JP6287416B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus and an image forming method.

  Among image forming apparatuses, there is a configuration called a series tandem machine in which two print engines are connected in series.

  This series tandem machine is an image forming apparatus in which the same print engines are connected in series, and mainly intended to output double-sided printing at high speed. For this reason, printing is performed on one side (front surface) of the sheet by the print engine (master unit) that performs printing first, and then the other side of the sheet by the print engine (slave unit) connected to the print output port of the master unit. Is printed on the front side (back side).

  When performing double-sided printing with a single printing engine, after printing the front side, the paper is reversed and the back side is printed after returning to the entrance side of the printing engine. In this regard, in the above-described serial tandem machine, double-sided printing can be executed quickly because the paper does not need to be returned (for example, Patent Document 1).

JP 2012-58426 A

  However, in a serial tandem machine, both sides of a single sheet are printed by separate printing engines, so there are subtle differences in the color and blurring of the printed matter depending on the degree of wear of each printing engine and the difference in printing execution history. I found out. In particular, when creating printed materials in booklet form, if the left and right pages of the spread pages are bound so that they are the front and back sides of the paper, the left and right pages of the spread pages are printed separately by the print engine of the master and slave units. Will be. Then, even if there is a subtle difference between the printing results of the master unit and the slave unit, it may appear as a difference that can be recognized by a person.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus and an image forming method capable of reducing the difference between the printing results of the spread left and right pages in an image forming apparatus that prints by connecting a master unit and a slave unit in series. It is to be.

    The above object of the present invention is achieved by the following means.

(1) a master unit including a printing unit that prints an image on the first surface of the paper;
A slave unit including a printing unit that prints an image on a second surface opposite to the first surface of the paper printed by the master device;
An output reversing unit for inverting the paper after printing output from the slave unit;
During double-sided printing, the image to be printed first is imprinted for the first side, and the image to be printed next is impositioned for the second side.
When printing on a plurality of sheets so as to form a booklet, with respect to a sheet designated in advance, the impositioned image for the first surface is used for the second surface and the impositioned first image is printed. Replace the image for the second side with the one for the first side,
The image for the first surface after the replacement is printed by the master unit, and the image for the second surface after the replacement is printed by the slave unit, respectively.
A control unit that inverts and outputs the designated sheet output from the slave unit by the output inversion unit;
I have a,
The control unit detects a page having an object other than a character on both pages of the spread page, and sets a sheet on which one of the two pages of the spread page having the object other than the character is printed on the sheet. An image forming apparatus characterized in that a designated sheet is used.

  (2) When the saddle stitching is designated in the booklet form, the control unit replaces the images of the left and right pages to be printed for the first surface after the replacement, and the replacement of the first page The image forming apparatus according to (1), wherein the images on the left and right pages to be printed on two sides are switched.

( 3 ) a master unit having a printing unit that prints an image on the first side of the paper;
A slave unit including a printing unit that prints an image on a second surface opposite to the first surface of the paper printed by the master device;
An image forming method comprising: an output reversing unit that reverses the printed paper output from the slave unit;
A step (a) of imposing an image to be printed first for the first side and an image to be printed next for the second side during duplex printing;
When printing on a plurality of the sheets so as to be in a booklet form, for the previously designated sheets, the impositioned image for the first surface is used for the second surface and the impositioned image Replacing the image for the second surface with that for the first surface (b);
The step (c) of printing the first surface after the replacement by the master unit and the second surface after the replacement by the slave unit;
And step (d) to output the inverted by the output inverting unit the paper that is the specified output from the slave unit,
At least before the step (b) of switching, a page having an object other than a character on both pages of a spread page is detected, and one of the pages having an object other than a character on both pages of the spread page is detected. A step (g) of setting the paper on which the page is printed as the designated paper;
An image forming method comprising:

( 4 ) If saddle stitching is specified in the booklet form, the left and right page images to be printed for the first side after the replacement are replaced before the step (d) of printing, and the replacement is performed. The image forming method according to ( 3 ), further comprising a step (f) of replacing left and right page images to be printed for the second side later.

  According to the present invention, when duplex printing and booklet printing are performed, for a designated sheet, an image for the first surface and an image for the second surface that are preliminarily imposed on the sheet. It was decided to replace. As a result, the printed matter output as double-sided printing or booklet form is printed on the left and right pages, which are spread pages, by the same print engine, and a good-looking printed matter can be obtained.

1 is an explanatory diagram for explaining a schematic configuration of an image forming apparatus according to an embodiment to which the present invention is applied. FIG. 2 is a block diagram illustrating a configuration in the control unit 11 of the image forming apparatus 1 and a network connection with other external devices. 6 is a flowchart for explaining a booklet-type print processing procedure in double-sided printing according to the first exemplary embodiment. 6 is a flowchart for explaining a booklet-type print processing procedure in double-sided printing according to the first exemplary embodiment. It is explanatory drawing for demonstrating the example of a setting screen at the time of performing appearance priority setting. It is explanatory drawing for demonstrating the printing of the conventional saddle stitch booklet form, (a) is explanatory drawing of printing, (b) is explanatory drawing of a completed booklet. FIG. 3 is an explanatory diagram for explaining printing in a saddle stitch booklet form in which processing for improving the appearance by applying the first embodiment is performed, (a) and (b) are explanatory diagrams of printing, and (c) is an explanatory diagram of printing. It is explanatory drawing of a completed booklet. It is explanatory drawing for demonstrating the printing of the conventional left bound booklet form, (a) is explanatory drawing of printing, (b) is explanatory drawing of a completed booklet. 4A and 4B are explanatory diagrams for explaining printing in a left-bound booklet form in which processing for improving the appearance by applying the first embodiment is performed, where FIG. 5A is an explanatory diagram of printing, and FIG. FIG. 6 is a flowchart for explaining a booklet-type print processing procedure in duplex printing according to Embodiment 2. 6 is a flowchart for explaining a booklet-type print processing procedure in duplex printing according to Embodiment 2. It is a subroutine flowchart which shows the process sequence of appearance priority page determination. It is explanatory drawing explaining the process which detects objects other than a character. It is explanatory drawing explaining the version based on color gradation information and classification information. It is explanatory drawing for demonstrating the printing of the saddle stitch booklet form which performed the process for improving the appearance by applying this Embodiment 2, (a) is explanatory drawing of printing, (b) is a completed booklet. It is explanatory drawing. In Embodiment 2, it is explanatory drawing for demonstrating the example of a setting screen in which a user can select whether it gives priority to the appearance only in the page with an object other than a character, or gives priority to the appearance in all the pages. FIG. 6 is an explanatory diagram illustrating an example of a printer driver setting screen for performing appearance priority setting by a printer driver.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
FIG. 1 is an explanatory diagram for explaining a schematic configuration of an image forming apparatus according to an embodiment to which the present invention is applied.

