Patent Publication Number: US-2013229441-A1

Title: Portable display device, and method for controlling operation of same

Description:
TECHNICAL FIELD 
     This invention relates to a portable control device and to a method for controlling the operation of this device. 
     BACKGROUND ART 
     There is a device in which, when a document is displayed on a display screen, user-designated text is enlarged so as to facilitate reading of the document (Japanese Patent Application Laid-Open No. 2008-250948). Further, there is a device in which scrolling is performed automatically in accordance with the reading speed of the user (Japanese Patent Application Laid-Open No. 2001-282414). However, in a case where an imaged document is displayed on a small-size display screen as on a display screen provided on a mobile telephone, there are instances where one cannot discern which portion of the document is being read. 
     DISCLOSURE OF THE INVENTION 
     An object of the present invention is to arrange it so that when an imaged document is displayed on a display screen, one can discern which portion of the document is being read. 
     A portable display device according to the present invention is characterized by comprising: portion-of-interest decision device for deciding, from within a document image representing an imaged document, a sentence of interest or a paragraph of interest the form of display of which is to be changed from that of other sentences or paragraphs; display form changing device for changing the form of display of the sentence of interest or paragraph of interest, which has been decided by the portion-of-interest decision device, from the form of display of other sentences and paragraphs; a display device for displaying, on a display screen, a portion of the document image that includes at least a part of the sentence of interest or paragraph of interest the form of display of which has been changed by the display form changing device; scrolling device for scrolling, in response to a portion-of-interest scroll command, the portion of the document image displayed on the display screen; first determination device for determining, in response to scrolling by the scrolling device, whether the sentence of interest or paragraph of interest the form of display of which has been changed by the display form changing device has been displayed up to the end thereof on the display screen in accordance with character alignment sequence; and decision control device for controlling the portion-of-interest decision device, in response to a determination by the first determination device that the sentence of interest or paragraph of interest the form of display of which has been changed by the display form changing means has been displayed up to the end thereof on the display screen, in such a manner that a sentence or paragraph that follows the sentence of interest or paragraph of interest the form of display of which has been changed by the form changing device is decided upon as a sentence of interest or paragraph of interest. 
     The present invention provides also an operation control method suited to the portable display device described above. Specifically, the method comprises: portion-of-interest decision device deciding, from within a document image representing an imaged document, a sentence of interest or a paragraph of interest the form of display of which is to be changed from that of other sentences or paragraphs; display form changing device changing the form of display of the sentence of interest or paragraph of interest, which has been decided by the portion-of-interest decision device, from the form of display of other sentences and paragraphs; a display device displaying, on a display screen, a portion of the document image that includes at least a part of the sentence of interest or paragraph of interest the form of display of which has been changed by the display form changing device; scrolling device scrolling, in response to a portion-of-interest scroll command, the portion of the document image displayed on the display screen; first determination device determining, in response to scrolling by the scrolling device, whether the sentence of interest or paragraph of interest the form of display of which has been changed by the display form changing device has been displayed up to the end thereof on the display screen in accordance with character alignment sequence; and determination control device controlling the portion-of-interest decision device, in response to a determination by the first determination device that the sentence of interest or paragraph of interest the form of display of which has been changed by the display form changing device has been displayed up to the end thereof on the display screen, in such a manner that a sentence or paragraph that follows the sentence of interest or paragraph of interest the form of display of which has been changed by the form changing device is decided upon as a sentence of interest or paragraph of interest. 
     The present invention also provides a recording medium storing a computer-readable program for implementing the method of controlling the operation of the above-described portable display device. Furthermore, it may be arranged so that such a program is also provided. 
