JP2005039448A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which determines whether a concealed pattern is added, based on the required conditions of the gradation and the resolution for printing an original such as specific originals of high fidelity when images are formed in colors. <P>SOLUTION: The image forming apparatus capable of burying a concealed pattern containing identification information of the image forming apparatus in a print image composed of pixels having a specified resolution allows the gradation to be selected for the pixels at printing, and determines whether the concealed pattern is buried in the print image, based on the selected gradation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus that embeds a hidden pattern in a print image so that illegal printing of a specific document such as securities can be traced.
[0002]
[Prior art]
Conventionally, there are color copiers and color printers as color image forming apparatuses. In recent years, with technological innovation in the technical fields related to color image formation such as digital technology, image processing technology, image forming technology, etc., color image forming apparatuses capable of copying and printing faithful to manuscripts are increasing. There is also an increased risk of illegal copying of securities and securities using color image forming apparatuses, particularly recent digital color copying machines and printers.
[0003]
Therefore, in such digital color image forming apparatuses, when the original is read, regardless of whether the original is a specific original such as banknotes or securities, the identification code or image formation date of the image forming apparatus is used. Information relating to image formation such as a pattern or color that is difficult to be recognized by human eyes is embedded in an image as a so-called hidden pattern and printed.
[0004]
Japanese Patent Application Laid-Open No. H10-260260 proposes printing with an image forming apparatus manufacturing number and user ID information added to an image as a hidden pattern in yellow which is difficult to be recognized by human eyes. However, in such a conventional method, since a specific pattern is added regardless of whether the document is a specific document, a print result unexpected by the user may be output. In addition, the yellow color material of the hidden pattern is certainly difficult for human eyes to identify if the paper is white, but when printed on the color paper, the hidden pattern will stand out and stand out depending on the color. It is possible.
[0005]
In order to avoid such a problem, Patent Document 2 discloses that the color of the hidden pattern is automatically selected according to the background color of the paper or the like. However, superimposing a hidden pattern on an image consumes a great deal of time for image processing and increases the time required for printing. Also, if the background color is analyzed to determine the color of the hidden pattern, the process will take more time.
[0006]
For this reason, Patent Document 3 has an achromatic color (black and white) image data determination unit. When achromatic color image data is input, the image is printed out without adding a hidden pattern to the image. An image processing apparatus is disclosed in which, when color (color) image data is input, a hidden pattern is added to the image data and printed out.
[0007]
Patent Document 4 analyzes input image data and determines whether the image data is an achromatic color, if it is a color, whether it is a monocolor (a single color other than black), next, whether it is image data, Whether the image data has a resolution higher than a specific resolution, whether the selected paper is thick enough to be used for a specific original, and whether the paper type is used for a specific original It is proposed to sequentially determine whether or not the paper size is a size that can be used for a specific document, and to add a hidden pattern only when all the conditions are met.
[0008]
[Patent Document 1]
JP-A-4-294682 [Patent Document 2]
JP 2000-324326 A [Patent Document 3]
JP-A-5-14682 [Patent Document 4]
Japanese Patent Laid-Open No. 2000-307845
[Problems to be solved by the invention]
However, the method disclosed in Patent Document 3 that solves the problem caused by adding a hidden pattern is effective only when a color image forming apparatus prints a monochrome image. However, in a color image forming apparatus, since most of the work is print output in color, a hidden pattern is added to all the output of such a color image, and the problem that occurs when a hidden pattern is added, that is, hidden. The increase in the printing time due to the image processing time for synthesizing the pattern and the analysis time of the background color cannot be substantially solved.
[0010]
Since Patent Document 4 prints a hidden pattern only when the image quality and printing conditions are likely to be regarded as a specific document, only an extra image processing time is required only during specific printing. On the other hand, it is necessary to perform analysis of various images and papers in several stages until that point, and extra analysis and judgment time are required until there is no need to add a hidden pattern. The time until it will be extended.
[0011]
The present invention has been made in view of such a situation. When an image is formed in color, it is concealed based on gradation and resolution conditions necessary for faithfully printing a document such as a specific document. An object of the present invention is to provide an image forming apparatus that determines whether or not to add a pattern.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, in an image forming apparatus capable of embedding a hidden pattern including identification information of the image forming apparatus in a print image composed of pixels having a predetermined resolution, The gradation can be selected at the time of printing, and it is determined whether or not the hidden pattern is embedded in the print image based on the selected gradation.