  As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment is a series tandem machine in which two printing machines, a master machine 101 and a slave machine 102, are continuously connected. The serial tandem machine prints using the master unit 101 and the slave unit 102 continuously. The series tandem machine is particularly suitable for duplex printing.

  The master unit 101 and the slave unit 102 have the same function and performance for printing. Therefore, here, in the master unit 101 and the slave unit 102, members having the same function are denoted by the same reference numerals, and redundant description is omitted.

  The image forming apparatus 1 includes a control unit 11 in the master unit 101, and integrally controls both the master unit 101 and the slave unit 102, a conveyance path 110 that conveys a sheet, and the like (control unit). Details of 11 will be described later).

  A paper feeding unit 12 is provided on the master device 101 side, and supplies a sheet as a printing medium to the master device 101 and the slave device 102. The paper feed unit 12 has a paper feed tray, and can store a plurality of papers having different sizes and materials, for example. In this embodiment, the slave unit 102 is not provided with a paper feeding unit. However, if it is necessary to perform single printing only by the slave unit 102, the slave unit 102 is used to supply paper without the master unit 101. There may be a paper feeding unit on the side.

  The master unit 101 and the slave unit 102 include a printing unit 13 that is a print engine. The printing unit 13 prints an image on a printing medium such as paper by, for example, a known electrophotographic image forming process. The printing unit 13 prints an image on the sheet conveyed from the sheet feeding unit 12 and then outputs the image. The printing unit 13 includes, for example, a color printing function such as monochrome / color, an enlargement / reduction function, a page allocation function such as 2in1, 4in1, and a function of changing the orientation of an image. Each of these print functions is set as one of the print settings, and is executed by a command from the control unit 11 based on the settings.

  The sheet feeding unit 12, the parent device 101, the child device 102, and the post-processing device 14 are connected by a conveyance path 110 that conveys the sheet.

  The transport path between the master unit 101 and the slave unit 102 has an intermediate reversing unit 111 that reverses the sheet. The intermediate reversing unit 111 is provided with a switching device 113 that switches between reversing the paper through the intermediate reversing path 112 and not reversing the paper without passing through the intermediate reversing path 112. When it is necessary to invert the sheet input to the slave unit 102, the control unit 11 switches the switching unit 113 to pass the sheet through the intermediate reversing path 112 of the intermediate reversing unit 111 to invert the sheet so that the slave unit 102. To transport. On the other hand, when it is not necessary to reverse the sheet, the sheet is conveyed to the slave unit 102 without passing through the intermediate inversion path 112.

  An output reversing unit 121 that reverses the paper is also provided in the transport path 110 after output from the slave unit 102. The output inversion unit 121 has an output inversion path 122. A switching device 123 is provided for switching whether the paper is reversed through the output reversing path 122 or not reversed. When it is necessary to invert the sheet output from the slave unit 102, the control unit 11 controls the switching unit 123 to pass the sheet through the output reversal path 122 to invert the sheet and output the sheet. On the other hand, when it is not necessary to reverse the paper, the paper is output without passing through the output reversing path 122.

  In the present embodiment, both the parent device 101 and the child device 102 use the same print engine as the printing unit 13. This is to make the printing characteristics of both the same as much as possible.

  In the present embodiment, description will be made assuming that both the master unit 101 and the slave unit 102 use a print engine having a specification that prints on the surface facing upward of the sheet being conveyed. In this case, in normal double-sided printing, first, the master unit 101 prints on a first surface facing upward during conveyance (hereinafter, this first surface is referred to as a front surface). After that, the sheet is reversed by the intermediate reversing path 111, and printing is performed on the second surface (hereinafter, this second surface is referred to as the back surface) facing upward when input to the slave unit 102. After the slave printing, it is output (discharged) as it is, so that it is output by the face-down method.

  In a normal printing operation, printing is executed in the order of pages of print data, that is, in order of the first page, the second page,. In this case, the papers output after printing are overlapped in page order with the paper facing down. Of course, you may print so that it may become reverse order of a page. In that case, printing is executed in the order of the last page,..., The second page, and the first page. In this case, the last page facing down is printed at the bottom of the paper output after printing (however, if the total number of pages is an odd number, the bottom down side is a blank page), and the top Will overlap in page order.

  As described above, in duplex printing, an image including a page to be printed first (for example, the first page) is printed on the front surface (first surface) of the sheet by the master unit 101 in accordance with a predetermined page order. An image including a page (for example, the second page) is printed by the slave unit 102 on the back surface (second surface) of the same sheet. In duplex printing, imposition is performed in such a printing order.

  The output form may be a face-up method. In that case, the paper after the slave printing is reversed by the output reversing unit 121 before being output.

  Note that the surface printed by the parent device 101 and the child device 102 is not limited to the surface facing upward. When both the master device 101 and the slave device 102 have the same print engine, both may be printed on the surface facing downward during conveyance. In this case, when outputting the pages in the face-down manner so as to be overlapped in the page order, the paper after the slave printing is reversed by the output reversing unit 121 before being outputted. When outputting by the face-up method, the paper after the slave printing is output without passing through the output inversion path 122.

  Furthermore, the printing surface for the paper may be different between the master unit 101 and the slave unit 102. For example, the master unit 101 has a specification for printing on the surface facing the top (or bottom) of the paper being conveyed, and the slave unit 102 has a specification for printing on the side facing the bottom (or top). That is, it is possible to print from the top and bottom on the sheet being conveyed by the master unit and the slave unit. In this case, the sheet output from the master unit 101 can be directly flown to the slave unit 102 without performing the sheet reversal through the intermediate reversal path 111, so that the printing speed can be further increased. In particular, in the case of the present embodiment, since the front and back surfaces of the spread pages that are the left and right pages can be printed by the same print engine (described later in detail), there is a slight difference in the original print characteristics between the master unit 101 and the slave unit 102. Even if there is, there will be no difference in the printing results (color tone, blurring, etc.) on the spread pages.

  The post-processing device 14 performs post-processing on the printed paper output from the slave unit 102. The post-processing device 14 performs various post-processing on the paper output from the slave unit 102 under the control of the control unit 11. The post-processing includes, for example, a punch function that opens a punch hole at a predetermined position (binding direction) of the paper, a staple function that stops the predetermined position of the paper with staples, and a folding function that folds the paper in a predetermined folding method. Each of these post-processing functions is set in the print settings.