     In accordance with the present invention, a sentence of interest or a paragraph of interest the form of display of which is to be changed from that of other sentences or paragraphs is decided from within a document image representing an imaged document. The decided form of display of the sentence of interest or paragraph of interest is changed from the form of display of other sentences and paragraphs. A portion of the document image that includes at least a part of the sentence of interest or paragraph of interest the form of display of which has been changed is displayed on the display screen of a display unit. When a portion-of-interest scroll command is applied, the portion of the document image displayed on the display screen is scrolled. In response to such scrolling, it is determined whether the sentence of interest or paragraph of interest has been displayed up to the end thereof on the display screen in accordance with the alignment sequence of the characters. When the sentence of interest or paragraph of interest is displayed up to the end thereof on the display screen in accordance with the alignment sequence of the characters, a sentence or paragraph that follows the sentence of interest or paragraph of interest the form of display of which has been changed is decided upon as a new sentence of interest or paragraph of interest. The form of display of the new sentence of interest or paragraph of interest thus decided is displayed on the display screen upon being changed from the form of display of other sentences or paragraphs. 
     The sentence of interest or paragraph of interest is the sentence or paragraph being read by the user. Since the form of display of the sentence of interest or paragraph of interest is displayed so as to appear different from the form of display of other sentences or paragraphs, the user can easily discern the sentence or paragraph being read. 
     The device may further comprise a storage device for storing the position of a sentence of interest or paragraph of interest contained in a portion of the document image displayed last on the display screen; and second determination device for determining whether the position of a sentence of interest or paragraph of interest has been stored in the storage device. In this case, by way of example, the portion-of-interest decision device decides, in response to a determination by the second determination device that the position of a sentence of interest or paragraph of interest has been stored, that a sentence or paragraph that follows the position of the sentence of interest or paragraph of interest stored in the storage device is a sentence of interest or paragraph of interest, and decides, in response to a determination by the second determination device that the position of a sentence of interest or paragraph of interest has not been stored, that a first sentence or first paragraph of the document image is a sentence of interest or paragraph of interest. 
     The device may further comprise display control device for controlling the display device so as to display a portion of the document image on the display screen; and designation device for designating a desired sentence or desired paragraph from within the portion of the document image being displayed on the display screen under the control of the display control device. In this case, the portion-of-interest decision device decides for example that the desired sentence or desired paragraph designated by the designation device is a sentence of interest or paragraph of interest. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overview of a document image communication system; 
         FIG. 2  is a block diagram illustrating the electrical configuration of a mobile telephone; 
         FIGS. 3 and 4  are block diagrams illustrating the electrical configuration of a document image server; 
         FIGS. 5 and 6  are flowcharts illustrating the processing procedure of a mobile telephone; 
         FIG. 7  is an example of a document image; 
         FIG. 8  is an example of layout information; 
         FIG. 9  is an example of a document image; 
         FIGS. 10 to 12  are examples of document images displayed on the display screen of a mobile telephone; 
         FIG. 13  is an example of a document image; 
         FIG. 14  is an example of a document image displayed on the display screen of a mobile telephone; and 
         FIGS. 15 and 16  are flowcharts illustrating a sentence-of-interest decision processing procedure. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
       FIG. 1 , which shows an embodiment of the present invention, illustrates an overview of a document image communication system (where the document is not one represented by a text file but one represented by an image file, and for this reason the image document is referred to as a “document image”). 
     The document image communication system according to this embodiment includes a mobile telephone  1  and a document image server  20  capable of communicating with each other via the Internet [the network is not limited to the Internet and may just as well be an in-house LAN (Local-Area Network) or the like]. A file representing a document image is transmitted from the document image server  20  to the mobile telephone  1  in response to a request from the mobile telephone  1 . 
       FIG. 2  is a block diagram illustrating the electrical configuration of the mobile telephone  1 , referred to as a so-called “smart phone”. 
     The overall operation of the mobile telephone  1  is controlled by a control unit  2 . 
     The mobile telephone  1  is provided with a communication device  10  and antenna  11  for communicating with other mobile telephones and for accessing the Internet. A program  12  for performing an operation described later is downloaded via the antenna  11 . By installing the downloaded program  12  in the mobile telephone  1 , the mobile telephone  1  will operate as described later. The mobile telephone  1  is provided with a memory card reader writer  13  as well. It may be arranged so that a program stored on a memory card  14  is read using the memory card reader writer  13  so that the program is installed in the mobile telephone  1 . 
