JP2015104065A - Image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compound machine 100 capable of enhancing the visibility of a stamp image even when the print sheet is a colored sheet.SOLUTION: A compound machine 100 includes: sheet color detection means 403 for detecting the color of a sheet for image formation; image generation means 402 for generating image data containing a stamp image with the detected sheet color as a background; boundary determination means 404 for determining whether or not a color of the stamp image in the vicinity of an overlapping part of the stamp image and the print image of the image data is similar to the color of the print image in the vicinity of the overlapping part; and color inversion means 405 for converting the color of a boundary of the overlapping part to an inversion color when the color of the stamp image in the vicinity of the overlapping part is, as a result of the determination, similar to the color of the print image in the vicinity of the overlapping part.

Description

  The present invention relates to an image forming apparatus and an image forming method, and more particularly, to an image forming apparatus and an image forming method capable of improving the visibility of a stamp image even on a colored printing sheet.

  Conventionally, an image forming apparatus has a stamp function for adding a stamp image to image data. The following conventional techniques exist for this stamp function.

  For example, Japanese Patent Laying-Open No. 2013-5345 (Patent Document 1) discloses an image forming apparatus that forms an output image by adding an additional image according to settings on a document image. In this apparatus, an image determination unit that determines the presence / absence and attribute of an object of the document image that overlaps the additional image, and a portion where the additional image and the object overlap each other according to the attribute of the object And an image adding unit for sharpening and adding the additional image. As a result, only the portion where the additional image and the original image object overlap can be sharpened according to the attribute of the object, so that the recognition when the additional image and the original image object overlap is recognized. It can be improved.

  In addition, JP-A-9-186850 (Patent Document 2), JP-A 2002-262107 (Patent Document 3), JP-A 2003-274133 (Patent Document 4), JP-A 2003-244422 ( Patent Document 5) exists.

JP 2013-5345 A JP-A-9-186850 JP 2002-262107 A JP 2003-274133 A JP 2003-244422 A

  However, with the technique described in Patent Document 1, the recognition when the stamp image and the document image overlap is improved, but for example, the recognition product (visibility) when the printing paper itself has a predetermined color (visibility). Whether to improve is unknown. In the technique described in Patent Literature 2-5, the relationship between the color of the printing paper itself and the color of image data for image formation is not taken into consideration.

  Accordingly, the present invention has been made to solve the above-described problem, and an image forming apparatus and an image forming apparatus capable of improving the visibility of a stamp image even on a colored printing sheet. It aims to provide a method.

  In order to solve the above-described problems and achieve the object, an image forming apparatus according to the present invention is an image forming apparatus including an image forming unit that forms an image on a sheet based on image data to which a stamp image is added. Therefore, the following configuration is adopted.

  That is, the image forming apparatus includes a sheet color detecting unit that detects a sheet color for image formation, an image generating unit that generates image data with a stamp image with the detected sheet color as a background, Boundary determination means for determining whether or not the color of the stamp image in the vicinity of the overlap portion between the stamp image and the print image of the image data approximates the color of the print image in the vicinity of the overlap portion; As a result, when the color of the stamp image in the vicinity of the overlapped portion approximates the color of the print image in the vicinity of the overlapped portion, color inversion means for converting the border color of the overlapped portion into an inverted color is provided. It is characterized by that.

  Further, the boundary determination means is a pixel adjacent to the pixel constituting the boundary of the overlapping portion, the color information of the pixel of the stamp image, and the pixel adjacent to the pixel constituting the boundary of the overlapping portion, and the print image Is obtained by subtracting the color information of the pixel of the print image from the color information of the pixel of the stamp image, and whether the subtraction value exceeds a preset threshold value. By determining whether or not, it is determined whether or not the color of the stamp image in the vicinity of the overlapping portion approximates the color of the print image in the vicinity of the overlapping portion.

  Further, the paper color detection means detects the color of the paper to be conveyed using a sensor provided in advance at a predetermined position in a conveyance path from the paper feed cassette containing the paper to the image forming unit. Detect.

  The present invention can be configured as an image forming method including a step of forming an image on a sheet based on image data to which a stamp image is added. In this method, a step of detecting a paper color for image formation, a step of generating image data with a stamp image using the detected paper color as a background, a print image of the stamp image and the image data Determining whether the color of the stamp image in the vicinity of the overlapping portion is similar to the color of the printed image in the vicinity of the overlapping portion, and as a result of the determination, the stamp image in the vicinity of the overlapping portion And a step of converting the color of the boundary of the overlapping portion into an inverted color when the color approximates the color of the printed image in the vicinity of the overlapping portion.

