distance between them. The code of each AddOn line is determined from the measured phase difference, and the determined codes are arranged as shown in FIG. 6, and after binarized, a00 to a30, b00 to b1
Assigned as information of 12 addresses.

Here, a00 to a32 are manufacturer IDs.
(Maker name), a22, a30, a
31 and a32 are parity bits.

First, when analyzing the ID of the manufacturer, a
00 to a32 are arranged as shown in FIG. 7, and a22, a30, a
It is confirmed that 31 and a32 become even parity in the direction of the arrow in the figure. If an error occurs in the parity check, the measurement is restarted as a maker ID reading error (analysis error).

On the other hand, if no error occurs in the parity check, a00 to a21 are arranged as follows and the manufacturer I
D is to be obtained.

Manufacturer ID = (a21, a20, a12, a11, a10, a02, a01, a00) In the example of FIG. 6, the manufacturer ID is (a21, a20, a12, a11, a10, a02, a01, a00) = 0,0,1,0,0,0,1,0 (B) = 34 (D).

Based on the maker ID obtained here, the maker that manufactured the image processing apparatus involved in the formation of the color image is analyzed.

After analyzing the maker ID, additional information such as a product name and a serial number can be analyzed by a method corresponding to each maker. This is because the method of adding the additional information such as the product name and the serial number may be different for each manufacturer. Therefore, a parity bit is independently added to the maker ID, product name, and serial number.

Subsequently, b00 to b112 (including parity bits) indicating additional information such as a product name and a serial number are analyzed (parity check) independently of the manufacturer ID.

The additional information of b00 to b112 is obtained by decoding the additional information of b00 to b112 and performing a parity check using a method suitable for each manufacturer, and then acquiring a model number and a machine number.

As described above, the maker ID (the maker name)
And product name, serial number (model number, machine number, etc. may be used)
By independently adding a parity bit, even when additional information such as a maker ID and additional information such as a product name and a serial number are added to an image in a different manner, various analyzed additional information can be added. It is possible to reliably check whether or not it is accurate.

FIG. 9 shows a conceptual diagram of additional information of the manufacturer ID, product name, and serial number added in the above embodiment.

In FIG. 9, reference numeral 202 denotes a unit area 2 in FIG.
02. The manufacturer ID is added (expressed) using the AddOn line (AddOn lines 0 to 3) in the area 901 above the unit area 202, and the product name and serial number are assigned to the unit area 2
02 in the lower area 902 (AddOn line 4
To 15) are added (expressed).

The procedure for decrypting the additional information will be described with reference to FIG.

When decoding is started, first, a color image is read by a scanner. However, since the additional information of this embodiment is added to the yellow plane, only the yellow plane is read (step S1). Next, the reference dot is detected, the head of the AddOn line and the direction of the AddOn line are recognized, and the phase difference between the AddOn lines 0 to 3 (AddOn lines 15 and 0, 0 and 1, 1, 2, and 2 and 3) is measured. (Step S
2).

From the measured phase difference, AddOn lines 0 to 3
Is obtained (step S3), converted to a binary number and a0
Assigned to 0 to a32 (step S4). Next, the parity check of FIG. 7 described above is performed (step S5), and if an error occurs, the measurement is repeated from the measurement of the phase difference (step S2). On the other hand, if no error occurs, a maker ID is obtained (step S6).

Next, the phase difference between the AddOn lines 4 to 15 is measured (step S7). From this measured phase difference, Ad
Acquire the codes of dOn lines 4 to 15 (step S
8) Binary numbers are assigned to b00 to b112 (step S9).

Here, the maker I obtained in step S6
It is determined whether D indicates company A (step S10),
If it is company A, a module for company A is started (step S11). Here, the module for Company A rearranges b00 to b112 in accordance with the regulations of Company A, performs a parity check and the like, and acquires a product name, a serial number, and the like.

On the other hand, if it is not company A in step S10, it is next determined whether or not the manufacturer ID indicates company B (step S12). If it is company B, a module for company B is started (step S12). S13) In the same manner as in step S11, b00 to b112 are rearranged in accordance with the rules of Company B, and after performing a parity check and the like, a product name, a serial number, and the like are obtained.

Similarly, if it is not the company B in step S12, the maker IDs are checked next for the number of the registered manufacturers such as company C, company D, and so on.

In the present embodiment, the number of AddOn lines for storing information for each maker is fixed to 12 AddOn lines 4 to 15, but the number of AddOn lines may be variable for each maker. good.

In the above-described embodiment, the parity bit is such that the error can be simply detected in each of the manufacturer ID corresponding to the area 901 in FIG. 9 and the product name and serial number corresponding to the area 902 in FIG. Is added, but the present invention is not limited to this.
1. For each of the additional information corresponding to the area 902,
An error correction code that can correct the error of the additional information may be provided.

Thus, even if there is an error in the analysis of the additional information, the operation of reading the phase difference again can be omitted.

