Abstract:
For a duplex print job a display portion of the image forming apparatus shows a stack image of one or more papers. A top paper in the image appears to have a corner turned over revealing a portion of the back side of the top paper, and revealing a portion of a front side of a second paper in the stack. Within the stack image, the image portion of the front side of the top paper shows a print preview of a front side of a first sheet in the duplex print job. Image portions corresponding to the back side of the top paper and the front side of the second paper show, respectively, print preview of the back side of the first sheet and front side of a second sheet. The page images may be displayed at a glance for multiple pages in a two up fashion.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image forming apparatus with a display function for print preview, and a computer program to perform print preview processing. 
     2. Description of the Related Art 
     In the image forming apparatuses, such as copiers and facsimiles, there is a kind that comprises the print preview function. The print preview function enables displaying an image (a preview image) of the appearance of when the page image, that is the image of one page or a plurality of pages scanned from an original manuscript, is output (formed) onto a paper, on a display unit of such as a liquid crystal panel, based on a print data of the above-mentioned page image. This print preview function plays an important role for preventing unwilling image formation and useless consumption of paper and developer. 
     For example, Literature 1 (Japanese Unexamined Patent Application Publication No. 2004-164105) discloses, when performing both-side printing (printing on the front and back) for a planned book binding, the print result is previewed by displaying each of the page images aligned on a display unit. 
     And also, Literature 2 (Japanese Unexamined Patent Application Publication No. H04-373073) discloses to display reduced page images of a plurality of pages partially overlapped and aligned on a display unit. 
     And now, it is important to confirm a print result of both-side printing to be confirmable on a preview image about both of the page order and the front-back relationship (relations between the front and back) of each of the page image prior to printing (image forming). Especially, when a plurality of paper obtained by both-side printing is planned to be bound up (for a book), it is desirable to intuitively confirm about both of the page order and the front-back relationship of each page image, on a preview image in an actually bound status. 
     However, when previewing the print result of both-side printing, as in Literatures 1 and 2, it has been difficult to intuitively understand both of the page order and the front-back relationship of each of the page images only by displaying a preview image of each of the aligned page images. 
     In view of the above problems residing in the prior arts, it is a purpose of the present invention to provide an image forming apparatus and a program for print preview which enables to display a preview image of a print result of both-side printing that allows intuitive understanding of both of the page order and the front-back relationship of each of the page images. 
     SUMMARY OF THE INVENTION 
     In order to achieve the above purpose, an image forming apparatus according to the present invention comprises a function for displaying a print preview image of a page image on a display unit based on a print data related to the page image of a plurality of pages recorded in a prescribed memory, and further comprises the following constituent elements described in (1) and (2). 
     (1) a page identifying member for identifying a page of the page image, that is to be formed on a front surface of a print media when both-side printing based on the print data is performed, according to an information input through a prescribed operating member. 
     (2) a preview outputting member for displaying on the display unit the print preview image which includes an image: turned-over image, indicating partially the page images of three pages counted from the page that is identified by the page identifying member. Said page images of three pages are, under a condition where a plurality of print medias are stacked and the uppermost one is partially turned over, displayed on each of: a first area corresponding to the front surface section of the uppermost print media, a second area corresponding to the back surface section of the uppermost print media, and a third area corresponding to the front surface section of the second print media. 
     The print preview image prepared by an image forming apparatus according to the present invention is an image collectively displaying partial page images of each of at least three continuing pages. Moreover, the print preview image is therefore an image indicating the appearance of when the actual print medias obtained by both-side printing is turned over with fingers, and it is immediately obvious that the order of the images: the first area, and the second area, and then the third area, indicates the page order of the page images. Consequently, the print preview image prepared by an image forming apparatus according to the present invention is an image which allows intuitive (immediate) understanding of the content and the page order of the page images of at least continuing three pages, with only a glance. 
     And also, in the print preview image, the page images of the second and the third pages are partially displayed on the sections (the second area and the third area) disposed by partially turning over the print media on which the page image of the first page is formed in its front surface. Consequently, the print preview image prepared by an image forming apparatus according to the present invention is an image, which allows intuitive (immediate) understanding of the front-back relationship telling how the page images from the first page to the third page are formed on the print media, with only a glance. 
     Additionally, in a print media on which an image is to be formed by both-side printing processing, the surface on which a page image of relatively smaller page number is to be formed is the front surface, and the surface on which a page image of relatively larger page number is formed is the back surface. 
     And also, the preview outputting member may display on the display unit the print preview image, in which the page image of a page previous to the page identified by the page identifying member and the turned-over image are aligned in a double-page spread. 
     This allows displaying a print preview image, which enables intuitive understanding of the content, the page order and the front-back relationship in a print media about the page images of continuing four pages. 
     More particularly, the preview outputting member may, for example, display on the first area in the turned-over image, a part of the page image to be formed on a section corresponding to the first area by both-side printing based on the print data, just as it is. 
     And also, an image forming apparatus according to the present invention may further comprise a partial image extractor for extracting a partial image from each of the page images of two pages (the second and the third pages) subsequent to the page which is identified by the page identifying member, in accordance with a predetermined rule. In this case, the preview outputting member displays each of the images extracted by the partial image extractor on each of the second area and the third area in the turned-over image. 
     This allows a particular part for easy understanding of the content of each page image to be extracted and displayed on a narrow section of turned-over (the second and the third areas). 
     For example, the partial image extractor may extract an image of a partial area predetermined in the page image, an image of the area having the highest image density in the page image, or a photographic image included in the page image. 
     Additionally, the preview outputting member may switch two conditions according to an input operation through a prescribed operating member: one condition in which a part of the page image to be formed on a section corresponding respectively to the second area and the third area by both-side printing based on the both-side print data is displayed on each of the second and the third areas in the turned-over image just as it is, and another condition in which an image extracted by the partial image extractor is respectively displayed on each of the second area and the third area in the turned-over image. 
     In addition, the preview outputting member may display on the display unit the print preview image including an image: extracting-position indicating image, which indicates the position of an image that was extracted by the partial image extractor to display it on each of the second area and the third area in the turned-over image from. 
     For example, the extracting-position indicating image is such as an arrow image that is vector-representing a position of each of the images extracted by the partial image extractor started from each of the first area and the second area. Displaying the extracting-position indicating image allows easy understanding of the content of a page image in a page corresponding to the turned-over section (the first and the second areas). 
     The present invention may also be realized as a print preview program for a computer to perform the above-mentioned process (display processing of the print preview image on a display unit) conducted by an image forming apparatus according to the present invention. 
     According to the present invention, in regard to a print result of both-side printing, to display a preview image which allows intuitive understanding of both of the page order and the front-back relationship in a print media of each page image can be achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a structure of a main part of an image forming apparatus X according to an embodiment of the present invention; 
         FIG. 2  is a flowchart showing the steps of display processing of a print preview according to an image forming apparatus X; 
         FIG. 3  shows a first example of a print preview screen according to an image forming apparatus X; 
         FIG. 4  shows a second example of a print preview screen according to an image forming apparatus X; 
         FIG. 5  shows a third example of a print preview screen according to an image forming apparatus X; 
         FIG. 6  shows a fourth example of a print preview screen according to an image forming apparatus X. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With embodiments of the present invention described hereinafter with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims. 
     Here,  FIG. 1  is a block diagram showing the structure of a main part of an image forming apparatus X according to an embodiment of the present invention;  FIG. 2  is a flowchart showing the steps of print preview displaying processing according to an image forming apparatus X;  FIG. 3  shows a first example of a print preview screen according to an image forming apparatus X;  FIG. 4  shows a second example of a print preview screen according to an image forming apparatus X;  FIG. 5  shows a third example of a print preview screen according to an image forming apparatus X; and  FIG. 6  shows a fourth example of a print preview screen according to an image forming apparatus X. 
     An image forming apparatus X according to an embodiment of the present invention is an image forming apparatus such as a copier, a printer, and a facsimile, and comprises a function for displaying a print preview image of a page image on a display unit based on a print data that is related to the page image of a plurality of pages and previously recorded in a data memory such as a hard disk. 
     Firstly, as referring now to the block diagram illustrated in  FIG. 1 , the structure of a main part of an image forming apparatus according to an embodiment of the present invention is described. 
     An image forming apparatus X is an MFP (Multifunction Printer), comprising functions for scanning, printing, copying, and facsimile. 
     As illustrated in  FIG. 1 , the image forming apparatus X comprises: a main controller  1 , an operation/display member  2 , a data memory  3 , an image processor  4 , an NIC (Network Interface Card)  5 , a scanning unit  6 , a printing unit  7 , and a facsimile unit  8  that are connected so as to be capable of passing information through a bus  11 . 
     The operation/display member  2  comprises a operation member  2   a  for inputting data and a display unit  2   b  for displaying data (including images). The operation member  2   a  is, for example, a touch panel or a sheet key provided on the surface of a liquid crystal display device. The display unit  2   b  is, for example, a liquid crystal display device. The operation/display member  2  constructs a man-machine interface for a user. 
     The data memory  3  is a readable/writable, high-capacity nonvolatile memory for recording data as need arises, when conducting processing image data obtained by scanning an original manuscript or printing processing by using image data. 
     The image processor  4  is composed of such as a dedicated signal processing circuit or a DSP (Digital Signal Processor), and conducts conversion processing from a print job described in a prescribed page description language into a bitmap image data to be used for image formation, as well as production processing of image data to be transmitted to an external device (for example, image data encoded into a prescribed format, such as JPEG format), in addition to various image processing for image data. 
     The NIC 5  is an communication interface for performing data transmission (including image data obtained by the scanning unit  6 ) between external devices such as information processing terminal and a e-mail server through, for example, a network composed of such as LAN (Local Area Network) complying with the standard of IEEE 802.3 and internet. 
     The scanning unit  6  is a color image scanner which scans, from an original manuscript put on a glass platen (not shown) or delivered from an ADF (Auto Document Feeder) (not shown), an image formed on the original manuscript as distinguishing its colors (R, G, and B). 
     The printing unit  7  is, so-called, a printing engine controlled by the main controller  1 , and is also an assembly of components, such as a device for conducting image formation and an MPU (Micro Processing Unit) for controlling said device. The printing unit  7  feeds a paper stacked in a paper feeding cassette (not shown) sequentially and one-by-one, and delivers the paper to a paper catch tray via a prescribed image forming position, and furthermore, forms (outputs) at the image forming position an image on a paper (an example of print media) based on an image data of the original manuscript scanned by the scanning unit  6  or on an image data produced by the image processor  4  for printing. And also, the printing unit  7  comprises a function for conducting the both-side printing which performs image formation on both of the front and back surfaces of a paper. 
     The facsimile unit  8  comprises communication members such as an NCU (Network Control Unit) and a modem, and performs such as dial-up processing to a communication partner (opposing station) as well as negotiation processing for determining a communication method between the communication partner (opposing station), so as to conduct transmission of facsimile data (image data obtained by the scanning unit  6 ) with other facsimile via a telephone circuit. 
     The main controller  1  controls each of the scanning unit  6 , the printing unit  7 , the facsimile unit  8 , the operation/display member  2 , the data memory  3 , and the image processor  4 . 
     For example, the main controller  1  instructs the printing unit  7  to perform the print processing (image forming processing) based on a print job received via the NIC 5 . The main controller also instructs the facsimile unit  8  to conduct a facsimile-sending processing in which an image data of the sending subject is sent by calling a telephone number of a designated destination. Moreover, the main controller  1  instructs the scanning unit  6  to perform scanning processing to obtain from an original manuscript an image formed on the original manuscript. 
     In addition, the main controller  1  also conducts, based on a print data (such as image data and print job data) related to an image of one or a plurality of pages (hereinafter referred to as “page image”) obtained from an original manuscript by the scanning unit  6 , a print preview processing for displaying on the display unit  2   b  an image (preview image) of when the page image is output (formed) on a paper. 
     Subsequently, as referring to the flowchart in  FIG. 2  and the print preview screens in  FIGS. 3 to 6 , the steps for the print preview processing to be performed by the image forming apparatus X is described. 
     The print data is previously recorded in the data memory  3  prior to the execution of the processing illustrated in  FIG. 2 . The print data is, as described above, a print job input from an external device via the NIC, or an image data scanned by the scanning unit  6 . In addition, S 1 , S 2  and so on in below are identification symbols representing the processing steps. 
     [Steps S 1  to S 4 ] 
     Firstly, the main controller  1  instructs the display unit  2   b  to display a prescribed start menu screen (S 1 ), and monitors whether or not the selecting operation of a processing item in the start menu through the operation member  2   a  is detected (S 2 ). 
     And then, on detecting that any of processing items is selected during display of the start menu, the main controller  1  conducts a processing according to the selecting operation. 
     In short, when the operation selected from the start menu is a requesting operation: a print preview operation, for a displaying print preview, the main controller  1  sets a parameter i representing the default page number (=1) (S 3 ). The main controller  1  further distinguishes whether or not the print data recorded in the data memory  3  as the processing subject is a both-side print data, that has been previously selected as the subject for both-side printing (S 4 ). The both-side print data is, such as a print job data or a scanned image data related to page images of a plurality of pages. 
     Additionally, the parameter i is representing the page number of a page image to be formed on the front surface of a paper when the later-described both-side printing is performed according to the both-side print data. In this embodiment, the parameter i is 1 or more of an odd value. Then the main controller performing the processing in the step S 3  is an example of the page identifying member, which identifies the value of the parameter i on the basis of the data input through the operation member  2   a  (a data requesting the print preview display). 
     [Steps S 5  and S 6 ] 
     When the print data is distinguished as a both-side print data in the step S 4 , the main controller  1  then produces the data of page images of four pages: from the page (i−1) to the page (i+2), on the basis of the both-side print data (S 5 ). In the step S 5 , in the page image of four pages: from the page (i−1) to the page (i+2), the image data related to the page not included in the both-side print data is apparently not the producing subject. 
     Next, the main controller  1  distinguishes, at this point, the display mode status of the print preview: “normal mode” or “extraction mode” (S 6 ). The display mode is the information for identifying the kind of a print preview image to be displayed on the display unit  2   b , in the display processing of a print preview image based on the both-side print data. The content of the display mode is described later. And also, the default state of the display mode is “normal mode”, and then is switchable between “normal mode” and “extraction mode” according to the input operation through the operation member  2   a.    
     [Step S 7 ] 
     When the display mode is “normal mode”, the main controller  1  produces data of a print preview image in “normal mode” based on the data of page images of four pages: from the page (i−1) to the page (i+2) produced in the step S 5 , and instructs the display unit  2   b  to display the print preview image. 
       FIGS. 3 and 4  are the example of a display screen showing a print preview image in “normal mode”.  FIG. 3  shows an example where a page image of the page (i−1) does not exist since the parameter i is 1, and  FIG. 4  shows an example where page images of four pages from the page (i−1) to the page (i+2) exist since the parameter i is 3. 
     As shown in  FIGS. 3 and 4 , the print preview image displayed on the display unit  2   b  by instruction of the main controller  1  (an example of the preview outputting member) includes an image (hereinafter referred to as “turned-over image g 1 ”) indicating that a part (for example, bottom-right part) of the uppermost paper (page i) on the stacked plurality of paper is turned over. Therefore, there exist in the turned-over image g 1 , a first area p 1  corresponding to the section on the front surface of the uppermost paper (page i), a second area p 2  corresponding to the section on the back surface of the uppermost paper (page i+1), and a third area p 3  corresponding to the section on the front surface of the second paper (page 1+2). 
     Additionally, the main controller  1  displays respectively on the first, second, and third areas p 1 , p 2  and p 3  in the turned-over image g 1  partial page images g 12 , g 22 , and g 32  of each of three pages counted from the page i that is identified by the processing in the step S 3  or in the later-described step S 9 . 
     More particularly, the main controller  1 , regardless of the display modes, displays on the first area p 1  in the turned-over image g 1  the image g 12  (a partial page image) just as it is, that is formed by the both-side printing according to the both-side print data on the section corresponding to the first area p 1 , in other word, on the section that is remained in the page image of page i, excepting the part hidden by turning over the paper. 
     And also, in the normal mode, the main controller  1  displays, on each of the second area p 2  and the third area p 3  in the turned-over image g 1 , the partial page images g 22  and g 32  that is a part of the page images formed on the sections respectively corresponding to the second area p 2  and the third area p 3  by the both-side printing according to the both-side print data. This allows, in the example illustrated in  FIG. 4 , respectively the image g 22  of the section in lower left corner of the page image of the page (i+1) to be displayed on the second area p 2 , and the image g 32  of the section in lower right corner of the page image of the page (i+2) to be displayed on the third area p 3 . 
     Furthermore, the main controller  1  also displays respectively, on the first area p 1 , the second area p 2 , and the third area p 3 , page number data g 11 , g 21 , and g 31  corresponding to each of the areas. 
     As shown in  FIG. 4 , the main controller  1  also displays on the display unit  2   b  a print preview image, in which a page image g 0  of the page (i−1) that is previous to the page i, and the turned-over image g 1  are aligned in a double-page spread (S 7 ). 
     And the main controller  1  also displays a n operation button g 4  for switching the subject page for displaying, an operation button g 5  for switching the display mode, and an exit button g 6 , together with the print preview image, on the display unit  2   b , which is also the operation member  2   a  (S 7 ). 
     [Step S 8 ] 
     On the other hand, when the display mode is identified as “extraction mode”, the main controller  1  instructs the image processor  4  to conduct an image extracting processing described in the following (S 8 ). The image extracting processing is extracting a partial image respectively from the page images of two pages: the page (i+1) and the page (i+2), subsequent to the page i identified following to a predetermined role by the processing in the step S 3  or a step S 11  to be described later. Here, the image processor  4  identifies a position of the extracted image (extracting-position) in the page image, and report the position to the main controller  1 . In addition, the image processor  4  is an example of the partial image extractor. 
     In the step S 8 , the image processor  4  performs, for example, the processing as described in below. 
     Firstly the image processor  4  distinguishes whether or not a photographic image is included in each of both page images of the page (i+1) and the page (i+2), and if so, extracts the photographic image. 
     Also, when distinguished that there is no photographic image included in both of the page images, the image processor  4  divides the entire page image into a plurality of predetermined-sized areas, and then, extracts an image having the highest image density among those divided areas. 
     Other than the above, in regard to the divided areas, when the density gap between the area having the highest image density and the area having the second highest image density is within a predetermined range (when the gap is small), the image processor  4  may also extract an image of a predetermined partial area in each of both of the page images, i.e., for example, an area of a prescribed range in vicinity of the upper-left corner. 
     Since the processing for identifying and extracting an area of a photographic image on the basis of an image data including the photographic image is a known art, and a detailed description thereof is omitted. 
     [Step S 9 ] 
     When the display mode is “extraction mode”, the main controller  1  produces a data of the print preview image in “extraction mode” based on the data of page images of four pages: from the page (i−1) to the page (i+2) produced in the step S 5 , and instructs the display unit  2   b  to display the print preview image (S 9 ). 
       FIG. 5  shows an example of a display screen of a print preview image in “extraction mode”. In the example in  FIG. 5 , the page parameter i is 3, and the page images of four pages from page 2 to page 5 (from the page (i−1) to the page (i+2)) is shown. 
     Even in “extraction mode”, the main controller  1  displays on the first area p 1  in the turned-over image g 1  the image g 12  just as it is, that is formed on the area corresponding to the first area p 1  (i.e. the remaining section in the page image of the page i, excepting the section hidden by the turning-over of the paper) by the both-side printing processing based on the both-side print data. 
     On the other hand, in “extraction mode”, the main controller  1  displays images g 23  and g 33  extracted by the image processor  4  in the step S 8  respectively on the second area p 2  and the third area p 3  in the turned-over image g 1  (S 9 : an example of the preview outputting member). 
     This allows extracting and displaying a particular part on a narrow section of turned-over (the second area p 2  and the third area p 3 ) for easy understanding of the content of each page image. 
     Additionally, in the “extraction mode”, the main controller  1  also instructs the display unit  2   b  to display arrow images g 24  and g 34  indicating the extracting position (the position extracted in the processing in the step S 8 ) of the images g 23  and g 33  to be displayed on each of the second area p 2  and the third area p 3  in the turned-over image g 1  (S 9 ). The arrow images g 24  and g 34  are for vector-representing the extracting-position of each of the images g 23  and g 33  extracted in the step S 8  and are examples of the extracting-position indicating image. 
     Displaying the arrow images g 24  and g 34  allows easy understanding of the content of the page images of the page (i+1) and the page (i+2). 
     As an image indicating the extracting-position of the extracted images g 23  or g 33 , instead of the arrow images g 24  and g 34 , for example, an image having a prescribed mark (a circle or a star) arranged in a position corresponding to the extracting images g 23  or g 33  in a rectangle frame representing the entire page may be displayed. 
     [Steps S 10  and S 11 ] 
     Then, after completion of the processing in the steps S 7  or S 9 , the main controller  1  monitors whether or not any of the operations for operation buttons g 4 , g 5 , and g 6  on the operation member  2   a  are detected (S 10 ), and performs the processing according to the operation. 
     In other words, when the operation (page switching operation) of the operation button g 4  for switching the subject page for displaying is detected, the main controller  1  changes the value (page number) of the parameter i according to the operation (S 11 ), and performs the processing described in the above steps  5  to  9  on the newly set page i. 
     For example, in the step S 1 , when the main controller  1  detects the operation of the ‘Previous page’ button or the ‘Next page’ button that are the example of the operation button g 4  for switching the subject page for displaying, the main controller  1  reduces (−2) or adds (+2) the value of the parameter i. The main controller also set the value of the parameter i to 1 (the front page) or to the final odd number page (the back page) in the both-side print data, when the operation of the ‘First page’ button or the ‘Last page’ button is detected. Additionally, when the page is directly specified by the operation of a numerical key not shown, the main controller  1  set the parameter i to the value of the specified page when the specified page is an odd number, or to the value added 1 to the specified page when the specified page is an even number. 
     As just described, in the step S 11 , when the both-side printing based on the both-side print data is conducted according to the data input through the operation member  2   a , the main controller  1  set (specify) the page of one page image to be formed on the front surface of a paper (one example of the page identifying member). 
     [Steps S 12 , S 20 , and S 21 ] 
     In addition, when the operation of the operation button g 5  for switching the display mode (mode switching operation) is detected, the main controller  1  switches the display mode (S 12 ) and performs the processing described in the above steps S 5  to S 9  in the newly set display mode. 
     As described, the main controller  1  (an example of the preview outputting member) switches tow conditions according to the input operation through the operation member  2   a : one condition in which a part of the page images g 22  and g 32  to be formed on the sections corresponding respectively to the second area p 2  and the third area p 3  by both-side printing based on the both-side print data is displayed on each of the second and the third areas p 2  and p 3  in the turned-over image g 1  just as it is (the condition in  FIG. 4 ), and another condition in which the images g 23  and g 33  extracted by the processing in the step S 8  are respectively displayed on each of the second and the third areas p 2  and p 3  in the turned-over image g 1  (the condition in  FIG. 5 ). 
     This allows easy understanding of page images of the page (i+1) and the page (i+2). 
     In addition, the main controller  1  goes back to the processing in the above-mentioned step S 1  when the operation of the Exit button g 6  (finishing operation) is detected. 
     In the step S 2 , when an operation other than the print preview operation is detected while displaying the start menu, the main controller  1  performs the other processing according to the operation (S 20 ), and after that, goes back to the processing in the above-mentioned step S 1 . 
     When the print data recorded in the data memory  3  as a processing subject is distinguished as a single-side print data preselected as a subject for single-side printing (not the both-side print data), the main controller  1  also conducts the print preview processing of the single-side print data (S 21 ), and then, goes back to the processing in the above-mentioned step S 1 . Since the processing in the step S 21  is not directly related to the processing according to the present invention, a detailed description thereof is omitted. 
     The image forming apparatus X described in the above instructs the display unit  2   b  to display, for example, the print preview image including the turned-over image g 1  as illustrated in the  FIGS. 3 and 4 , and therefore, allows intuitive understanding of both of the page order of each page image and the front-back relationship of the paper as a print result of both-side printing. 
     According to the input of an operation button (e.g., the button g 7  shown in  FIG. 6 ) for selecting whether or not to display the turned-over image g 1 , the main controller  1  may also switch the print preview image to be displayed on the display unit  2   b  between the one including the turned-over image g 1  as illustrated in  FIGS. 3 to 5  and the one not including the turned-over image g 1  as illustrated in  FIG. 6 . The example in  FIG. 6  illustrates a print preview image, in which a page image g 0  of the page (i−1) and a page image g 1 ′ of the page i are aligned in a double-page spread and displayed on the display unit  2   b.    
     Additionally, in the examples shown in  FIGS. 3 to 5 , the turned-over image g 1  indicates the state that the lower-right portion of a paper is turned over, however, the turned-over image, indicating that a section including the entire lower hem of the paper or the upper-right portion of the paper is turned over, may be displayed in a print preview image. 
     And the present invention may also realize as a print preview program for computers such as a personal computer to carry out the processing in  FIG. 2  performed by the above-mentioned image forming apparatus X. 
     For example, prior to a transmittance of a print job from a computer to a printer, the computer may perform the print preview program and display a print preview image as illustrated in  FIGS. 3 to 5  on a graphic display (display unit). The present invention is applicable to, such as, an image forming apparatus and a program for computers to conduct a print preview display processing.