  Further, the present invention can be provided as a program for causing a computer to circulate individually via a telecommunication line or the like. In this case, the central processing unit (CPU) realizes the control operation in cooperation with each circuit other than the CPU according to the program of the present invention. Each means realized by using the program and the CPU can also be configured by using dedicated hardware. The program can also be distributed in a state where it is recorded on a computer-readable recording medium such as a CD-ROM.

  According to the image forming apparatus and the image forming method of the present invention, it is possible to improve the visibility of a stamp image even for colored printing paper.

1 is a conceptual diagram illustrating an overall configuration inside a multifunction peripheral according to the present invention. It is a conceptual diagram which shows the whole structure of the operation part which concerns on this invention. It is a figure which shows the structure of the control system hardware of the multifunctional device which concerns on this invention. FIG. 2 is a functional block diagram of a multifunction machine according to an embodiment of the present invention. It is a flowchart for showing the execution procedure of the embodiment of the present invention. FIG. 6A shows an example of an initial screen displayed on the touch panel according to the embodiment of the present invention (FIG. 6A), and FIG. 6B shows an example of a stamp image screen displayed on the touch panel according to the embodiment of the present invention. 6 (B)). FIG. 7A shows a configuration of a sensor according to an embodiment of the present invention, image data after adding a stamp image (FIG. 7A), and a diagram showing a specific example of boundary determination according to the embodiment of the present invention (FIG. 7B). ).

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not. Moreover, the alphabet S added before the number in a flowchart means a step.

<Image forming apparatus>
The image forming apparatus according to the embodiment of the present invention is, for example, a normal image forming apparatus, and this image forming apparatus will be described below. FIG. 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention. However, details of each part not directly related to the present invention are omitted.

  The image forming apparatus according to the present invention corresponds to, for example, a printer, a single scanner, or a multi-function machine including a printer, a copy, a scanner, a fax, and the like, and includes a copy function, a scanner function, a facsimile function, a printer function, and the like. Function as an image forming apparatus.

  The operation of the MFP 100 (MFP: Multi Function Peripheral) when using the copy function will be briefly described below.

  First, when the user uses the multifunction machine 100, the document is placed on the document table 101a provided on the upper surface of the housing unit or the document table 101b of the automatic document feeder. Subsequently, the user uses the operation unit 102 (operation panel) provided in the vicinity of the document table 101 to input setting conditions related to image formation from the operation screen of the operation unit 102. When the user presses a start key provided on the operation unit 102, the multifunction peripheral 100 starts image formation (print processing).

  Next, in the image reading unit 103, the light emitted from the light source 104 is reflected by the document placed on the document table 101. The reflected light is guided to the image sensor 108 by the mirrors 105, 106, and 107. The guided light is photoelectrically converted by the image sensor 108, and image data corresponding to the original is generated.

  An image forming unit 109 forms a toner image based on the image data. The image forming unit 109 is provided with a photosensitive drum 110. The photosensitive drum 110 rotates in a predetermined direction at a constant speed, and around the charger drum, the exposure unit 112, the developing unit 113, the transfer unit 114, the cleaning unit 115, and the like, in that order from the upstream side in the rotation direction. Is arranged.

  The charger 111 uniformly charges the surface of the photosensitive drum 110. The exposure unit 112 irradiates the charged surface of the photosensitive drum 110 with a laser based on the image data to form an electrostatic latent image. The developer 114 forms a toner image by attaching toner to the formed electrostatic latent image. The formed toner image is transferred to a recording medium (for example, paper, sheet) by the transfer device 114. The cleaning unit 115 removes excess toner left on the surface of the photosensitive drum 110. A series of these processes is executed by rotating the photosensitive drum 110.

  The sheets are conveyed from a plurality of paper feed cassettes 116 provided in the multi function peripheral 100. When the sheet is conveyed, the sheet is pulled out from any one of the sheet feeding cassettes 116 to the conveyance path by the pickup roller 117. Each sheet cassette 116 stores sheets of different paper types, and the sheets are fed based on setting conditions relating to image formation.

  The sheet pulled out to the conveyance path is fed between the photosensitive drum 110 and the transfer device 114 by the conveyance roller 118 and the registration roller 119. When the sheet is fed, the toner image is transferred to the sheet by the transfer unit 114 and conveyed to the fixing device 120.

