Abstract:
An apparatus and method provide logic for processing information. In one implementation, an apparatus includes a display unit configured to display content to a user. The display unit includes a display surface, and the content is associated with at least a portion of a first page of an electronic document. A detection unit is configured to detect a first type of user activation associated with a first-type activation position on the display surface. A control unit is configured to determine whether the first-type activation position falls within a predetermined portion of the display screen, which is visually imperceptible to the user. The control unit is further configured to identify a first successive page of the electronic document based on at least the type of user activation, when the activation falls within the pre-determined portion.

Description:
BACKGROUND 
     The disclosed exemplary embodiments relate to an information processing apparatus, an information processing method, and a computer-readable medium storing a program for displaying a content of an electronic book and the like on a display screen such as a touch panel. 
     From the past, there is known a terminal apparatus such as an electronic book reader that displays electronic books including characters and figures. Such a terminal apparatus is demanded to enable a user to view electronic books with good operability, and various display methods, GUIs (Graphical User Interfaces), etc. for an electronic book, onto which, for example, an operation carried out when the user views an actual book is reflected, are being developed. 
     For example, when a real book is viewed, such an operation is frequently performed as to turn pages to search for a target page. As an operation that is based on this operation, there is known a page-scrolling operation to search for a target page from multiple pages of an electronic book. 
     In a mobile apparatus disclosed in Japanese Patent Application Laid-open No. 2008-234372, a horizontal touch sensor and a vertical touch sensor are provided on an outer edge of a display screen for displaying contents of electronic books. Pages of an electronic book are scrolled by an operation to those touch sensors (see, for example, paragraph [0028] and FIG. 1). 
     Further, a mobile information terminal disclosed in Japanese Patent Application Laid-open No. 2009-205565 is provided with a flexible display that can be curved and bend sensors capable of detecting a curve amount of the display. When the display is curved by a user, pages of an electronic book are scrolled based on a curve amount detected by the bend sensors (see, for example, paragraph [0041] and FIG. 5). 
     SUMMARY 
     However, the page-scrolling operations discussed above are performed using hardware devices, such as a touch sensor, a flexible display, and a bend sensor. Thus, dedicated interfaces are required in many cases, and hence those operations are difficult to perform by versatile operating systems (OSs). 
     Meanwhile, scroll bars and the like for the page-scrolling operations may be displayed as GUI components. 
     However, in this case, the GUI components impose a limitation on a region in which contents of an electronic book are displayed. Further, for example, when a small display screen is used, GUI components displayed on the small display screen are difficult to operate. 
     In view of the circumstances as described above, there is a need for an information processing apparatus, an information processing method, and a program that enable such an operation as to switch a displayed page to a target page to be performed with good operability without using dedicated hardware devices or GUI components for switching pages. 
     Consistent with an exemplary embodiment, an information processing apparatus includes a display unit configured to display content to a user. The display unit includes a display surface, and the content is associated with at least a portion of a first page of an electronic document. The detection unit is configured to detect a type of user activation, and the type of user activation being associated with an activation position on the display surface. A control unit is configured to determine whether the activation position falls within a predetermined portion of the display screen. The predetermined portion is visually imperceptible to the user. The control unit is further configured to identify a first successive page of the electronic document based on at least the type of user activation, when the activation position falls within the pre-determined portion. 
     Consistent with an additional exemplary embodiment, a computer-implemented method for processing information includes displaying content on a display surface of a display unit. The content is associated with at least a portion of a page of an electronic document. The method includes detecting a type of user activation. The type of user activation is associated with an activation position on the display surface. The method determines whether the activation position falls within a predetermined portion of the display screen. The predetermined portion is visually imperceptible to the user. A second page of the electronic document is identified based on at least the type of user activation, when the activation position falls within the pre-determined portion. 
     Consistent with a further exemplary embodiment, a non transitory, computer-readable storage medium stores a program that, when executed by a processor, causes the processor to perform a method for processing information. The method includes displaying content on a display surface of a display unit. The content is associated with at least a portion of a page of an electronic document. The method includes detecting a type of user activation. The type of user activation is associated with an activation position on the display surface. The method determines whether the activation position falls within a predetermined portion of the display screen. The predetermined portion is visually imperceptible to the user. A second page of the electronic document is identified based on at least the type of user activation, when the activation position falls within the pre-determined portion. 
     Consistent with another exemplary embodiment, an information processing apparatus includes a display unit configured to display a first portion of content to a user. The display unit includes a display surface. A receiving unit is configured to receive a position on the display surface corresponding to a first type of user activation, and a control unit is configured to determine whether the received position falls within a predetermined portion of the display surface. The control unit is further configured to generate a signal to display a second portion of content to the user, when the received position falls within the predetermined portion, and the display unit is further configured to display the second content portion, based on the generated signal. 