     The mobile telephone  1  is further provided with a display unit  3  for displaying documents and images and the like on a display screen. A touch panel  4  has been formed on the display screen of the display unit  3 . By touching the touch panel  4  formed on the display screen, a user can apply various commands to the mobile telephone  1 . 
     The mobile telephone  1  includes also a memory  5  in which prescribed data is stored. The mobile telephone  1  further includes a speaker  8  and a microphone  9 . A voice signal is amplified by an amplifier circuit  7  and applied to the speaker  8 , whereby voice is output from the speaker  8 . Further, a voice signal representing voice that has been input from the microphone  9  is amplified by the amplifier circuit  7  and input to the control unit  2 . 
     With the mobile telephone  1  according to this embodiment, a document image can be displayed on the display screen of the display unit  3  in the manner set forth above. Since the display screen of the mobile telephone  1  is comparatively small, the entirety of one sentence cannot be displayed on the display screen when character size is enlarged in order to facilitate the reading of characters. If the document is one represented by a text file, the characters need only be re-arrayed in conformity with the display screen. In the case of a document that is a document image, however, re-arraying characters in conformity with the display screen is difficult and, for this reason, scrolling is required. When scrolling is performed, however, there are occasions where one cannot discern which sentence (paragraph) of the document (paragraph) is being read. In this embodiment, which sentence (paragraph) is being read is made easy to discern. 
       FIG. 3  is a block diagram illustrating the electrical configuration of the document image server  20 . 
     The overall operation of the document image server  20  is controlled by a CPU  21 . 
     The document image server  20  includes a communication unit  22  for accessing the Internet, a memory  23  for storing prescribed data and the like, an input unit  24  such as a keyboard, a hard disk  25 , a hard-disk drive  26  for accessing the hard disk  25 , and a CD-ROM (Compact-Disk Read-Only Memory) drive  27 . A CD-ROM  28  storing a program for controlling an operation described later is loaded into the CD-ROM drive  27  and the program is read. The read program is installed in the document image server  20 . The program may just as well be received via the Internet without being stored on a recording medium such as the CD-ROM  28 . 
     A text file representing a document has been stored on the hard disk  25 . The text file is read from the hard disk  25  and is converted by the CPU  21  to a document image file representing a document image. The document image file obtained by the conversion is stored on the hard disk  25 . 
       FIG. 4  is a flowchart illustrating the processing procedure of the document image server  20 , and  FIGS. 5 and 6  are flowcharts illustrating the processing procedure of the mobile telephone  1 . 
     A document represented by a text file is imaged beforehand and converted to a document image, which is represented by an image file (document image file), in the document image server  20  (step  31  in  FIG. 4 ). The layout of the document image obtained by the conversion is then analyzed (step  32  in  FIG. 4 ). In layout analysis, such items as character alignment sequence (horizontal writing, vertical writing) of the document that has been converted to the document image and the position of each sentence constituting the document are detected. 
       FIG. 7  is an example of a document image  60 . 
     The document image  60  contains a number of sentences of horizontal writing. Among the sentences contained in the document image  60 , a first sentence is represented by a wavy line  61 A. A second sentence is represented by a series of round symbols  63 A and a third sentence is represented by a dashed line  65 A. Other sentences are represented by straight lines  60 A. Since the sentences contained in the document image  60  are written horizontally, they are represented by horizontal straight lines  60 A. Whether the alignment sequence of the characters is horizontal writing or vertical writing can be determined by detecting whether a blank space that occurs following the final sentence of a paragraph continues in the horizontal direction or in the vertical direction. Horizontal writing is determined if the blank space continues horizontally and vertical writing if the blank space continues vertically. Since the blank space in the document image  60  shown in  FIG. 7  continues in the horizontal direction, it is determined that the writing is horizontal writing. Further, processing for detecting a period is executed and it is judged that a detected period is the end of a sentence. A character that follows a detected period is judged to be the beginning of a sentence. 