  When the sheet on which the toner image is transferred passes between a heating roller and a pressure roller provided in the fixing device 120, heat and pressure are applied to the toner image, and the visible image is fixed on the sheet. The The amount of heat of the heating roller is optimally set according to the paper type, and the fixing is performed appropriately. The visible image is fixed on the sheet and the image formation is completed, and the sheet is guided to the path switching unit 121 by the conveyance roller 118.

  In the path switching unit 121, the sheet is guided to the sheet discharge tray 122 provided on the side surface of the casing unit or the casing through the sheet discharge port 123 according to a switching instruction from the multifunction peripheral 100. To the in-body tray 124 provided in the body cylinder. The sheets are stacked and stored on the paper discharge tray 122 or the in-body tray 124. Through the above procedure, the housing unit of the multifunction peripheral 100 provides a copy function to the user.

  Next, FIG. 2 is a conceptual diagram showing the overall configuration of the operation unit according to the embodiment of the present invention. The user uses the operation unit 102 to input setting conditions for image formation as described above, and to confirm the input setting conditions. When the setting conditions are input, a touch panel 201 (operation panel), a touch pen 202, and operation keys 203 provided in the operation unit 102 are used.

  The touch panel 201 has both a function for inputting setting conditions and a function for displaying the setting conditions. That is, by pressing a key in the screen displayed on the touch panel 201, a setting condition corresponding to the pressed key is input.

  A display unit (not shown) such as an LCD (Liquid Crystal Display) is provided on the back surface of the touch panel 201, and the display unit displays an operation screen such as the initial screen, for example. A touch pen 202 is provided in the vicinity of the touch panel 201. When the user touches the touch pen 201 with the tip of the touch pen 202, a sensor provided under the touch panel 201 detects the touch destination.

  Further, a predetermined number of operation keys 203 are provided in the vicinity of the touch panel 201, and for example, a ten key 204, a start key 205, a clear key 206, a stop key 207, a reset key 208, and a power key 209 are provided.

  Next, the configuration of the control system hardware of the multifunction peripheral 100 will be described with reference to FIG. FIG. 3 is a diagram showing the configuration of the control system hardware of the multifunction peripheral 100 according to the present invention. However, details of each part not directly related to the present invention are omitted.

  The control circuit of the MFP 100 includes a CPU (Central Processing Unit) 301, a ROM (Read Only Memory) 302, a RAM (Random Access Memory) 303, a HDD (Hard Disk Drive) 304, a driver 305 corresponding to each driving unit, and an operation. The units 306 (102) are connected by the internal bus 307.

  The CPU 301 uses, for example, the RAM 303 as a work area, executes a program stored in the ROM 302, the HDD 304, and the like, and based on the execution result, data and instructions from the driver 306 and the operation unit 307, key 1 is transmitted and received, and the operation of each drive unit shown in FIG. 1 is controlled.

  Also, each means (shown in FIG. 4) described later other than the drive unit is realized by the CPU 301 executing a program. The ROM 302, the HDD 304, and the like store programs and data for realizing each means described below.

<Embodiment of the present invention>
Next, the configuration and execution procedure according to the embodiment of the present invention will be described with reference to FIGS. 4 and 5. FIG. 4 is a functional block diagram of the multifunction machine of the present invention. FIG. 5 is a flowchart for showing the execution procedure of the present invention.

  First, when the user turns on the power of the multifunction device 100, the multifunction device 100 is activated, and the display receiving unit 401 displays an initial screen (operation screen) on the touch panel 201 (FIG. 5: S101).

  On the initial screen 600, as shown in FIG. 6A, a predetermined message “Can copy” 601 is displayed, and a function item key 602 for inputting setting conditions such as a copy function, A stamp key 603 for adding a stamp image to image data for image formation is displayed so as to be pressed.

  For example, when the user wants to form an image by adding a predetermined stamp image to the image data and presses the stamp key 603, the display receiving unit 401 receives the pressing of the stamp key 603, and Then, the initial screen is switched to the stamp image screen (FIG. 5: S102).

  In the stamp image screen 604, as shown in FIG. 6B, a predetermined message “Please select a stamp image” 605 and an instruction “Add a stamp image. Select a desired stamp image” ”Is displayed, and a stamp image key 607 for selecting the stamp image 607a, an OK key 608, and a cancel key 609 are displayed to be pressed.

  Here, examples of the stamp image 607a include a mark indicating secret (confidential mark), a mark indicating confidentiality, a logo mark of a company registered in advance, and the like.