  In addition, the image forming apparatus 1 includes one operation panel 15. There may be a plurality of operation panels 15, but usually only one image panel 1 is required to handle the image forming apparatus 1 having a series tandem configuration as one apparatus. The operation panel 15 includes a display with a touch panel that can perform various displays and inputs, a numeric keypad, a start button, a stop button, and the like, and is used for displaying various information and inputting various instructions. From this operation panel 15, print settings described later can be performed.

  FIG. 2 is a block diagram illustrating a configuration in the control unit 11 of the image forming apparatus 1 and a network connection with other external devices.

  The image forming apparatus 1 is connected to a client computer (hereinafter referred to as a PC (Personal Computer)) 30 that is an external device via a network 18.

  The PC 30 is a computer such as a general personal computer, and includes a network interface (not shown), and transmits a print job to and from the image forming apparatus 1. Also, print settings are made for each print job. For this purpose, a printer driver (program) suitable for the image forming apparatus 1 is installed in the PC 30. The user uses this printer driver to send a print job including print settings and a print command to the image forming apparatus 1 together with print data. In this embodiment, the print setting includes single-sided / double-sided printing, booklet-type printing designation, and the like. Of course, the print setting includes designation for executing functions provided as a general image forming apparatus 1, for example, designation of the number of copies to be printed, paper size, designation of both sides / one side, designation of color / monochrome, and the like.

  Although only one PC 30 is shown in FIG. 2, a plurality of PCs 30 are connected to the same network, and each PC 30 can transmit a print job to one image forming apparatus 1. You may keep it.

  The network 18 connects the PC 30 and the image forming apparatus 1 to transmit / receive a print job and other information. As such a network 18, for example, a LAN can be used. Further, a line or a dedicated line that directly connects the PC 30 and the image forming apparatus 1 may be used.

  Next, the control unit 11 and its operation will be described.

  2, the control unit 11 includes a CPU 21 (Central Processing Unit), a ROM 22 (Read Only Memory), a RAM 23 (Random Access Memory), a flash ROM 24 (Flash ROM), and a network interface (Network Interface: NIF 27). These units are connected to each other by a bus 28 for exchanging signals. The control unit 11 is connected so that control signals can be exchanged by the internal wiring 29 and the printing unit 13 of both the sheet feeding unit 12, the post-processing device 14, the operation panel 15, the master unit 101 and the slave unit 102. (See FIG. 1).

  The control unit 11 controls each unit of the image forming apparatus 1. The control performed here is mainly performed by the CPU 21 executing a program necessary for the processing, printing according to the print settings, post-processing control for the printed paper, and the like. Since the program necessary for controlling the printing itself is the same as that used in the general image forming apparatus 1, detailed description thereof is omitted. Here, when printing in double-sided printing or booklet form, A process for improving the appearance of the spread page will be described. The CPU 21 also performs rasterization of print data included in the print job, imposition of images, and the like. The impositioned image is stored in the flash ROM 24 and is sequentially provided to the printing unit 13 under the control of the control unit 11.

  The ROM 22 stores various programs for executing basic operations necessary as a minimum for the image forming apparatus 1. For example, it stores a program for basic operations such as determining whether or not each unit operates normally when the image forming apparatus 1 is turned on, and reading a program necessary for subsequent processing from the flash ROM 24. doing.

  The RAM 23 temporarily stores programs and data as a work area for the CPU 21.

  The flash ROM 24 stores programs and print settings necessary for control. In the present embodiment, a processing program for improving the appearance of the spread page is also stored in the flash ROM 24. The flash ROM 24 is also used when developing data to be printed such as print data. In place of the flash ROM 24, a hard disk (HDD) or other nonvolatile memory can be used.

  A network interface (NIF) is a receiving unit that receives print data. The network interface is an interface for communicating with an external device via the network 18. Here, it is used for connection with PC30. In this embodiment, the print job is described as being transmitted from the PC 30. However, for example, the image forming apparatus 1 is provided with a wired interface such as a USB or a wireless interface. The print job may be received directly from various terminal devices (for example, a USB memory or a portable terminal). In such a case, these interfaces can be a receiving unit that receives print data.

  Next, a processing procedure when printing a booklet form by double-sided printing will be described. FIG. 3 and FIG. 4 are flowcharts for explaining a booklet-type print processing procedure in duplex printing in the first embodiment.

  First, the CPU 21 extracts print settings, print data, and the like from the received print job and temporarily stores them (S1). Note that the print settings need only be stored in the normal RAM if there is no other purpose of use. On the other hand, the print data is stored in the flash ROM 24. This is usually stored in the flash ROM 24 because the print data capacity is large enough to be stored in the RAM 23, but it may be stored in the RAM 23 as long as it can be stored.

  Subsequently, the CPU 21 rasterizes the extracted print data to create an image (S2). The rasterized image data is stored in the flash ROM 24. This process is a so-called RIP (Raster Image Processor), which is performed by the CPU 21 executing the RIP program. However, rasterization may use a dedicated processor.

  Subsequently, the CPU 21 interprets the print setting and determines whether or not double-sided printing and a booklet form are present (S3). Here, even if the print setting is other than the booklet form and the booklet form is not designated for duplex printing (S3: NO), a normal printing operation is performed according to the print setting (S200). Since the process of S200 is a conventional normal printing process, description thereof is omitted.

  Subsequently, when the CPU 21 determines that the double-sided printing and the booklet form are designated in S3, the CPU 21 further determines whether or not the appearance priority process for the spread pages is performed (S4). The designation of appearance priority is designated in the print setting by the user, or designated by input from the operation panel 15 of the image forming apparatus 1.

  FIG. 5 is an explanatory diagram for explaining an example of a setting screen when such appearance priority setting is performed.

  The setting screen shown in FIG. 5 is displayed on the operation panel 15, for example. The setting screen 300 is a screen for setting processing for a spread page. In the setting screen 300, items of speed priority 301 and appearance priority 302 and radio buttons corresponding to them (any form may be used as long as it indicates selection such as a check button) are arranged (in the figure, appearance priority). 302 is selected).

  Speed priority 301 is an item for completing printing quickly without replacing images. The appearance priority 302 is an item for improving the appearance of the spread page by executing the processing of the first embodiment.

  When the appearance priority 302 is selected from the setting screen 300, the control unit 11 temporarily stores it in the RAM 23. And the control part 11 will judge whether the setting of the appearance priority 302 was performed in S4 by the memory | storage of the item selected from this screen.

  If appearance priority is not given in S4 (S4: NO), normal printing processing is performed in S200.