     When horizontal writing is determined, the positions of the beginning and end of the sentence are detected. If the position of the beginning of a sentence is that of horizontal writing, the position at the upper left of the character at the beginning of the sentence is detected by its coordinates. In the case of vertical writing, the position at the upper right of the character at the beginning of the sentence is detected by its coordinates. Regardless of whether the position of the end of the sentence is that of horizontal writing or vertical writing, the position of the period at the end of the sentence is detected by its coordinates. In a case where a sentence extends over two lines or more, the position of the character at the beginning of each line (the position is at the upper left of the character if writing is horizontal writing, and the position is at the upper right of the character if writing is vertical writing) and the position of the character at the end of each line (the position is at the upper right of the character if writing is horizontal writing, and the position is at the lower right of the character if writing is vertical writing) are also detected. 
     The first sentence  61 A of the document image  60  shown in  FIG. 7  is enclosed by frames  61  and  62 . With regard to the position of the first sentence, the position of the beginning of sentence  61 A has coordinates (x 11 , y 11 ) and the position of the end of sentence  61 A has coordinates (x 14 , y 14 ). The first sentence  61 A extends over two or more lines. The position of the final character on the first line has coordinates (x 12 , y 12 ), and the position of the first character on the second line has coordinates (x 13 , y 13 ). Accordingly, the positions of the first sentence  61 A are indicated by (x 11 , y 11 ), (x 12 , y 12 )+(x 13 , y 13 ), (x 14 , y 14 ). The second sentence  63 A is enclosed by frames  63  and  64 . In a manner similar to that of the first sentence  61 A, the positions of the second sentence  63 A are (x 21 , y 21 ), (x 22 , y 22 )+(x 23 , y 23 ), (x 24 , y 24 ). The positions of the third sentence  65 A are (x 31 , y 31 ), (x 32 , y 32 ). With regard to the other sentences  60 A, the positions of these sentences  60 A are detected in similar fashion. The fact that a sentence extends over multiple lines can be understood from the “+” symbol. A number obtained by adding “1” to the number of “+” symbols represents the number of lines over which the sentence extends. If the number of “+” symbols is zero, then the sentence does not extend over multiple lines and fits on one line of the document image  60 . If the number of “+” symbols is one, the sentence extends over two lines of the document image  60 , and if the number of “+” symbols is two, the sentence extends over three lines of the document image  60 . 
       FIG. 8  is an example of layout information. 
     The layout information includes the positions of the sentences constituting the document image in addition to the data indicating the character alignment sequence (horizontal writing or vertical writing), as mentioned above. These positions are detected on a per-sentence basis in the manner described above. The layout information is generated as one set of information in association with one document image. It may be arranged so that the layout information is recorded in the header of the image file representing the document image or so that it is stored in a layout information file for accommodating the layout information. In a case where the layout information is stored in a layout information file separate from the image file, it would be necessary to place the information in the same folder or to make common use of part of the file name in such a manner that the layout information that corresponds to the image file can be identified. 
     Although the above-described layout analysis is carried out after the document is imaged, it may be arranged so that it is performed before the document is imaged. If considered from the standpoint of ease of layout analysis, analysis would be performed before the document is imaged. Naturally, even in a case where layout analysis is performed after the document is imaged, it may be arranged so that the layout analysis is performed utilizing the header information that has been stored in the header of the text file that represents the document prior to its imaging, as well as the text file itself. 
     With reference again to  FIG. 4 , when layout analysis ends, the document image and the layout information are stored on the hard disk  25  (step  33 ). If the document image and layout information are separate files, then the separate files are stored on the hard disk  25 , and if the layout information has been placed in the header of the image file representing the document image, this image file is stored on the hard disk  25 . 
     In a case where the document image is to be displayed on the mobile telephone  1 , document-image request data is transmitted from the mobile telephone  1  to the document image server  20  (step  41  in  FIG. 5 ). 