  When the user presses the stamp image key 607 corresponding to the desired stamp image 607a (confidential mark) while pressing the OK key 608 while looking at the stamp image 607a, the display accepting unit 401 displays the stamp image 607a. In response to pressing of 607a and the OK key 608 (FIG. 5: S103), the initial screen 600 is displayed again.

  While viewing the initial screen 600, the user presses the function item key 602, inputs predetermined setting conditions, places the document on the document table 101a or the document table 101b, and presses the start key 205. The display accepting unit 401 accepts the setting condition and the pressing of the start key 205 (FIG. 5: S104 YES), and notifies the image generating unit 402 to that effect. Upon receiving the notification, the image generation unit 402 reads the image data of the original by the image reading unit 103, adds the input stamp image 607a to the read image data, and adds the stamp image 607a. Data is generated (FIG. 5: S105).

  Here, the image generation unit 402 may add any method for adding the stamp image 607a to the image data. For example, a method in which the image generation unit 402 places and adds an enlarged stamp image 607a at the center of the read image data can be cited. As another configuration, a known method related to adding a stamp image, such as a method in which the image generating unit 402 adds a plurality of stamp images 607 a in a polka dot pattern to the entire surface of the image data, can be employed.

  When the image generation unit 402 completes generation of image data for image formation, the sheet is transported from a predetermined paper feed cassette 116, for example, the paper feed cassette 116 corresponding to the setting condition, for image formation. (Feeding) is started (FIG. 5: S106).

  Here, when the image generation unit 402 starts conveying the paper, the image color detecting unit 403 notifies the paper color detecting unit 403 to that effect, and the paper color detecting unit 403 receiving the notification detects the color of the conveyed paper ( FIG. 5: S107).

  Any method may be used for the paper color detection unit 403 to detect the color of the paper. For example, the method is as follows.

  For example, the paper color detection unit 403 detects the color of the conveyed paper using a sensor provided in advance in a predetermined position on the conveyance path from the paper feed cassette 116 to the image forming unit 109. In this case, first, as shown in FIG. 7A, a contact image sensor 701 (CIS) that can detect the color of the paper P, and a paper detection sensor 702 that can detect the passage (edge, tip) of the paper P. Are installed in advance on the conveyance path W closest to the image forming unit 109. Here, when the paper detection sensor 702 of the sensor 700 is arranged on the upstream side of the contact image sensor 701 in the transport direction of the paper P and the paper P is transported, the paper detection sensor 702 first detects the paper P. The presence is detected, and thereafter the contact image sensor 701 can detect the color of the paper P. The contact image sensor 701 is long in a straight line and is arranged in a direction perpendicular to the conveyance direction of the paper P, and can detect a linear color perpendicular to the conveyance direction of the paper P. The linear direction of the detected color corresponds to the scanning direction of the image data.

  When the conveyance of the paper P is started, the paper color detection unit 403 activates the paper detection sensor 702 of the sensor 700 and starts detecting the edge of the paper P. When the paper P is conveyed and blocks the detection area of the paper detection sensor 702, the paper color detection means 403 detects it (using the detection of the leading edge of the paper P as a trigger) and the contact image sensor. 701 is activated, and the color of one line in the direction perpendicular to the transport direction of the paper P is detected. As a result, the color of the paper P can be detected. In the above description, the color of the paper P read by the contact image sensor 701 is one line color corresponding to the line shape of the contact image sensor 701. However, the detection area such as the two line color is enlarged. It doesn't matter.

  When the paper color detection means 403 completes the detection of the color of the paper P, it notifies the image generation means 402 to that effect, and the image generation means 402 that has received the notification, as shown in FIG. Using the detected color of the paper P as the background, image data 703 with the stamp image 704 is generated (FIG. 5: S108). Of the formed image data 703, a print image 703 a such as a character, graph, or photograph becomes image data that is converted into a toner image by the image forming unit 109.

  Here, since the stamp image 704 is arranged at a predetermined position of the image data 703, there is a possibility that the print image 703a of the image data 703 may overlap the stamp image 704.

  Further, when the image data 703 is formed, for example, the color of the print image 703a of the image data 703, that is, the color of characters, the color of the graph, the color of the photograph, etc., is used for improving the visibility. There is a case where it is changed corresponding to the color of P.