     As described above, according to the disclosed exemplary embodiments, such an operation as to switch a displayed page to a target page can be performed with high operability without using dedicated hardware devices or GUI components for switching pages. 
     These and other objects, features and advantages of the present disclosure will become more apparent in light of the following detailed description of best mode embodiments thereof, as illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic view of an external appearance of a portable terminal as an information processing apparatus according to a first exemplary embodiment; 
         FIG. 2  is a block diagram illustrating a configuration example of the portable terminal illustrated in  FIG. 1 ; 
         FIG. 3  is an explanatory view of an image displayed on a display screen of the portable terminal illustrated in  FIG. 1 ; 
         FIG. 4  is a schematic view for illustrating a page-zooming operation region; 
         FIG. 5  is a flowchart showing an operation of the portable terminal as the information processing apparatus according to the first exemplary embodiment; 
         FIG. 6  is a schematic view illustrating a timing when a multi-touch operation with respect to the page-zooming operation region illustrated in  FIG. 3  is detected; 
         FIG. 7  is a schematic view of a display screen to which a pinch-in operation is performed in the state illustrated in  FIG. 6 ; 
         FIG. 8  is a graph showing a relative relation between a distance between two touch positions illustrated in  FIG. 6  and a page-scroll amount; 
         FIG. 9  illustrates verification of such an operation as to search for a page by pinching and turning pages of a real book; 
         FIG. 10  is a schematic view of a scrolling image at the time when a twin-drag operation by a user is detected; 
         FIG. 11  is an explanatory view of a operation method for a determination of execution of a page-switching process; 
         FIG. 12  is an explanatory view of a operation method for a determination of cancellation of the page-switching process; 
         FIG. 13  is a schematic view of a display screen of a portable terminal according to a second exemplary embodiment; 
         FIG. 14  is an explanatory view of an operation of a page-switching process into a reverse direction by a touch operation with respect to a left page-switching operation region illustrated in  FIG. 13 ; 
         FIG. 15  is a schematic view of a display screen of a portable terminal according to a third exemplary embodiment; and 
         FIG. 16  are schematic views of a display screen of a portable terminal according to another exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, exemplary embodiments will be described with reference to the drawings. 
     1. First Exemplary Embodiment 
     a. Information Processing Apparatus 
       FIG. 1  is a schematic view of an external appearance of an information processing apparatus according to a first exemplary embodiment. In this exemplary embodiment, a portable terminal  100  provided with a touch panel is used as the information processing apparatus. The portable terminal  100  in this exemplary embodiment enables an electronic document, such as electronic book  50 , to be viewed. 
     As illustrated in  FIG. 1 , the portable terminal  100  includes a casing  1  to be held by a user  30  and a display screen  3  provided to a front surface  2  of the casing  1 . The casing  1  is formed of, for example, metal such as aluminum and stainless steel, or plastic. For example, as illustrated in  FIG. 1 , that is, when viewed from the user  30 , the casing  1  has the following size: a vertical dimension of approximately 25 cm, a lateral dimension of approximately 30 cm, and a thickness of approximately 1 cm. However, the material and the size of the casing  1  are not limited to this example. 
     The display screen  3  is provided over almost the entire front surface  2  of the casing  1 . The electronic book  50  is displayed on the display screen  3  so that contents of the electronic book  50  are browsed. 
       FIG. 2  is a block diagram illustrating a structural example of the portable terminal  100 . The portable terminal  100  includes a display unit  104  having the above-mentioned display screen  3 , a touch panel  105 , a central processing unit (CPU)  106 , a random access memory (RAM)  107 , and a storage  108 . For example, the CPU  106 , the RAM  107 , and an input-output interface (not shown) are connected to each other via a bus and the like. In addition, the display unit  104 , the touch panel  105 , and the storage  108  are connected to the input/output interface. 
     The display unit  104  is a display device that uses, for example, liquid crystal, EL (Electro-Luminescence), or CRT (Cathode Ray Tube). 
     The touch panel  105  functions as an input unit for receiving various instructions from the user  30 . The touch panel  105  includes a detection unit, for example, a sensor portion (not shown) provided integrally with the display screen  3  and an operation circuit unit. When an operator  31  such as a finger of the user  30  (that being, a human appendage) comes close to or comes in contact with the display screen  3 , an approach signal or a contact signal is output from the sensor portion to the operation circuit unit. Based on the approach signal or the contact signal thus output, the operation circuit unit generates, for example, an information piece on an approach position or a contact position of the operator  31  and information pieces on a moving direction, a moving amount, and a moving speed of the operator. In addition, for example, an information piece on a contact area of the operator  31  may be generated. The various information pieces thus generated are output, for example, to the CPU  106 , and undergo predetermined processes by the CPU  106 . 