     When the document-image request data transmitted from the mobile telephone  1  is received at the document image server  20  (“YES” at step  34  in  FIG. 4 ), the document image and layout information (the file representing it) specified by this request information are read from the hard disk  25  (step  35  in  FIG. 4 ). The read document information and layout information (the file representing it) are transmitted from the document image server  20  to the mobile telephone  1  (step  36  in  FIG. 5 ). 
     When the document image and layout information (the file representing it) transmitted from the document image server  20  are received at the mobile telephone  1  (“YES” at step  42  in  FIG. 5 ), a sentence of interest is decided (step  43  in  FIG. 5 ). A sentence of interest refers to a sentence thought to be one that will be read now or one that is being read by the user of the mobile telephone  1 . For example, if the document image is displayed on the display screen of the mobile telephone  1  the first time, it is decided that the first sentence of this document image is the sentence of interest. If it is construed that the user of the mobile telephone  1  has finished reading the first sentence, then the second sentence, which follows the first sentence, becomes the sentence of interest, as will be described later. Processing for deciding the sentence of interest will be described in detail later. 
     When the sentence of interest is decided, the display area is positioned in such a manner that the decided sentence of interest falls within the display area (step  44  in  FIG. 5 ). The document image within the display area is displayed on the display screen of the mobile telephone  1 . 
       FIG. 9  illustrates the document image  60 . 
     Assume that the first sentence  61 A has been decided upon as the sentence of interest in the manner described above. The first sentence  61 A extends from the first line to the second line and is enclosed by frames  81  and  82 . 
     If the document image  60  has not been displayed even one time, then, as mentioned above, the first sentence  61 A is decided as the sentence of interest and a display area  70  is positioned in such a manner that the left side of the character at the beginning of the sentence of interest becomes the left edge of the display area. If the character at the beginning of the sentence of interest is a blank space equivalent to one character owing to a paragraph change or the like, the display area  70  is positioned in such a manner that the left side of the blank space equivalent to one character becomes the left edge of the display area. Whether a blank space equivalent to one character is in front of a character at the beginning of the sentence of interest can be determined from the positions contained in the layout information as shown in  FIG. 8  For example, since the x coordinate of the first character of the first sentence  61 A is x 11  and the x coordinate of the first character on the second line of the first sentence  61 A is x 13  (the first x coordinate of the “+” symbol), then it can be determined whether the blank space is in front of the first character of the first sentence  61 A by comparing these x coordinates x 11  and x 13 . For example, there is blank space present if x 11 &gt;x 13  holds and there is no blank space present if x 11 =x 13  holds. Thus, if the document image  60  has not been displayed even once, the display area  70  is positioned at a position  71  at the upper left of the document image  60 . 
     When the display area is positioned, the document image  60  within the display area  70  is displayed on the display screen of the mobile telephone  1  in such a manner that the sentence of interest is highlighted relative to other sentences (step  45  in  FIG. 5 ). 
       FIG. 10  is an example of a display screen  90  of the mobile telephone  1 . 
     The portion inside the display area  70  from within the document image  60  is being displayed on the display screen  90 . Also being displayed on the display screen  90  is a portion of the first sentence  61 A, which is the sentence of interest decided in the manner described above. This portion of the first sentence  61 A is displayed in highlighted form (indicated by the hatching) as if it were enclosed by frames  91  and  92 . Since the sentence of interest is highlighted, the user of the mobile telephone  1  can identify which sentence should be read among the number of sentences being displayed on the display screen  90 . 
     With reference to  FIG. 6 , the mobile telephone  1  accepts a command from the user (step  46 ). 
     The display area  70  is reduced in size if the command is an enlargement command and is enlarged in size if the command is a reduction command (step  47 ). If a quit command is not applied (“NO” at step  48 ), the display area  70  is reduced in case of the enlargement command and therefore a portion of the enlarged document image  60  is displayed on the display screen of the mobile telephone  1 . In case of the reduction command, the display area  70  is enlarged and therefore a portion of the reduced document image  60  is displayed on the display screen of the mobile telephone  1  (step  45  in  FIG. 5 ). It goes without saying that in the case of the enlargement command, the display area  70  is reduced in such a manner that the sentence of interest is included in the portion of the display after the enlargement thereof. 
