Patent Publication Number: US-2020301645-A1

Title: Display apparatus and display method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2019-052008 filed on Mar. 19, 2019 in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein. 
     BACKGROUND 
     Technical Section 
     The present invention relates to a display apparatus and a display method. 
     Description of the Related Art 
     There is a display apparatus such as an electronic whiteboard implemented as a flat panel display equipped with a touch panel. With the touch panel, the display apparatus detects the coordinates of a position on a display surface of the display contacted by a pointer such as an electronic pen or a user&#39;s finger, and renders a trajectory of the coordinates on a screen of the display as a handwritten input. Thereby, a user is able to use the screen of the display as a whiteboard. 
     The display apparatus may be connected to a personal computer (PC) to display the screen image of the PC on the display and render the handwritten input as superimposed on the screen image. 
     The display apparatus may further display, on the display surface of the display, instruction receiving sections with descriptions such as “CUT OUT,” “READ DOCUMENT,” and “EXIT” to receive user instructions. 
     SUMMARY 
     In one embodiment of this invention, there is provided an improved display apparatus that includes, for example, a display with a display surface, at least two data input devices, and circuitry. The circuitry detects, from the at least two data input devices, a data input device to which data is input, generates an instruction receiving image including an instruction receiving section to receive an instruction from a user, and displays the instruction receiving image on the display surface. The instruction receiving section is arranged at a position according to a result of the detection. 
     In one embodiment of this invention, there is provided an improved display method executed by a display apparatus including a display with a display surface and at least two data input devices. The display method includes, for example, detecting, from the at least two data input devices, a data input device to which data is input, generating an instruction receiving image including an instruction receiving section to receive an instruction from a user, and displaying the instruction receiving image on the display surface. The instruction receiving section is arranged at a position according to a result of the detecting. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       A more complete appreciation of the disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein: 
         FIG. 1  is a diagram illustrating exemplary general arrangement of a display system according to an embodiment of the present invention; 
         FIG. 2  is a block diagram illustrating an exemplary hardware configuration of an electronic whiteboard in the display system of the embodiment; 
         FIG. 3  is a block diagram illustrating an exemplary functional configuration of the electronic whiteboard of the embodiment; 
         FIG. 4  is a diagram illustrating an exemplary configuration of images superimposed by the electronic whiteboard; 
         FIGS. 5A and 5B  are diagrams each illustrating an exemplary table referred to by a user interface (UI) image generating unit of the electronic whiteboard to generate a UI image,  FIG. 5A  illustrating a table with identification information without a priority order, and  FIG. 5B  illustrating a table with the identification information with a priority order; 
         FIG. 6  is a conceptual diagram illustrating page data stored in the electronic whiteboard; 
         FIG. 7  is a conceptual diagram illustrating stroke sequence data included in the page data; 
         FIG. 8  is a conceptual diagram illustrating coordinate sequence data included in the stroke sequence data; 
         FIG. 9  is a conceptual diagram illustrating media data included in the page data; 
         FIG. 10  is a conceptual diagram illustrating watermark image data stored in the electronic whiteboard; 
         FIG. 11  is a block diagram illustrating an exemplary functional configuration of a file processing unit of the electronic whiteboard; 
         FIG. 12  is a block diagram illustrating an exemplary functional configuration of a server unit and a client unit of the electronic whiteboard; 
         FIG. 13  is a conceptual diagram illustrating operation data stored in the electronic whiteboard; 
         FIGS. 14 and 15  are sequence diagrams illustrating exemplary processes of electronic whiteboards in the display system; 
         FIG. 16  is a flowchart illustrating an exemplary process in which an electronic whiteboard of the display system receives data input from an external apparatus and displays the UI image on a display surface of the electronic whiteboard; 
         FIG. 17  is a diagram illustrating an example of a superimposed image displayed when an external apparatus is connected to the right side of the electronic whiteboard; 
         FIG. 18  is a diagram illustrating an example of a superimposed image displayed when an output image is stored in the electronic whiteboard as a still image; 
         FIGS. 19 and 20  are diagrams illustrating exemplary operations of an electronic whiteboard according to another embodiment of the present invention; and 
         FIGS. 21A and 21B  are diagrams illustrating exemplary operations of an electronic whiteboard according to still another embodiment of the present invention,  FIG. 21A  illustrating the electronic whiteboard displaying UIs, and  FIG. 21B  illustrating the electronic whiteboard not displaying the UIs. 
     
    
    
     The accompanying drawings are intended to depict embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. 
     DETAILED DESCRIPTION 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. In the drawings illustrating embodiments of the present invention, members or components having the same function or shape will be denoted with the same reference numerals to avoid redundant description. 
     In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result. 
     A typical display apparatus such as an electronic whiteboard displays instruction receiving sections on the right side thereof, as viewed from a position facing the electronic whiteboard. Therefore, when a user stands by the left side of the display apparatus, as viewed from the position facing the electronic whiteboard, and inputs instructions to the display apparatus by touching the instruction receiving sections, for example, it may be inconvenient for the user to perform the instruction input operation owing to the distance from the user standing by the left side of the display apparatus to the instruction receiving sections displayed on the right side of the display apparatus. 
     There is a display apparatus allowing the user to change the display position of the instruction receiving sections by changing user settings. Such a display apparatus, however, causes the user extra work of changing the settings. Further, the user may be unaware of how to change the display position of the instruction receiving sections. 
     At least one of embodiments of the present invention provides a display apparatus facilitating a user to perform the instruction input operation. 
     Herein, a display apparatus refers to an apparatus that displays an image. An electronic whiteboard is an example of the display apparatus. In the following description of the embodiments, the term “electronic whiteboard” will be used to describe the display apparatus. 
     A display surface refers to a surface of an image display device, such as a display, on which an image is displayed. 
     A data input device refers to a device that inputs data to the electronic whiteboard from an external apparatus. In the embodiments, the data input device is disposed on each of two opposing sides of the display surface of the electronic whiteboard. 
     A user interface (UI) is an example of an instruction receiving section that receives an instruction from a user to the electronic whiteboard. 
     An external apparatus refers to an apparatus located outside of the electronic whiteboard and connectable to the electronic whiteboard via a cable, a network, or the data input device. Examples of the external apparatus include a laptop personal computer (PC), an apparatus or device equivalent thereto, and a portable storage medium. 
     Identification information refers to information assigned to each of a plurality of data input devices, such as a universal serial bus (USB) port, a wired port, and an antenna, to identify the data input device. The identification information of the data input device is distinguished from the identification (ID) of infrared ray output to a sensor controller by a contact sensor. The ID of the infrared ray will be simply referred to as the ID. 
     The following description of the embodiments will be given of a display system including electronic whiteboards, as an example. 
     A configuration of a display system according to an embodiment of the present invention will be described. 
       FIG. 1  is a diagram illustrating an exemplary configuration of a display system  1  according to an embodiment of the present invention. For simplification of illustration,  FIG. 1  simply illustrates two electronic whiteboards  2   a  and  2   b  and accompanying electronic pens  4   a  and  4   b . The display system  1 , however, may include three or more electronic whiteboards and three or more electronic pens. 
     As illustrated in  FIG. 1 , the display system  1  includes the electronic whiteboards  2   a  and  2   b , the electronic pens  4   a  and  4   b , USB memories  5   a  and  5   b , laptop PCs  6   a  and  6   b , television (video) conference terminals (hereinafter simply referred to the television conference terminals)  7   a  and  7   b , and a PC  8 . The electronic whiteboards  2   a  and  2   b  and the PC  8  are communicably connected to each other via a communication network  9 . The electronic whiteboards  2   a  and  2   b  are equipped with displays  3   a  and  3   b , respectively. The displays  3   a  and  3   b  include display surfaces  301   a  and  301   b , respectively. 
     The electronic whiteboard  2   a  displays, on the display  3   a , an image rendered based on an event caused by the electronic pen  4   a  (e.g., a touch of a tip or end of the electronic pen  4   a  on the display  3   a ). The electronic whiteboard  2   a  further changes the image displayed on the display surface  301   a  of the display  3   a  based on an event caused by the electronic pen  4   a  or a user&#39;s hand Ha, for example (e.g., a gesture such as scaling-up, scaling-down, or page-turning). The electronic pen  4   a  and the user&#39;s hand Ha are examples of a pointer. 
     Each of two opposing sides of the electronic whiteboard  2   a  is equipped with at least one USB port connectable with the USB memory  5   a . The electronic whiteboard  2   a  records or reads an electronic file (hereinafter simply referred to as file), such as a portable document format (PDF) file, to and from the USB memory  5   a.    
     The electronic whiteboard  2   a  further includes a wired data input device that performs communication in conformity with a standard such as DisplayPort (registered trademark), digital visual interface (DVI), high-definition multimedia interface (HDMI, registered trademark), or video graphics array (VGA). The wired data input device is disposed on one side or two opposing sides of the electronic whiteboard  2   a . In  FIG. 1 , the laptop PC  6   a  is connected to the wired data input device via a cable  10   a   1 . 
     Herein, two opposing sides of the electronic whiteboard  2   a  correspond to the right and left sides in the horizontal direction of the electronic whiteboard  2   a . Further, one side of the electronic whiteboard  2   a  corresponds to one side in the horizontal direction of the electronic whiteboard  2   a . The display surface  301   a  is positioned at the center in the horizontal direction of the electronic whiteboard  2   a . Therefore, two opposing sides of the electronic whiteboard  2   a  are an example of two opposing sides of the display surface  301   a , and one side of the electronic whiteboard  2   a  is an example of one side of the display surface  301   a.    
     In response to an event on the display  3   a  such as contact thereon, the electronic whiteboard  2   a  transmits event information of the event to the laptop PC  6   a  similarly as in response to an event on an input device such as a mouse or keyboard. 
     The electronic whiteboard  2   a  is connected to the television conference terminal  7   a  via a cable  10   a   2  that enables communication conforming to the above-described standard. The electronic whiteboard  2   a  also includes a wireless data input device that performs wireless communication in conformity with a wireless communication protocol such as the infrared or Bluetooth (registered trademark) protocol. The wireless data input device is disposed on each of two opposing sides of the electronic whiteboard  2   a  or on one side of the electronic whiteboard  2   a  not equipped with the wired data input device. The electronic whiteboard  2   a  is thereby capable of wirelessly communicating with the laptop PC  6   a.    
     At a site different from a site of the electronic whiteboard  2   a , the electronic whiteboard  2   b  with the display  3   b , the electronic pen  4   b , the USB memory  5   b , the laptop PC  6   b , the television conference terminal  7   b , and cables  10   b   1  and  10   b   2  are used similarly as described above. The electronic whiteboard  2   b  also changes the image displayed on the display  3   b  based on an event caused by a user&#39;s hand Hb, for example. 