     The touch panel  105  in this exemplary embodiment is a so-called multi-touch-type touch panel and is capable of detecting contacts or approaches of multiple operators with respect to the display screen  3 . Then, contact-position information pieces and movement information pieces of the multiple operators are generated. Thus, for example, the user  30  can input various instructions by a pinching operation with two fingers. The pinching operation is such an operation as to simultaneously bring, for example, two fingers into contact with the display screen  3 , and then open and close the two fingers. In this case, such an operation as to open two fingers held in contact with each other is referred to as, for example, a pinch-out operation, and such an operation as to close two fingers is referred to as, for example, a pinch-in operation. 
     The touch panel  105  used in this exemplary embodiment is of a capacitance type. However, touch panels of other types such as a resistive-film type, a surface-acoustic-wave type, and an infrared-type may also be used. 
     The storage  108  is a non-volatile storage device such as a hard disk drive (HDD), a flash memory, and other solid-state memories. A part or all of the RAM  107  and the storage  108  corresponds/correspond to a storage means of this exemplary embodiment. 
     Alternatively, the portable terminal  100  may include a read only memory (ROM) (not shown), and the storage means may include the ROM. 
     The portable terminal  100  may be provided with a drive unit and a communication unit (which are not shown). The drive unit is a device capable of driving removable recording media such as an optical recording medium, a floppy (registered trademark) disk, a magnetic recording tape, and a flash memory. 
     The communication unit is a modem, a router, and other communication devices that are capable of connecting with a LAN (Local Area Network) or a WAN (Wide Area Network) and used for communicating with other devices. Communication by the communication unit may either be by wires or wireless. 
     For example, the electronic book  50  stored in a recording medium is read out by the CPU  106  via the drive unit and displayed on the display screen  3 . Alternatively, the electronic book  50  may be downloaded via the communication unit and displayed on the display screen  3 . 
     Data processing by the portable terminal  100  is realized by software stored in the storage  108  and the like in cooperation with hardware resources of the portable terminal  100 . Specifically, by the CPU  106  loading a program that is stored in the storage  108  and the like and constitutes software in the RAM  107  and executing it, various types of data processing are realized. In this exemplary embodiment, the CPU  106  functions as a setting unit, a processor, a display switching unit, and the like. Note that the RAM  107  includes an image-display video RAM (VRAM) (not shown). 
       FIG. 3  is an explanatory view of an image displayed on the display screen  3  of the portable terminal  100  according to an exemplary embodiment. For example, the electronic book  50  which has been read out from the recording medium or downloaded via the communication portion has multiple pages assigned with page numbers. Each of the pages contains content data of the contents. The content data includes text data and image data. Further, the electronic book  50  contains bibliographic data including a title, an author, a total page number, a thickness of a unit page, and left binding/right binding. 
     As illustrated in  FIG. 3 , on the display screen  3 , there are displayed a page image  51  expressing a shape of a page and content data  52  contained in a predetermined page of the electronic book  50 . By the content data  52  of the predetermined page being mapped to the page image  51 , a display page  53  (that is, a first page) is displayed on the display screen  3 . For example, when content data of a fourth page is mapped to a display page  53 , the display page  53  is a fourth display page  53  of the electronic book  50 . 
     The page image  51  displayed in this exemplary embodiment is left-bound and left-open. A bound portion  54  is displayed on a root side of the page image  51  (left side of  FIG. 3 ). Meanwhile, an edge portion  55  corresponding to an edge of a real book is displayed on a leading end side of the page image  51  (right side of  FIG. 3 ). 
     In this exemplary embodiment, the page image  51  is generated as a mesh map constituted of multiple polygons (not shown), and the content data  52  of each page of the electronic book  50  are attached as textures to the page image  51 . By appropriately moving positions of vertexes of each of the polygons, for example, such a moving image (animation) that a part or all of the display page  53  is turned is generated and displayed on the display screen  3 . 
     As illustrated in  FIG. 3 , invisible regions are set respectively on the right side of the display screen  3 , that is, an edge side of the display page  53 , and a side corresponding to an inner-margin side of a real book. The term “invisible” represents a state in which, for example, coloring for distinguishing the regions is not performed, and hence sizes of the regions and the edge portions are visually imperceptible to the user and cannot be visually recognized. With this, the user  30  is not hindered from browsing the content data  52 . However, as long as browsing of the content data  52  is not hindered, the regions may be displayed so as to be visually recognized. 
     In this exemplary embodiment, the region on the edge side is set as a page-switching operation region  60  which is a region for a page-switching operation. The region on the inner-margin side is set as a page-zooming operation region  61  used for a page-zooming operation. 