  If it is determined that the appearance priority is designated in S4 (S4: YES), the CPU 21 further confirms the designation of the binding position (S5). Here, it is determined whether saddle stitching or left (or right) binding. Hereinafter, a case where the saddle stitch booklet form is designated will be described first. Processing in the case of left binding will be described later.

  If it is determined in S5 that saddle stitching is designated, each page is imprinted so as to be printed on both sides and in a booklet form (S6). Imposition is a process of creating an image that is actually printed on a sheet. Since saddle stitching is selected here, two pages of images are imposed on one side of one sheet.

  The imposition process at this stage is the same as a normal printing operation. For example, assuming that the total number of pages is from the first page to the nth page (n is the last page number, and so on), and the total number of pages is an even number (that is, n is an even number), the first page and the nth page are Imposition is performed so as to be printed on the surface of the first sheet. Subsequently, the second page and the (n-1) th page immediately before the last page are impositioned so as to be printed on the back surface of the first sheet. Subsequently, the surface of the second sheet, which is the next sheet, the n-2 page two pages before the third page and the last page, and the n-3 page, the third page three pages before the fourth page and the last page. The back side of the second sheet is impositioned.

  On the other hand, when the total number of pages is an odd number (that is, n is an odd number), the first page and the blank page are imposed so as to be printed on the surface of the first sheet. Subsequently, the second page and the nth page are impositioned so as to be printed on the back surface of the first sheet. Subsequently, the surface of the second sheet, the n-1 page immediately before the third page and the last page is the next sheet, the n-2 page two pages before the fourth page and the last page The back side of the second sheet is impositioned.

  The rasterized images are combined and stored in the flash ROM 24 so that the impositioned image is in an impositioned state (here, two pages of images).

  At this stage, the impositioned images are for the front side and the back side. This means that the image sending order is associated with the parent device 101 and the child device 102. That is, the image for the front side of the first sheet including the first page is sent to the printing unit 13 of the master unit 101, and the image for the back side of the first sheet of paper including the second page is set to the printing unit 13 of the slave unit 102. Next, the image for the front side of the second sheet including the third page is sent to the printing unit 13 of the main unit 101, the image for the back side of the second sheet including the fourth page is the sub unit 102,. Thus, the ordering and the association with the parent device 101 and the child device 102 are made. In this embodiment, such imposition processing is performed by the CPU 21 executing a program necessary for imposition processing. Therefore, the control unit 11 including the CPU 21 serves as an imposition unit. However, instead of the control unit 11, a processor dedicated to image processing may be provided to execute imposition processing.

  Subsequently, the CPU 21 issues a print execution instruction and feeds one sheet of paper (S7). Subsequently, it is determined whether or not the fed paper is an even number (S8). This even number of sheets is a sheet designated in advance. If the paper fed in S8 is not an even-numbered sheet (that is, odd-numbered sheet) (S8: NO), the image data after imposition is sent as it is to the master unit 101 and for the back side to the slave unit 102. (S11), printing is performed (S12).

  On the other hand, when the sheet fed in S8 is an even number (S8: YES), it is stored that the sheet is an even number, and the image after imposition printed on the even number sheet is stored. For the front side and the back side are switched (S9).

  In S9, the front and back are switched by designating the image composed of the third page and the (n-2) th page printed on the front surface of the second sheet, which is an even number of sheets, for the back side, and the fourth page and the nth page. -3 pages are redesignated for the front side. The images on the other even-numbered sheets are similarly replaced.

  Subsequently, the CPU 21 replaces the imposed left and right images (S10). This is because, in S9, the front and back of the image for one sheet are switched, so that the printing order of the images for two pages imposed on one sheet is reversed. To correct this, the left and right images are swapped. The image after the replacement is overwritten and saved over the original image in the flash ROM.

  After the above processing is completed, the CPU 21 transmits the replaced image for the front surface to the parent device 101, and similarly transmits the image for the rear surface after the replacement to the child device 102 (S11), and prints them (S12). ). In S11 and S12, after the processes of S9 and S10 are performed, an image in which the front and back images and the left and right images are exchanged is transmitted to the master unit 101 and the slave unit 102 and printed.

  Subsequently, if the printing is finished and the number of sheets output from the slave unit 102 is an even number (based on the storage at YES in S8), the printed sheet is reversed (S13). At this time, if the setting is not reversed in normal printing (for example, face-down output), the output is reversed by the output reversing unit 121. On the other hand, if the setting is reversed in normal printing (for example, face-up output), the reversal path is not passed. In S13, if YES in S8, if there is no even-numbered memory, the printed paper is output without being inverted.

  Thereafter, the CPU 21 determines whether or not all printing has been completed (S14). If all printing has not been completed (S14: NO), the CPU 21 returns to S7 and continues the subsequent processing. On the other hand, if all printing has been completed in S14 (S14: YES), the CPU 21 ends the printing process. After the printing is finished, the post-processing device 14 is caused to execute post-processing designated by the print setting (S15). In the post-processing, if the saddle stitch booklet form is designated, the post-processing device 14 performs a folding operation or the like. This completes all processing.

  Next, the case where left binding (or right binding) is selected in S5 will be described with reference to FIG. This is basically the same as saddle stitching, and when the appearance priority is selected, the imprinted front and back images are replaced and printed. However, the left and right pages are not exchanged. Details will be described below. Here, a case where left binding is selected will be described as an example, but the same applies to right binding, and only the binding position in post-processing is different.

  When the left binding is designated (S5: NO (left (right) binding)), the CPU 21 imposes each page (S21). In this imposition, an image for one page is associated with one side of one sheet of paper, and duplex printing is performed. That is, the first page on the front side of the first sheet, the second page on the back side of the first sheet, the third page on the front side of the second sheet, and the fourth page on the back side of the second sheet. .., And finally, the nth page is imposed. The impositioned image is stored in the flash ROM 24 so as to be impositioned.

  At this stage, the impositioned images are for the front side and the back side, and are associated with the master unit 101 and the slave unit 102 in the order in which the images are sent out. That is, the image for the front side of the first sheet is related to the printing unit 13 of the master unit 101, the image for the back side of the first sheet is set to the printing unit 13 of the slave unit 102, and so on. ing.

  Subsequently, the CPU 21 issues a print execution instruction and feeds one sheet of paper (S22). Subsequently, it is determined whether the fed paper is an even number (S23). Again, like the saddle stitching, the treated sheet is the sheet designated in advance. If the paper fed in S23 is not an even-numbered sheet (that is, an odd-numbered sheet) (S23: NO), the imposition image data is transmitted as it is to the master unit 101 and the back side is transmitted to the slave unit 102 ( S25), and printing is performed (S26).