     With the above-described configuration, the image rendered on the display  3   a  of the electronic whiteboard  2   a  at one site is also displayed on the display  3   b  of the electronic whiteboard  2   b  at another site. Similarly, the image rendered on the display  3   b  of the electronic whiteboard  2   b  at the another site is also displayed on the display  3   a  of the electronic whiteboard  2   a  at the one site. The display system  1  thus enables a remote sharing process of sharing the same image between multiple remote sites, and therefore is convenient for use in a conference or meeting between remote sites, for example. 
     Hereinafter, a given one of the electronic whiteboards  2   a  and  2   b  will be described as the electronic whiteboard  2 , and a given one of the displays  3   a  and  3   b  will be described as the display  3 . Further, a given one of the electronic pens  4   a  and  4   b  will be described as the electronic pen  4 , and a given one of the USB memories  5   a  and  5   b  will be described as the USB memory  5 . Similarly, a given one of the laptop PCs  6   a  and  6   b  will be described as the laptop PC  6 , and a given one of the television conference terminals  7   a  and  7   b  will be described as the television conference terminal  7 . Further, a given one of the user&#39;s hands Ha and Hb will be described as the user&#39;s hand H, and a given one of the cables  10   a   1 ,  10   a   2 ,  10   b   1 , and  10   b   2  will be described as the cable  10 . 
     The following description of the embodiment will be given of the electronic whiteboard  2  as an example of the display apparatus, but the display apparatus is not limited thereto. Other examples of the display apparatus include digital signage, a telestrator for use in sport news or weather forecast presentation, for example, and remote image (video) diagnostic equipment. Further, the following description will also be given of the laptop PC  6  as an example of the external apparatus. The external apparatus, however, is not limited thereto. Other examples of the external apparatus include apparatuses capable of supplying image frames, such as a desktop PC, a tablet PC, a personal digital assistant (PDA), a smartphone, a digital video camera, a digital camera, and a game console. Further, the communication network  9  includes the Internet, a local area network (LAN), and a mobile phone communication network, for example. The following description of the embodiment will further be given of the USB memory  5  as an example of a recording medium. The recording medium, however, is not limited thereto. Other examples of the recording medium include various recording media such as a secure digital (SD) card. 
     A hardware configuration of the electronic whiteboard  2  of the embodiment will be described. 
       FIG. 2  is a block diagram illustrating an exemplary hardware configuration of the electronic whiteboard  2  of the embodiment. As illustrated in  FIG. 2 , the electronic whiteboard  2  includes a central processing unit (CPU)  101 , a read only memory (ROM)  102 , a random access memory (RAM)  103 , a solid state drive (SSD)  104 , a network controller  105 , and an external memory controller  106 . 
     The CPU  101  controls an overall operation of the electronic whiteboard  2 . The ROM  102  stores a program used to drive the CPU  101  such as an initial program loader (IPL). The RAM  103  is used as a work area for the CPU  101 . The SSD  104  stores various data of a program for the electronic whiteboard  2 , for example. The network controller  105  controls communication with the communication network  9 . The external memory controller  106  controls communication with the USB memory  5  via a USB port  51 . 
     The electronic whiteboard  2  further includes a capture device  111 , a graphics processing unit (GPU)  112 , a display controller  113 , wired ports  117   a  and  117   b , a near field communication circuit  118 , and an antenna  119  for the near field communication circuit  118 . 
     The capture device  111  inputs image information from the external apparatus such as the laptop PC  6  as a still or video image. The GPU  112  is a device dedicated to processing of graphics. The display controller  113  controls and manages screen display to output an image from the GPU  112  to the display  3 , for example. The image information input from the external apparatus by the capture device  111  is displayed on the display  3  of the electronic whiteboard  2  via the GPU  112  and the display controller  113 . 
     The wired ports  117   a  and  117   b  conform to a standard such as DisplayPort, DVI, HDMI, or VGA, as described above. The image information from the PC  6  is input to the capture device  111  via the wired port  117   a , and image information from the television conference terminal  7  is input to the capture device  111  via the wired port  117   b . The near field communication circuit  118  is a communication circuit conforming to a standard such as near field communication (NFC) or Bluetooth. The image information from the laptop PC  6  or the television conference terminal  7  may be input to the electronic whiteboard  2  through wireless communication via the antenna  119  and the near field communication circuit  118 . 
     Herein, the USB port  51 , the wired ports  117   a  and  117   b , and the antenna  119  are examples of the data input device. In the present embodiment, the USB port  51  and the antenna  119  are disposed on the left side (i.e., the left side in  FIG. 2 ) of the electronic whiteboard  2 , and the wired ports  117   a  and  117   b  are disposed on the right side (i.e., the right side in  FIG. 2 ) of the electronic whiteboard  2 . 
       FIG. 2  illustrates an example in which the electronic whiteboard  2  includes one USB port  51 , two wired ports  117   a  and  117   b , and one antenna  119 . However, the respective numbers of these data input devices are not limited thereto. The electronic whiteboard  2  may include one or more USB ports, one or more wired ports, and one or more antennas. 
     Further, the electronic whiteboard  2  may include one or more wired ports conforming to part or all of standards such as DisplayPort, DVI, HDMI, and VGA and one or more antennas conforming to part or all of standards such as NFC and Bluetooth. 
     The electronic whiteboard  2  further includes a sensor controller  114 , a contact sensor  115 , an electronic pen controller  116 , and a bus line  120 . 
     The sensor controller  114  controls the processing of the contact sensor  115  that detects the contact of the electronic pen  4  or the user&#39;s hand H, for example, on the display  3 . The contact sensor  115  performs input and detection of coordinates in accordance with an infrared ray blocking method. According to this method of inputting and detecting coordinates, two light emitting and receiving devices disposed on opposite end portions on the upper side of the display  3  emit rays of infrared light parallel to the display  3 , and receive the rays of infrared light reflected by reflecting members disposed around the display  3  and returning on the same optical paths as those of the rays of infrared light emitted by the light emitting and receiving devices. 
     The contact sensor  115  outputs, to the sensor controller  114 , the IDs of the rays of infrared light emitted from the two light emitting and receiving devices and blocked by an object. Then, the sensor controller  114  identifies a coordinate position corresponding to the contact position of the object on the display  3 . 
     The method employed by the contact sensor  115  is not limited to the infrared ray blocking method. The contact sensor  115  may include various detectors such as a capacitive touch panel that identifies the contact position by detecting a change in capacitance, a resistive touch panel that identifies the contact position based on a change in voltage of two facing resistance films, or an electromagnetic induction touch panel that identifies the contact position by detecting electromagnetic induction caused by the contact of an object on the display  3 . 
     The electronic pen controller  116  communicates with the electronic pen  4  to determine whether there is a touch of the tip or end of the electronic pen  4  on the display  3 . The electronic pen controller  116  may also determine whether there is a touch on the display  3  by a part of the electronic pen  4  other than the tip or end thereof, such as a part of the electronic pen  4  held by the user. 
     The bus line  120  includes buses such as an address bus and a data bus to electrically connect the CPU  101 , the ROM  102 , the RAM  103 , the SSD  104 , the network controller  105 , the external memory controller  106 , the capture device  111 , the GPU  112 , the sensor controller  114 , and the electronic pen controller  116 , as illustrated in  FIG. 2 . 
     The program for the electronic whiteboard  2  may be distributed as recorded on a computer-readable recording medium, such as a compact-disc (CD)-ROM. 
     A functional configuration of the electronic whiteboard  2  of the embodiment will be described with  FIGS. 3 to 12 . An overall functional configuration of the electronic whiteboard  2  will first be described with  FIG. 3 . 
       FIG. 3  is a block diagram illustrating an exemplary functional configuration of the electronic whiteboard  2  of the embodiment. The electronic whiteboard  2  includes functional units illustrated in  FIG. 3 , which are implemented by the hardware components and programs described above with  FIG. 2 . 
     The electronic whiteboard  2  may serve as a host apparatus that starts the remote sharing process or as a participant apparatus that, when the remote sharing process has already started, joins the remote sharing process. 
     The electronic whiteboard  2  includes two major units: a client unit  20  and a server unit  90 . The client unit  20  and the server unit  90  are functions implemented within a housing of one electronic whiteboard  2 . When the electronic whiteboard  2  serves as the host apparatus, the client unit  20  and the server unit  90  are implemented in the electronic whiteboard  2 . When the electronic whiteboard  2  serves as the participant apparatus, the client unit  20  is implemented in the electronic whiteboard  2 , but the server unit  90  is not implemented in the electronic whiteboard  2 . 
     For example, when the electronic whiteboard  2   a  and the electronic whiteboard  2   b  in  FIG. 1  serve as the host apparatus and the participant apparatus, respectively, the client unit of the electronic whiteboard  2   a  communicates with the client unit  20  of the electronic whiteboard  2   b  via the server unit  90  implemented in the electronic whiteboard  2   a . The client unit  20  of the electronic whiteboard  2   b , on the other hand, communicates with the client unit  20  of the electronic whiteboard  2   a  via the server unit  90  implemented in the electronic whiteboard  2   a.    
     A functional configuration of the client unit  20  will be described with  FIGS. 3 to 12 . 
     The client unit  20  includes an image acquiring unit  21 , a coordinate detecting unit  22 , an automatic adjustment unit  23 , a contact detecting unit  24 , an event sorting unit  25 , an operation processing unit  26 , a gesture processing unit  27 , an image superimposing unit  28 , an image processing unit  30 , and a communication control unit  60 . 
     The image acquiring unit  21  acquires an output image from an image output apparatus (e.g., the laptop PC  6 ) connected to the wired data input device or the wireless data input device of the electronic whiteboard  2 . The image acquiring unit  21  receives an image signal from the image output apparatus, analyses the image signal to derive image information therefrom, and outputs the image information to an image acquiring unit  31  of the image processing unit  30 . The image information includes the resolution of the image frame of the image displayed by the image output apparatus, i.e., the image formed by the image signal, and the frequency of updating the image frame. The image output apparatus is an example of the external apparatus, and is specifically a laptop PC, a smartphone, or a tablet PC, for example. 
     When acquiring the image from the image output apparatus by wire via the wired port  117   a  or  117   b , the image acquiring unit  21  directly acquires, as the image signal, the image of the screen displayed on a display of the image output apparatus. 