  When the image generation unit 402 generates image data 703 for forming an image, the image generation unit 402 notifies the boundary determination unit 404 to that effect. Upon receiving the notification, the boundary determination unit 404 approximates the color of the stamp image 704 in the vicinity of the overlap portion between the stamp image 704 and the print image 703a of the image data 703 to the color of the print image 703a in the vicinity of the overlap portion. It is determined whether or not (FIG. 5: S109).

  Here, what method is used by the boundary determination unit 404 to determine whether the color of the stamp image 704 in the vicinity of the overlapping portion approximates the color of the print image 703a in the vicinity of the overlapping portion. However, for example, it is made as follows. The print image 703a will be described below as a linear image extending in the left-right direction. This image is, for example, a character image.

  First, the boundary determination unit 404 searches for an overlapping portion 705 between the stamp image 704 and the print image 703a of the image data 703, as shown in FIG. 7B. Then, the boundary determination unit 404 identifies the pixel 706 of the stamp image 704 with pixels adjacent to the pixel constituting the boundary of the searched overlap portion 705, and color information (for example, numerical value A) of the identified pixel 706. ) To get. Next, the boundary determination unit 404 identifies the pixel 707 of the print image 703a with pixels adjacent to the pixel constituting the boundary of the overlapping portion 705, and color information (for example, numerical value B) of the identified pixel 707. To get.

  Here, the pixel 706 of the stamp image 704 may be a predetermined pixel or a plurality of pixels among the pixels adjacent to the pixels constituting the boundary of the overlapping portion 705. When the stamp image 704 includes a plurality of pixels 706, the color information of the pixels 706 is averaged. The same applies to the pixel 707 of the print image 703a.

  The boundary determination unit 404 calculates a subtraction value obtained by subtracting the color information (numerical value B) of the pixel 707 of the print image 703a from the color information (numerical value A) of the pixel 706 of the stamp image 704, and the subtraction value is calculated. It is determined whether or not a preset threshold value is exceeded. The magnitude of this threshold indicates the degree of approximation between the color of the stamp image 704 and the color of the print image 703a, and the design of this threshold is appropriately changed by a user such as an administrator.

  As a result of the determination, when the subtraction value does not exceed the threshold value, that is, when the color of the stamp image 704 in the vicinity of the overlapping portion approximates the color of the print image 703a in the vicinity of the overlapping portion (FIG. 5: S109 YES), the boundary determination unit 404 notifies the color inversion unit 405 to that effect, and the color inversion unit 405 that has received the notification converts the color of the boundary of the overlapping portion 705 into an inversion color (FIG. 5). : S110).

  Any method may be used for the color reversing unit 405 to convert the color of the boundary of the overlapping portion 705 into a reversed color. For example, the method is as follows.

  That is, as shown in FIG. 7B, the color reversing unit 405 identifies all (or a part of) pixels constituting the boundary 705a of the overlapping portion 705, and inverts the color information of the identified pixels. The color information after the inversion is used. For example, if the color information (for example, RGB) of the pixel is expressed by a numerical value of 0-255, a subtraction value obtained by subtracting the color information of the pixel from 255, which is the upper limit value of the color information, It becomes the color information after the inversion.

  In FIG. 7B, since the color of the stamp image 704 in the vicinity of the overlap portion 705 and the color of the print image 703a in the vicinity of the overlap portion 705 are black, the boundary 705a of the overlap portion 705 is shown. The color of is inverted to white. As a result, the print image 703a of the image data 703 changed according to the color of the paper P and the stamp image 704 can be clearly distinguished. Therefore, even if the print paper is colored, the stamp image 704 Visibility can be improved.

  When the color inversion unit 405 completes the conversion of the inversion color, the image generation unit 402 is notified to that effect, and the image generation unit 402 that has received the notification outputs the image data in which the boundary color of the overlapping portion 705 is inverted. Regeneration is performed (FIG. 5: S111), and the fact is notified to the image forming unit 406. Upon receiving the notification, the image forming unit 406 executes image formation on the paper P transported earlier (FIG. 5: S112). In the printed material 708 corresponding to this image formation, as shown in FIG. 7B, the stamp image 704 (printed portion) is trimmed, and the visibility of the stamp image 704 can be improved. Become.

  On the other hand, if the subtraction value exceeds the threshold value as a result of the determination in S109, that is, the color of the stamp image 704 in the vicinity of the overlap portion approximates the color of the print image 703a in the vicinity of the overlap portion. If not (FIG. 5: S109 NO), the boundary determination unit 404 determines that it is not necessary to invert the boundary color, and notifies the image generation unit 402 to that effect, and the image generation unit 402 receives the notification. Notifies the image forming means 406 that the image data need not be regenerated. Receiving the notification, the image forming unit 402 executes image formation on the paper P conveyed earlier based on the image data generated in S105 (FIG. 5: S112).