  On the other hand, when the sheet fed in S23 is an even number (S23: YES), this is stored, and the imposition image printed on the even sheet is for the front side and the back side. Are replaced (S24). The second page imposed on the front surface of the second sheet, which is an even number of sheets, is used for the back surface, and the image on the third page is redesignated for the front surface of the second sheet. The other even-numbered sheets are similarly replaced.

  Subsequently, the CPU 21 transmits the front-side image with the front and back images exchanged to the master unit 101 and the back-side image with the same image exchanged to the slave unit 102 (S25), and prints them (S26).

  Subsequently, the CPU 21 inverts the paper output from the slave unit 102 after printing is completed (S27). In the case of printing that is not reversed by normal printing, the output is reversed through the output reversing path 122, and in the case of printing that is reversed by normal printing, the reversal is performed without passing through the output reversing path 122.

  Thereafter, the CPU 21 determines whether or not all printing has been completed (S28). If all printing has not been completed (S28: NO), the process returns to S22 and the subsequent processing is continued. On the other hand, if all printing has been completed in S28 (S28: YES), the CPU 21 ends the printing process. Thereafter, the CPU 21 causes the post-processing device 14 to execute post-processing in accordance with the print setting instruction in order to perform post-processing designated in the print settings, in this case, to form a left-binding form (S15). .

  Next, a specific example of a printed booklet will be further described. First, a saddle stitch booklet form will be described as an example. In order to facilitate understanding of the present embodiment, the description here starts with the conventional saddle-stitched booklet printing. 6A and 6B are explanatory diagrams for explaining printing in a conventional saddle-stitched booklet form. FIG. 6A is an explanatory diagram of printing, and FIG. 6B is an explanatory diagram of a finished booklet. FIG. 7 is an explanatory diagram for explaining printing of a saddle-stitched booklet form in which processing for improving the appearance by applying the first embodiment is performed, (a) and (b) are explanatory diagrams of printing, (C) is an explanatory diagram of a completed booklet. Here, for the sake of easy understanding, a description will be given by taking a printed matter of 12 pages as an example. 6 and 7, [Numeric] indicates a page number when printed on the front surface, and (Numeral) indicates a page number when printed on the back surface.

  With reference to FIG. 6, conventional saddle-stitched booklet printing will be described. First, the first page and the twelfth page are printed on the surface of the first sheet by the master unit 101. Thereafter, the first sheet is conveyed to the slave unit 102 and the second and eleventh pages are printed on the back side. Subsequently, the third page and the tenth page are printed on the front surface of the second sheet by the master unit 101, and the second sheet is conveyed to the slave unit 102 and the fourth page and the ninth page are printed on the back side. The page is printed. Thereafter, similarly, the front side of each page is printed by the master unit 101, and the back side is printed by the slave unit 102.

  As shown in FIG. 6B, the sheet printed and output in this way becomes a double-page spread when the second and third pages are bound in a booklet form. Then, since the second page is printed by the slave unit 102 and the third page is printed by the master unit 101, a subtle difference between the master unit 101 and the slave unit 102 may appear. The same applies to the other left and right pages.

  There are various reasons why printing differs between the master unit 101 and the slave unit 102. For example, individual differences between the original print engines, and the printing frequency of color and monochrome images are different between the master unit 101 and the slave unit 102. This is due to differences in the degree of progress of deterioration due to differences in running time.

  Next, the case of the first embodiment will be described with reference to FIG. First, the first page and the twelfth page are printed on the surface of the first sheet by the master unit 101. Thereafter, the first sheet is conveyed to the slave unit 102 and the second and eleventh pages are printed on the back side. Subsequently, the ninth page and the fourth page are printed on the front surface of the second sheet by the master unit 101, and the second sheet is conveyed to the slave unit 102 and the tenth page and the third page on the back side. The page is printed.

  As shown in FIG. 7B, the printing on the second sheet of paper is the front and back of the paper after the front and back and left and right are switched compared to the initial imposition state (that is, conventional printing (FIG. 6)). The images printed on the left and right pages are switched, and the images on the left and right pages are also switched. The second sheet printed and output in this way is reversed when it is output from the slave unit 102.

  After that, printing is performed as usual for odd-numbered sheets, printing is performed with the front and back sides switched and the left and right images are also switched for the even-numbered sheets, and finally inverted and output.

  As shown in FIG. 7C, when the paper printed in this way is bound in a booklet form, the second and third pages are spread pages. At this time, since the second page and the third page are printed by the slave unit 102, a difference due to the difference in the print engines does not appear. Similarly, since the fourth page and the fifth page, which are spread pages, are printed by the master unit 101, a difference due to a difference in print engines does not appear. Similarly, since the other spread pages are printed by the same print engine, a difference due to the difference of the print engines does not appear.

  Next, the case of left binding will be described. 8A and 8B are explanatory diagrams for explaining printing in the form of a conventional left-bound booklet. FIG. 8A is an explanatory diagram of printing, and FIG. 8B is an explanatory diagram of a finished booklet. FIG. 9 is an explanatory diagram for explaining the printing of the left-bound booklet form in which the processing for improving the appearance is applied by applying this embodiment, (a) is an explanatory diagram of printing, and (b) is a finished product. It is explanatory drawing of a booklet. In any case, a printed matter of 12 pages will be described as an example. 8 and 9, [Numeral] indicates a page number when printed on the front surface, and (Numeral) indicates a page number when printed on the back surface.

  With reference to FIG. 8, a conventional left-bound booklet printing will be described. First, the first page is printed by the master unit 101 on the surface of the first sheet. Thereafter, the first sheet is conveyed to the slave unit 102 and the second page is printed on the back side. Subsequently, the third page is printed on the front side of the second sheet by the master unit 101, the second sheet is conveyed to the slave unit 102, and the fourth page is printed on the back side. Thereafter, similarly, the front side of each page is printed by the master unit 101, and the back side is printed by the slave unit 102.

  As shown in FIG. 8B, the sheet printed and output in this way becomes a double-page spread when the second and third pages are bound in a booklet form. Then, since the second page is printed by the slave unit 102 and the third page is printed by the master unit 101, a subtle difference between the master unit 101 and the slave unit 102 may appear. The same applies to the other left and right pages.

  Next, the case of the first embodiment will be described with reference to FIG. First, the first page is printed by the master unit 101 on the surface of the first sheet. Thereafter, the first sheet is conveyed to the slave unit 102 and the second page is printed on the back side. Subsequently, the fourth page is printed on the front surface of the second sheet by the master unit 101, the second sheet is conveyed to the slave unit 102, and the third page is printed on the back side. As described above, the printing on the second sheet has the front and back sides switched compared to the state of the first imposition (conventional printing (FIG. 8)). The second sheet printed and output in this way is reversed when it is output from the slave unit 102. After that, printing is performed as usual for odd-numbered sheets, printing is performed with the front and back sides switched for even-numbered sheets, and finally the output is reversed.