     Sizes and positions of the page-switching operation region  60  and the page-zooming operation region  61  may be determined based on a predetermined pixel number or position coordinates on the display screen  3 . Alternatively, the sizes and the positions may be appropriately set by the user  30 . 
     It suffices that the page-switching operation region  60  is set in at least a part of the display screen  3 , and a region except the page-switching operation region  60  may be arbitrarily used. As in this exemplary embodiment, when the region on the edge side is set as the page-switching operation region  60 , an intuitive page-switching operation can be performed which is based on such an operation as to pinch the side corresponding to the edge side of a real book and turn pages. 
       FIG. 4  is a schematic view for explaining the page-zooming operation region  61 . As illustrated in  FIG. 4 , the pinch-out operation is performed on the page-zooming operation region  61  by the user  30 . Then, the content data  52  in the display page  53  is displayed in a zoomed manner. For example, a zoom rate of the content data  52  is set based on a variation in a distance between touch positions  62  and  63  of two fingers. Typically, the content data  52  is zoomed more as the distance between the touch positions  62  and  63  increases. When the pinch-in operation is performed on the page-zooming operation region  61  by the user  30 , the content data  52  is displayed in a reduced manner based on the variation in the distance between the touch positions  62  and  63 . 
     b. Operation of Information Processing Apparatus 
       FIG. 5  is a flowchart showing an operation of the portable terminal  100  as the information processing apparatus according to an exemplary embodiment. Here, a description is made on the operation of the portable terminal  100  at the time when a multi-touch operation is performed with respect to the above-mentioned page-switching operation region  60 . 
     First, a judgment is made as to whether or not a type of user activation, for example, a multi-touch operation such as two-point-touch operation, with respect to the page-switching operation region  60  has been detected (ST 101 ).  FIG. 6  is a schematic view illustrating a timing when the multi-touch operation with respect to the page-zooming operation region  60  is detected. 
     As illustrated in  FIG. 6 , in this exemplary embodiment, a judgment is made as to whether or not an intermediate position  64  between the respective touch positions  62  and  63  of two fingers is within a pre-determined portion of the display screen, that is, the page-switching operation region  60 . When the intermediate position  64  between the touch positions  62  and  63  is within the page-switching operation region  60 , the multi-touch operation with respect to the page-switching operation region  60  is detected. When the intermediate position  64  is out of the page-switching operation region  60 , the multi-touch operation with respect to the page-switching operation region  60  is not detected. 
     However, detecting conditions of the multi-touch operation with respect to the page-switching operation region  60  can be appropriately set. For example, the multi-touch operation may be detected when both the two touch positions  62  and  63  are within the page-switching operation region  60 . Alternatively, the multi-touch operation may be detected when, of the two touch positions  62  and  63 , the touch position  63 , which is positioned more approximately to the edge side (positioned on the right side of the display screen  3 ), is within the page-switching operation region  60 . Appropriate setting of the detecting conditions with main focus on the touch position  63  positioned on the edge side enables an intuitive operation to be made based on such an operation as to apply a finger to an edge of a real book. 
     Then, page scrolling in an amount corresponding to one page is performed, and a part of the next page is previewed (ST 102 ). As illustrated in  FIG. 6 , there is displayed a scrolling image  70  as a partially replaced image in which a part  53   a  of the display page  53  displayed on the display screen  3  is replaced with a part  65   a  of a next page  65  (this is, a first successive page) as a destination candidate. The part  65   a  of the next page  65  in the scrolling image  70  corresponds to a preview image  66  (that is, a first successive page preview), and the user  30  can view the preview image  66  within a corresponding region of display screen  3  for search for a target page. 
     In this exemplary embodiment, such a moving image that the part  53   a  of the display page  53  is turned is displayed, and a turned part is replaced with the part  65   a  of the next page  65  (preview image  66 ). The display page  53  is turned over to the intermediate position  64  between the two touch positions  62  and  63 . Further, a state in which the part  53   a  of the display page  53  is turned is displayed by an emphasis image  67 , which emphasizes that the preview image  66  of the next page  65  as the destination candidate is displayed at a turned part. With this, contents of a destination page can be easily understood, and a target page can be searched for with high operability. Further, intuitive page-searching operation and page-switching operation in which, as in a real book, a part of a page is pinched and the pinched part is turned for search for a target page can be performed. 