     If the command is a vertical scroll command (applied by sliding a finger or touch pen or the like upward or downward on the surface of the touch panel  4 ), the display area  70  is moved up or down in accordance with the amount of scrolling (step  49 ). If a quit command is not applied (“NO” at step  48 ), the portion of the document image  60  that is contained in the display area  70  after the movement thereof is displayed on the display screen  90  (step  45  in  FIG. 5 ). In a case where the sentence of interest is no longer contained in the moved display area  70  owing to vertical scrolling, it is preferred that the sentence in the portion contained in the moved display area  70  be decided upon as a new sentence of interest. For example, the portion of a sentence to be made the sentence of interest is designated by the user from among sentences (portions thereof) being displayed on the display screen  90 . Naturally, even in a case where the sentence of interest is no longer contained in the display area  70  after movement thereof owing to vertical scrolling, the sentence of interest need not be changed. 
     If the command is a horizontal scroll command (applied by sliding a finger or touch pen or the like leftward or rightward on the surface of the touch panel  4 ), it is determined whether the entire sentence of interest has been displayed in its entirety in accordance with the character alignment sequence (step  50  in  FIG. 6 ). 
     If the entire sentence of interest has not been displayed (“NO” at step  50  in  FIG. 6 ), the display area  70  is moved in the scrolling direction by an amount equivalent to the width of the display area  70  (step  51  in  FIG. 6 ). For example, the display area  70  is moved rightward (or leftward) if a finger or touch pen or the like is slid rightward on the surface of the touch panel  4  and is moved leftward (or rightward) if a finger or touch pen or the like is slid leftward on the surface of the touch panel  4 . As a result, the display area  70  moves to a position indicated at  72  shown in  FIG. 9 . If a quit command is not applied (“NO” at step  48 ), the portion inside the display area  70  at the position indicated at  72  within the document image  60  is displayed on the display screen  90  (step  45  in  FIG. 5 ). 
       FIG. 11  is an example of the document image  60  displayed on the display screen  90 . 
     The document image  60  inside the display area  70  in the case where the display area  70  has been moved to the position indicated at  72 , as shown in  FIG. 9 , is being displayed on the display screen  90 . The sentence of interest is enclosed by a frame  93  on the display screen  90  in a manner similar to that shown in  FIG. 10 . The sentence of interest is being displayed in highlighted form as indicated by the hatching. Since the sentence of interest is thus highlighted, the user can discern the sentence the user is reading even though a number of sentences are being displayed on the small display screen. 
     With reference again to  FIG. 6 , if further horizontal scrolling is performed and the entire sentence of interest has not been displayed in accordance with the character alignment sequence (step  50 ), then the display area  70  is moved (step  51 ). 
     In a case where the display area  70  is the position indicated at  72 , as illustrated in  FIG. 9 , moving the display area  70  rightward by the width of the display area  70  will bring the position of the display area  70  to that indicated at  73 A. Since the document image  60  now is no longer on the right side internally of the display area  70 , the document image  60  is no longer displayed on the right-side portion of the display screen of mobile telephone  1 . For this reason it may be arranged so that the range of movement of the display area  70  is limited to be within the document image  60 . If a rightward horizontal scroll command is applied in a case where the display area  70  is at the position indicated at  72 , the position of the display area  70  where the right edge of the display area  70  and the right edge of the document image  60  coincide, as indicated at  73 B, will be taken as the limit on movement of the display area  70 . 
     If, when the display area  70  has attained the position indicated by  73 A or  73 B shown in  FIG. 9 , a scroll command for further rightward scrolling is applied and, moreover, the entire sentence of interest has not been displayed on the display screen  90  in the character alignment sequence (“NO” at step  50 ), then the display area  70  is moved so as to bring the left edge of the display area  70  into coincidence with the left edge of the document image  60  (step  51 ). Further, the display area  70  is moved downward by one line. As a result, the display area  70  attains the position indicated at  74 . Naturally, if the sentence of interest is contained in the display area  70  after the movement of the display area, then the display area  70  need not necessarily be moved one line downward. 