  As shown in FIG. 9B, when the paper printed in this way is bound as a left-bound booklet, the second page and the third page are spread pages. At this time, since the second page and the third page are printed by the slave unit 102, a difference due to the difference in the print engines does not appear. Similarly, in the other spread pages, the pages on the left and right sides of the spread are printed by the same print engine, so that the difference due to the difference in the print engines does not appear.

  As described above, in the first embodiment, printing on even-numbered sheets as designated sheets is performed by switching the front and back images with respect to printing on other sheets (that is, odd-numbered sheets). did. In saddle stitching, the left and right images are also replaced. Thereby, in all the spread pages, the pages on the left and right sides of the spread are printed by the same print engine, and printing can be performed so that a difference due to the difference in the print engines does not appear. The paper designated in advance for replacing the image may be an odd number of sheets, and the same effect can be obtained.

[Embodiment 2]
In the first embodiment described above, printing on all even-numbered sheets as designated sheets is performed by replacing the front and back images with respect to printing on other sheets. However, it may not be necessary to replace the images to be printed on all even-numbered sheets. For example, if only the characters are printed on a spread page, you may not be concerned about subtle differences due to differences in print engines. Also, for example, an object such as a photo, graphic, or other image that is completed on one page of a two-page spread page is printed only on one page, so there must be no objects other than these characters on the other page. For example, the difference between the print engines on the left and right pages may not matter.

  On the other hand, when objects other than characters, such as photographs, graphics, and images, are printed on both spread pages, it is easy to notice subtle differences due to differences in print engines in conventional printing.

  Therefore, in the second embodiment, an object other than characters (for example, a photograph, a graphic, an image, etc., which is the same below) printed on the left and right sides of a spread page is detected, and the paper on which such a page is printed is detected. Only to replace the image to be printed.

  FIGS. 10 and 11 are flowcharts for explaining a booklet-type print processing procedure in duplex printing in the second embodiment. FIG. 12 is a subroutine flowchart showing a processing procedure of appearance priority page determination.

  In the print processing procedure of the booklet form in the duplex printing according to the second embodiment, a part different from the procedure shown in FIGS. 3 and 4 includes the step (S30) of determining the appearance priority page after the sheet feeding in S7. The step corresponding to S8 is looked good and it is determined whether or not it is a priority page (S31). That is, the step of turning on the reverse flag (S32) is inserted after the left and right image replacement in S10, and the step corresponding to S13 is looked at and the step of reversing the priority sheet is made. Therefore, the processing different from those of the first embodiment will be mainly described here, and the description of other processing similar to that of the first embodiment will be omitted or simplified.

  In the second embodiment, after feeding one sheet of paper, it is determined whether or not there are objects other than characters on both spread pages (S30: Appearance priority page determination).

  With reference to FIG. 12, the processing procedure of the appearance priority page determination will be described. First, the CPU 21 determines whether or not the reverse flag is on (S301). The inversion flag is a flag indicating that the images to be printed on the paper on which the appearance priority page is printed are replaced with the front and back images and the left and right images in the order of imposition. If the inversion flag is on (S301: YES), the inversion flag is turned off (S302), the process proceeds to S11 of the main routine as it is, and printing (S12) is executed.

  The inversion flag will be described. At this stage, that is, the reverse flag was turned on immediately after feeding one sheet of paper, the paper printed before that was printed with the front and back and left and right images switched in the order of imposition. It is. In this state, if it is determined that there is an object other than a character on both the spread pages on the next sheet, the front and back images and the left and right images are exchanged. Then, the image to be printed with the previous paper is replaced and the spread page is printed with the same print engine, but if the next paper is also reversed, the print engine is different, only the printing order is reversed It will be printed with things. Therefore, S301 and S302 and S32 described later are used to prevent such a situation. Therefore, after S302, in S11 and S12, images to be printed on the front and back as they are in the order of imposition are printed by the master unit 101 and the slave unit 102, respectively.

  If the reverse flag is not turned on in S301 (S301: NO), the first page and the previous page and the last page and the last page among the pages (there are four pages) printed on the fed paper. Compare the images to be printed on the next page. Then, it is determined whether there is an object other than a character on both the first page and the previous page, or whether there is an object other than a character on both the last page and the next page (S303).

  Here, the first page and the last page among the pages printed on the fed paper (there are four pages) are the pages printed on the front side in the order of imposition (that is, the master unit 101). Printing). On the other hand, the previous page is a page that has already been printed on the previous sheet at this stage, and in the order of imposition, is a page printed on the back side (that is, printed by the slave unit 102). is there. Similarly, the next page is a page that has already been printed on the previous sheet at this stage, and in the order of imposition, it is a page printed on the back side (that is, printed by the slave unit 102).

  In other words, in step S303, the two pages printed on the front side of the paper fed at this stage are compared with the two pages printed on the back side of the paper that has been printed before. It is determined whether or not there are objects other than characters on both pages.

  If there are no objects other than characters on both spread pages (S303: NO), the absence of objects other than characters is stored in the RAM 23 (S304), and the process returns to the main routine. On the other hand, if there are objects other than characters on both spread pages (S303: YES), the presence of objects other than characters is stored in the RAM 23 (S305), and the process returns to the main routine.

  This determination can be made, for example, as follows.

  FIG. 13 is an explanatory diagram illustrating processing for detecting objects other than characters.

  When there are objects other than characters on both spread pages, there are objects 401 other than characters continuous on the left and right of the spread pages as shown in FIG. 13A, or spreads as shown in FIG. 13B. This means that there are objects 401 other than characters on the left and right of the page.

  Whether or not there is an object 401 other than a character on both the left and right pages as shown in FIGS. 13A and 13B is, for example, the type information of an object added in units of pixels together with the color gradation information of each object. (Referred to as tag bits).

  FIG. 13C is an enlarged view of a pixel portion, and FIG. 13D is an explanatory diagram of color gradation information and type information assigned to each pixel. As shown in the figure, type information (Tag) is added to each pixel together with color gradation information of cyan (c), magenta (M), yellow (Y), and black (K). In the type information (tag bit), information for identifying which object the pixel belongs to, for example, a character (text), a photograph, a graphic, an image, or the like is recorded. Yes.