     The emphasis image  67  is not limited to an image that expresses the state in which the part  53   a  of the display page  53  is turned. For example, an image such as a colored frame may be displayed as an emphasizing image, for example, around the preview image  66 . Note that, in this exemplary embodiment, the display page  53  is turned over to the intermediate position  64  (that being, an activation position) between the two touch positions  62  and  63  (that being, the first and second contact positions). However, this should not be construed restrictively. For example, the display page  53  may be turned over to a position of either one of the two touch positions  62  and  63 . Alternatively, a position up to which the display page  53  is turned, that is, a size and a shape of the preview image  66  can be appropriately set. 
     Next, the distance between the two touch positions  62  and  63  (that is, a first displacement) is calculated, for example, in pixel units (ST 103 ). 
     Then, a judgment is made as to whether or not the pinch-in operation by the user  30  has been detected (ST 104 ). In a case where the pinch-in operation has been detected, a page-scroll amount is judged based on respective drag-moving amounts of two fingers, that is, the variation in the distance between the two touch positions  62  and  63 , and the page-scroll amount is updated (ST 105 ). Next, the preview image  66 , which is previewed in ST 102 , of the next page  65  is updated to a preview image  69  of a page  68  as a new destination candidate (that is, a second successive page) (ST 106 ) (refer to  FIG. 7 ). Update of the preview image  66  corresponds to an update of the scrolling image  70 . 
     In  FIGS. 7 to 9 , the update process of the preview image by the pinch-in operation is illustrated in detail.  FIG. 7  is a schematic view of the display screen  3  at the time when the pinch-in operation is performed, and  FIG. 8  is a graph showing a relative relation between the distance between the two touch positions  62  and  63  and the page-scroll amount. 
     As illustrated in  FIGS. 7 and 8 , as the distance between the two touch positions  62  and  63  (that is, a second displacement) becomes smaller (that is, the ratio of the second displacement to the first displacement decreases), the page-scroll amount (that is, a number of pages between a first page and the second successive page) increases. That is, as two fingers are brought closer to each other, the page  68  which is subsequent to and farther from the display page  53  is previewed. Further, as the distance between the touch positions  62  and  63  increases when the page-switching operation region  60  is touched first, a range in which the page-scroll amount varies becomes larger. As a result, more pages can be scrolled at one time. At each update of the preview image  66  or  69 , such an animation that pages are flipped through may be displayed. Alternatively, only the preview image  66  or  69  may be updated. 
     With regard to an amount of the variation in the distance between the two touch positions  62  and  63 , setting may be appropriately made as to how much the page-scroll amount is varied. For example, such a setting can be made that the scroll amount increases by one page when the two touch positions  62  and  63  come close to each other by a predetermined pixel. 
     Such a touch operation as to appropriately vary the distance between the two touch positions  62  and  63  enables the preview image  66  or  69  respectively representing the page  65  or  68  as a destination in the scrolling image  70  as a partially replaced image to be changed. As a result, intuitive page-searching operation and page-switching operation onto which such an operation as to flip through pages for search for a target page as in a real book is reflected can be performed. 
     Note that, when the pinch-out operation is performed by the user  30 , for example, during a page-update process, the page-scroll amount may be reduced. That is, a page previous to a page being previewed may be previewed. 
       FIG. 9  illustrates a verification of such an operation as to search for a target page by pinching and turning pages of a real book. In a real book  900 , for scrolling of more pages, it is necessary to pinch many pages  902  near an edge  901 . As illustrated in  FIG. 9 , in this exemplary embodiment, such an operation as to pinch many pages  902  is associated with such an operation as to bring two fingers of the user  30  close to each other. Thus, such a setting is made that the page-scroll amount becomes larger when two fingers are brought close to each other, which enables intuitive operations to be made. 
     In a case where the pinch-in operation has not been detected in ST 104 , a judgment is made as to whether or not a twin-drag operation by the user  30  has been detected (ST 107 ). The twin-drag operation is a drag operation made while the distance between two fingers are maintained to be substantially constant by the user  30 . By this twin-drag operation, the touch positions  62  and  63  move while maintaining the distance therebetween. 
       FIG. 10  is a schematic view of the scrolling image  70  at the time when the twin-drag operation is detected. When the twin-drag operation is performed in such a manner that a state illustrated in Part (A) of  FIG. 10  is shifted to a state illustrated in Part (B) of  FIG. 10 , a size of a preview image of a destination page in the scrolling image  70  varies in accordance with moving amounts of the two touch positions  62  and  63 . In this case, the next page  65  is displayed as a destination page, and the preview image  66  of the next page  65  is displayed. In this exemplary embodiment, the display page  53  is further turned following movements of the two touch positions  62  and  63  and the intermediate position  64 . With this, a size of the preview image  66  displayed after the turned part becomes larger, and a shape of the emphasis image  67  varies in accordance therewith (ST 108 ). 