[0013]
When the selected gradation property is larger than the predetermined gradation property, the hidden pattern is embedded in the print image.
[0014]
Further, according to the present invention, a hidden pattern including identification information of the image forming apparatus is embedded in a print image composed of pixels formed by performing main scanning and sub scanning at the main scanning resolution and the sub scanning resolution, respectively. In the image forming apparatus that enables the pixel, at the time of printing, it is possible to select only the main scanning resolution or the main scanning resolution and the sub-scanning resolution together with the selection of the gradation, and the selected gradation is selected. On the basis of the selected main scanning resolution or the main scanning resolution and the sub-scanning resolution, it is determined whether or not the image to be printed has a high image quality. Embed in.
[0015]
When the product of the selected gradation and the selected main scanning resolution or the main scanning resolution and the sub-scanning resolution is larger than a predetermined value determined as high image quality, a hidden pattern is included in the print image. Embed.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the details of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic front view showing a schematic structure of a color image forming apparatus according to this embodiment. In FIG. 1, a color image forming apparatus (hereinafter referred to as an image forming apparatus) 1 is schematically composed of a scanner unit 2 that reads an image of a document and a printing unit 10 that prints an image that has been read and processed on a sheet. . When the image forming apparatus 1 is connected to an information processing apparatus (not shown), print data including image data and a print command is sent from the information processing apparatus to the printer controller 36.
[0017]
The scanner unit 2 includes an optical unit 30 including a lens, a mirror, or a prism (not shown), a CCD 31 on which light from the original enters through the optical unit 30 and forms an image, and each pixel of the formed image. An analog signal processing unit 32 that converts the charge level of each element of the corresponding CCD 31 into an analog signal, an A / D conversion unit 33 that converts the analog signal into a digital signal, and image processing that performs image processing on the digital signal of each pixel Part 34.
[0018]
The printing unit 10 includes image forming units 3Y, 3M, 3C, and 3K for Y (yellow), M (magenta), C (cyan), and K (black), and toner hoppers 4Y and 4M corresponding to these colors. 4C and 4K, a paper feed unit 5 that stores paper P as a recording medium, a paper feed guide 6, a paper feed timing roller 7, a paper feed timing motor 7a that drives the paper feed timing roller 7, and conveyance A belt 8, a conveyor belt roller 11 and a conveyor belt motor 11 a that drive the conveyor belt, a transfer roller 12, a fixing unit 13, paper discharge rollers 14 to 16, a paper discharge roller 18, and a paper discharge unit 19. The unit 20 includes an operation input unit (not shown) and an operation unit 27 having a display unit.
[0019]
The image forming units 3Y, 3M, 3C, and 3K for each color include a developing unit 22, a photoreceptor 23, a charger 24, an exposure device 25, and a cleaning unit 26, respectively.
[0020]
Next, a schematic operation of the image forming apparatus 1 having the above configuration will be described. First, after setting a document on the scanner unit 2, when the operation unit 27 is operated to start copying, the optical unit 30 operates to scan the document. Light from the document is input to the image processing unit 34 as image data of a digital signal via the CCD 31, the analog signal processing unit 32, and the A / D conversion unit 33. The image processing unit 34 performs pre-image processing such as shading correction on the input image data. The image data processed in this way or the image data sent from the information processing apparatus is added with a hidden pattern in the image by the hidden pattern addition processing unit 37 as necessary, and the colors are respectively yellow, magenta and cyan. After the decomposition, the image processing according to each mode is performed, a black color element is added, and temporarily stored in the image memory 35 according to an instruction from the control unit 20. Thereafter, the images are sent to the image forming units 3Y to 3K for printing.
[0021]
On the other hand, the photosensitive member 23 charged by the charger 24 of each of the image forming units 3Y to 3K is exposed by the exposure device 25 in accordance with the image signal for each color of YMCK that has been color-separated, and an electrostatic latent image is formed on the surface. Form. The photoreceptor 23 on which the electrostatic latent images of the respective colors are recorded in this way is developed with the corresponding color toner by the developing device 22, and a visible image is formed on the surface thereof. Such an image forming process is performed for each color.