  FIG. 14 is an explanatory diagram for explaining a version based on color gradation information and type information. Each plate is produced based on color gradation information and type information. A Tag version is completed along with C, M, Y, and K color versions. By looking at the Tag version, it is possible to determine what type of object exists at which position in the page. The figure shows that an object 401 other than characters and text (characters) 402 exist.

  Note that the Tag version shown in FIG. 14 is for explanation, and it is not necessary to produce the Tag version as shown in FIG. 14 in the actual determination of S303, and other than characters from the type information (Tag). If it is known that the object exists, it is determined that the page is a preferential appearance page.

  In response to the determination result of S303, the process returns to the main routine, and the CPU 21 determines whether or not to print the preferential appearance page on the current sheet (S31). Here, if there is no appearance-priority page based on the storage in S304 (S31: NO), the front and back images are transmitted to the parent device 101 and the child device 102 as they are in order of imposition. (S11), printing (S12) is performed. On the other hand, if there is an appearance priority page based on the storage in S305 (S31: YES), it is stored in S31, and the images for the front side and the back side are replaced in the order of imposition (S9). Further, the images of the pages printed on one side of one sheet are switched left and right (S10).

  Thereafter, the CPU 21 turns on the inversion flag (S32) in order to memorize that the replacement of images (S9 and S10) has been performed.

  After that, the images for the front side and the back side are transmitted to the master unit 101 and the slave unit 102 (S11) and printed (S12). Thereafter, since it is stored in S31 that the appearance is prioritized, the paper is reversed and output (S33). Thereafter, as in the first embodiment, it is determined whether or not the printing has been completed.

  The case of left (right) binding will be described with reference to FIG. The case of left (right) binding is the same as that of saddle stitching. Of the pages printed on the fed paper, whether or not there are images on both the first page and the previous page is the page order. Determine (S30: Appearance priority page determination). At this time, unlike the saddle stitching, it is not necessary to compare with a subsequent page. This is because, in left (right) binding, comparison with a subsequent page is the same as comparing the first page printed on that sheet with the previous page on the sheet to be printed next. If the left (right) binding routine is entered, after the reverse flag is turned off (S302) in the appearance priority page determination subroutine (see FIG. 12), the process proceeds to S25.

  If there are objects other than characters on both pages (S31: YES), the front and back images to be printed are switched (S24), the reverse flag is turned on (S32), and the subsequent processing is performed. Just do it.

  Next, a specific example of a printed booklet will be further described. Here, a saddle stitch booklet form will be described as an example. In the case of left (right) binding, the completed state is the same as that of saddle stitching, and therefore description of a specific example is omitted.

  FIG. 15 is an explanatory diagram for explaining printing of a saddle-stitched booklet form in which processing for improving the appearance by applying the second embodiment is performed, (a) is an explanatory diagram of printing, and (b) is an explanatory diagram of printing. It is explanatory drawing of a completed booklet. Here, a 16-page printed material will be described as an example. In FIG. 15, [Numeral] indicates a page number when printed on the front surface, and (Numeral) indicates a page number when printed on the back surface.

  Here, a case will be described in which the second page and the third page are spread pages, and objects other than characters are printed on both pages.

  Referring to FIG. 15, first, the first page and the 16th page are printed on the surface of the first sheet by the master unit 101. Thereafter, the first sheet is conveyed to the handset 102 and the second and fifteenth pages are printed on the back side. Subsequently, the fourth page and the thirteenth page are printed on the front surface of the second sheet by the master unit 101, the second sheet is conveyed to the slave unit 102, and the fourteenth page and the third page are printed on the back side. The page is printed. In the printing on the second sheet, there is an object other than a character following the second page on the third page. For this reason, the front and back images are switched from the first impositioned state, and the left and right images are also switched. The second sheet printed and output in this way is reversed when it is output from the slave unit 102.

  Thereafter, the fifth and twelfth pages are printed on the front side of the third sheet by the master unit 101, and the sixth and eleventh pages are printed on the back side by the slave unit 102. The seventh and tenth pages are printed on the front side of the fourth sheet by the master unit 101, and the eighth and ninth pages are printed on the back side by the slave unit 102.

  As shown in FIG. 15B, when the paper printed in this way is bound in a booklet form, the second and third pages are spread pages. At this time, since the second page and the third page are printed by the slave unit 102, the difference due to the difference in the print engines does not appear. On the other hand, in the case of other pages in this example, there are no objects other than characters on both of the spread pages, so even if the print engines are different, the difference between them is hardly recognized.

  Next, an example of a setting screen when performing appearance priority setting in the second embodiment will be described.

  Also in the second embodiment, as described in the first embodiment (see FIG. 5), when the appearance priority is selected, the page is automatically spread when there are objects other than characters on both spread pages. The image for the paper on which one page is printed may be exchanged (the left and right sides are also exchanged for saddle stitching).

  However, only the processing unique to the second embodiment is performed, and it becomes impossible to print all spread pages with the same print engine as in the first embodiment. Therefore, the user can select whether to give priority to appearance only for objects other than characters or to give priority to appearance on all pages.

  FIG. 16 is an explanatory diagram for explaining an example of a setting screen in which the user can select whether to give priority to the appearance of only a page having an object other than a character or to give priority to the appearance of all pages in the second embodiment.

  The setting screen 310 is displayed on the operation panel 15 as in the first embodiment. In this setting screen 310, items of speed priority 301, appearance priority (all) 302, and appearance priority (image only) 303 are prepared, and each has a radio button. The appearance priority (all) 302 is an item for performing the processing of the first embodiment. An appearance priority (only an image) 303 is an item for performing the processing of the second embodiment. Note that “(image only)” in the appearance priority (image only) 303 refers to an object other than a character as an image in contrast to the character.

  When the user selects any item from the setting screen 310, the control unit 11 executes each process.

  By providing such setting items, the user can select what appearance priority processing is performed. The speed priority 301 is, of course, selected when it is desired to obtain duplex output and a booklet-type output giving priority to speed regardless of appearance. The appearance priority (all) 302 is selected in the case where priority is given to appearance in all spread pages, although the processing speed is somewhat sacrificed. The appearance priority (only the image) 303 is selected in the case where the appearance priority is given only to an object other than a character in which a subtle difference is easily discriminated when the left and right pages are printed differently in a spread page. For this reason, the appearance priority (only the image) 303 has a higher processing speed than the appearance priority (all) 302, and the printed page is printed in double-sided printing so that the page that looks good looks better. it can.