Further, if the additional information of the area 901 cannot be analyzed, the area 902 may not be able to be analyzed. For example, the additional information (manufacturer ID) of the area 901 corresponds to the additional information (product name, serial number) corresponding to the area 902. Etc.) When it is considered that the importance is higher, the additional information in the area 901 is provided with an error correction code having a high error correction capability, and
02 may have an error correction code having a lower error correction capability than the area 901.

According to this, it is possible to reliably analyze an important part of the additional information. Specifically, since the manufacturer ID can be reliably analyzed, a method for analyzing the product name, the serial number, and the like can be determined thereafter.

In the above embodiment, the method of adding the maker ID to the area 901 and the method of adding the product name, serial number, etc. to the area 902 have been described as the same method. However, the present invention is not limited to this. But not areas 901 and 90
This includes the case where the additional information of the second additional information is different.

That is, in the above-described embodiment, a maker ID capable of specifying the addition method of the area 902 is assigned to the area 90.
2 is added to an area 901 different from the area 901, even if the additional information addition method of the areas 901 and 902 is different, if the analysis is performed in the order of the areas 901 and 902 as described above, all of the additional information is There is an effect that can be sufficiently decoded.

In the above embodiment, the additional information is simply added by the AddOn dot obtained by modulating the original image to the highest density. However, the present invention is not limited to this. For example,
Even if an area where the density of the original image is + α and an area where the density is −α are combined to form one AddOn dot, sufficient analysis can be performed. In this case, since the density of the original image is preserved, it is possible to maintain better image quality than in the above embodiment. Further, one AddOn dot may be configured by combining an area where the density of the original image is modulated to the highest density and an area where the density is modulated to the lowest density. According to this, the AddOn dot can be easily decoded regardless of the density of the original image.

(Modification) The present invention may be applied to a part of a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), but may be applied to one device (for example, a copying machine). , A printer, and a facsimile machine).

Further, the present invention is not limited to only the apparatus and method for realizing the above-described embodiment, but includes a computer (CPU or MP) in the above-described system or apparatus.
U), a program code of software for realizing the above-described embodiment is supplied, and the computer of the system or the apparatus operates the various devices according to the program code to realize the above-described embodiment. It is included in the category of the present invention.

In this case, the program code of the software implements the functions of the above-described embodiment, and the program code itself and means for supplying the program code to the computer, specifically, A storage medium storing the above program code is included in the scope of the present invention.

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

In addition to the case where the computer controls various devices in accordance with only the supplied program code to realize the functions of the above-described embodiment, the program code operates on the computer. Such a program code is included in the scope of the present invention even when the above-described embodiment is realized in cooperation with an OS (Operating System) or other application software.

Further, after the supplied program code is stored in a memory provided in a function expansion board of a computer or a function expansion unit connected to the computer, the function expansion board or the function is stored based on the instruction of the program code. The case where the CPU or the like provided in the storage unit performs part or all of the actual processing, and the above-described embodiment is realized by the processing is also included in the scope of the present invention.

[0069]

As described above, according to the first aspect of the present invention, predetermined additional information is added to an input image by using one of a plurality of conceivable methods, so that the additional information is hardly recognized by human eyes. In such a case, the additional information that can specify the method of adding the predetermined additional information is hard to be discerned by the human eye, and the additional information is efficiently extracted from the image to which the predetermined additional information is added. Can be decoded.

According to the fifteenth aspect, the first additional information including the error correction code having the first error correction capability is added to the input image so as to be difficult for the human eye to recognize and the first additional information is added. Since the second additional information including the error correction code having the second error correction capability different from the error correction capability is added so that it is difficult for the human eye to identify the second additional information, the second additional information is added to the image so that it is difficult for the human eye to identify the image. When a plurality of pieces of additional information have different degrees of importance, the additional information having a higher degree of importance can be reliably decoded.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an image processing apparatus applied to the present invention.

FIG. 2 is a diagram illustrating a state in which additional information is added to an input image.

FIG. 3 is a diagram showing a state of a register for storing a tracking code (additional information).

FIG. 4 is a block diagram of an AddOn dot addition processing unit.

FIG. 5 is a diagram illustrating a method of expressing information by using AddOn dots.

FIG. 6 is a diagram showing a code indicated by each AddOn line.

FIG. 7 is a diagram showing parity bits of a maker ID.

FIG. 8 is a diagram showing a procedure for decoding additional information from an image to which additional information has been added.