[0022]
The paper P fed from the paper feed unit 5 is guided and sent out by the paper feed guide 6, but temporarily stops in a state where its leading end is sandwiched between the paper feed timing rollers 7. When the paper feed timing motor 7a is driven by a signal from the control unit 20 in synchronization with the image formation on the photosensitive member 23, the paper feed timing roller 7 transports the paper P and the transport belt motor 11a. The belt roller 11 conveys it to the upper surface of the conveyor belt 8 rotating counterclockwise. Then, the paper P is attracted to the upper surface of the transport belt 8 and when passing through the image forming units 3Y, 3M, 3C, and 3K for each color, the image for each color is transferred to the paper by the transfer roller 12 to which a transfer voltage is applied. Sequentially transferred to P.
[0023]
In this way, the four color toners that are superimposed on the paper P to form a full color image are fixed to the paper P by being heated and pressurized when the paper P passes through the fixing unit 13. Thereafter, the paper P is sequentially conveyed by the paper discharge rollers 14, 15, and 16 and is guided to the discharge unit 19 via the discharge roller 18.
[0024]
The above configuration will be specifically described with reference to a block diagram. FIG. 2 is a block diagram showing the main part of the image forming apparatus 1 according to the present invention. The image forming apparatus 1 includes the control unit 20, the operation unit 27, the paper feeding unit 5, the image forming units 3Y, 3M, 3C, and 3K, the fixing unit 13, and the scanner unit 2 described with reference to FIG. In addition to this, the printer controller 36 that receives print data from an information processing device (not shown) and performs print control, preprocessing of an image read by the scanner unit 2, and transmission from the preprocessed image data and the information processing device The processed image data is subjected to image processing in accordance with the print mode and the like, and an image processing unit 34 for color separation into YMCK color elements, an image memory 35 for temporarily storing the processed image data, and an image memory 35 A hidden pattern addition processing unit 37 adds a hidden pattern to the accumulated image data as necessary.
[0025]
As described above, the image forming apparatus 1 according to the present embodiment performs image processing on the image data of the document read by the scanner unit 2 by the image processing unit 34 and adds a hidden pattern by the hidden pattern addition processing unit 37 if necessary. Then, an image data portion of print data including a copy function to be printed by the printing unit 10, an image data input from an information processing device (not shown) via a communication circuit (not shown) and the printer controller 36, and a print command is processed by image processing. And a printer function for printing out by the printing unit 10 (FIG. 1) after adding a hidden pattern.
[0026]
Next, the image quality of the conventional color image forming apparatus or the image forming apparatus 1 according to the present embodiment will be described with reference to FIG. FIGS. 3A and 3B are diagrams for explaining the relationship between the resolution for determining the image quality and the gradation. FIG. 3A shows the case of a binary image, and FIG. 3B shows the case of a multi-value image. When viewing a binary image of black and white or monocolor whose pixels do not have gradation, such as characters and lines, the image quality becomes better as the resolution becomes higher. Here, the resolution is represented by the number of dots per unit length dpi (dots per inch). As shown in FIG. 3A, the increase in image quality usually reaches a peak at about 1200 dpi.
[0027]
However, the image quality of a photograph or an image having continuous shading is influenced not only by resolution but also by gradation. For example, as shown in FIG. 3B, in order for an image to be generally judged to have high image quality through the human eye, a certain degree of resolution and high gradation, a medium resolution and a medium resolution This is determined by a combination of gradation and resolution such as gradation, very high resolution and a certain degree of gradation or binary.
[0028]
In the color image forming apparatus, each color point of YMCK has such resolution and gradation, but in the following description, one color will be described as a representative. 4A and 4B are diagrams for explaining dither processing that expresses gradation characteristics by area, where FIG. 4A is ¼ density, FIG. 4B is 2/4 density, and FIG. 4C is 3/4 density. (D) shows 4/4 density. Four dot units that can be formed by the image forming apparatus, so-called pixels, are grouped into one halftone cell (hereinafter cell). Furthermore, this is a processing method that expresses the density in four stages (2 bits) as an apparent point. Pixels indicated by hatches are exposed and developed with color materials. When a cell is composed of 4 × 4 pixels, 16 densities, that is, 16 gradations can be expressed.