  As described above, in the second embodiment, when there are objects other than characters, such as photographs, graphics, images, etc., on both spread pages as the designated paper, the paper on which one of the spread pages is printed. In this case, the front and back images are exchanged on the paper on which the other page is printed. In saddle stitching, the left and right images are also replaced. As a result, printing is performed so that the difference due to the difference in the print engine does not appear especially in the spread page where the objects other than the characters (photos, graphics, images, etc.) where the subtle difference due to the difference in the print engine is easily recognized exist be able to.

[Embodiment 3]
In the first and second embodiments, the setting example for setting the print setting with the appearance priority from the operation panel 15 provided in the image forming apparatus 1 has been described. In the third embodiment, an example in which the user performs spread setting for each job from the printer driver will be described.

  The print job is created on a PC or the like. At that time, the printer driver is activated and various print settings are made. Therefore, in the third embodiment, an item for performing appearance priority processing is added to the setting screen of the printer driver.

  FIG. 17 is an explanatory diagram for explaining an example of a printer driver setting screen for performing appearance priority setting by the printer driver.

  As shown in FIG. 17A, items such as imposition 501, duplex printing 502, saddle stitching 503, left binding 504, right binding 505, and spread setting 506 are set on the printer driver setting screen 500. Provided to do. Although not shown, other items for print settings may be displayed.

  The imposition 501 is a pull-down menu. FIG. 17B shows an example of a pull-down menu for imposition 501. In the imposition 501 menu, for example, there is a booklet 511 item.

  The duplex printing 502, the saddle stitching 503, the left binding 504, and the right binding 505 are all provided with check boxes, and their functions are set by checking the corresponding check boxes.

  The spread setting 506 is a pull-down menu. FIG. 17C shows an example of a pull-down menu for the spread setting 506. In the spread setting 506 menu, for example, speed priority 516, appearance priority (all) 526, and appearance priority (image only) 536 are provided. Note that “(image only)” in the appearance priority (image only) 536 refers to an object other than a character as an image in contrast to the character.

  From the setting screen 500 in which these items are provided, for example, double-sided printing 502 and saddle stitching 503 are checked, and a booklet 511 is selected from the pull-down menu for imposition 501 and appearance priority (all) 526 is displayed from the pull-down menu for spread setting 506. When selected, an instruction to execute printing in a saddle-stitched booklet form with double-sided printing with priority on the appearance of all spread pages is embedded in the print job. Upon receiving this instruction, the image forming apparatus 1 executes the processing of the first embodiment.

  For example, when the double-sided printing 502 and the saddle stitch 503 are checked from the setting screen 500 and the booklet 511 is selected from the pull-down menu of the imposition 501 and the appearance priority (only images) 536 is selected from the pull-down menu of the spread setting 506, An instruction to execute printing in a saddle-stitched booklet form with double-sided printing with priority on the appearance only for pages that have objects other than characters on both pages of the spread pages is embedded in the print job. Upon receiving this instruction, the image forming apparatus 1 executes the processing of the second embodiment.

  In this way, by giving the appearance priority instruction to the printer driver built in the PC, the image forming apparatus 1 is caused to perform the printing with the appearance priority of the spread page when the print job is transmitted. Will be able to.

  As mentioned above, although embodiment applied with this invention was described, this invention is not limited to these embodiment.

  For example, in the above-described embodiment, the configuration in which the control unit is incorporated in the image forming apparatus has been described. However, the control unit of the image forming apparatus may be a separate control device. Specifically, a control device (a so-called printer controller, printer server, or the like) for executing the processing of the first and second embodiments may be used separately from the parent device and the child device each having a printing unit.

  In addition, it goes without saying that the present invention is construed according to the claims, and is not construed as being limited to the above-described embodiments and examples.

1 image forming apparatus,
11 Control unit,
12 Paper feeder,
13 Printing department,
14 post-processing equipment,
21 CPU,
22 ROM,
23 RAM,
24 Flash ROM,
27 Network interface,
28 Bus,
29 Internal wiring,
101 Master unit,
102 handset,
110 transport path,
111 intermediate inversion part,
121 output inverting unit,
300 setting screen,
301 Speed priority,
302 Appearance priority or Appearance priority (all),
303 Appearance priority (image only),
500 Printer driver setting screen,
501 Imposition,
502 duplex printing,
503 Saddle Stitch,
504 Left binding,
505 Right binding,
506 spread setting,
511 booklet.

Claims (4)

A master unit having a printing unit for printing an image on the first side of the paper;
A slave unit including a printing unit that prints an image on a second surface opposite to the first surface of the paper printed by the master device;
An output reversing unit for inverting the paper after printing output from the slave unit;
During double-sided printing, the image to be printed first is imprinted for the first side, and the image to be printed next is impositioned for the second side.
When printing on a plurality of sheets so as to form a booklet, with respect to a sheet designated in advance, the impositioned image for the first surface is used for the second surface and the impositioned first image is printed. Replace the image for the second side with the one for the first side,
The image for the first surface after the replacement is printed by the master unit, and the image for the second surface after the replacement is printed by the slave unit, respectively.
A control unit that inverts and outputs the designated sheet output from the slave unit by the output inversion unit;
I have a,
The control unit detects a page having an object other than a character on both pages of the spread page, and sets a sheet on which one of the two pages of the spread page having the object other than the character is printed on the sheet. An image forming apparatus characterized in that a designated sheet is used.   When the saddle stitching is specified in the booklet form, the control unit replaces the images of the left and right pages to be printed for the first surface after the replacement, and for the second surface after the replacement. The image forming apparatus according to claim 1, wherein the images on the left and right pages to be printed on are exchanged. A master unit having a printing unit for printing an image on the first side of the paper;
A slave unit including a printing unit that prints an image on a second surface opposite to the first surface of the paper printed by the master device;
An image forming method comprising: an output reversing unit that reverses the printed paper output from the slave unit;
A step (a) of imposing an image to be printed first for the first side and an image to be printed next for the second side during duplex printing;
When printing on a plurality of the sheets so as to be in a booklet form, for the previously designated sheets, the impositioned image for the first surface is used for the second surface and the impositioned image Replacing the image for the second surface with that for the first surface (b);
The step (c) of printing the first surface after the replacement by the master unit and the second surface after the replacement by the slave unit;
And step (d) to output the inverted by the output inverting unit the paper that is the specified output from the slave unit,
At least before the step (b) of switching, a page having an object other than a character on both pages of a spread page is detected, and one of the pages having an object other than a character on both pages of the spread page is detected. A step (g) of setting the paper on which the page is printed as the designated paper;
An image forming method comprising: When saddle stitching is specified in the booklet form, before the step (d) of printing, the left and right page images to be printed for the first side after the replacement are replaced, and the replaced The image forming method according to claim 3 , further comprising a step (f) of replacing the images of the left and right pages to be printed for the second side.