     When wirelessly acquiring the image from the image output apparatus via the antenna  119 , the image acquiring unit  21  directly acquires, as the image signal, the image of the screen displayed on the display of the image output apparatus, or may acquire a file, such as an image file, from a memory of the image output apparatus. 
     When acquiring a file, the image acquiring unit  21  may automatically acquire a predetermined type of file, such as a portable network graphics (PNG) file, from the image output apparatus wirelessly connected to the electronic whiteboard  2 , or may acquire therefrom a user-specified file. Further, the image acquiring unit  21  may acquire a file stored in a user-specified folder of a plurality of folders stored in the image output apparatus. 
     The coordinate detecting unit  22  detects the coordinate position at which an event caused on the display  3  by the user (e.g., action such as touching the display  3  with the user&#39;s hand H) has occurred. The coordinate detecting unit  22  also detects the dimensions of the touched area. 
     The automatic adjustment unit  23  is started at the start or restart of the electronic whiteboard  2  to adjust parameters for image processing such that the coordinate detecting unit  22  outputs appropriate values. In this image processing, the coordinate detecting unit  22 , which detects coordinates by using an optical sensor, processes the image of a sensor camera. 
     The contact detecting unit  24  detects the event caused by the user (e.g., action such as touching (pressing) the display  3  with the tip or end of the electronic pen  4 ). 
     The event sorting unit  25  sorts the coordinate positions of events detected by the coordinate detecting unit  22  and results of detection by the contact detecting unit  24  into events: stroke rendering, UI operation, and gesture operation. 
     Herein, the stroke rendering refers to an event in which the user presses the electronic pen  4  against the display  3 , moves the electronic pen  4  over the display  3  with the electronic pen  4  kept pressed thereon, and releases the electronic pen  4  from the display  3 , to thereby display a stroke image B in  FIG. 4  on the display  3 . 
     With the stroke rendering, a letter such as an alphabetic letter “S” or “T,” for example, is rendered on the display  3 . As well as the event of rendering an image, events such as deleting and editing a rendered image are also included in the stroke rendering. 
     The UI operation refers to an event in which, when a UI image A in  FIG. 4  is displayed on the display surface  301  of the display  3 , the user presses a predetermined position on the display surface  301  with the electronic pen  4  or the user&#39;s hand H. The UI operation corresponds to an instruction issued to the electronic whiteboard  2  by the user to operate the electronic whiteboard  2 . The UI operation is therefore an example of a user instruction. 
     The UI operation is performed to set parameters such as the color and width of the line rendered with the electronic pen  4 . The UI operation may also be performed to store the image displayed on the display  3  into the electronic whiteboard  2  as a still image, or to input the image of the external apparatus (e.g., the laptop PC  6 ) connected to the electronic whiteboard  2  into the electronic whiteboard  2 . 
     The gesture operation refers to an event in which, when the stroke image B in  FIG. 4  is displayed on the display  3 , the user touches the display  3  with the user&#39;s hand H or moves the user&#39;s hand H over the display  3 . With the gesture operation, such as moving the user&#39;s hand H while in contact with the display  3 , for example, the user is able to perform an operation such as scaling up or down an image, changing a display area, or switching pages, for example. 
     The operation processing unit  26  executes various operations in accordance with UI elements at which events are caused, starting with the operation determined as the UI operation by the event sorting unit  25 . The UI elements include buttons, lists, checkboxes, and textboxes, for example. The gesture processing unit  27  executes the operation determined as the gesture operation by the event sorting unit  25 . 
     The image superimposing unit  28  displays a superimposed image on a display unit  29  as an image. The superimposed image includes images superimposed by a display superimposing unit  36  of the image processing unit  30 . The display unit  29  is a display function implemented by the display  3 . The image superimposing unit  28  further superimposes, on the image from the image output apparatus (e.g., the laptop PC  6 ), the image from another image output apparatus (e.g., the television conference terminal  7 ) in the picture-in-picture format. The image superimposing unit  28  further switches between the image displayed in a part of the display unit  29  in the picture-in-picture format and the image displayed on the entire display unit  29 . 
     The image processing unit  30  executes processes such as a process of superimposing images as illustrated in  FIG. 4 . The image processing unit  30  includes an image acquiring unit  31 , a stroke processing unit  32 , a UI image generating unit  33 , a background generating unit  34 , a watermark image generating unit  38 , a layout managing unit  35 , a display superimposing unit  36 , a page processing unit  37 , a file processing unit  40 , a page data storing unit  300 , a remote license management table  310 , and an input detecting unit  33   a . These functional units except the input detecting unit  33   a  are implemented by the GPU  112  in  FIG. 2 , and the input detecting unit  33   a  is implemented by the CPU  101  in  FIG. 2 . 
     The image acquiring unit  31  acquires, as the image, each of frames of the image acquired by the image acquiring unit  21 , and outputs the data of the image to the page processing unit  37 . This image corresponds to an output image C in  FIG. 4  from the image output apparatus (e.g., the laptop PC  6 ). 
     Based on the event sorted as the stroke rendering by the event sorting unit  25 , the stroke processing unit  32  renders an image or deletes or edits a rendered image. The image generated based on the stroke rendering corresponds to the stroke image B in  FIG. 4 . The result of rendering, deletion, or editing of the image based on the stroke rendering is stored in an operation data storing unit  840  in  FIG. 12  as operation data. 
     From the USB port  51 , the wired port  117   a , the wired port  117   b , and the antenna  119  (i.e., an example of at least two data input devices), the input detecting unit  33   a  detects the data input device to which data is input. 
     The input detecting unit  33   a  detects connection of an external apparatus to at least one of the USB port  51 , the wired port  117   a , the wired port  117   b , and the antenna  119 , and detects the data input device to which data is input. 
     Further, the input detecting unit  33   a  previously associates the identification information assigned to each of the USB port  51 , the wired port  117   a , the wired port  117   b , and the antenna  119  with information representing the right side or the left side of the electronic whiteboard  2 , and outputs the identification information to the UI image generating unit  33  as a detection result. 
     The UI image generating unit  33  generates a UI image previously set in the electronic whiteboard  2 . The UI image is an example of an instruction receiving image, and corresponds to the UI image A in  FIG. 4 . In the example of  FIG. 4 , the UI image A includes UIs  620   a ,  620   b , and  620   c  for the user to perform the UI operation. Via the UIs  620   a ,  620   b , and  620   c , the electronic whiteboard  2  receives instructions from the user (i.e., UI operations). In the following description, the UIs  620   a ,  620   b , and  620   c  will be simply described as the UIs  620 . 
     Based on the identification information of the data input device detected by the input detecting unit  33   a , the UI image generating unit  33  generates the UI image A with the UIs  620  arranged on one side of the electronic whiteboard  2  connected to the external apparatus. More specifically, if the external apparatus is connected to the left side of the electronic whiteboard  2 , the UI image generating unit  33  generates the UI image A with the UIs  620  arranged therein to be displayed on the left side of the display surface  301 . If the external apparatus is connected to the right side of the electronic whiteboard  2 , the UI image generating unit  33  generates the UI image A with the UIs  620  arranged therein to be displayed on the right side of the display surface  301 . If a plurality of external apparatuses are connected to two opposing sides of the electronic whiteboard  2 , the UI image generating unit  33  generates the UI image A with the UIs  620  arranged therein to be displayed on two opposing sides of the display surface  301 . 
     Based on the identification information input from the input detecting unit  33   a , the UI image generating unit  33  acquires the image for forming the UI image with reference to a table, and generates the UI image with the acquired image. 
       FIGS. 5A and 5B  are diagrams each illustrating an exemplary table referred to by the UI image generating unit  33  to generate the UI image. In the tables of  FIGS. 5A and 5B , the identification information is included in the leftmost column, and description of the identification information is included in the second leftmost column. Further, the image for forming the UI image is included in the third leftmost column, and description of the UI image is included in the fourth leftmost column. As illustrated in  FIGS. 5A and 5B , the identification information and the UI image are associated with each other. The tables of  FIGS. 5A and 5B  are previously created and stored in a memory such as the SSD  104 . 
     Based on the identification information input from the input detecting unit  33   a , the UI image generating unit  33  acquires the image for forming the UI image with reference to the table of  FIG. 5A or 5B , to thereby generate the UI image. 
     In the present embodiment, when the input detecting unit  33   a  detects the input of data to a plurality of data input devices, the UI image may be generated in accordance with a predetermined priority order of the identification information. The table of  FIG. 5A  includes the identification information without the priority order, and the table of  FIG. 5B  includes the identification information with the priority order. 
     When using the table of  FIG. 5B  with the priority order in response to the detection of data input to a plurality of data input devices by the input detecting unit  33   a , the UI image generating unit  33  generates the UI image based on the identification information of the highest priority. 
     The background generating unit  34  receives, from the page processing unit  37 , media data included in page data read from the page data storing unit  300  by the page processing unit  37 . The background generating unit  34  outputs the received media data to the display superimposing unit  36 . The image based on the media data corresponds to a background image D illustrated in  FIG. 4 . The background image D has a pattern such as a plain pattern or a grid pattern. 
     The watermark image generating unit  38  outputs, to the display superimposing unit  36 , watermark image data stored in the page data storing unit  300  as a memory of the electronic whiteboard  2 . The watermark image data corresponds to a watermark image E illustrated in  FIG. 4 . The watermark image generating unit  38  processes the watermark image data stored in the page data storing unit  300  to adjust the resolution and the aspect ratio of the watermark image data to match those of the display  3 , for example. 
     Information of the transparency of the watermark image E may previously be included in the watermark image data, or may be set in the electronic whiteboard  2  by the user. In other words, the watermark image data of the watermark image E may include at least the information of the transparency of the watermark image E. 
     The layout managing unit  35  manages layout information representing the layout of the images output to the display superimposing unit  36  from the image acquiring unit  31 , the stroke processing unit  32 , the UI image generating unit  33  or the background generating unit  34 , and the watermark image generating unit  38 . 
     The layout managing unit  35  thereby transmits, to the display superimposing unit  36 , an instruction as to the respective positions of the output image C, the stroke image B, and the watermark image E in the UI image A or the background image D, at which the output image C, the stroke image B, and the watermark image E should be displayed or should not be displayed. 
     Based on the layout information output from the layout managing unit  35 , the display superimposing unit  36  lays out (i.e., superimposes) the respective images output from the image acquiring unit  31 , the stroke processing unit  32 , the UI image generating unit  33  or the background generating unit  34 , and the watermark image generating unit  38 . 