[0029]
When the pixel size that can be formed by the image forming apparatus is determined, the method of expressing gradation by this dither processing increases the gradation (when the number of pixels in the cell is increased), the cell size increases. The apparent resolution is reduced, and the image is rendered rough. When the image quality is in a region other than the hatched region in FIG. 3B when the specific gradation property and the apparent resolution are present, the apparent resolution is lowered even if the gradation property is increased. The image quality is not greatly changed. This is a method adopted in a conventional general image forming apparatus.
[0030]
FIG. 5 is an example of an exposure pattern formed using a laser exposure apparatus used in an image forming apparatus. (A) shows one pixel, (b) shows four gradations per pixel, and (c) shows one. It is an example of a pixel represented by 8 gradations of pixels. Many recent laser exposure apparatuses or LED exposure apparatuses are capable of expressing multi-level gradation within one pixel. In particular, as shown in FIGS. 5A, 5B, and 5C, there are laser exposure apparatuses that can be used by switching the pixel size, that is, the resolution in several stages. FIG. 5A is an example of a binary representation pixel having a resolution of 2400 dpi and having a density of 1 pixel. (B) is a pixel size of 1200 dpi, although the pixel size is slightly larger, when laser irradiation is performed up to point 50 within one pixel, 1/4 density, up to point 51, 2/4 density, up to point 52 In this example, 3/4 density and 4/4 density up to point 53 are shown. Similarly, (c) has a pixel size of 600 dpi and can express 8 gradations by laser irradiation from points 60 to 67.
[0031]
As in the example of laser exposure shown in FIG. 5, even in the case of a pixel that can express gradation in one pixel, the pixel size changes and the so-called apparent resolution also changes. According to the control method, it is possible to improve gradation without reducing the apparent resolution as much as the dither processing method shown in FIG. It is also possible to switch the resolution according to the type of image data.
[0032]
As another example, in the case of a sublimation printer, it is generally possible to express 256 gradations per pixel at 300 dpi, and the image quality is comparable to a silver salt photograph.
[0033]
As in the above example of gradation and resolution, when the gradation can be changed with a fixed resolution, when the resolution and gradation can also be changed, or when the gradation can be fixed and the resolution can be changed (binary processing) The image forming apparatus) can be considered in various cases, but the specific image is printed faithfully to the image quality of the document, and the image quality that is mistaken for the human eye is the high image quality shown in FIG. This can be obtained when the resolution and gradation are located in the region. In other words, in the case of an image forming apparatus in which the resolution is fixed and the gradation can be selected, it is determined whether or not the specific document has a high image quality that is faithfully printed based on the in-pixel gradation. Only when this is done, the hidden pattern addition processing unit of FIGS. 1 and 2 may synthesize the hidden pattern with the image data. Normally, the gradation selection data is included in a print command sent together with image data from the information processing apparatus when the image forming apparatus 1 is used as a printer. 1 is included in the instruction by the selection operation via the operation unit 27 in FIGS. 1 and 2, and can be easily determined without analyzing image data having a huge amount of information. .
[0034]
A procedure for adding the hidden pattern by judging the intra-pixel gradation as described above will be described with reference to FIG. FIG. 6 is a flowchart for judging the intra-pixel gradation and adding a hidden pattern. In S1 (step 1), print data including image data and a print command is received. In this case, when the image forming apparatus 1 is used as a printer, it is received from an information processing apparatus (not shown). When the image forming apparatus 1 is used as a copying machine, it is image data read by a scanner and a print command by an operation from an operation unit.
[0035]
In S2, it is determined whether or not full-color printing is performed based on the print command. If it is not full-color printing, there is no problem even if a specific document is printed. Therefore, the process proceeds to S5 without adding a hidden pattern. Printing is performed according to the print command. If it is determined in S2 that full-color printing is performed, the print command is analyzed in S3, and it is determined whether or not the intra-pixel gradation is a predetermined value that is determined to be high image quality, for example, 8 or more. If not, it is not determined that the image quality is high-quality printing, and the process proceeds to S5 to perform printing according to the print command. If it is determined in S3 that the in-pixel gradation is equal to or greater than a predetermined value, the process proceeds to S4, where the hidden pattern addition processing unit 37 (FIGS. 1 and 2) prints a previously registered hidden pattern. Append to image. Thereafter, in S5, the image is printed according to the print command.