FIG. 9 is a conceptual diagram of additional information of a maker ID, a product name, and a serial number.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 photosensitive drum 101 charger 102 transfer drum 103 cleaner 1000 image processing unit

Claims (30)

[Claims] 1. An image processing method according to claim 1, further comprising:
In addition to adding to the human eye by the method of
An adding unit that adds the second additional information to the human eye by the second method so that the second additional information is hard to be identified by human eyes; and an output unit that outputs an image to which the predetermined additional information is added by the adding unit to an image forming unit. The image processing apparatus according to claim 1, wherein the first additional information is information capable of specifying the second method. 2. The image processing apparatus according to claim 1, wherein the first addition method is different from the second addition method. 3. The image processing apparatus according to claim 1, wherein the first addition method and the second addition method are the same. 4. The input image is a color image composed of planes of a plurality of colors, and the adding unit performs the first and second additions only on some of the planes of the plurality of colors. The image processing apparatus according to claim 1, wherein information is added. 5. The image processing apparatus according to claim 1, wherein the first additional information is a maker of the image processing apparatus. 6. The image processing apparatus according to claim 1, wherein the second additional information is a model number or a product name of the image processing apparatus. 7. The image processing apparatus according to claim 1, wherein the second additional information is a machine number or a serial number of the image processing apparatus. 8. The image processing apparatus according to claim 1, further comprising the image forming unit. 9. The method according to claim 1, wherein the first additional information is a pattern composed of a plurality of dots.
An image processing apparatus according to claim 1. 10. The image processing apparatus according to claim 1, wherein the second additional information is a pattern including a plurality of dots. 11. The image processing apparatus according to claim 1, wherein the additional information is periodically added to the input image. 12. The first additional information is added to a first area of the input image, and the second additional information is added to the first area of the input image.
The image processing apparatus according to claim 1, wherein the image processing apparatus is added to a second area different from the area. 13. The method according to claim 1, wherein the first additional information is added to the input image by the first method so that the first additional information is not easily discriminated by human eyes, and the second additional information is hardly discriminated by the second method. An adding step of adding an image to which predetermined additional information has been added in the adding step to an image forming unit, wherein the first additional information specifies the second method. An image processing method characterized in that the information can be processed. 14. The method according to claim 1, wherein the first additional information is added to the input image by the first method so as not to be easily discerned by human eyes, and the second additional information is hardly discriminated by the second method to human eyes. An adding step of adding an image to which predetermined additional information has been added in the adding step to an image forming unit, wherein the first additional information specifies the second method. A storage medium storing an image processing program characterized in that the image processing program is information that can be read by a computer. 15. An input image, wherein first additional information including an error correction code having a first error correction capability is added to the input image so as to be difficult for a human eye to recognize, and a first additional information different from the first error correction capability is added. Adding means for adding second additional information including an error correction code having an error correction capability of 2 to the human eye so that the additional information is difficult to recognize, and outputting an image to which predetermined additional information has been added by the adding means to an image forming unit. An image processing apparatus comprising: 16. The image processing apparatus according to claim 15, wherein the first additional information is information capable of specifying a method of adding the second additional information by the adding unit. 17. The image processing apparatus according to claim 15, wherein said first error correction capability is higher than said second error correction capability. 18. The image processing apparatus according to claim 15, wherein a method of adding the first additional information and a method of adding the second additional information are different. 19. The image processing apparatus according to claim 15, wherein a method of adding the first additional information and a method of adding the second additional information are the same. 20. The input image is a color image composed of planes of a plurality of colors, and the adding unit performs the first and second additions only on some of the planes of the plurality of colors. The image processing apparatus according to claim 15, wherein information is added. 21. The image processing apparatus according to claim 15, wherein the first additional information is a maker of the image processing apparatus. 22. The image processing apparatus according to claim 15, wherein the second additional information is a model number or a product name of the image processing apparatus. 23. The image processing apparatus according to claim 15, wherein the second additional information is a machine number or a serial number of the image processing apparatus. 24. The image processing apparatus according to claim 15, further comprising the image forming unit. 25. The image processing apparatus according to claim 15, wherein the first additional information is a pattern composed of a plurality of dots. 26. The image processing apparatus according to claim 15, wherein the second additional information is a pattern composed of a plurality of dots. 27. The image processing apparatus according to claim 15, wherein the additional information is periodically added to the input image. 28. The method according to claim 28, wherein the first additional information is added to a first area of the input image, and the second additional information is added to the first area.
The image processing apparatus according to claim 1, wherein the image processing apparatus is added to a second area different from the area. 29. An input image, in which first additional information including an error correction code having a first error correction capability is added to the input image so as to be hardly discernible to human eyes, and a first additional information different from the first error correction capability is added. An additional step of adding the second additional information including an error correction code having an error correction capability of 2 to the human eye so that the second additional information is hardly discernable, and outputting an image to which predetermined additional information has been added to the image forming unit in the additional step. An image processing method. 30. An input image, wherein first additional information including an error correction code having a first error correction capability is added to the input image so as to be difficult for a human eye to identify, and a first additional information different from the first error correction capability is added. An additional step of adding the second additional information including an error correction code having an error correction capability of 2 to the human eye so that the second additional information is hardly discernable, and outputting an image to which predetermined additional information has been added to the image forming unit in the additional step. A storage medium storing an image processing program in a state readable by a computer.