     The page processing unit  37  stores the data of the stroke image B and the data of the output image C in the page data storing unit  300  as one page data item. The data of the stroke image B forms a part of the page data item as stroke sequence data (i.e., stroke data items) represented by a stroke sequence data ID illustrated in  FIG. 6 . The data of the output image C forms a part of the page data item as media data represented by a media data ID illustrated in  FIG. 6 . When the media data stored in the page data storing unit  300  is read therefrom, the read media data is handled as the data of the background image D. 
     Further, the page processing unit  37  may transmit the media data of the page data stored in the page data storing unit  300  to the display superimposing unit  36  via the background generating unit  34  such that the image superimposing unit  28  redisplays the background image D on the display  3 . Further, the page processing unit  37  may transmit the stroke sequence data (i.e., stroke data items) of the page data back to the stroke processing unit  32  such that the stroke processing unit  32  reedits the stroke. The page processing unit  37  may also delete or duplicate the page data. 
     That is, when the page processing unit  37  stores the page data in the page data storing unit  300 , the data of the output image C displayed on the display  3  is stored in the page data storing unit  300 . Then, when the page processing unit  37  reads the thus-stored data of the output image C from the page data storing unit  300 , the data of the output image C is read as the media data representing the background image D. 
     The page processing unit  37  further outputs the stroke sequence data representing the stroke image B to the stroke processing unit  32 . The stroke sequence data is included in the page data read from the page data storing unit  300 . The page processing unit  37  also outputs the media data representing the background image D to the background generating unit  34 . The media data is included in the page data read from the page data storing unit  300 . 
     The page processing unit  37  further transmits the watermark image data stored in the page data storing unit  300  to the watermark image generating unit  38 . The watermark image generating unit  38  transmits the watermark image E to the display superimposing unit  36 . 
     The display superimposing unit  36  superimposes the output image C from the image acquiring unit  31 , the stroke image B from the stroke processing unit  32 , the UI image A from the UI image generating unit  33 , the background image D from the background generating unit  34 , and the watermark image E from the watermark image generating unit  38  in accordance with the layout specified by the layout managing unit  35 . Thereby, the UI image A, the stroke image B, the watermark image E, the output image C, and the background image D are superimposed upon each other in the order making each of the superimposed images viewable to a user U, as illustrated in  FIG. 4 . 
     The display superimposing unit  36  may superimpose one of the output image C and the background image D in  FIG. 4  on the UI image A, the stroke image B, and the watermark image E by switching between the output image C and the background image D, i.e., by setting an exclusive relationship between the output image C and the background image D. For example, when the cable  10  connecting the electronic whiteboard  2  and the image output apparatus (e.g., the laptop PC  6 ) is unplugged when the UI image A, the stroke image B, and the output image C are displayed, the display superimposing unit  36  may remove the output image C from the superimposed images, and may display the background image D in accordance with the layout specified by the layout managing unit  35 . In this case, the layout managing unit  35  switches the watermark image E from a non-display state to a display state. The display superimposing unit  36  also executes processes such as scaling up the displayed image, scaling down the displayed image, and moving the display area. 
     The page data storing unit  300  stores page data as illustrated in  FIG. 6 .  FIG. 6  is a conceptual diagram illustrates the page data. The page data is one page of data displayed on the display  3 , i.e., the stroke sequence data (i.e., stroke data items) and the media data. Since the page data includes various parameters, the contents of the page data will be described as divided into parts illustrated in  FIGS. 6 to 9 . 
     As illustrated in  FIG. 6 , a page data ID, a start time, an end time, a stroke sequence data ID, and a media data ID are stored in the page data in association with each other. The page data ID is used to identify a given page. The start time represents the time at which the page starts to be displayed. The end time represents the time at which rewriting of the contents of the page based on an action such as a stroke or gesture is stopped. The stroke sequence data ID is used to identify the stroke sequence data generated based on the stroke with the electronic pen  4  or the user&#39;s hand H. The media data ID is used to identify the media data. The stroke sequence data is data for displaying the stroke image B in  FIG. 4  on the display  3 . The media data is data for displaying the background image D in  FIG. 4  on the display  3 . 
     According to the above-described page data, when the user writes the alphabetic letter “S” with the electronic pen  4 , for example, the letter “S” is normally written in one stroke and thus is represented by one stroke data ID. When user writes the alphabetic letter “T” with the electronic pen  4 , on the other hand, the letter “T” is normally written in two strokes and thus is represented by two stroke data IDs. 
     The stroke sequence data includes detailed information as illustrated in  FIG. 7 .  FIG. 7  is a conceptual diagram illustrating the stroke sequence data. As illustrated in  FIG. 7 , each stroke sequence data item is represented by a plurality of stroke data items. Further, each of the stroke data items includes a stroke data ID, a start time, an end time, the color of the stroke, the width of the stroke, and a coordinate sequence data ID. The stroke data ID is used to identify the stroke data item. The start time represents the time at which a stroke starts to be written. The end time represents the time at which the writing of the stroke ends. The coordinate sequence data ID is used to identify coordinate sequence data representing a sequence of waypoints passed by the stroke. 
     The coordinate sequence data includes detailed information as illustrated in  FIG. 8 .  FIG. 8  is a conceptual diagram illustrating the coordinate sequence data. As illustrated in  FIG. 8 , the coordinate sequence data includes information items: the X coordinate value and the Y coordinate value representing a point on the display  3 , the time difference (milliseconds) between the start time of the stroke and the time at which the point is passed by the stroke, and the writing pressure of the electronic pen  4  at the point. That is, a collection of points illustrated in  FIG. 8  represents one coordinate sequence data item illustrated in  FIG. 7 . When the user writes the alphabetic letter “S” in one stroke with the electronic pen  4 , for example, the stroke passes a plurality of waypoints until the user finishes writing the letter “S.” The coordinate sequence data item represents information of the plurality of waypoints. 
     The media data included in the page data illustrated in  FIG. 6  includes detailed information as illustrated in  FIG. 9 .  FIG. 9  is a conceptual diagram illustrating the media data. As illustrated in  FIG. 9 , the media data includes information items: media data ID, data type, recording time, X coordinate value, Y coordinate value, width, height, and data, which are associated with each other. The media data ID is the same as that in the page data illustrated in  FIG. 6 . The data type represents the type of the media data. The recording time represents the time at which the page data is recorded in the page data storing unit  300  by the page processing unit  37 . The X coordinate value and the Y coordinate value represent the position of the image displayed on the display  3  based on the page data. The width and the height represent the size of the image. The data represents the contents of the media data. When the coordinates of the upper-left corner of the display  3  are expressed as (X coordinate value, Y coordinate value)=(0, 0), the position of the image displayed on the display  3  based on the page data corresponds to the position of the upper-left corner of the image displayed on the display  3  based on the page data. 
     Referring back to  FIG. 3 , the page data storing unit  300  stores the watermark image data, which includes information as illustrated in  FIG. 10 .  FIG. 10  is a conceptual diagram illustrating the watermark image data stored in the page data storing unit  300 . As illustrated in  FIG. 10 , the watermark image data is stored as a file in association with information items: file name, update time, type, and creator. These information items are attributes of a file held by an information processing apparatus. Other possible attributes of a file may also be registered as the watermark image data. 
     Although three files are registered as the watermark image data in  FIG. 10 , one or more files may be registered as the watermark image data. Further, no file may be registered as the watermark image data. In this case, the watermark image is not displayed. If a plurality of files are registered as the watermark image data, one of the plurality of files is selected as appropriate for use. For example, the file of the watermark image data displayed most recently, selected by the user, updated most or least recently, or created by a logged-in user of the electronic whiteboard  2  is selected for use. 
     The type of the file is transmission PNG (hereinafter simply referred to as PNG) capable of handling the transparency, but may be any file type capable of expressing the transparency such as transmission graphics interchange format (GIF). If the file does not have a function of holding transparency information, the watermark image generating unit  38  may generate a transparency-controlled watermark image from a file such as a joint photographic experts group (JPEG) file. 
     The remote license management table  310  will now be described. 
     The remote license management table  310  manages license information for executing the remote sharing process. In the remote license management table  310 , a product ID of the electronic whiteboard  2 , a license ID for use in authentication, and an expiration period of the license are managed in association with each other as the license information. 
     A functional configuration of the file processing unit  40  illustrated in  FIG. 3  will be described with  FIG. 11 . 
       FIG. 11  is a block diagram illustrating an exemplary functional configuration of the file processing unit  40  of the embodiment. The file processing unit  40  includes a recovery unit  41 , a file input unit  42   a , a file output unit  42   b , a file converting unit  43 , a file transmitting unit  44 , an address book input unit  45 , a backup unit  46 , a backup output unit  47 , a setting managing unit  48 , a setting file input unit  49   a , and a setting file output unit  49   b.    
     The file processing unit  40  further includes an address book management table  410 , a backup data storing unit  420 , a setting file storing unit  430 , and a connection destination management table  440 . 
     In the event of abnormal termination of the electronic whiteboard  2 , the recovery unit  41  detects the abnormal termination and recovers unsaved page data. For example, when the electronic whiteboard  2  is normally terminated, the page data is recorded on the USB memory as a PDF file via the file processing unit  40 . In the event of abnormal termination of the electronic whiteboard  2  due to a power failure, for example, the page data recorded in the page data storing unit  300  remains therein without being read therefrom. When the electronic whiteboard  2  is powered on again, therefore, the recovery unit  41  reads the page data from the page data storing unit  300  to recover the page data. 
     The file input unit  42   a  reads a PDF file from the USB memory  5 , and stores each page of the PDF file in the page data storing unit  300  as the page data. The file converting unit  43  converts the page data stored in the page data storing unit  300  into a file in the PDF format. 
     The file input unit  42   a  further acquires image data such as the watermark image data, and stores the image data in the page data storing unit  300 . The file input unit  42   a  may automatically acquire a predetermined type of file, such as a PNG file, from the USB memory connected to the electronic whiteboard  2 , or may acquire a user-specified file from the UBS memory  5  and copy the acquired file in the page data storing unit  300 . Further, the file input unit  42   a  may acquire a file from a user-specified folder of a plurality of folders stored in the UBS memory  5  and copy the acquired file in the page data storing unit  300 . 
     Further, the user may communicate with the electronic whiteboard  2  by operating a given terminal and input the watermark image data to the electronic whiteboard  2  by uploading the watermark image data via a world wide web (Web) page provided by the electronic whiteboard  2 . In this case, the file input unit  42   a  serves as a Web server. The given terminal specifies the internet protocol (IP) address of the electronic whiteboard  2  via a browser, for example, and receives from the electronic whiteboard  2  hypertext markup language (HTML) data, which is transmittable as a file. The browser receives the selection of a file by the user, and the given terminal transmits the file of the watermark image data selected by the user to the file input unit  42   a . The file input unit  42   a  stores the file of the watermark image data in the page data storing unit  300 . In other words, the file input unit  42   a  is capable of receiving input of (i.e., acquiring) the watermark image data with the transparency information of the watermark image E from outside the electronic whiteboard  2  and storing the thus-acquired watermark image data in the page data storing unit  300 . 
     The file output unit  42   b  records the PDF file output by the file converting unit  43  on the USB memory  5 . 
     The file transmitting unit  44  transmits the PDF file generated by the file converting unit  43  by attaching the PDF file to an electronic mail. The display superimposing unit  36  displays the contents of the address book management table  410  on the display  3 , and the user operates an input device such as a touch panel to select an address from the displayed contents of the address book management table  410 . Then, the file transmitting unit  44  receives the selection of the address to thereby determine the transmission destination of the PDF file. In the address book management table  410 , the name and electronic mail address of the transmission destination are managed in association with each other. 
     The file transmitting unit  44  is also capable of receiving the electronic mail address of the transmission destination input through the user operation of the input device such as a touch panel. 
     The address book input unit  45  reads a file of an electronic mail address list (i.e., an address book) from the USB memory  5 , and manages the file of the address book in the address book management table  410 . The file of the address book is in the comma separated values (CSV) format, for example. 
     The backup unit  46  stores the file output by the file output unit  42   b  or the file transmitted by the file transmitting unit  44  into the backup data storing unit  420  to back up the file. If backup is not set by the user, the backup unit  46  does not execute the backup process. The data of the backed-up file is stored in the PDF format. 
     The backup output unit  47  stores the backed-up file in the USB memory  5 . When storing the backed-up file in the USB memory  5 , the user inputs a passcode for security by operating the input device such as a touch panel. 
     The setting managing unit  48  manages various setting information of the electronic whiteboard  2  by storing and reading the various setting information in and from the setting file storing unit  430 . The various setting information includes network settings, date and time settings, region and language settings, electronic mail server settings, address book settings, connection destination list settings, and backup settings, for example. The network settings include setting of the IP address of the electronic whiteboard  2 , netmask settings, default gateway settings, and domain name system (DNS) settings, for example. 
     The setting file output unit  49   b  records the various setting information of the electronic whiteboard  2  on the USB memory  5  as a setting file. The contents of the setting file are not viewable to the user for security reasons. 
     The setting file input unit  49   a  reads a setting file stored in the USB memory  5  and reflects various setting information of the setting file in various settings of the electronic whiteboard  2 . 
     An address book input unit  50  reads from the USB memory  5  a file of a list of connection destination IP addresses (i.e., a connection destination list) for the remote sharing process, and manages the file of the connection destination list in the connection destination management table  440 . The file of the connection destination list is in the CSV format, for example. 
     The connection destination management table  440  previously stores and manages the IP addresses of other electronic whiteboards  2  capable of serving as the host apparatus such that, when the electronic whiteboard  2  is going to participate in the remote sharing process as a participant apparatus, the time for the user of the participant apparatus to input the IP address of the host apparatus is saved. In the connection destination management table  440 , the name of the site of each electronic whiteboard  2  capable of participating in the remote sharing process as the host apparatus and the IP address of the electronic whiteboard  2  are managed in association with each other. 
     The connection destination management table  440  may be removed from the electronic whiteboard  2 . In this case, the user of the participant apparatus inputs the IP address of the host apparatus via an input device such as a touch panel to participate in the remote sharing process hosted by the host apparatus. The user of the participant apparatus therefore obtains the IP address of the host apparatus from the user of the host apparatus by telephone or electronic mail, for example. 
     A functional configuration of the communication control unit  60  will be described with  FIG. 12 . 
       FIG. 12  is a block diagram illustrating an exemplary functional configuration of the server unit  90  and the client unit  20 . The communication control unit  60  controls communication of the electronic whiteboard  2  with another electronic whiteboard  2  via the communication network  9  and communication of the client unit  20  with a communication control unit  70  of the server unit  90 . The communication control unit  60  includes a remote process starting unit  61 , a remote process participation processing unit  62 , a remote image transmitting unit  63 , a remote image receiving unit  64 , a remote operation transmitting unit  65 , a remote operation receiving unit  66 , and a participant site management table  610 . 
     The remote process starting unit  61  transmits a request to start the remote sharing process (hereinafter referred to as the remote sharing process start request) to the server unit  90  of the electronic whiteboard  2 , and receives a result of the remote sharing process start request from the server unit  90 . In this process, the remote process starting unit  61  refers to the remote license management table  310 . Then, if the license information (i.e., the product ID, the license ID, and the expiration period) for the remote sharing process is managed in the remote license management table  310 , the remote process starting unit  61  is able to transmit the remote sharing process start request to the server unit  90 . If the license information for the remote sharing process is not managed in the remote license management table  310 , the remote process starting unit  61  is unable to transmit the remote sharing process start request to the server unit  90 . 
     When the electronic whiteboard  2  serves as the host apparatus, the participant site management table  610  manages information of each electronic whiteboard  2  currently participating in the remote sharing process as the participant apparatus. In the participant site management table  610 , the name of the site of the electronic whiteboard  2  participating in the remote sharing process and the IP address of the electronic whiteboard  2  are managed in association with each other. 
     When another electronic whiteboard  2  has already started the remote sharing process as the host apparatus, the remote process participation processing unit  62  transmits, via the communication network  9 , a request to participate in the remote sharing process (hereinafter referred to as the remote sharing process participation request) to a remote connection request receiving unit  71  of the server unit  90  of the another electronic whiteboard  2  serving as the host apparatus. In this case, too, the remote process participation processing unit  62  refers to the remote license management table  310 . 
     To participate in the already-started remote sharing process, the remote process participation processing unit  62  refers to the connection destination management table  440  and acquires the IP address of the electronic whiteboard  2  having started the remote sharing process as the host apparatus. Alternatively, the IP address of the electronic whiteboard  2  as the host apparatus may be input through the user operation of the input device such as a touch panel, with the remote process participation processing unit  62  not referring to the connection destination management table  440 . 
     The remote image transmitting unit  63  transmits, to the server unit  90 , the output image C transmitted from the image acquiring unit  21  via the image acquiring unit  31 . 
     The remote image receiving unit  64  receives, from the server unit  90 , the image data from the image output apparatus connected to another electronic whiteboard  2 , and outputs the image data to the display superimposing unit  36  to enable the remote sharing process. 
     The remote operation transmitting unit  65  transmits various operation data for the remote sharing process to the server unit  90 . The various operation data includes data related to the addition, deletion, and editing (e.g., scaling-up, scaling-down, and movement) of the stroke, the storage, generation, duplication, and deletion of the page data, and switching of the displayed page, for example. The remote operation receiving unit  66  receives, from the server unit  90 , the operation data input to another electronic whiteboard  2 , and outputs the operation data to the image processing unit  30  to execute the remote sharing process. 
     A functional configuration of the server unit  90  will be described with  FIG. 12 . 
     Each electronic whiteboard  2  includes the server unit  90  that functions as a server. The server unit  90  includes a communication control unit  70  and a data managing unit  80 . 
     A functional configuration of the communication control unit  70  will be described with  FIG. 12 . 
     The communication control unit  70  controls communication with the communication control unit  60  of the client unit  20  in the electronic whiteboard  2  and communication with the communication control unit  60  of the client unit  20  in another electronic whiteboard  2  via the communication network  9 . The data managing unit  80  manages data such as the operation data and the image data. 
     More specifically, the communication control unit  70  includes a remote connection request receiving unit  71 , a remote connection result transmitting unit  72 , a remote image receiving unit  73 , a remote image transmitting unit  74 , a remote operation receiving unit  75 , and a remote operation transmitting unit  76 . 
     The remote connection request receiving unit  71  receives the remote sharing process start request from the remote process starting unit  61 , and receives the remote sharing process participation request from the remote process participation processing unit  62 . The remote connection result transmitting unit  72  transmits a result of the remote sharing process start request to the remote process starting unit  61 , and transmits a result of the remote sharing process participation request to the remote process participation processing unit  62 . 
     The remote image receiving unit  73  receives the image data (i.e., the data of the output image C) from the remote image transmitting unit  63 , and transmits the image data to a remote image processing unit  82  of the data managing unit  80 . The remote image transmitting unit  74  receives the image data from the remote image processing unit  82 , and transmits the image data to the remote image receiving unit  64 . 
     The remote operation receiving unit  75  receives the operation data (e.g., the data of the stroke image B) from the remote operation transmitting unit  65 , and transmits the operation data to a remote operation processing unit  83  of the data managing unit  80 . The remote operation transmitting unit  76  receives the operation data from the remote operation processing unit  83 , and transmits the operation data to the remote operation receiving unit  66 . 
     A functional configuration of the data managing unit  80  will be described with  FIG. 12 . 
     The data managing unit  80  includes a remote connection processing unit  81 , a remote image processing unit  82 , a remote operation processing unit  83 , an operation data combining unit  84 , a page processing unit  85 , a passcode managing unit  810 , a participant site management table  820 , an image data storing unit  830 , an operation data storing unit  840 , and a page data storing unit  850 . 
     The remote connection processing unit  81  starts and terminates the remote sharing process. Further, based on the license information that the remote connection request receiving unit  71  receives from the remote process starting unit  61  together with the remote sharing process start request or the license information that the remote connection request receiving unit  71  receives from the remote process participation processing unit  62  together with the remote sharing process participation request, the remote connection processing unit  81  determines the presence or absence of a license. Then, if the presence of a license is determined, the remote connection processing unit  81  determines whether the license is within the expiration period. The remote connection processing unit  81  further determines whether the number of remote sharing process participation requests from other electronic whiteboards  2  as participant apparatuses is within a predetermined maximum allowed number of participant apparatuses. 
     The remote connection processing unit  81  further determines whether the passcode transmitted as well as the remote sharing process participation request from another electronic whiteboard  2  is the same as the passcode managed in the passcode managing unit  810 . If the transmitted passcode is the same as the managed passcode, the remote connection processing unit  81  allows the another electronic whiteboard  2  to participate in the remote sharing process. 
     When starting the remote sharing process, the remote connection processing unit  81  issues the passcode. The passcode is then informed by the user of the electronic whiteboard  2  as the host apparatus to the user of the another electronic whiteboard  2 , which is going to participate in the remote sharing process as the participant apparatus, via telephone or electronic mail, for example. 
     Then, the user of the another electronic whiteboard  2  that is going to participate in the remote sharing process as the participant apparatus inputs the passcode to the another electronic whiteboard  2  (i.e., the participant apparatus) via the input device such as a touch panel, to thereby transmit the remote sharing process participation request to the electronic whiteboard  2  as the host apparatus. Thereby, the another electronic whiteboard  2  is allowed to participate in the remote sharing process as the participant apparatus. When user convenience is given priority over security, the remote connection processing unit  81  may simply check the license status and omit the process of checking the passcode. 
     When the electronic whiteboard  2  serves as the host apparatus, the remote connection processing unit  81  stores, in the participant site management table  820  of the server unit  90 , participant site information included in the remote sharing process participation request transmitted, via the communication network  9 , from the remote process participation processing unit  62  of another electronic whiteboard  2  as the participant apparatus. The remote connection processing unit  81  then reads remote site information stored in the participant site management table  820 , and transmits the remote site information to the remote connection result transmitting unit  72 . The remote connection result transmitting unit  72  transmits the remote site information to the remote process starting unit  61  of the client unit of the electronic whiteboard  2  as the host apparatus. 
     The remote process starting unit  61  stores the remote site information in the participant site management table  610 . In the electronic whiteboard  2  as the host apparatus, therefore, the remote site information is managed in both the client unit  20  and the server unit  90 . 
     The remote image processing unit  82  receives image data items of the output images C from image output apparatuses (e.g., the laptop PCs  6 ) connected to the respective client units  20  of all electronic whiteboards  2  participating in the remote sharing process (including the client unit  20  of the electronic whiteboard  2  as the host apparatus), and stores the image data items in the image data storing unit  830 . The remote image processing unit  82  further determines the order of displaying image data items in the remote sharing process based on the chronological order of arrival of the image data items arriving at the server unit  90  of the electronic whiteboard  2  as the host apparatus. With reference to the participant site management table  820 , the remote image processing unit  82  then transmits the image data items to the client units  20  of all electronic whiteboards  2  participating in the remote sharing process (including the client unit  20  of the electronic whiteboard  2  as the host apparatus) in the above-determined order via the communication control unit  70  (i.e., the remote image transmitting unit  74 ). 
     The remote operation processing unit  83  receives various operation data items such as data items of the stroke images B rendered by the client units  20  of all electronic whiteboards  2  participating in the remote sharing process (including the client unit  20  of the electronic whiteboard  2  as the host apparatus), and determines the order of displaying images in the remote sharing process based on the chronological order of arrival of the various operation data items arriving at the server unit  90  of the electronic whiteboard  2  as the host apparatus. Herein, the various operation data is the same as the above-described various operation data. With reference to the participant site management table  820 , the remote operation processing unit  83  then transmits the operation data items to the client units  20  of all electronic whiteboards  2  participating in the remote sharing process (including the client unit  20  of the electronic whiteboard  2  as the host apparatus) in the above-determined order. 
     The operation data combining unit  84  combines the operation data items of the electronic whiteboards  2  output from the remote operation processing unit  83 , stores operation data resulting from combining the operation data items in the operation data storing unit  840 , and transmits the operation data to the remote operation processing unit  83 . The operation data is then transmitted, via the remote operation transmitting unit  76 , to the client unit  20  of the electronic whiteboard  2  as the host apparatus and the client unit  20  of any other electronic whiteboard  2  as the participant apparatus. Thereby, the image based on the same operation data is displayed on the respective electronic whiteboards  2 .  FIG. 13  illustrates an example of the operation data. 
     As illustrated in  FIG. 13 , a sequence number SEQ, an operation name, an IP address and a port number of a transmitter, an IP address and a port number of a receiver, an operation type, an operation target, and data are stored in the operation data in association with each other. Herein, SEQ represents the sequence number of the operation data. The operation name represents the name of the operation corresponding to the operation data. The IP address and the port number of the transmitter represent the IP address of the electronic whiteboard  2  as the transmitter of the operation data and the port number of the client unit  20  (or the server unit  90 ) of the electronic whiteboard  2  as the transmitter. The IP address and the port number of the receiver represent the IP address of the electronic whiteboard  2  as the receiver of the operation data and the port number of the client unit  20  (or the server unit  90 ) of the electronic whiteboard  2  as the receiver. The operation type represents the type of the operation data. The operation target represents the data to which the operation data is applied. The data represents the contents of the operation data. 
     For example, the first row in  FIG. 13  corresponding to a sequence number SEQ 1  indicates that, in response to rendering of a stroke by the client unit  20  (represented by a port number “50001”) of the electronic whiteboard  2  as the host apparatus (represented by an IP address “192.0.0.1”), the operation data has been transmitted to the server unit  90  (represented by a port number “50000”) of the electronic whiteboard  2  as the host apparatus. In this case, the operation type is “STROKE,” the operation target is the page data represented by a page data ID “p005,” and the data as the contents of the operation data is the data representing the stroke. Further, the second row in  FIG. 13  corresponding to a sequence number SEQ 2  indicates that the server unit  90  (represented by the port number “50000”) of the electronic whiteboard  2  as the host apparatus (represented by the IP address “192.0.0.1”) has transmitted the operation data to the client unit  20  (represented by the port number “50001”) of another electronic whiteboard  2  as the participant apparatus (represented by an IP address “192.0.0.2”). 
     The operation data combining unit  84  combines the operation data items in the order of input of the operation data items to the operation data combining unit  84 . Therefore, the stroke image B is displayed on the displays  3  of all electronic whiteboards  2  participating in the remote sharing process in the order of strokes rendered by the users of the electronic whiteboards  2 , unless the communication network  9  is congested. 
     The page processing unit  85  has similar functions to those of the page processing unit  37  of the image processing unit  30  in the client unit  20 . Therefore, the page data illustrated in  FIGS. 6 to 8  is also stored in the page data storing unit  850  of the server unit  90 . The page data storing unit  850  is similar in configuration to the page data storing unit  300  of the image processing unit  30 , and thus description thereof will be omitted. 
     Processes of the electronic whiteboards  2  of the embodiment will be described with  FIGS. 14 and 15 . 
     In the example illustrated in  FIGS. 14 and 15 , the electronic whiteboard  2   a  (i.e., the server unit  90  and the client unit  20  thereof) functions as the host apparatus that hosts the remote sharing process, and each of electronic whiteboards  2   b  and  2   c  (i.e., the client unit  20  thereof) functions as the participant apparatus that participates in the remote sharing process. 
     In the present example, the electronic whiteboards  2   a ,  2   b , and  2   c  include displays  3   a ,  3   b , and  3   c , respectively. Further, the electronic whiteboards  2   a ,  2   b , and  2   c  are connected to laptop PCs  6   a ,  6   b , and  6   c , respectively, and electronic pens  4   a ,  4   b , and  4   c  are used for the electronic whiteboards  2   a ,  2   b , and  2   c , respectively. 
     A process for the electronic whiteboards  2   a  and  2   b  to participate in the remote sharing process will be described with  FIG. 14 . 
     When the user of the electronic whiteboard  2   a  turns on a power switch of the electronic whiteboard  2   a , the client unit  20  of the electronic whiteboard  2   a  is started. Then, the user performs an operation of starting the server unit  90  with the input device such as a touch panel, and the remote process starting unit  61  of the client unit  20  outputs an instruction to start the processing of the server unit  90  to the remote connection request receiving unit  71  of the server unit  90  in the electronic whiteboard  2   a . Thereby, as well as the client unit  20 , the server unit  90  is prepared to start various processes in the electronic whiteboard  2   a  (step S 21 ). 
     Then, in the client unit  20  of the electronic whiteboard  2   a , the UI image generating unit  33  generates connection information for the electronic whiteboards  2   b  and  2   c  to establish connection with the electronic whiteboard  2   a , and the image superimposing unit  28  displays, on the display  3   a , the connection information acquired from the UI image generating unit  33  via the display superimposing unit  36  (step S 22 ). 
     The connection information includes the IP address of the electronic whiteboard  2   a  as the host apparatus and the passcode generated for the current remote sharing process. In this case, the passcode stored in the passcode managing unit  810  is read by the remote connection processing unit  81  in  FIG. 12 , and is transmitted to the remote connection result transmitting unit  72  and then to the remote process starting unit  61  of the communication control unit  60 . The passcode is then transmitted from the communication control unit  60  to the image processing unit  30  in  FIG. 11  to be input to the UI image generating unit  33  in  FIG. 3 . Thereby, the passcode is included in the connection information. The user of the electronic whiteboard  2   a  informs the users of the electronic whiteboards  2   b  and  2   c  of the connection information by telephone or electronic mail, for example. If the connection destination management table  440  is stored in the electronic whiteboards  2   b  and  2   c , the electronic whiteboards  2   b  and  2   c  as the participant apparatuses are able to transmit the remote sharing process participation request to the electronic whiteboard  2   a  as the host apparatus, even if the IP address of the electronic whiteboard  2   a  as the host apparatus is not included in the connection information. 
     Then, in each of the electronic whiteboards  2   b  and  2   c , in response to receipt of the connection information input by the user through the operation of the input device such as a touch panel, the remote process participation processing unit  62  of the client unit  20  transmits the passcode to the communication control unit  70  of the server unit  90  of the electronic whiteboard  2   a  via the communication network  9  based on the IP address included in the connection information (steps S 23  and S 24 ). Thereby, the remote connection request receiving unit  71  of the communication control unit  70  receives the remote sharing process participation request and the passcode from each of the electronic whiteboards  2   b  and  2   c , and outputs the passcode to the remote connection processing unit  81 . 
     Then, the remote connection processing unit  81  executes an authentication process on the passcodes received from the electronic whiteboards  2   b  and  2   c  based on the passcodes managed in the passcode managing unit  810  (step S 25 ). 
     Then, the remote connection result transmitting unit  72  notifies each of the client units  20  of the electronic whiteboards  2   b  and  2   c  of a result of the authentication process (steps S 26  and S 27 ). 
     If it is determined in the authentication process of step S 25  that each of the electronic whiteboards  2   b  and  2   c  is a valid electronic whiteboard  2 , communication for the remote sharing process is established between the electronic whiteboard  2   a  as the host apparatus and the electronic whiteboards  2   b  and  2   c  as the participant apparatuses. In each of the client units  20  of the electronic whiteboards  2   b  and  2   c , the remote process participation processing unit  62  prepares to start the remote sharing process with the other electronic whiteboards  2  (steps S 28  and S 29 ). 
     An output image display process included in the remote sharing process will be described with  FIG. 14 . 
     The electronic whiteboard  2   b  first displays the output image C on the display  3   b  (step S 30 ). Specifically, the image acquiring unit  31  of the electronic whiteboard  2   b  receives the data of the output image C displayed on the laptop PC  6   b  from the laptop PC  6   b  via the image acquiring unit  21 , and transmits the data of the output image C to the display  3   b  via the display superimposing unit  36  and the image superimposing unit  28 . Thereby, the display  3   b  displays the output image C. 
     Then, in the electronic whiteboard  2   b , the image processing unit  30  including the image acquiring unit  31  transmits the data of the output image C to the remote image transmitting unit  63  of the communication control unit  60 . The communication control unit  60  then transmits the data of the output image C to the communication control unit  70  of the electronic whiteboard  2   a  as the host apparatus via the communication network  9  (step S 31 ). Then, the remote image receiving unit  73  of the electronic whiteboard  2   a  receives the data of the output image C, and outputs the data of the output image C to the remote image processing unit  82 , which then stores the data of the output image C in the image data storing unit  830 . 
     Then, the electronic whiteboard  2   a  as the host apparatus displays the output image C on the display  3   a  (step S 32 ). Specifically, the remote image processing unit  82  of the electronic whiteboard  2   a  receives the data of the output image C from the remote image receiving unit  73 , and outputs the data of the output image C to the remote image transmitting unit  74   
     The remote image transmitting unit  74  then outputs the data of the output image C to the remote image receiving unit  64  of the client unit  20  in the electronic whiteboard  2   a  as the host apparatus. The remote image receiving unit  64  outputs the data of the output image C to the display superimposing unit  36 , which then outputs the data of the output image C to the image superimposing unit  28 . The image superimposing unit  28  outputs the data of the output image C to the display  3   a . Thereby, the display  3   a  displays the output image C. 
     Then, in the server unit  90  of the electronic whiteboard  2   a  as the host apparatus, the communication control unit  70  including the remote image transmitting unit  74  transmits the data of the output image C to the communication control unit  60  of the electronic whiteboard  2   c , i.e., the electronic whiteboard  2  other than the electronic whiteboard  2   b  that has originally transmitted the data of the output image C, via the communication network  9  (step S 33 ). Then, the remote image receiving unit  64  of the electronic whiteboard  2   c  as the participant apparatus receives the data of the output image C. 
     Then, the electronic whiteboard  2   c  displays the output image C on the display  3   c  (step S 34 ). Specifically, the remote image receiving unit  64  of the electronic whiteboard  2   c  outputs the data of the output image C received at step S 33  to the display superimposing unit  36  of the electronic whiteboard  2   c . The display superimposing unit  36  outputs the data of the output image C to the image superimposing unit  28 , which then outputs the data of the output image C to the display  3   c . Thereby, the display  3   c  displays the output image C. If the image superimposing unit  28  receives input of the data of the UI image A, the stroke image B, and the watermark image E, as well as the data of the output image C, the display superimposing unit  36  generates a superimposed image including the UI image A, the stroke image B, and the output image C superimposed upon each other (hereinafter referred to as the superimposed image ABC). Then, the image superimposing unit  28  outputs the data of the superimposed image ABC to the display  3   c.    
     In this process, the watermark image E is not displayed. Further, if the data of an image for television conference (hereinafter referred to as the television conference image F) is transmitted to the image superimposing unit  28  from the television conference terminal  7 , the image superimposing unit  28  superimposes the data of the television conference image F on the superimposed image ABC in the picture-in-picture format and outputs a resultant superimposed image to the display  3   c.    
     The watermark image E is not transmitted or received between the host apparatus and the participant apparatus. Therefore, whether the watermark image E is displayed depends on each of the electronic whiteboards  2 . Further, the watermark images E displayed by the electronic whiteboards  2  may be different (or the same) between the electronic whiteboards  2 . 
     Further, watermark image data may be transmitted and received between the electronic whiteboards  2 . Each of the electronic whiteboards  2  has a function of transmitting setting information describing settings related to the operation of the electronic whiteboard  2 . The setting information includes, for example, settings for the electronic whiteboard  2  to appropriately operate (e.g., synchronization time and restart time), settings for allowing or restricting the operation of the electronic whiteboard  2  (i.e., settings related to security such as the passcode), ON-OFF settings of various functions, and settings for communication with the Internet or another apparatus via a network (e.g., the IP address). With the function of transmitting the setting information, the electronic whiteboards  2  are capable of sharing the watermark image data as well as the setting information. 
     A superimposed image display process included in the remote sharing process will be described with  FIG. 15 . 
     The user of the electronic whiteboard  2   b  first renders the stroke image B on the electronic whiteboard  2   b  with the electronic pen  4   b  (step S 41 ). 
     Then, the display superimposing unit  36  of the electronic whiteboard  2   b  superimposes the stroke image B on the UI image A and the output image C, as illustrated in  FIG. 4 , to display the superimposed image ABC on the display  3   b  of the electronic whiteboard  2   b  (step S 42 ). Specifically, the stroke processing unit  32  of the electronic whiteboard  2   b  receives the data of the stroke image B as the operation data from the coordinate detecting unit  22  and the contact detecting unit  24  via the event sorting unit  25 , and transmits the data of the stroke image B to the display superimposing unit  36 . Thereby, the display superimposing unit  36  superimposes the stroke image B on the UI image A and the output image C, and the image superimposing unit  28  displays the superimposed image ABC on the display  3   b  of the electronic whiteboard  2   b.    
     Then, in the electronic whiteboard  2   b , the image processing unit  30  including the stroke processing unit  32  transmits the data of the stroke image B to the remote operation transmitting unit  65 , which then transmits the data of the stroke image B to the communication control unit  70  of the electronic whiteboard  2   a  as the host apparatus via the communication network  9  (step S 43 ). 
     Then, the remote operation receiving unit  75  of the electronic whiteboard  2   a  receives the data of the stroke image B, and outputs the data of the stroke image B to the remote operation processing unit  83 , which then outputs the data of the stroke image B to the operation data combining unit  84 . When the electronic whiteboard  2   b  renders a plurality of strokes as the stroke image B, a plurality of data items of the stroke image B are sequentially transmitted to the remote operation processing unit  83  of the electronic whiteboard  2   a  as the host apparatus, as described above. 
     The data of the stroke image B correspond to the data items represented by the stroke data IDs illustrated in  FIG. 7 . For example, therefore, when a user writes the alphabetic letter “T” with the electronical pen  4 , the letter “T” is normally written in two strokes, as described above. Thus, two data items represented by two stroke data IDs are sequentially transmitted as the data of the stroke image B. 
     Then, the electronic whiteboard  2   a  as the host apparatus receives the superimposed image ABC with the data of the stroke image B from the electronic whiteboard  2   b , and displays the superimposed image ABC with the data of the stroke image B on the display  3   a  (step S 44 ). Specifically, the operation data combining unit  84  of the electronic whiteboard  2   a  combines the data items of the stroke image B sequentially transmitted via the remote operation processing unit  83 . The operation data combining unit  84  then stores the combined data items in the operation data storing unit  840 , and transmits the combined data items back to the remote operation processing unit  83 . 
     Then, the remote operation processing unit  83  outputs, to the remote operation transmitting unit  76 , the combined data items of the stroke image B received from the operation data combining unit  84 . The remote operation transmitting unit  76  outputs the combined data items of the stroke image B to the remote operation receiving unit  66  of the client unit  20  in the electronic whiteboard  2   a  as the host apparatus. 
     The remote operation receiving unit  66  outputs the combined data items of the stroke image B to the display superimposing unit  36  of the image processing unit  30 . Then, the display superimposing unit  36  superimposes the combined data items of the stroke image B on the UI image A and the output image C. Finally, the image superimposing unit  28  displays, on the display  3   a , the superimposed image ABC including the UI image A, the stroke image B, and the output image C superimposed by the display superimposing unit  36 . 
     Then, in the server unit  90  of the electronic whiteboard  2   a  as the host apparatus, the communication control unit  70  including the remote operation transmitting unit  76  transmits the combined data items of the stroke image B to the communication control unit  60  of the electronic whiteboard  2   c , i.e., the electronic whiteboard  2  other than the electronic whiteboard  2   b  that has originally transmitted the data items of the stroke image B, via the communication network  9  (step S 45 ). Then, the remote operation receiving unit  66  of the electronic whiteboard  2   c  as a participant apparatus receives the combined data items of the stroke image B. 
     Then, the electronic whiteboard  2   c  displays the superimposed image ABC on the display  3   c  (step S 46 ). Specifically, the remote operation receiving unit  66  of the electronic whiteboard  2   c  outputs the combined data items of the stroke image B received at step S 45  to the image processing unit  30  of the electronic whiteboard  2   c . The display superimposing unit  36  of the image processing unit  30  superimposes the data of the UI image A, the combined data items of the stroke image B, and the data of the output image C upon each other, and outputs the data of the resultant superimposed image ABC to the image superimposing unit  28 . The image superimposing unit  28  outputs the data of the superimposed image ABC to the display  3   c . Thereby, the display  3   c  displays the superimposed image ABC. 
     In the above-described process, the output image C is displayed on the display  3 . Alternatively, the display  3  may display the background image D in place of the output image C. Further, the exclusive relationship between the output image C and the background image D may be cancelled to enable the display  3  to display both the output image C and the background image D at the same time. 
     A process for a participant apparatus to terminate the participation in the remote sharing process will be described with  FIG. 15 . 
       FIG. 15  illustrates an exemplary process of terminating the participation of the electronic whiteboard  2   c  in the remote sharing process. 
     In the electronic whiteboard  2   c , in response to receipt of a participation termination request input by the user through the operation of the input device such as a touch panel, the remote process participation processing unit  62  transmits the participation termination request to the communication control unit  70  of the server unit  90  of the electronic whiteboard  2   a  as the host apparatus (step S 47 ). 
     Then, the remote connection request receiving unit  71  of the communication control unit  70  receives the participation termination request from the electronic whiteboard  2   c , and outputs the participation termination request to the remote connection processing unit  81  together with the IP address of the electronic whiteboard  2   c . Then, based on the IP address transmitted from the remote connection request receiving unit  71 , the remote connection processing unit  81  of the electronic whiteboard  2   a  deletes, from the participant site management table  820 , the IP address of the electronic whiteboard  2   c  having transmitted the participation termination request and the name of the site of the electronic whiteboard  2   c . The remote connection processing unit  81  then outputs, to the remote connection result transmitting unit  72 , a notification indicating that the IP address of the electronic whiteboard  2   c  and the name of the site of the electronic whiteboard  2   c  have been deleted. 