       FIG. 12  is an example of the document image  60  displayed on the display screen  90 . 
     The document image  60  within the display area  70  is being displayed on the display screen  90  at the position indicated at  74  in  FIG. 9 . The sentence of interest enclosed by a frame  94  is displayed in highlighted form as indicated by the hatching. 
     By moving the display area  70  in the manner indicated by the reference numerals  71 ,  72 ,  73 A or  73 B and  74  in  FIG. 9 , the first sentence  61 A taken as the sentence of interest will be displayed in its entirety in accordance with the alignment sequence of its characters. Since the first sentence  61 A taken as the sentence of interest is displayed in highlighted form, the user can discern the sentence the user is reading even if the document image  60  is scrolled. 
     As to whether the entire sentence of interest has been displayed in its entirety in accordance with the character alignment sequence can be determined using the position information contained in the layout information shown in  FIG. 8 . That is, since the position information contained in the layout information is in accordance with the character alignment sequence, the characters specified by these positional coordinates are displayed in the order of the position information. As a result, the fact that the sentence of interest has been displayed in accordance with the character alignment sequence can be determined. Owing to the fact that the character having the coordinates at the beginning of the positional coordinates [namely (x 11 , y 11 ) in the case of the first sentence  61 A] is displayed first, the sentence of interest is displayed in accordance with the order of the positional coordinates and finally the character having the final coordinates of the positional coordinates [namely (x 14 , y 14 ) in the case of the first sentence  61 A] is displayed last, it can be determined that the entire sentence of interest has been displayed in its entirety in accordance with the character alignment sequence. 
     If the entire sentence of interest is displayed in its entirety in accordance with the character alignment sequence (“YES” at step  50  in  FIG. 6 ), then it is decided that the sentence that follows the sentence that was the sentence of interest is now the sentence of interest (step  52  in  FIG. 6 ). If a quit command is not applied (“NO” at step  53  in  FIG. 6 ), then the display area  70  is positioned so as to bring the decided sentence of interest into the display area  70  (step  44  in  FIG. 6 ). 
     Thus, when display of the first sentence  61 A ends, the second sentence  63 A is decided upon as the sentence of interest. 
       FIG. 13  is an example of the document image  60 . 
     The second sentence  63 A that has been decided is enclosed by frames  83  and  84 . The position of the display area  70  is decided so as to contain a portion of the second sentence  63 A decided. Since the second sentence  63 A is included in the document image  60  being displayed on the display screen  90  when the display of the first sentence  61 A ends, as shown in  FIG. 12 , it is decided the position of the display area  70  when the display of the first sentence  61 A ends (the position indicated at  74  shown in  FIG. 9 ) is the position of the display area  70  as is. 
       FIG. 14  is an example of the display screen  90 . 
     As will be understood from a comparison with  FIG. 12 , the content of the document image  60  being displayed on the display screen  90  shown in  FIG. 14  is the same as that of the document image  60  being displayed on the display screen  90  shown in  FIG. 12 . In  FIG. 12 , however, the sentence of interest is the first sentence  61 A and therefore the first sentence  61 A is highlighted as indicated by frame  94 . In  FIG. 14 , on the other hand, the sentence of interest is the second sentence  63 A and therefore the second sentence  63 A is highlighted as indicated by frames  95  and  96 . 
     With regard to the second sentence  63 A as well, as was the case with the first sentence  61 A, it is highlighted in such a manner that the user can discern the sentence being read even though scrolling is performed, as described above. 
     In the foregoing embodiment, the display area  70  is moved horizontally by the width of the display area  70  with regard to the horizontal scroll command. However, it may be arranged so that the display area  70  is moved by an amount that conforms to the amount of scrolling (the length traced on the surface of the touch panel  4 ). 