[0036]
Next, when the resolution is fixed and the gradation can be changed, the resolution and the gradation can be changed, the gradation is fixed and the resolution can be changed, etc. What is necessary is just to judge whether the product of resolution and gradation becomes more than a predetermined value. In the case of the dither processing shown in FIG. 4, if the gradation is increased, the resolution (including the apparent resolution) is lowered, so the product of both is not changed. Further, in the method using laser exposure shown in FIG. 5, the resolution is not as inversely proportional to the gradation as the dithering process, so both the resolution and the gradation are important as image quality criteria.
[0037]
Further, printing of the image forming apparatus is performed by scanning with the resolution in the main scanning direction and scanning with the resolution in the sub scanning direction, and each resolution affects the image quality. It may be performed according to scanning resolution and gradation. An example of a combination of main scanning resolution, sub-scanning resolution, and gradation that is determined as high image quality will be described below as an example.
[0038]
The main scanning resolution is selected from 300, 600, 1200, 2400 dpi, the sub-scanning resolution is switched from 300, 600, 1200, 2400 dpi, and the gradation is switched from 2, 4, 16, 64. It is done from the gradation. In this example, the combination (main scanning resolution × sub-scanning resolution × gradation) determined as high image quality is as follows.
1) 300 dpi × 300 dpi × 64 gradations = 5,760,000
2) 600 dpi × 600 dpi × 16 gradations = 5, 760,000
3) 1200 dpi × 1200 dpi × 4 gradations = 5,760,000
4) 2400 dpi × 2400 dpi × 1 gradation = 5,760,000
[0039]
For example, when it is possible to determine that all the combinations 1) to 4) have high image quality when printing a specific document, the value of main scanning resolution × sub-scanning resolution × gradation is 5,760,000 or more. It is possible to determine whether or not to add a hidden pattern simply by determining whether or not. Of course, this value may vary depending on the image forming apparatus to be used.
[0040]
Next, a procedure for adding a hidden pattern using the above-described determination criteria will be described with reference to FIG. FIG. 7 is a flowchart for adding a hidden pattern by determining main scanning resolution × sub-scanning resolution × gradation. In S11 (step 11), print data including image data and a print command is received. In this case, when the image forming apparatus 1 is used as a printer, it is received from an information processing apparatus (not shown). When the image forming apparatus 1 is used as a copying machine, it is image data read by a scanner and a print command by an operation from an operation unit.
[0041]
In S12, it is determined whether or not full-color printing is performed based on the information included in the print command. If it is not full-color printing, there is no problem even if a specific document is printed. Then, printing according to the print command is performed. If it is determined in S12 that full-color printing is performed, in S13, the image quality is defined as main scanning resolution × sub-scanning resolution × gradation, and the calculation is performed. In this case, main scanning resolution, sub-scanning resolution, and gradation are all data included in the print command. In S14, it is determined whether or not the image quality level is a predetermined value that is determined to be high image quality, for example, 5,760,000 or more. Printing according to the print command is performed. If it is determined in S14 that the image quality level is equal to or greater than a predetermined value, the process proceeds to S15, and the hidden pattern addition processing unit 37 (FIGS. 1 and 2) adds a previously registered hidden pattern to the image data. To do. Thereafter, in S16, the image data is printed according to the print command.
[0042]
In the present embodiment, an image forming apparatus that forms a color image using four colors has been described as an example. However, a color copying machine that can implement the present invention is not limited to four colors, for example, three colors or five colors. It may be more than color.
[0043]
In addition, the numerical value 8 of the intra-pixel gradation used in the description based on FIG. 6 and the numerical value 5, 760,000 of the image quality used in the description based on FIG. 7 are examples for simply explaining the present embodiment. In practice, it is determined by analyzing the image quality of each image forming apparatus.
[0044]
Furthermore, in the description based on FIG. 7, the resolution is divided into the main scanning resolution and the sub scanning resolution. However, in an image forming apparatus in which the sub scanning resolution is fixed and cannot be selected, the image quality level = main scanning resolution × It may be set so as to have gradation, and it may be determined whether to add a hidden pattern based on the image quality level.