  In S109, for example, when there is no overlapping portion 705 between the stamp image 704 and the print image 703a of the image data 703, the boundary determination unit 404 determines that the color of the stamp image 704 in the vicinity of the overlapping portion is It is determined that the color of the printed image 703a in the vicinity of the overlapping portion is not approximated, and the image forming unit 406 executes image formation based on the image data generated in S105 (FIG. 5: S112).

  When the stamp image 704 is not added to the image data 703, the steps S107, S109, S110, and S111 are skipped.

  As described above, according to the present invention, the sheet color detection unit 403 that detects the color of the sheet for image formation, and the image generation unit 402 that generates image data with a stamp image using the detected sheet color as a background. And a boundary determination unit 404 for determining whether the color of the stamp image in the vicinity of the overlap portion between the stamp image and the print image of the image data approximates the color of the print image in the vicinity of the overlap portion; As a result of the determination, when the color of the stamp image in the vicinity of the overlapping portion approximates the color of the printed image in the vicinity of the overlapping portion, a color inversion means for converting the boundary color of the overlapping portion into an inverted color 405. As a result, the visibility of the stamp image can be improved even with a colored printing paper.

  In the embodiment of the present invention, the electrophotographic image forming apparatus (multifunction machine) is used. However, there is no particular limitation, and an ink jet type image forming apparatus may be used.

  In the embodiment of the present invention, the MFP 100 is configured to include each unit. However, a program that realizes each unit may be stored in a storage medium, and the storage medium may be provided. In this configuration, the multifunction device 100 reads the program, and the multifunction device 100 implements the respective units. In that case, the program itself read from the recording medium exhibits the effects of the present invention. Furthermore, it is possible to provide a method for storing the steps executed by each means in a hard disk.

  As described above, the image forming apparatus and the image forming method according to the present invention are useful for scanners, copiers, printers and the like as well as multifunction peripherals, and even for colored printing paper, a stamp image This is effective as an image forming apparatus and an image forming method capable of improving the visibility.

DESCRIPTION OF SYMBOLS 100 MFP 102 Operation part 401 Display reception means 402 Function provision means 403 Paper color detection means 404 Boundary determination means 405 Color inversion means 406 Image formation means

Claims (4)

An image forming apparatus including an image forming unit that forms an image on a sheet based on image data to which a stamp image is added,
Paper color detection means for detecting the color of the paper for image formation;
Image generation means for generating image data with a stamp image using the detected paper color as a background;
Boundary determination means for determining whether the color of the stamp image in the vicinity of the overlap portion between the stamp image and the print image of the image data approximates the color of the print image in the vicinity of the overlap portion;
As a result of the determination, when the color of the stamp image in the vicinity of the overlapping portion approximates the color of the printed image in the vicinity of the overlapping portion, a color inversion means for converting the boundary color of the overlapping portion into an inverted color An image forming apparatus comprising: The boundary determining means is a pixel adjacent to the pixel constituting the boundary of the overlapping portion, the color information of the pixel of the stamp image, and the pixel adjacent to the pixel constituting the boundary of the overlapping portion, and the pixel of the print image And calculating a subtraction value obtained by subtracting the color information of the pixel of the print image from the color information of the pixel of the stamp image, and whether or not the subtraction value exceeds a preset threshold value The image forming apparatus according to claim 1, wherein it is determined whether or not the color of the stamp image in the vicinity of the overlapping portion approximates the color of the printed image in the vicinity of the overlapping portion. The paper color detection means detects the color of the paper to be transported using a sensor provided in advance at a predetermined position in a transport path from the paper feed cassette containing the paper to the image forming unit. The image forming apparatus according to claim 1. An image forming method comprising a step of forming an image on a sheet based on image data to which a stamp image is added,
Detecting the color of the paper for image formation;
Generating image data with a stamp image using the detected paper color as a background; and
Determining whether the color of the stamp image in the vicinity of the overlap portion between the stamp image and the print image of the image data approximates the color of the print image in the vicinity of the overlap portion; and
As a result of the determination, if the color of the stamp image in the vicinity of the overlapped portion approximates the color of the print image in the vicinity of the overlapped portion, the step of converting the boundary color of the overlapped portion into an inverted color; An image forming method comprising the steps of: