Patent Publication Number: US-2019196766-A1

Title: Preview display apparatus, multifunction peripheral, and preview display method

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates to a preview display apparatus, a multifunction peripheral having the preview display apparatus, and a preview display method. 
     2. Description of the Related Art 
     When a print job is performed on a multifunction peripheral, text characters on a printed material are sometimes too small to read. Such a situation arises when text characters used in the original document layout are excessively small or the size of a sheet used for printing is excessively small. 
     To cope with such an illegibility issue due to excessively small text characters on a printed material, previewing has been proposed to check the size of the text characters before printing. For example, Japanese Unexamined Patent Application Publication No. 2009-116734 discloses a method for visual inspection or the like of preview images when content includes text characters smaller than the smallest text size that has been set. However, since the preview order is not determined in consideration of the illegibility level of each page, a user has to search for the most problematic page before displaying the most problematic page, and it takes time to determine whether to perform printing without changing the settings. This situation is aggravated when a large number of pages are to be printed. 
     Japanese Unexamined Patent Application Publication No. 2010-149316 discloses a method for displaying enlarged individual images of a plurality of preview images obtained by dividing a single page so as to enable a user to recognize print data content. However, when a plurality of pages are to be previewed, the issue that a user has to search for the most problematic page before displaying the most problematic page and that it takes time to determine whether to perform printing without changing the settings persists. 
     Thus, it is desirable to provide a preview display apparatus, a multifunction peripheral, and a preview display method that enable a user to find at an early stage a situation in which a print lob, if performed, produces an undesirable print output. 
     SUMMARY 
     According to an aspect of the present disclosure, there is provided a preview display apparatus including an evaluation-value acquisition unit that acquires an evaluation value for each of a plurality of pages in accordance with a predetermined purpose, the plurality of pages being to be previewed, a page-priority adjustment unit that adjusts a priority of each of the plurality of pages in accordance with the evaluation value for the page, and a preview display unit that displays a preview image of each of the plurality of pages in accordance with the priority of the page adjusted by the page-priority adjustment unit. 
     According to another aspect of the present disclosure, there is provided a multifunction peripheral including the aforementioned preview display apparatus. 
     According to another aspect of the present disclosure, there is provided an information processing apparatus including the aforementioned preview display apparatus. 
     Further, according to another aspect of the present disclosure, there is provided a preview display method including acquiring an evaluation value for each of a plurality of pages in accordance with a predetermined purpose, the plurality of pages being to be previewed, adjusting a priority of each of the plurality of pages in accordance with the evaluation value for the page, and displaying a preview image of each of the plurality of pages in accordance with the priority of the page adjusted by the adjusting of the priority of each of the plurality of pages. 
     Further, according to another aspect of the present disclosure, there is provided a non-transitory computer-readable medium storing a preview display program causing a computer to function as the preview display apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flowchart for illustrating a first method and a second method for performing processing from previewing to printing according to a first embodiment; 
         FIG. 2  is another flowchart for illustrating the first method for performing processing from previewing to printing according to the first embodiment; 
         FIG. 3  is another flowchart for illustrating the second method for performing processing from previewing to printing according to the first embodiment; 
         FIG. 4  is a flowchart for illustrating a method for determining the priority of a page according to the first embodiment; 
         FIG. 5A  illustrates an example set of document pages to which a preview display method according to the first embodiment of the present disclosure is applied, and  FIG. 5B  illustrates the order of the document pages to preview in accordance with the preview display method; 
         FIG. 6  is a flowchart for illustrating a method for determining the priority of a page according to a second embodiment; 
         FIG. 7A  illustrates an example set of document pages to which a preview display method according to the second embodiment of the present disclosure is applied, and  FIG. 7B  illustrates the order of the document pages to preview in accordance with the preview display method; 
         FIG. 8  is a flowchart for illustrating a method for determining the priority of a page according to a third embodiment; 
         FIG. 9A  illustrates an example set of document pages to which a preview display method according to the third embodiment of the present disclosure is applied, and  FIG. 9B  illustrates the order of the document pages to preview in accordance with the preview display method; 
         FIG. 10  is a flowchart for illustrating a method for determining the priority of a page according to a fourth embodiment and a fifth embodiment; 
         FIG. 11A  illustrates an example set of document pages to which a preview display method according to the fourth embodiment of the present disclosure as applied, and  FIG. 11B  illustrates the order of the document pages to preview in accordance with the preview display method; 
         FIG. 12A  illustrates an example set of document pages to which a preview display method according to the fifth embodiment of the present disclosure is applied, and  FIGS. 12B and 12C  illustrate the orders of the document pages to preview in accordance with the preview display method; 
         FIG. 13  is a flowchart for illustrating a method for determining the priority of a page according to a sixth embodiment; 
         FIG. 14A  illustrates an example set of document pages to which a preview display method according to the sixth embodiment of the present disclosure is applied, and  FIG. 14B  illustrates the order of the document pages to preview in accordance with the preview display method; 
         FIG. 15  is a flowchart for illustrating a method for determining the priority of a page according to a seventh embodiment; 
         FIG. 16A  illustrates an example set of document pages to which a preview display method according to the seventh embodiment of the present disclosure is applied, and  FIG. 16B  illustrates the order of the document pages to preview in accordance with the preview display method; 
         FIG. 17  is a flowchart for illustrating a method for determining the priority of a page according to an eighth embodiment; 
         FIG. 18A  illustrates an example set of document pages to which a preview display method according to the eighth embodiment of the present disclosure is applied, and FIG.  18 B illustrates the order of the document pages to preview in accordance with the preview display method; 
         FIG. 19A  illustrates an example set of document pages to which a preview display method according to a ninth embodiment of the present disclosure is applied, and  FIG. 19B  illustrates the order of the document pages to preview in accordance with the preview display method; 
         FIG. 20  is a block diagram illustrating a configuration of a preview display apparatus according to an eleventh embodiment; 
         FIG. 21  illustrates a home screen displayed in the first embodiment of the present disclosure; 
         FIG. 22  illustrates an initial screen for copying displayed in the first embodiment of the present disclosure; 
         FIG. 23  illustrates a preview screen normally displayed in the first embodiment of the present disclosure; 
         FIG. 24  illustrates a preview screen with a pop-up dialog box displayed when a document includes a page having many small text characters in the first embodiment of the present disclosure; 
         FIG. 25  illustrates a preview screen displayed when “Yes” is selected on the dialog box in  FIG. 24  and other figures in the first embodiment of the present disclosure; 
         FIG. 26  illustrates a screen for setting a copy ratio displayed when a selection button denoted by “Change Copy Ratio for This Page” is touched on the screen in  FIG. 25  in the first embodiment of the present disclosure; 
         FIG. 27  illustrates a screen for setting a sheet size displayed when a selection button denoted by “Change Sheet Size for This Page” is touched on the screen in  FIG. 25  in the first embodiment of the present disclosure; 
         FIG. 28  illustrates a preview screen with a pop-up dialog box displayed when a document includes a page with a high blank portion ratio in the second embodiment of the present disclosure; 
         FIG. 29  illustrates a preview screen with a pop-up dialog box displayed when a document includes a page with a high blank portion ratio at the top of a page in the third embodiment of the present disclosure; 
         FIG. 30  illustrates a preview screen with a pop-up dialog box displayed when a document includes a page having a small color area in the fourth embodiment of the present disclosure; 
         FIG. 31  illustrates a preview screen with a pop-up dialog box displayed when a document includes a page with a keyword in the sixth embodiment of the present disclosure; 
         FIG. 32  illustrates a preview screen with a pop-up dialog box displayed when a document includes a page for which the ratio of the total image area in the page to the total page area is equal to a predetermined value or larger in the seventh embodiment of the present disclosure; 
         FIG. 33  illustrates a preview screen with a pop-up dialog box displayed when a document includes a page for which the ratio of the total table area in the page to the total page area is equal to a predetermined value or larger in the eighth embodiment of the present disclosure; 
         FIG. 34  illustrates a preview screen with a pop-up dialog box displayed when a document includes a page subjected to a background removal processing in the ninth embodiment of the present disclosure; 
         FIG. 35  is a conceptual cross sectional view of a multifunction peripheral according to a twelfth embodiment of the present disclosure; and 
         FIG. 36  is a functional block diagram of the multifunction peripheral according to the twelfth embodiment of the present disclosure. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. 
     First Embodiment 
     According to a first embodiment of the present disclosure, a page having text characters whose printed-text size is excessively small can be found at an early stage. To achieve this goal, generally speaking, as the printed-text size of text characters included on a page decreases, the assigned priority of the page in previewing increases. Then, each page is previewed in order of priority. In this way, a page having text characters whose printed-text size is excessively small is found at an early stage, and consequently a user is able to perform at an early stage, for example, operation to change settings to increase the magnification or reduction ratio for printing. 
     For example, in a method of the related art, when a document is printed from the first page to the tenth page and the settings are to be changed to increase the magnification or reduction ratio for the tenth page, which is the last page, because of excessively small text characters on the tenth page, the user has to view the preview images of ten pages to find the text size that is too small on the tenth page. In contrast, according to this embodiment, since the tenth page is previewed first, the user views a preview screen for only a single page to find the text size that is too small on the tenth page. As the number of pages to print increases, the difference between the two cases increases. 
     In addition, pages are previewed in order of increasing text size. Thus, once the user is able to verify that text characters on a previewed page are not too small, the user is able to deduce that text characters on pages following the previewed page are not too small either. Consequently, the user has to view no further preview screen to check the text size. 
     In addition to the page content, the page number is also displayed on the preview display screen. Accordingly, the user is able to visually determine which page is to be magnified. 
       FIGS. 1 and 2  are flowcharts for illustrating a method for performing processing from previewing to printing according to the first embodiment. 
     Referring to  FIG. 1 , the priority of each page is determined by repeating processing from step S 201 S to step S 201 E for each page (step S 203 ). 
     When the repetition finishes, the pages are rearranged in accordance with priority (step S 207 ). Specifically, the pages are rearranged in order of priority. 
     Referring to  FIG. 2 , the page with the highest priority is subsequently previewed (step S 211 ). 
     Then, if a request for the subsequent page is received (YES in step S 213 ), the page with the next highest priority is previewed (step S 215 ), and the process returns to step S 213 . If no subsequent page exists, the process bypasses step S 215  and returns to step S 213 . 
     If a request for the preceding page is received (YES in step S 217 ), the page with the preceding priority is previewed (step S 219 ), and the process returns to step S 213 . If no preceding page exists, the process bypasses step S 219  and returns to step S 213 . 
     If a request to zoom in on a portion of a page is received (YES in step S 221 ), an enlarged image of the portion is displayed (step S 223 ). While the enlarged image of the portion is being displayed, if a request to terminate zooming in is received (step S 225 ), displaying the enlarged image of the portion is terminated (step S 227 ), and the page with the current priority is previewed again (step S 229 ). Then, the process returns to step S 213 . 
     In step S 223 , an enlarged image of a portion of a previewed page can be displayed. Accordingly, for example, when a user is not able to determine whether to change the magnification or reduction ratio for a page by only viewing a normal preview image of the page, the user applies step S 223  to a portion whose enlarged image on the preview screen enables the user to determine whether to change the magnification or reduction ratio for the page, and consequently the user can actually determine whether to change the magnification or reduction ratio. 
     If a request to change the magnification or reduction ratio is received (YES in step S 231 ), the magnification or reduction ratio for the page with the current priority is changed (step S 233 ), and the page with the current priority is previewed again (step S 235 ). 
     If printing is requested (YES in step S 237 ), the page order before performing step S 207  is restored (step S 239 ), and printing is performed (step S 241 ). Step S 239  may be omitted. In addition, after step S 237 , the user may be asked whether only the current page is to be printed. If the reply is YES, only the current page may be printed, and the process may return to step S 213  thereafter. 
     If a request to abort printing is received (YES in step S 243 ), printing is aborted. 
     If no request to abort printing is received (NO in step S 243 ), the process returns to step S 213 . 
     The function of zooming in on a portion of a page may be omitted. In such a case, steps S 221 , S 223 , S 225 , S 227  and S 229  of the flowchart in  FIG. 2  are omitted from the flowchart in  FIG. 3 . 
     Next, step S 203 , in which the priority of a page is determined, will be described in detail. 
     For example, the size of the smallest text character included on a page may be used as the text size for determining the priority. 
     Alternatively, the text size for determining the priority may be determined as follows. 
     As illustrated in  FIG. 4 , a page is divided into a plurality of areas (step S 263 ). Examples of such areas are three regions, which are the header, the footer, and the body. Step S 263  may be omitted for a certain page, and a page may have only one area, which is the body. 
     Next, a corrected text size is calculated for each of the text characters in each area (from step S 267 S to step S 267 E) by using the following equation (step S 269 ): 
       corrected text size=text size+area correction factor  (1).
 
     The same calculation is repeated for all the areas of a page (from step S 265 S to S 265 E). Each area generally has a different area correction factor. For example, the area correction factor is set to zero for the body area and to a predetermined positive value for each of the header area and the footer area. In this way, if a page has a header area and a footer area whose text sizes are smaller than the text size in the body area, such a page can be dealt with appropriately. 
     Next, the text size far determining the priority of a page is calculated in accordance with the corrected text sizes of all the text characters on the page (step S 271 ). 
     The text size for determining the priority is a text size used to determine the priority and may be the actual text size, the corrected text size, or a text size determined by using a predetermined method in accordance with any of the actual or corrected text sizes. 
     For example, the corrected text size of each text character included on a page may be compared with the corrected text size of other text characters included on the page, and the smallest size among the corrected text sizes may be selected as the text size for determining the priority of the page. 
     Alternatively, for example, a weighted average of corrected text sizes over an entire page may be selected as the text size for determining the priority. As an overall tendency, the weighting factor may increase as the corrected text size decreases or may be equal to zero for the corrected text size equal to or above a predetermined value and equal to a fixed value or dependent on the corrected text size for the corrected text size below the predetermined value. 
     Next, the priority of a page is calculated in accordance with the text size for determining the priority of the page (step S 273 ). Specifically, if a rule specifies that a larger value indicates a higher priority, the text size for determining the priority with a minus sign may be used as the priority. If a rule specifies that a smaller value indicates a higher priority, the text size for determining the priority may be used as the priority without changing. 
     For example, as illustrated in  FIG. 5A , if the page order in ascending order of corrected text size is the third page, the second page, and the first page, the preview images are displayed in this order as illustrated in  FIG. 5B . 
     Next a description including a user interface will be provided. 
     If “Copy” is selected on the home screen illustrated in  FIG. 21 , the initial screen for copying is displayed as illustrated in  FIG. 22 . 
     Then, while the initial screen for copying illustrated in  FIG. 22  is displayed, if a user touches the preview button after setting a document having one or more pages on the automatic document feeder, a document scanner successively scans pages of the document having one or more pages. 
     When the document scanner finishes scanning pages, a preview screen is displayed as illustrated in  FIG. 23 . This preview screen displays a page number  501  that indicates the position of the currently displayed page in the scanning sequence and a scroll bar  503  for switching pages to preview. This preview screen also displays buttons  505  and  507  for changing the magnification or reduction ratio for the entire preview image and a button  509  for displaying a scroll bar used to zoom in or out. Zooming in corresponds to enlarging a portion of a document. An enlarged portion of a previewed document can be moved by touching the enlarged portion with a finger and sliding the finger on the preview screen while the finger is in contact with the screen. 
     Next, each scanned page is subjected to character recognition processing, and consequently text characters included on each page and the sizes of the text characters are obtained. If it is determined by using a predetermined method that a page having small text characters is present among the scanned pages, a dialog box presenting a question “A page having many small text characters is present. Change settings?” is displayed as illustrated in  FIG. 24 , and if “Yes” is selected, additional buttons for transitioning to a setting change screen are displayed as illustrated in  FIG. 25 . 
     A selection button  511  to select “Change Copy Ratio for This Page” and a selection button  513  to select “Change Sheet Size for This Page” are added to the screen as illustrated in  FIG. 25 . If the former selection button is touched on this screen, a details setting screen as illustrated in  FIG. 26  is displayed. If the latter selection button is touched, a details setting screen as illustrated in  FIG. 27  is displayed. 
     When the copy ratio is changed and the “OK” button is touched on the details setting screen in  FIG. 26 , the details setting screen is closed, and the screen in  FIG. 25  reappears displaying a preview image incorporating the change in the settings. Buttons  515  and  517  to start copying and a button  519  to abort copying are also displayed on the screen in  FIG. 25 , and a user can choose to start or abort copying. Further, the selection buttons  511  and  513  are also displayed, and a user may additionally change the copy ratio or the sheet size before starting copying. 
     Second Embodiment 
     According to a second embodiment of the present disclosure, an occurrence of an additional page due to printing an overflowing portion of a text region (referred to as “overflow print”) can be found at an early stage. This overflow print is caused because a portion of a text region to be originally included on the same page as the other portions of the text region overflows into another page. To achieve this goal, generally speaking, as the blank portion ratio for a page increases, the assigned priority of the page in previewing increases. Then, each page is previewed in order of priority. In this way, for example, a page used for printing an overflowing portion of a spreadsheet (referred to as “overflow print page”) or a page having only a few lines in a document that overflow into another page (also referred to as “overflow print page”) is found at an early stage, and consequently a user is able to perform at an early stage, for example, operation to change settings to decrease the magnification or reduction ratio for printing. 
     When a spreadsheet is printed, if the magnification or reduction ratio for the spreadsheet is not adequately adjusted, an overflow print page is sometimes produced to allocate a print space to only text characters and numerals located near the right end of the spreadsheet. In addition, for example, when a letter document is printed, an overflow print page that has only a few lines is sometimes produced. Many of such pages have a high blank portion ratio, and thus previewing a page having a high blank portion ratio at an early stage enables a user to check the contents of such a page at an early stage and to change settings to decrease the magnification or reduction ratio accordingly or abort printing. 
     For example, in a case where a file having ten spreadsheets has an overflow on the tenth spreadsheet, each page from the first spreadsheet to the tenth spreadsheet is to be previewed before the overflow is found if a method of the related art is used. However, according to this embodiment, a user is able to find the overflow by displaying only a preview image of a page allocated for printing an overflowing portion of the tenth spreadsheet. 
     A method of processing from previewing to printing according to the second embodiment is the same as or similar to the method according to the first embodiment illustrated in  FIG. 1  and  FIG. 2 or 3 , and thus a duplicate description will be omitted. 
     Next, step S 203 , in which the priority of a page is determined, will be described in detail. 
     As illustrated in  FIG. 6 , for each text character on a page, a text character area is calculated as follows (steps S 281 S, S 283 , and S 281 E): 
       text character area=font size×font size×normalization factor   (2).
 
     Here, the normalization factor is the reciprocal of the area of a text character of one point in size. 
     Next, the total area of all the text characters on a page is calculated in accordance with the area of each of all the text characters included on the page (step S 285 ). 
     Then, the blank portion ratio for the page is calculated as follows (step S 287 ): 
       blank portion ratio for a page=(sheet area−total area of all the text characters)/sheet area×100(%)   (3).
 
     Next the priority of a page is calculated in accordance with the blank portion ratio for the page (step S 289 ). If a rule is specified that a larger value indicates a higher priority, the blank portion ratio for the page may be used as the priority without changing. If a rule is specified that a smaller value indicates a higher priority, (total area of all the text characters)/(sheet area) may be used as the priority. 
     For example, as illustrated in  FIG. 7A , if the page order in descending order of blank portion ratio for a page is the third page, the second page, and the first page, the preview images are displayed in this order as illustrated in  FIG. 7B . 
     The user interface according to the second embodiment is the same as or similar to the user interface according to the first embodiment. 
     However, in the first embodiment, each scanned page is subjected to character recognition processing, and consequently text characters included on each page and the sizes of the text characters are obtained. If it is determined by using the method illustrated in  FIG. 4  that a page having small text characters is present among the scanned pages, a dialog box presenting a question “A page having many small text characters is present. Change settings?” is displayed as illustrated in  FIG. 24 , and if “Yes” is selected, additional buttons for transitioning to the setting change screen are displayed as illustrated in  FIG. 25 . 
     In the second embodiment, each scanned page is subjected to character recognition processing, and consequently text characters included on each page and the sizes of the text characters are obtained. In contrast to the first embodiment, calculations based on Equations 2 and 3 are performed by using the text characters and the sizes thereof, and if it is determined that a page having the blank portion ratio higher than a predetermined value is present among the scanned pages, a dialog box presenting a question “A page having a high blank portion ratio is present. Change settings?” is displayed as illustrated in  FIG. 28 . If “Yes” is selected, additional buttons for transitioning to the setting change screen are displayed as illustrated in  FIG. 25 . 
     Third Embodiment 
     According to a third embodiment of the present disclosure, for the second section or a subsequent section in a document, if the top of a section does not coincide with the top of a page and the section begins at a position several lines behind the top of the page, such a situation can be found at an early stage. To achieve this goal, generally speaking, for a page having a blank at the top of the page, as the blank portion ratio of the page increases, the assigned priority of the page in previewing increases. Then, each page is previewed in order of priority. 
     In a normal operation, when a section break is placed on a document, the section break triggers a page break, and the document content following the section break is from the top of a new page. The document content following the section break sometimes begins at an intermediate position on a page against the intention of a user. 
     The preview display described above enables the user, for example, to find at an early stage a page for which document content following a section break begins at an intermediate position on a new page and, for example, to reduce the time that it takes to abort printing and start re-editing the document. For example, in a case where a document has ten sections and only the tenth section does not begin at the top of a page, each page from the first page of the first section to the first page of the tenth section has to be successively previewed before the blank at the top of a page is found if a method of the related art is used. However, according to this embodiment, the first page of the tenth section is previewed first, and thus a user is able to find that the top of the tenth section does not coincide with the top of a page viewing a preview image of only one page. 
     A method of processing from previewing to printing according to the third embodiment is the same as or similar to the method according to the first embodiment illustrated in  FIG. 1  and  FIG. 2 or 3 , and thus a duplicate description will be omitted. 
     Next, step S 203 , in which the priority of a page is determined, will be described in detail. 
     As illustrated in  FIG. 8 , a blank at the top of a page is detected first (step S 301 ). For example, consecutive lines that have no printed text character and are located at the top of a page are detected. 
     Next, the total area of a blank at the top is determined in accordance with a height of each line (in the case of horizontal writing), a width of each line (in the case of vertical writing) or the like in a blank at the top (step S 307 ). 
     Steps S 301  and S 307  may be performed using image data of a print image (such as bitmap data). 
     Then, the blank portion ratio at the top is calculated as follows (step S 309 ): 
       blank portion ratio at the top=total area of a blank at the top/sheet area×100(%)   (4).
 
     Next, the priority of a page is calculated in accordance with the total area of a blank at the top (step S 311 ). Specifically, the assigned priority increases as the blank portion ratio at the top increases. If a rule is specified that a larger value indicates a higher priority, the blank portion ratio at the top may be used as the priority without changing. If a rule is specified that a smaller value indicates a higher priority, the blank portion ratio at the top with a minus sign may be used as the priority. 
     For example, as illustrated in  FIG. 9A , if the page order in descending order of blank portion ratio at the top is the third page, the second page, and the first page, the preview images are displayed in this order as illustrated in  FIG. 9B . 
     The user interface according to the third embodiment is the same as or similar to the user interface according to the first embodiment. 
     However, in the first embodiment, each scanned page is subjected to character recognition processing, and consequently text characters included on each page and the sizes of the text characters are obtained. If it is determined by using a predetermined method that a page having small text characters is present among the scanned pages, a dialog box presenting a question “A page having many small text characters is present. Change settings?” is displayed as illustrated in  FIG. 24 , and if “Yes” is selected, additional buttons for transitioning to the setting change screen are displayed as illustrated in  FIG. 25 . 
     In contrast, in the third embodiment, the total area of a blank at the top of each scanned page is obtained. Calculations based on Equations 4 and 3 are performed in the method illustrated in  FIG. 8 , and if it is determined that a page having the blank portion ratio at the top higher than a predetermined value is present among the scanned pages, a dialog box presenting a question “A page having a high blank portion ratio at the top present. Change settings?” is displayed as illustrated in  FIG. 29 . If “Yes” is selected, additional buttons for transitioning to the setting change screen are displayed as illustrated in  FIG. 25 . 
     Fourth Embodiment 
     According to a fourth embodiment of the present disclosure, for a document that has a color portion and that is to be printed in color, if a user selects grayscale printing without recognizing that the document has a color portion, such a situation can be found at an early stage. To achieve this goal, a page having a color portion is prioritized in previewing in color. In particular, if a color portion is small, such a mistake is likely to occur through oversight, and thus a page having a smaller color portion among pages having a color portion is prioritized in previewing. 
     A method of processing from previewing to printing according to the fourth embodiment is the same as or similar to the method according to the first embodiment illustrated in  FIG. 1  and  FIG. 2 or 3 , and thus a duplicate description will be omitted. 
     Next, step S 203 , in which the priority of a page is determined, will be described in detail. 
     As illustrated in  FIG. 10 , for each text character on a page, processing from step S 333 S to step S 333 E is repeated. 
     In this repetition, if the font of a text character is not in grayscale (NO in step S 335 ) or the decoration of a text character is not in grayscale (NO in step S 337 ), a new color area is created, or one of the existing color areas is enlarged (step S 339 ). 
     A color area is defined as an area in which one or more text characters each of which has the font or decoration not in grayscale are continuously arranged. If a newly found text character whose font or decoration is not in grayscale touches as existing color area in any direction, the existing color area is enlarged. If a newly found text character whose font or decoration is not in grayscale does not touch as existing color area, a new color area is created. 
     When the repetition is finished, the evaluation value for a page is determined in accordance with the color area having the smallest size of all the color areas created on the page (step S 341 ). For example, the evaluation value is calculated as follows: 
       evaluation value=the size of the smallest color area/sheet size (if one or more color areas are present)   (5), or
 
       evaluation value=1(if no color area is present) (6). 
     Then, a rule under which a page having a smaller evaluation value is prioritized is applied. 
     For example, as illustrated in  FIG. 11A , in a case where the evaluation value for the first page having no color portion is equal to 1 and the evaluation value for the third page is smaller than the evaluation value for the second page because the third page has a color portion indicated by a frame that is smaller than a frame indicating a color portion on the second page, in other words, in a case where the evaluation value for each page decreases with the order the first, second, and third pages, previewing is performed in order of increasing evaluation value as illustrated in  FIG. 11B . 
     The user interface according to the fourth embodiment is the same as or similar to the user interface according to the first embodiment. 
     However, in the first embodiment, each scanned page is subjected to character recognition processing, and consequently text characters included on each page and the sizes of the text characters are obtained. If it is determined by using a predetermined method that a page having small text characters is present among the scanned pages, a dialog box presenting a question “A page having many small text characters is present. Change settings?” is displayed as illustrated in  FIG. 24 , and if “Yes” is selected, additional buttons for transitioning to the setting change screen are displayed as illustrated in  FIG. 25 . 
     In contrast, in the fourth embodiment, the size of the smallest color area is obtained for each scanned page. Calculations based on Equations 5 and 6 are performed in the method illustrated in  FIG. 10 , and if it is determined that a page having the evaluation value smaller than a predetermined value is present among the scanned pages, a dialog box presenting a question “A page having a small color area is present. Change settings?” is displayed as illustrated in  FIG. 30 . If “Yes” is selected, additional buttons for transitioning to the setting change screen are displayed as illustrated in  FIG. 25 . 
     Fifth Embodiment 
     According to a fifth embodiment of the present disclosure, similarly to the fourth embodiment, for a document that has a color portion and that is to be printed in color, if a user selects grayscale printing without recognizing that the document has a color portion, such a situation can be found at an early stage. In addition, operation that is not performed in the fourth embodiment can be performed, that is, for a document that has a color portion but that is to be printed in grayscale for cost-saving, if a user selects color printing, such a situation can be found at an early stage. To achieve this goal, a page having a color portion is prioritized in previewing, and preview images displayed in accordance with selected color modes are also placed for comparison. 
     Operation in this embodiment is the same as or similar to the operation in the fourth embodiment and is not repeatedly described herein. 
     In this embodiment, when images are displayed in steps S 211 , S 215 , S 219 , and S 229 , a preview image with colors in the document retained without changing and another preview image processed in accordance with the selected color modes are simultaneously placed. Similar operation may be performed for an enlarged image of a portion of a page in step S 223 . If the two preview images are compared with each other and it is found that a portion in the former preview image is presented in color and the corresponding portion in the latter preview image is presented in monochrome, it can easily be found that, for a document that has a color portion and that is to be printed in color, a user has selected grayscale printing without recognizing that the document has a color portion. Further, if the two preview images are compared with each other and it is found that a portion in the former preview image is presented in color and the corresponding portion in the latter preview image is also presented in color, it can be found at an early stage that, for a document that has a color portion but that is to be printed in grayscale for cost-saving or the like, a user has selected color printing. 
     The evaluation value for a page and the relation between the evaluation value and the priority are also used in the fifth embodiment as in the fourth embodiment. For example, the evaluation value is calculated as follows: 
       evaluation value=the size of the smallest color area/sheet size (if one or more color areas are present)   (7), or
 
       evaluation value=1 (if no color area is present)   (8).
 
     Then, a rule under which a page having a smaller evaluation value is prioritized is applied. 
     For example, as illustrated in  FIG. 12A , in a case where the evaluation value for the first page having no color portion is equal to 1 and the evaluation value for the third page is smaller than the evaluation value for the second page because the third page has a color portion indicated by a frame that is smaller than a frame indicating a color portion on the second page, in other words, in a case where the evaluation value for each page decreases with the order the first, second, and third pages, preview images having the sequences illustrated in  FIG. 12B  and in  FIG. 12C  are placed on a single screen. 
     The user interface according to the fifth embodiment is the same as or similar to the user interface according to the fourth embodiment. The fifth embodiment differs from the fourth embodiment in that preview images with colors in the document retained without changing and preview images processed in accordance with the selected color modes are simultaneously placed. 
     Sixth Embodiment 
     According to a sixth embodiment of the present disclosure, a document having a specific keyword (such as “important”, “internal use only”, or “summary”) can be checked at an early stage. A keyword that is likely to be included on a document that is to be checked at an early stage is set, and then a page having the keyword is prioritized in previewing. Not only a single keyword but also a plurality of keywords may be set, and a page having any of the plurality of keywords may be prioritized in previewing. Further, found keywords may be displayed next to preview images. 
     A method of processing from previewing to printing according to the sixth embodiment is the same as or similar to the method according to the first embodiment illustrated in  FIG. 1  and  FIG. 2 or 3 , and thus a duplicate description will be omitted. 
     Next, step S 203 , in which the priority of a page is determined, will be described in detail. 
     As illustrated in  FIG. 13 , the number of occurrences is reset to zero in the beginning (step S 351 ). 
     Then, for each of all the provided keywords, processing from step S 353 S to step S 353 E is repeated. 
     In each repetition, if the current keyword is included on the page (YES in step S 355 ), the number of occurrences is increased by one (step S 357 ), and the current keyword is set for display (step S 359 ). 
     When the repetition finishes, the priority is determined in accordance with the number of occurrences (step S 361 ). Specifically, if a rule is specified that a larger value indicates a higher priority, the number of occurrences may be used as the priority without changing. If a rule is specified that a smaller value indicates a higher priority, the number of occurrences with a minus sign may be used as the priority. 
     The maximum number of occurrences for a keyword may be set to a predetermined value (for example, 1). In this case, pages in which the same keyword is found are not to be rearranged. Further, the number of occurrences may be increased by the increment depending on a keyword. In other words, when pages are prioritized, each keyword may have a different degree of importance. Further, the maximum number of occurrences for all the keywords may be set to a predetermined value (for example, 1). In this case, pages in which any of the keywords is found are not to be rearranged. 
     For example, as illustrated in  FIG. 14A , if the numbers of occurrences for the first page and for the third page are equal to zero and the number of occurrences for the second page is equal to 1, the preview images are displayed in order of decreasing number of occurrences as illustrated in  FIG. 14B . 
     The user interface according to the sixth embodiment is the same as or similar to the user interface according to the first embodiment. 
     However, in the first embodiment, each scanned page is subjected to character recognition processing, and consequently text characters included on each page and the sizes of the text characters are obtained. If it is determined by using a predetermined method that a page having small text characters is present among the scanned pages, a dialog box presenting a question “A page having many small text characters is present. Change settings?” is displayed as illustrated in  FIG. 24 , and if “Yes” is selected, additional buttons for transitioning to the setting change screen are displayed as illustrated in FIG.  25 . 
     In contrast, in the sixth embodiment, the number of occurrences for each scanned page is calculated by using the method illustrated in  FIG. 13 . If it is determined that a page having a nonzero number of occurrences is present among the scanned pages, a dialog box presenting a question “A page having a specified keyword is present. Change settings?” is displayed as illustrated in  FIG. 31 . If “Yes” is selected, additional buttons for transitioning to the setting change screen are displayed as illustrated in  FIG. 25 . 
     Seventh Embodiment 
     According to a seventh embodiment of the present disclosure, a page having an image can be checked at as early stage. To achieve this goal, a page having an image is prioritized in previewing. Of pages having an image, for example, a page having many images may be prioritized in previewing, or a page having a large total image area may be prioritized in previewing. 
     A method of processing from previewing to printing according to the seventh embodiment is the same as or similar to the method according to the first embodiment illustrated in  FIG. 1  and  FIG. 2 or 3 , and thus a duplicate description will be omitted. 
     Next, step S 203 , in which the priority of a page is determined, will be described in detail. 
     As illustrated in  FIG. 15 , the number of occurrences is reset to zero (step S 371 ), and the total image area is also reset to zero (step S 373 ) in the beginning. 
     Then, for each of all the objects on the page, processing from step S 375 S to step S 375 E is repeated. 
     In the repetition, if an object is an image object (YES in step S 377 ), the number of occurrences is increased by one (step S 379 ), and the area of the current image object is added to the total image area (step S 381 ). 
     When the repetition finishes, the priority is determined in accordance with the number of occurrences or the total image area (step S 383 ). Specifically, if a rule is specified that a larger value indicates a higher priority, the number of occurrences or the total image area may be used as the priority without changing. If a rule is specified that a smaller value indicates a higher priority, the number of occurrences or the total image area with a minus sign may be used as the priority. 
     The maximum number of occurrences may be set to a predetermined value (for example, 1). In this case, pages in which images are found are not to be rearranged. 
     For example, as illustrated in  FIG. 16A , if the number of occurrences for the first page is equal to zero, the number of occurrences for the second page is equal to 1, and the number of occurrences for the third page is equal to 2, preview images are displayed in order of decreasing number of occurrences as illustrated in  FIG. 16B . 
     The user interface according to the seventh embodiment is the same as or similar to the user interface according to the first embodiment. 
     However, in the first embodiment, each scanned page is subjected to character recognition processing, and consequently text characters included on each page and the sizes of the text characters are obtained. If it is determined by using a predetermined method that a page having small text characters is present among the scanned pages, a dialog box presenting a question “A page having many small text characters is present. Change settings?” is displayed as illustrated in  FIG. 24 , and if “Yes” is selected, additional buttons for transitioning to the setting change screen are displayed as illustrated in  FIG. 25 . 
     In contrast, in the seventh embodiment, the total image area for each scanned page is calculated by using the method illustrated in  FIG. 15 . If it is determined that a page having the total image area equal to a predetermined value or larger is present among the scanned pages, a dialog box presenting a question “A page having the total image area equal to a predetermined value or larger is present. Change settings?” is displayed as illustrated in  FIG. 32 . If “Yes” is selected, additional buttons for transitioning to the setting change screen are displayed as illustrated in  FIG. 25 . 
     Eighth Embodiment 
     According to an eighth embodiment of the present disclosure, a page having a table can be checked at an early stage. To achieve this goal, a page having a table is prioritized in previewing. Of pages having a table, for example, a page having many tables may be prioritized in previewing, or a page having a large total table area may be prioritized in previewing. 
     A method of processing from previewing to printing according to the eighth embodiment is the same as or similar to the method according to the first embodiment illustrated in  FIG. 1  and  FIG. 2 or 3 , and thus a duplicate description will be omitted. 
     Next, step S 203 , in which the priority of a page is determined, will be described in detail. 
     As illustrated in  FIG. 17 , the number of occurrences is reset to zero (step S 401 ), and the total table area is also reset to zero (step S 403 ) in the beginning. 
     Then, for each of all the objects on the page, processing from step S 405 S to step S 405 E is repeated. 
     In the repetition, if an object includes a table (YES in step S 407 ), the number of occurrences is increased by one (step S 409 , and the area of the table included in the current object is added to the total table area (step S 411 ). If a table object is detected after each object included on a page has been developed, the number of occurrences is increased by one. Further, for example, if a table constituted by ruled lines represented by the Shift_JIS code is found in a text character sequence, the number of occurrences is increased by one for the entire table, and the area of the table is added to the total table area. 
     When the repetition finishes, the priority is determined in accordance with the number of occurrences or the total table area (step S 413 ). Specifically, if a rule is specified that a larger value indicates a higher priority, the number of occurrences or the total table area may be used as the priority without changing. If a rule is specified that a smaller value indicates a higher priority, the number of occurrences or the total table area with a minus sign may be used as the priority. 
     The maximum number of occurrences may be set to a predetermined value (for example, 1). In this case, pages in which tables are found are not to be rearranged. 
     For example, as illustrated in  FIG. 18A , if the number of occurrences for the first page is equal to zero, the number of occurrences for the second page is equal to 1, and the number of occurrences for the third page is equal to 2, preview images are displayed in order of decreasing number of occurrences as illustrated in  FIG. 18B . 
     The user interface according to the eighth embodiment is the same as or similar to the user interface according to the first embodiment. 
     However, in the first embodiment, each scanned page is subjected to character recognition processing, and consequently text characters included on each page and the sizes of the text characters are obtained. If it is determined by using a predetermined method that a page having small text characters is present among the scanned pages, a dialog box presenting a question “A page having many small text characters is present. Change settings?” is displayed as illustrated in  FIG. 24 , and if “Yes” is selected, additional buttons for transitioning to the setting change screen are displayed as illustrated in  FIG. 25 . 
     In contrast, in the eighth embodiment, the total table area for each scanned page is calculated by using the method illustrated in  FIG. 17 . If it is determined that a page having the total table area equal to a predetermined value or larger is present among the scanned pages, a dialog box presenting a question “A page having the total table area equal to a predetermined value or larger is present. Change settings?” is displayed as illustrated in  FIG. 33 . If “Yes” is selected, additional buttons for transitioning to the setting change screen are displayed as illustrated in  FIG. 25 . 
     Ninth Embodiment 
     According to a ninth embodiment of the present disclosure, the extent of a change in image contents from document contents, the change being caused by the application of a background removal function to an image obtained by scanning a document by using a document scanner, can be checked at an early stage, and a parameter such as a threshold used in the background removal function can be adjusted accordingly at an early stage. The background removal function is a function to remove contents due to show-through from the other side of a sheet of a document that is produced, for example, by using double-sided printing. For example, if settings in which a density equal to or lower than a predetermined threshold is set to zero are used and contents due to show-through from the other side of a sheet have a density equal to or lower than the threshold, the contents due to the show-through from the other side of the sheet can be removed. However, depending on the relation between a predetermined threshold level and the density of contents printed on a surface to be scanned, the background removal function is sometimes applied to the contents printed on the surface to be scanned. A user deals with such a case, for example, by reducing the threshold in spite of the possibility of causing the background removal function to be insufficient. In the present embodiment, a page to which the background removal function has been applied is prioritized in previewing, and thus the threshold can be checked for the adequacy and adjusted accordingly at an early stage. 
     Document images scanned by a document scanner are printed by an image forming apparatus or stored in a storage device. 
     The background removal function may also be applied when a surface on which contents due to show-through have been printed is scanned by a document scanner or when a document having contents due to show-through is printed in accordance with instructions from a computer that retains the data of the document. 
     A method of processing from previewing to printing according to the ninth embodiment is the same as or similar to the method according to the first embodiment illustrated in  FIG. 1  and  FIG. 2 or 3 , and thus a duplicate description will be omitted. 
     For example, as illustrated in  FIG. 19A , when the first page has not been subjected to the background removal processing and the second and third pages have been subjected to the background removal processing, the pages that have been subjected to the background removal processing are prioritized in previewing as illustrated in  FIG. 19B . 
     In the above embodiments, a device driver in a computer that causes a multifunction peripheral to print may have a preview display function, or a multifunction peripheral that receives instructions for printing from a computer may have the preview display function. 
     In the embodiments in which a magnification or reduction ratio is adjusted, a device driver in a computer that causes a multifunction peripheral to print may have such a function to adjust the magnification or reduction ratio, or a multifunction peripheral that receives instructions for printing from a computer may have such a function to adjust the magnification or reduction ratio. 
     In addition, a multifunction peripheral may perform the preview display function before a multipage document scanned by using a document scanner is printed at a single time or before a multipage document read from a storage device is printed at a single time. 
     Further, a multifunction peripheral may perform the preview display function before transmitting a multipage document (for example, facsimile transmission and email transmission). 
     The user interface according to the ninth embodiment is the same as or similar to the user interface according to the first embodiment. 
     However, in the first embodiment, each scanned page is subjected to character recognition processing, and consequently text characters included on each page and the sizes of the text characters are obtained. If it is determined by using a predetermined method that a page having small text characters is present among the scanned pages, a dialog box presenting a question “A page having many small text characters is present. Change settings?” is displayed as illustrated in  FIG. 24 , and if “Yes” is selected, additional buttons for transitioning to the setting change screen are displayed as illustrated in  FIG. 25 . 
     In contrast, in the ninth embodiment, it is determined whether each scanned page has been subjected to the background removal processing. If it is determined that a page that has been subjected to the background removal processing is present among the scanned pages, a dialog box presenting a question “A page that has been subjected to a background removal processing is present. Change settings?” is displayed as illustrated in  FIG. 34 , and if “Yes” is selected, additional buttons for transitioning to the setting change screen are displayed as illustrated in  FIG. 25 . 
     Tenth Embodiment 
     A tenth embodiment is a combination of the first to ninth embodiments. For example, a page to be prioritized in previewing in some of the first to ninth embodiments may be prioritized in previewing, and afterwards a page to be prioritized in previewing in none of the first to ninth embodiments may be previewed. In addition, the priority may be determined in accordance with a combination of evaluation values in some of the embodiments. 
     Eleventh Embodiment 
       FIG. 20  is a block diagram illustrating a configuration of a preview display apparatus according to an eleventh embodiment for performing the preview display methods according to the first to tenth embodiments. 
     Referring to  FIG. 20 , the preview display apparatus includes an evaluation-value acquisition unit  401 , a page-priority adjustment unit  403 , a preview display unit  405 , a zoom unit  407 , and a print-settings change unit  409 . 
     The evaluation-value acquisition unit  401  acquires in accordance with a predetermined purpose an evaluation value for each page among a plurality of pages to preview. 
     The page-priority adjustment unit  403  adjusts the priorities of the plurality of pages in accordance with the evaluation values. 
     The preview display unit  405  displays a preview image of each of the plurality of pages in accordance with the priority adjusted by the page-priority adjustment unit  403 . 
     The zoom unit  407  zooms in on a portion of a preview image. 
     The print-settings change unit  409  changes print settings for at least one of the plurality of pages in an image forming unit  30  after the preview display unit  405  displays preview images. 
     Twelfth Embodiment 
     A twelfth embodiment relates to a multifunction peripheral  800  that includes the document scanner according to the first to ninth embodiments.  FIGS. 35 and 36  illustrate a configuration and the like of the multifunction peripheral  800 . 
     As illustrated in  FIGS. 35 and 36 , the multifunction peripheral  800  includes a document scanner  820  that scans a document image, a multifunction peripheral body  830  (body of an image forming unit) that forms an image on a sheet, an operation panel  843  for operating the document scanner  820  and the multifunction peripheral body  830 , and a calculation processing unit  841  that controls the document scanner  820  and the multifunction peripheral body  830  in accordance with an operation performed on the operation panel  843 . 
     The document scanner  820  can be used for image scanning on a stand-alone basis, or the multifunction peripheral body  830  can be used for image forming on a stand-alone basis. In addition, the document scanner  820  and the multifunction peripheral body  830  can be operated in combination for image copying. In addition, the multifunction peripheral  800  may include a storage device or a facsimile device, neither of which is shown. The storage device can store images scanned by the document scanner  820  and images received by the facsimile device. The facsimile device can transmit images scanned by the document scanner  820  or stored in the storage device and receive images from outside. Furthermore, the multifunction peripheral  800  may include an interface for connecting to a personal computer via a network. The personal computer connected to the multifunction peripheral  800  can use a function of the multifunction peripheral  800  to process the data that can be managed by the personal computer. 
     The document scanner  820  includes an automatic document feeder  824  (single pass feeder or SPF) that automatically feeds a document and a scanner body  822  that scans a document image. The document scanner  820  includes, in addition to the components illustrated in  FIG. 36 , components that are not illustrated in  FIG. 36  but illustrated in  FIG. 35 . The scanner body  822  also includes a platen  826  as illustrated in  FIG. 35 . 
     The multifunction peripheral body  830  includes a sheet feeder  10  that feeds a sheet, a manual sheet feeder  20  that enables manual sheet feeding, and the image forming unit  30  that forms an image on a sheet fed by the sheet feeder  10  or the manual sheet feeder  20 . 
     The sheet feeder  10  includes a sheet housing unit  11  that houses sheets and a separating feeder  12  that separately feeds sheets housed in the sheet housing unit  11  one by one. The sheet housing unit  11  includes an inner plate  14  that pivots around a rotating shaft  13 , and the inner plate  14  lifts a sheet by pivoting when the sheet is fed. The separating feeder  12  includes a pick-up roller  15  that feeds a sheet lifted by the inner plate  14  and a separating roller pair  16  that separates sheets that are fed by the pick-up roller  15  one by one. 
     The manual sheet feeder  20  includes a manual feed tray  21  that can contain sheets and a separating feeder  22  that separately feeds sheets in the manual feed tray  21  one by one. The manual feed tray  21  is pivotally supported by the multifunction peripheral body  830  and is fixed at a predetermined angle to accommodate a sheet when the sheet is fed manually. The separating feeder  22  includes a pick-up roller  23  that feeds a sheet in the manual feed tray  21  and a separating roller  24  and a separating pad  25  that separate sheets that are fed by the pick-up roller  23  one by one. 
     The image forming unit  30  includes four process cartridges  31 Y,  31 M,  31 C, and  31 K that form yellow (Y), magenta (N), cyan (C), and black (K) images and photosensitive drums  740 Y,  740 M,  740 C, and  740 K described below. The image forming unit  30  also includes an exposure unit  32  by which surfaces of the photosensitive drums  740 Y,  740 M,  740 C, and  740 K are exposed to light, a transfer unit  33  that transfers toner images formed on the surfaces of the photosensitive drums  740 Y,  740 M,  740 C, and  740 K to a sheet, and a fixing unit  34  that fixes transferred toner images to the sheet. The alphabetical character (Y, M, C, or K) appended to each of the numerals represents the respective color (yellow, magenta, cyan, or black). 
     Each of the four process cartridges  31 Y,  31 M,  31 C, and  31 K is designed to be detachable from the multifunction peripheral body  830  and replaceable. The four process cartridges  31 Y,  31 M,  31 C, and  31 K are designed to have similar construction except for a color used to form an image. Thus, only the construction of the process cartridge  31 Y that forms an image of yellow (Y) will be described, and the process cartridges  31 M,  31 C, and  31 K will not be repeatedly described. 
     The process cartridge  31 Y includes the photosensitive drum  740 Y as an image carrying member, a charging unit  741 Y that electrically charges the photosensitive drum  740 Y, a developing unit  742 Y that develops an electrostatic latent image formed on the photosensitive drum  740 Y, and a drum cleaner that removes toner remaining on the surface of the photosensitive drum  740 Y. The developing unit  742 Y includes a developing unit body (not shown in detail) that develops the electrostatic latent image formed on the photosensitive drum  740 Y and a toner cartridge (not shown in detail) that supplies toner to the developing unit body. The toner cartridge is designed to be detachable from the developing unit body and can be removed from the developing unit body and replaced when the contained toner is exhausted. 
     The exposure unit  32  includes a light source (not shown in detail) that emits a laser beam, a plurality of mirrors (not shown in detail) that guide the laser beam to the photosensitive drums  740 Y,  740 M,  740 C, and  740 K, and other components. The transfer unit  33  includes an intermediate transfer belt  35  that carries toner images formed on the photosensitive drums  740 Y,  740 M,  740 C, and  740 K, primary transfer rollers  36 Y,  36 M,  36 C, and  36 K that perform primary transfer of the toner images formed on the photosensitive drums  740 Y,  740 M,  740 C, and  740 K to the intermediate transfer belt  35 , a secondary transfer roller  37  that performs secondary transfer of a toner image transferred to the intermediate transfer belt  35  to a sheet, and a belt cleaner  38  that removes toner remaining on the intermediate transfer belt  35 . The intermediate transfer belt  35  is wound around a drive roller  39   a  and an idle roller  39   b  and pressed against the photosensitive drums  740 Y,  740 M,  740 C, and  740 K by the primary transfer rollers  36 Y,  36 M,  36 C, and  36 K, respectively. The secondary transfer roller  37  nips (pinches) the intermediate transfer belt  35  with the drive roller  39   a  and transfers, at a nip portion N, the toner image carried by the intermediate transfer belt  35  to a sheet. The fixing unit  34  includes a heat roller  34   a  that heats a sheet and a pressure roller  34   b  that is pressed against the heat roller  34   a.    
     The operation panel  843  includes a display unit  845  that displays predetermined information and an input unit  847  used by a user to input instructions to the document scanner  820  and the multifunction peripheral body  830 . In the present embodiment, the operation panel  843  is disposed on the front side of the scanner body  822 . The front side and the back side of the scanner body  822  refer to one front side and the back side, respectively, of the sheet of  FIG. 35 . 
     As illustrated in  FIG. 36 , the calculation processing unit  841  includes a central processing unit (CPU)  841   a  that controls driving of the sheet feeder  10 , the manual sheet feeder  20 , the image forming unit  30 , and the document scanner  820  and a memory  841   b  that stores various programs to operate the CPU  841   a  and various pieces of information that are used by the CPU  841   a . The calculation processing unit  841  forms an image on a sheet by coordinately controlling operation of the sheet feeder  10 , the manual sheet feeder  20 , the image forming unit  30 , and the document scanner  820  in accordance with an operation performed on the operation panel  843  by the user. 
     Next, an image formation operation (image formation control performed by the calculation processing unit  841 ) performed by the multifunction peripheral  800  configured as described above will be described. In the present embodiment, as an example, a description will be given of an image forming operation in which the image forming unit  30  forms, on a sheet fed by the sheet feeder  10 , an image of a document that is fed by the automatic document feeder  824  and scanned by the scanner body  822 . 
     When an image forming start signal is output in accordance with an input by a user to the input unit  847  of the operation panel  843 , a document that has been placed on the automatic document feeder  824  by the user is automatically fed toward a document scanning position, and an image of the document is scanned at the document scanning position by the scanner body  822 . 
     Once the image of the document is scanned by the scanner body  822 , a plurality of laser beams are emitted onto the corresponding photosensitive drums  740 Y,  740 M,  740 C, and  740 K from the exposure unit  32  in accordance with image information of the scanned document. The photosensitive drums  740 Y,  740 M,  740 C, and  740 K have been charged in advance by the charging units  741 Y,  741 M,  741 C, and  741 K, respectively. Then, each of the photosensitive drums  740 Y,  740 M,  740 C, and  740 K is irradiated with a corresponding laser beam, which forms a respective electrostatic latent image on each of the photosensitive drums  740 Y,  740 M,  740 C, and  740 K. The electrostatic latent images formed on the photosensitive drums  740 Y,  740 M,  740 C, and  740 K are developed by the developing units  742 Y,  742 M,  742 C, and  742 K, respectively, and toner images of yellow (Y), magenta (M), cyan (C), and black (K) are formed on the photosensitive drums  740 Y,  740 M,  740 C, and  740 K. The toner images of respective colors formed on the photosensitive drums  740 Y,  740 M,  740 C, and  740 K are transferred to the intermediate transfer belt  35  by using the respective primary transfer rollers  36 Y,  36 M,  36 C, and  36 K to be superimposed on each other. A transferred and superimposed toner image (full-color toner image) is carried on the intermediate transfer belt  35  and conveyed to the nip portion N. 
     Simultaneously with the aforementioned image forming operation, sheets housed in the sheet housing unit  11  are separated one by one by the separating feeder  12  and conveyed to a sheet conveying path  26  by the pick-up roller  15 . Then, an obliquely conveyed sheet is corrected at a registration roller pair  27  disposed upstream of the nip portion N in the sheet conveying direction, and the sheet is conveyed to the nip portion N at a predetermined conveyance timing. The full-color toner image carried by the intermediate transfer belt  35  is transferred by the secondary transfer roller  37  to the sheet conveyed to the nip portion N. 
     The sheet to which the toner image has been transferred is heated and pressed in the fixing unit  34 , and the toner image is melted and fixed, after which the sheet is discharged from the body by a discharge roller pair  18  and contained in a discharge sheet containing unit  19 . 
     When images are formed on both sides (a first side and a second side) of a sheet, before the sheet that has an image formed on the first side of the sheet is discharged from the body, the sheet is conveyed to a duplex conveying path  17  by reverse rotation of the discharge roller pair  18  and then returned to the image forming unit  30  through the duplex conveying path  17 . Then, an image is formed on the second side of the sheet in a manner similar to the first side, and the sheet is discharged from the body. The sheet discharged from the body is contained in the discharge sheet containing unit  19 . 
     The aforementioned preview display apparatus can be realized by using hardware, software, or a combination of hardware and software. A method for preview display performed by the aforementioned preview display apparatus can also be realized by using hardware, software, or a combination of hardware and software. Realization by software mentioned here indicates realization by using a computer that reads and executes a program. 
     The program can be stored on various kinds of non-transitory computer readable media and supplied to the computer. The various kinds of non-transitory computer readable media include tangible storage media of various types. Examples of the non-transitory computer readable media include a magnetic recording medium (for example, a flexible disk, a magnetic tape, or a hard-disk drive), a magneto-optical recording medium (for example, a magneto-optical disk), a compact-disk read-only memory (CD-ROM), a CD-R, a CD-R/W, a semiconductor memory (for example, a mask ROM, a programmable ROM (PROM), an erasable PROM (EPROM), a flash ROM, or a random access memory (RAM)). The program may be supplied to the computer by using transitory computer readable media of various types. Examples of the transitory computer readable media include electric signals, optical signals, and electromagnetic waves. The transitory computer readable medium can supply the program via a wired transmission path, such as electric wires or optical fibers, or via a wireless transmission path. 
     The present disclosure can be executed in various different forms without departing from the spirit and major features of the present disclosure. Thus, each of the embodiments described above is merely illustrative and is not meant to be limiting. The scope of the present disclosure is defined by the claims and is not constrained by the specification in any way. Further, modifications and changes within the scope and range of equivalents of the claims are all within the scope of the present disclosure. 
     The embodiments of the present disclosure can be used for preview display of a document. 
     The present disclosure contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2017-249335 filed in the Japan Patent Office on Dec. 26, 2017, the entire contents of which are hereby incorporated by reference. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.