[0045]
【The invention's effect】
According to the present invention, when a specific original such as banknotes or securities is printed in an image forming apparatus that embeds identification information of an image forming apparatus in a hidden pattern and prints the image by adding the hidden pattern, it is recognized as a specific original. Since a hidden pattern is added only when printing is performed with an image quality that can be printed, the image forming apparatus does not perform unnecessary processing at the time of printing below the image quality, and it is possible to prevent a decrease in printing processing speed.
[0046]
In addition, since a hidden pattern is added only when printing with an image quality that can be recognized as a specific document, the hidden pattern is printed on a portion other than a white background when printing with an image quality that originally does not require a hidden pattern. The frequency of printing can be reduced.
[0047]
Furthermore, since the determination of whether or not the image quality can be recognized as a specific document is determined by the in-pixel gradation at the time of printing, or the product of resolution and gradation, analysis of image data with a huge amount of data is required. In addition, the time required for the judgment can be greatly shortened.
[Brief description of the drawings]
FIG. 1 is a schematic front view showing a schematic structure of a color image forming apparatus according to an embodiment.
FIG. 2 is a block diagram showing a main part of the image forming apparatus 1 according to the present invention.
3A and 3B are diagrams for explaining the relationship between resolution and gradation that determine image quality, where FIG. 3A shows a binary image and FIG. 3B shows a multi-value image.
FIGS. 4A and 4B are diagrams for explaining dither processing in which gradation is provided by area; FIG. 4A is a 1/4 density, FIG. 4B is a 2/4 density, FIG. 4C is a 3/4 density; d) shows 4/4 density.
FIGS. 5A and 5B are examples of exposure patterns formed using a laser exposure apparatus used in an image forming apparatus. FIG. 5A shows one pixel, FIG. 5B shows one pixel and four gradations, and FIG. It is an example of a pixel represented by 8 gradations of pixels.
FIG. 6 is a flowchart for determining the intra-pixel gradation and adding a hidden pattern.
FIG. 7 is a flowchart for adding a hidden pattern by determining main scanning resolution × sub-scanning resolution × gradation.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Scanner part 3Y, 3M, 3C, 3K Image forming part 4Y, 4M, 4C, 4K Toner supply container 5 Paper feed part 6 Paper feed guide 7 Paper feed timing roller 7a Paper feed timing motor 8 Conveyor belt 10 Printing Section 11 Conveyor Belt Roller 11a Conveyor Belt Motor 12 Transfer Roller 13 Fixing Section 14, 15, 16 Discharge Roller 18 Discharge Roller 19 Discharge Section 20 Control Section 22 Developer 23 Photoconductor 24 Charger 25 Exposure Device 26 Cleaning Section 27 Operation Section 30 Optical unit 32 Analog signal processing unit 33 A / D conversion unit 34 Image processing unit 35 Image memory 36 Printer controller 37 Hidden pattern addition processing units 50 to 53, 60 to 67 Point P Paper

Claims (4)

In an image forming apparatus capable of embedding a hidden pattern including identification information of an image forming apparatus in a printed image composed of pixels having a predetermined resolution,
The image forming apparatus, wherein the gradation of the pixel can be selected at the time of printing, and whether or not the hidden pattern is embedded in the print image is determined based on the selected gradation. The image forming apparatus according to claim 1, wherein the hidden pattern is embedded in the print image when the selected gradation is greater than a predetermined gradation. An image forming apparatus capable of embedding a hidden pattern including identification information of the image forming apparatus in a print image composed of pixels formed by performing main scanning and sub scanning at the main scanning resolution and the sub scanning resolution, respectively. In
At the time of printing, it is possible to select only the main scanning resolution, or the main scanning resolution and the sub-scanning resolution, and select the selected gradation and the main scanning. Based on the resolution or the main scanning resolution and the sub-scanning resolution, it is determined whether or not the image to be printed has high image quality. If it is determined that the image has high image quality, the hidden pattern may be embedded in the printed image. An image forming apparatus. When the selected gradation property and the selected main scanning resolution or each product of the main scanning resolution and the sub-scanning resolution are larger than a predetermined numerical value determined to be high image quality, the hidden pattern is converted into the print image. The image forming apparatus according to claim 3, wherein the image forming apparatus is embedded in the image forming apparatus.

Images