     In the foregoing embodiment, the mobile telephone  1  can be provided with an enlargement button, a reduction button, vertical scroll buttons (an up-arrow button and a down-arrow button) and horizontal scroll buttons (a left-arrow button and a right-arrow button) for the enlargement/reduction command, vertical scroll command and horizontal scroll command, respectively, and these scroll operations can be achieved in accordance with commands from these buttons. 
     In the foregoing embodiment, the document image is an image of horizontal writing. When a vertical scroll command is applied, therefore, the display area  70  moves in accordance with the amount of scrolling without execution of determination processing (the processing at step  50  in  FIG. 6 ) for determining whether the entire sentence of interest has been displayed. If the horizontal scroll command is then applied, the determination as to whether the entire sentence of interest has been displayed would be performed. However, in the case of a document image that is vertical writing, determination processing for determining whether the entire sentence of interest has been displayed would be executed by applying the vertical scroll command. If the horizontal scroll command is then applied, the determination as to whether the entire sentence of interest has been displayed would not be performed. 
       FIG. 15  is a flowchart illustrating a processing procedure for deciding a sentence of interest (the processing at step  43  of  FIG. 5 ). 
     The processing procedure shown in  FIG. 15  is such that if display of the document image  60  is quit in mid-course, the above-described highlighted display can be continued from the portion at which the display was quit. If the display of the document image  60  is quit in mid-course, therefore, the sentence of interest that was displayed last before the display was quit is stored in terms of the number of the sentence. Instead of storing the sentence of interest in terms of the number of the sentence, the position of this sentence of interest in the document image  60  may be stored. If the position is stored, the number of the sentence of interest can be determined from the layout information. If the number of the sentence can be determined, then so can the position of this sentence. Information indicating the position or the sentence number need only be appended updatably to the above-mentioned layout information. 
     If data indicating the position of the sentence of interest or the sentence number of the sentence of interest has been stored (“YES” at step  101 ), the sentence of interest specified by the stored data indicating the position or sentence number, or the sentence that follows this sentence, is decided upon as the sentence of interest (step  103 ). If the entirety of the sentence of interest specified by the stored data indicating the position or sentence number has been displayed, then it is deemed that the user has finished reading this sentence of interest and, hence, the sentence of interest that follows the sentence of interest displayed last is decided upon as the sentence of interest. If the entirety of the sentence of interest specified by the stored data indicating the position or sentence number has not been displayed, then it is deemed that the user has not finished reading this sentence of interest. The sentence of interest displayed last, therefore, is again decided upon as the sentence of interest. 
     If, on the other hand, data indicating the position of the sentence of interest or the sentence number of the sentence of interest has not been stored (“NO” at step  101 ), then the first sentence of the document image is decided upon as the sentence of interest (step  102 ). 
       FIG. 16  is another flowchart illustrating a processing procedure for deciding a sentence of interest (the processing at step  43  of  FIG. 5 ). 
     A part or all of the document image  60  is displayed on the display screen of the mobile telephone  1  (step  104 ). A desired sentence from among the sentences displayed on the display screen is touched using a finger or touch pen, whereby the sentence is designated (step  105 ). The designated sentence is decided upon as the sentence of interest (step  106 ). It goes without saying that scroll processing is executed as needed in such a manner that the desired sentence is displayed on the display screen. 
     In the foregoing embodiment, the unit of highlighting is the sentence. However, it may be arranged so that highlighting is performed on a per-paragraph basis. If highlighting is performed on a per-paragraph basis, the position information in the layout information also would be stored on a per-paragraph basis. Further, the comma in a sentence may be adopted as the unit of highlighting. 
     Further, in the foregoing embodiment, the sentence of interest is highlighted. However, this does not impose a limitation and it will suffice if a sentence of interest (paragraph of interest) can be made distinguishable from other sentences (paragraphs). For example, the font of the sentence of interest can be made different from the font of other sentences, or the font can be italicized. In a case where the font is changed or italicized, it will suffice if character recognition processing is applied to the document image as necessary, the document represented by a text file is restored, the font in the text file is changed or italicized and then the document is again converted to an image.