     In the state illustrated in Part (C) of  FIG. 10 , the display page  53  is still further turned and the size of the preview image  66  is larger. When the twin-drag operation is performed in such a manner that the state illustrated in Part (C) of  FIG. 10  is shifted to the state illustrated in Part (A) of  FIG. 10 , the size of the preview image  66  may become smaller. 
     In this way, the size of the preview image  66  varies by the twin-drag operation by the user  30 . As a result, the page  65  as a destination can be viewed well, thus facilitating search for a target page. Further, intuitive operations which are based on such an operation as to largely turn a page so that another page can be viewed well as in a real book can be performed. 
     In the flowchart shown in  FIG. 5 , when the pinch-in operation has not been detected in ST 104 , the judgment is made as to whether or not the twin-drag operation has been detected. Then, after the size of the preview image  66  is changed by the twin-drag operation, the judgment is made again as to whether or not the twin-drag operation has been detected. That is, the page-scroll amount and the preview image are updated after the size of the preview image is changed. However, for example, after the page-scroll amount and the preview image are updated once by the pinch-in operation, the size of the preview image may be changed by the twin-drag operation. That is, an operation obtained by an appropriate combination of the pinch-in operation (pinch-out operation) and the twin-drag operation may be performed by the user  30 . 
       FIGS. 11 and 12  are explanatory views of operation methods for determining execution and cancellation of a page-switching process. Of the two fingers illustrated in  FIG. 11 , when a finger near the inner-margin side of the display page  53  is released first (that is, contact is lost between the first human appendage and the display surface), that is, when a release operation is performed first at the touch position  62  (Yes in ST 109 ), the page-switching process is cancelled (ST 110 ). As a result, as illustrated in  FIG. 11 , the scrolling image  70  displayed on the display screen  3  is switched to an image of the display page  53  which has been displayed prior to the multi-touch operation. 
     Of the two fingers, when a finger near the edge side of the display page  53  is released first (that is, contact is lost between the second human appendage and the display surface), that is, when a release operation is performed first at the touch position  63  (Yes in ST 111 ), the page-switching process is executed (ST 112 ). That is, a page  71  being previewed is determined as a destination page. As a result, as illustrated in  FIG. 12 , the scrolling image  70  displayed on the display screen  3  is switched to an image of the page  71 , which has been displayed, as a destination. The image of the page  71  is displayed as an image of a new display page  53 . 
     In this way, of the two touch positions  62  and  63 , the page-switching process may be executed by the release operation at the one touch position  63 , and the page-switching process may be cancelled by the release operation at the other touch position  62 . 
     In this exemplary embodiment, when the finger near the edge side is released first, the page-switching process is executed. This setting is made based on such an operation as to switch, as in a real book, a page by flicking up the page with a lower finger of the fingers pinching the pages. Meanwhile, when the finger near the inner-margin side is released first, the page-switching process is cancelled. This setting is made based on such an operation as to open again a page displayed with an upper finger of the fingers pinching the pages. With this, intuitive operations can be performed in this exemplary embodiment. Note that, when the release operations are simultaneously performed at the two touch positions  62  and  63 , the page-switching process may be executed or cancelled. 
     With respect to the two touch positions  62  and  63 , assignments of interactions of the execution and cancellation of the page-switching process can be appropriately set. In the above-mentioned case, the interactions are assigned based on positions in a lateral direction of the display screen  3 . However, the interactions may be assigned based on positions in a vertical direction of the display screen  3 . For example, the execution of the page-switching process may be assigned to a release operation at a touch position near a top side of the display page  53  (upper side of  FIG. 11 ), and the cancellation of the page-switching process may be assigned to a release operation at a touch position near a bottom side of the display page  53  (lower side of  FIG. 11 ). 
     Further, a difference in the lateral direction between the two touch positions and a difference in the vertical direction therebetween are calculated. Then, based on coordinates of the touch positions in the direction involving a larger difference, the interactions of the execution and cancellation of the page-switching process may be respectively assigned. For example, when the difference in the vertical direction is larger, the execution of the page-switching process is assigned to a lower touch position, and the cancellation of the page-switching process is assigned to an upper touch position. When the difference in the lateral direction is larger, the execution of the page-switching process is assigned to a right touch position, and the cancellation of the page-switching process is assigned to a left touch position. In this way, a positional relation between the two touch positions may be appropriately judged, and the execution and the cancellation of the page-switching process may be respectively assigned based on the positional relation. 
     With respect to the two touch positions, the execution of the page-switching process is assigned to a touch position near a position as a page-turning starting point (lower right corner of the display page  53  in this exemplary embodiment). With this, an intuitive operation based on operations with respect to a real book can be performed. 
     As described above, in the portable terminal  100  as the information processing apparatus according to this exemplary embodiment, the page-switching operation region  60 , which is an invisible region for the page-switching operation, is provided on the display screen  3 . Based on the touch operation with respect to the page-switching operation region  60 , the scrolling image  70  which is a partially replaced image is generated. With this, the user  30  can view a part of the page  65  or  69  as a destination within the scrolling image  70  for search for a target page, and switch the page displayed on the display screen  3  to the searched target page. As a result, without using dedicated hardware devices or GUI components for switching pages, the page-searching operation and the page-switching operation can be performed with high operability. 
     Further, in this exemplary embodiment, the page-switching operation region  60  and the page-zooming operation region  61  are set in the display screen  3 . Such region partitioning enables a zooming-reducing process of the display page  53  and the page-switching process of the display page  53  to be executed also by the pinch-in operation and the pinch-out operation. With this, the user  30  can intuitively execute the page-switching process not by a special operation method but by a familiar operation method. 
     2. Second Exemplary Embodiment 
     A description is made on an information processing apparatus according to a second exemplary embodiment by way of an example of a portable terminal. In the description below, description on structures and operations that are the same as those of the portable terminal  100  described in the first exemplary embodiment is omitted or simplified. 
       FIG. 13  is a schematic view of a display screen  203  of a portable terminal  200  according to this exemplary embodiment. In this exemplary embodiment, page-switching operation regions  260   a  and  260   b  are set respectively on an edge side and an inner-margin side of the display screen  203 . The page-switching operation region  260   a  set on the edge side is similar to the page-switching operation region  60  described in the first exemplary embodiment. 
     The page-switching operation region  260   b  set on the inner-margin side is used for a page-switching operation in a reverse direction. That is, the page-switching operation region  260   b  is used for searching for a page previous to a display page  253  being displayed, and switching to the previous page. 
       FIG. 14  is an explanatory view of an operation of a page-switching process in the reverse direction. As illustrated in  FIG. 14 , the multi-touch operation is performed with respect to the page-switching operation region  260   b  set on the inner-margin side. Then, such a moving image that one previous page  272  is turned from a left side of the display page  253  onto the display page  253  is displayed. As a result, a scrolling image  270  in which a part  253   a  of the display page  253  is replaced with a part  272   a  of the previous page  272  is displayed. In this exemplary embodiment, the previous page  272  is turned over to an intermediate position  264  between two touch positions  262  and  263 . 
     The part  272   a  of the previous page  272  in the scrolling image  270  corresponds to a preview image  273 , and the user  30  can view the preview image  273  for search for a target page. 
     Based on a variation in a distance between the two touch positions  262  and  263 , a page-scroll amount is updated, and the preview image  273  is updated in accordance therewith. Further, a size of the preview image  273  is changed by the twin-drag operation. 
     As described above, in the portable terminal  200  in this exemplary embodiment, by the touch operation performed with respect to the page-switching operation region  260   a  on the edge side, a page-scrolling operation can be performed in a forward direction. Further, by the touch operation performed with respect to the page-switching operation region  260   b  on the inner-margin side, a page-scrolling operation in the reverse direction can be performed. Thus, the page-searching process and the page-switching process can be performed with respect to all the pages in an electronic book. 
     3. Third Exemplary Embodiment 
       FIG. 15  is a schematic view of a display screen  303  of a portable terminal  300  as an information processing apparatus according to a third exemplary embodiment. In the portable terminal  300  according to this exemplary embodiment, a page-switching operation region  360  set on an edge side of the display screen  303  is further partitioned into two regions  360   a  and  360   b . In other words, the regions  360   a  and  360   b  partition the page-switching operation region  360  into two regions (that is, sub-portions) in a vertical direction of the display screen  303 . 
     When a multi-touch operation is performed with respect to the region  360   a  as a lower half region of the page-switching operation region  360 , as described in the first exemplary embodiment, such a moving image is displayed that a part of a display page  353  is turned from a lower right corner O of the display page  353 , and a preview image is displayed. 
     When a multi-touch operation is performed with respect to the region  360   b  as an upper half region of the page-switching operation region  360 , as illustrated in  FIG. 15 , such a moving image that another part  353   a  of the display page  353  is turned from an upper right corner P of the display page  353  is displayed. Then, a preview image  374  of a destination page is displayed. 
     In this way, the display page is turned from both the lower side and the upper side of the display page  353 , and the preview image of the destination page is displayed. With this, a target page can be searched for on both the lower side and the upper side of the page, and hence the user  30  can intuitively execute the page-searching operation and the page-switching operation with high operability. 
     Note that, when the upper side of the display page  353  is turned as illustrated in  FIG. 15 , of two touch positions  362  and  363 , a release operation at a touch position near the upper right corner P of the display page  353  may be assigned with an execution process of the page-switching operation. 
     4. Other Exemplary Embodiments 
     However, exemplary embodiments of the present disclosure are not limited to those described above. Other various exemplary embodiments may be carried out. 
     In the above-mentioned first exemplary embodiment, the judgment is made in ST 104  shown in  FIG. 5  as to whether or not the pinch-in operation has been detected. Then, in the case where the pinch-in operation has been detected, the page-scroll amount is updated, and then the preview image is updated. In the first exemplary embodiment, the page-scrolling operation is performed in a forward direction from a display page to a page subsequent thereto. 
     However, a judgment may be made in ST 104  as to whether or not the pinch-in operation and the pinch-out operation have been detected. In a case where the pinch-out operation by the user has been detected, the page-scrolling operation is performed in the reverse direction from the display page to a previous page. It suffices that the image similar to the scrolling image  270  illustrated in  FIG. 14  is used as the scrolling image for the page scrolling in the reverse direction. In this way, such a setting may be made that both the page-scrolling operation in the forward direction and the page-scrolling operation in the reverse direction can be performed. 
       FIG. 16  are schematic views of a display screen  403  of a portable terminal  400  as an information processing apparatus according to another exemplary embodiment. In the portable terminal  400 , a page  453  corresponding to two pages is displayed on the display screen  403  in a two-page spread manner.  FIG. 16  illustrate a left-bound and leftward-open electronic book  450 . 
     As illustrated in  FIG. 16 , page-switching operation regions  460   a  and  460   b  are set respectively on edge sides at both ends of the display page  453  displayed in a two-page spread manner. In addition, a page-zooming operation region  461  is set on an inner-margin side of the display page  453  positioned between the two page-switching operation regions  460   a  and  460   b.    
     As illustrated in  FIG. 16A , when a touch operation is performed with respect to the page-switching operation region  460   a  set at the right end portion of the display page  453 , the page-switching operation is performed in the forward direction. As illustrated in  FIG. 16B , when a touch operation is performed with respect to the page-switching operation region  460   b  set at the left end portion of the display page  453 , the page-operation is performed in the reverse direction. 
     In ST 105  shown in  FIG. 5 , the page-scroll amount is updated based on the variation in the distance between the two touch positions. At this time, the moving speed of each of the touch positions may be reflected on a determination of the page-scroll amount. For example, even when the distance between the touch positions is maintained, the page-scroll amount may be set to be large in a case where the moving speeds are high. With this, for example, the user can appropriately set the page-scroll amount by controlling such a speed as to bring two fingers close to each other. 
     In the above-mentioned case, as illustrated in  FIG. 3 , the bound portion  54  is displayed on the root side of the page image  51 , and the edge portion  55  is displayed on the leading end side of the page image  51 . The edge portion  55  does not need to be displayed so that the content data  52  is displayed across the lateral direction of the display screen  3 . Also in this case, it suffices that the page-switching operation region  60  is set on the right side (edge side) on the display screen  3 . 
     In ST 101  and ST 102  shown in  FIG. 5 , when the multi-touch operation with respect to the page-switching operation region is detected, the partially replaced image is displayed and the next page is previewed. However, the distance between the two touch positions may be calculated, and a page which is distant from a display page by an amount corresponding to the calculated distance may be previewed. When the two touch positions are brought close to each other, pages between the previewed page and the display page may be sequentially previewed. 
     In the above-mentioned case, the pinch-in operation, the pinch-out operation, and the twin-drag operation are performed as the touch operation with respect to the page-switching operation region. However, those touch operations are mere examples, and other various touch operations may be performed. Further, there may be employed a touch operation with one operator or a multi-touch operation with three or more operators. For example, the scrolling image may be displayed by tapping the page-switching operation region with the one operator. Then, in accordance with a drag operation with the one operator, the page-scroll amount and the preview image may be updated. 
     In the above-mentioned case, such a moving image that parts of a page image and a display image which express a shape of a page are turned is displayed as 3D animation images that use multiple polygons. However, for example, 2D animation images using an affine transformation or the like may also be displayed. 
     In the above-mentioned case, a touch panel is used as the input unit. However, for example, the touch operations by the user may be input via a touch pad provided separately from the display screen. 
     Even when the content data of the display page is displayed, the page-searching process and the page-switching process can be executed by the touch operations with respect to the page-switching operation region described above. Further, zoomed content data may be displayed as a preview image. 
     In the above-mentioned case, in order to perform an intuitive page-switching operation, the page-switching operation region is set on the edge side of the display page. However, the page-switching operation region may be set at other positions on the display screen. 
     The present disclosure contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2010-224770 filed in the Japan Patent Office on Oct. 4, 2010, the entire content of which is 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.