     Then, the communication control unit  70  including the remote connection result transmitting unit  72  transmits a participation termination instruction to the communication control unit  60  of the client unit  20  of the electronic whiteboard  2   c  via the communication network  9  (step S 48 ). Then, the remote process participation processing unit  62  of the communication control unit  60  in the electronic whiteboard  2   c  executes a participation termination process by cutting off the communication for the remote sharing process, to thereby terminate the participation of the electronic whiteboard  2   c  in the remote sharing process (step S 49 ). The process for a participant apparatus to terminate the participation in the remote sharing process is thus executed. 
     A description will be given of a process in which the electronic whiteboard  2  receives data input from an external apparatus and displays the UI image A on the display surface  301 . In the following description of this process, a part of the process of displaying the output image C at step S 30  in  FIG. 14  will be described in more detail. 
       FIG. 16  is a flowchart illustrating an exemplary process in which the electronic whiteboard  2  receives data input from an external apparatus and displays the UI image A on the display surface  301 . As illustrated in  FIG. 16 , the electronic whiteboard  2  first receives input of data such as image data from an external apparatus such as the laptop PC  6  via a data input device such as the wired port  117   a  (step S 301 ). 
     Then, the input detecting unit  33   a  detects the data input device having received the data input, and outputs the identification information of the detected data input device to the UI image generating unit  33  (step S 302 ). 
     Based on the identification information input from the input detecting unit  33   a , the UI image generating unit  33  then acquires the image for forming the UI image by referring to the table illustrated in  FIG. 5A or 5B  (step S 303 ). 
     Then, the UI image generating unit  33  generates the UI image A with the acquired image, and outputs the UI image A to the display superimposing unit  36  (step S 304 ). 
     The display superimposing unit  36  then generates a superimposed image including the input UI image A, and outputs the superimposed image to the image superimposing unit  28  (step S 305 ). 
     Then, the image superimposing unit  28  displays the superimposed image including the UI image A on the display surface  301  (step S 306 ). 
     The electronic whiteboard  2  thus displays, on the display surface  301 , the UI image A generated based on the data input from the external apparatus. 
     Examples of the superimposed image of the embodiment will be described with  FIGS. 17 and 18 . 
       FIG. 17  is a diagram illustrating an example of the superimposed image displayed when an external apparatus is connected to the right side of the electronic whiteboard  2 . In  FIG. 17 , the laptop PC  6  is connected, via a cable, to the wired port  117   a  disposed on the right side of the electronic whiteboard  2 . Herein, the right side refers to the right side in  FIG. 17 . 
     The superimposed image including the output image C and the UI image A superimposed upon each other is displayed on the display surface  301  of the display  3 . Specifically, the output image C is displayed at the center of the display surface  301  of the display  3 , and a camera UI  621  and an image UI  622  included in the UI image A are displayed on the right side of the display surface  301  of the display  3 . 
     More specifically, in the electronic whiteboard  2 , the input detecting unit  33   a  detects the connection of the laptop PC  6  to the wired port  117   a , and outputs the identification information of the wired port  117   a  to the UI image generating unit  33 . In accordance with the input identification information, the UI image generating unit  33  generates the UI image A with the camera UI  621  and the image UI  622  arranged on the right side thereof, and outputs the UI image A to the display superimposing unit  36 . The display superimposing unit  36  generates the superimposed image including the input UI image A, and the image superimposing unit  28  displays the superimposed image including the UI image A on the display surface  301 . Thereby, the camera UI  621  and the image UI  622  are displayed on the right side of the display surface  301 . Herein, each of the camera UI  621  and the image UI  622  is an example of the instruction receiving section. 
     The camera UI  621  is a user interface for storing the output image C in the electronic whiteboard  2  as a still image. When the user performs the UI operation on the camera UI  621  on the display surface  301 , the output image C displayed on the display surface  301  is stored in a memory of the electronic whiteboard  2  such as the SSD  104  as a still image. Herein, the output image C is an example of screen data. 
     The image UI  622  is a user interface for inputting the image of the laptop PC  6  to the electronic whiteboard  2 . When the user performs the UI operation on the image UI  622  on the display surface  301 , the image displayed on a display of the laptop PC  6  is input to the electronic whiteboard  2  and displayed on the display surface  301 . 
       FIG. 17  illustrates an example in which the laptop PC  6  is connected to the wired port  117   a  on the right side of the electronic whiteboard  2 . However, the connection of the laptop PC  6  is not limited to this example. The laptop PC  6  may be connected to a wired port disposed on the left side of the electronic whiteboard  2 . In this case, based on the identification information of the wired port detected to be connected to the laptop PC  6  by the input detecting unit  33   a , the UI image generating unit  33  generates the UI image A with the camera UI  621  and the image UI  622  arranged on the left side thereof, and the image superimposing unit  28  displays a superimposed image including the UI image A on the display surface  301 . Thereby, the camera UI  621  and the image UI  622  are displayed on the left side of the display surface  301 . 
     Further, one laptop PC  6  may be connected to a wired port on the left side of the electronic whiteboard  2 , and another laptop PC  6  may be connected to a wired port on the right side of the electronic whiteboard  2 . In this case, based on the identification information of each of these wired ports detected to be connected to the laptop PCs  6  by the input detecting unit  33   a , the UI image generating unit  33  generates the UI image A with the camera UI  621  and the image UI  622  arranged on both the right and left sides thereof, and the image superimposing unit  28  displays the UI image A on the display surface  301 . Thereby, the camera UI  621  and the image UI  622  are displayed on both the right and left sides of the display surface  301 . 
     Further, a plurality of external apparatuses may be connected to a plurality of data input devices of the electronic whiteboard  2 , and a priority may be set for each of identification information items of the data input devices. In this case, based on the identification information item of the highest priority among the identification information items of the data input devices detected by the input detecting unit  33   a , the UI image generating unit  33  generates the UI image A with the camera UI  621  and the image UI  622  arranged on one side of the electronic whiteboard  2  equipped with the data input device corresponding to the identification information of the highest priority, and the image superimposing unit  28  displays a superimposed image including the UI image A on the display surface  301 . Thereby, the camera UI  621  and the image UI  622  are displayed on one side of the display surface  301  near the data input device corresponding to the identification information of the highest priority. 
       FIG. 17  illustrates the camera UI  621  and the image UI  622  as examples of the UI included in the UI image A. Examples of the UI included in the UI image A, however, are not limited thereto. For example, the UI image A may include a UI for setting parameters such as the color and width of the line rendered with the electronic pen  4 . 
       FIG. 18  is a diagram illustrating an example of the superimposed image displayed when the output image C is stored in the electronic whiteboard  2  as a still image. When the user performs the UI operation on the camera UI  621  on the display surface  301 , the output image C is stored in a memory of the electronic whiteboard  2  as a still image, and a thumbnail image  623  of the stored output image C is displayed in a lower-left area of the display surface  301 . 
     An operation of an electronic whiteboard  2 A according to another embodiment of the present invention will be described with  FIGS. 19 and 20 . Description of the same components as those of the above-described embodiment will be omitted. 
       FIG. 19  is a diagram illustrating an exemplary operation of the electronic whiteboard  2 A of the present embodiment.  FIG. 19  illustrates an example of the superimposed image displayed when a plurality of image output apparatuses are wirelessly connected to the electronic whiteboard  2 A. In the following description with  FIG. 19  and the subsequent drawings, the right and left sides refer to the right and left sides in the drawings. 
     As illustrated in  FIG. 19 , the electronic whiteboard  2 A includes a vertically long display  3 A with a display surface  301 A. Further, the right side in the horizontal direction of the electronic whiteboard  2 A is equipped with an antenna  119   a , and the left side in the horizontal direction of the electronic whiteboard  2 A is equipped with an antenna  119   b . The antenna  119   a  is an example of one data input device of at least two data input devices, and the antenna  119   b  is an example of other data input device of the at least two data input devices. Further, the antennas  119   a  and  119   b  are an example of one data input device and other data input device of the at least two data input devices. Each of the antennas  119   a  and  119   b  wirelessly receives data input. 
     A user  100   a  holds a smartphone  110   a , and a user  100   b  holds a smartphone  110   b . Each of the smartphones  110   a  and  110   b  is capable of outputting an image to outside thereof, and is also capable of outputting a file such as an image file to the electronic whiteboard  2 A. 
     The smartphone  110   a  held by the user  100   a  is connected to the electronic whiteboard  2 A via the antenna  119   a , and the smartphone  110   b  held by the user  100   b  is connected to the electronic whiteboard  2 A via the antenna  119   b.    
     The input detecting unit  33   a  detects the connection of one external apparatus to the right side of the electronic whiteboard  2 A via the antenna  119   a  and the connection of another external apparatus to the left side of the electronic whiteboard  2 A via the antenna  119   b . The input detecting unit  33   a  outputs the identification information of each of the antennas  119   a  and  119   b  to the UI image generating unit  33 . Based on the input identification information, the UI image generating unit  33  generates the UI image A with a camera UI  621   a  and an image UI  622   a  arranged on the right side thereof and a camera UI  621   b  and an image UI  622   b  arranged on the left side thereof. 
     Further, the image acquiring unit  21  acquires the output image C from the smartphone  110   a  via the antenna  119   a . Alternatively, the image acquiring unit  21  may acquire the output image C from the smartphone  110   b  via the antenna  119   b.    
     The display superimposing unit  36  outputs, to the image superimposing unit  28 , a superimposed image including the UI image A and the output image C superimposed upon each other. The image superimposing unit  28  displays the input superimposed image on the display surface  301 A of the display  3 A. 
     In the example of  FIG. 19 , both of the one data input device and the other data input device (i.e., the antennas  119   a  and  119   b ) wirelessly receive data input, but may receive data input by wire. 
       FIG. 20  is a diagram illustrating another exemplary operation of the electronic whiteboard  2 A of the present embodiment.  FIG. 20  illustrates an example of the superimposed image displayed when one image output apparatus is connected by wire to one side of the electronic whiteboard  2 A and another image output apparatus is wirelessly connected to the other side of the electronic whiteboard  2 A. 
     The right side of the electronic whiteboard  2 A is equipped with the wired port  117   a , and the left side of the electronic whiteboard  2 A is equipped with the antenna  119   b . The wired port  117   a  is an example of the one data input device, and receives data input by wire. The antenna  119   b  is an example of the other data input device, and wirelessly receives data input. 
     As illustrated in  FIG. 20 , the laptop PC  6  is connected to the right side of the electronic whiteboard  2 A via a cable, and the smartphone  110   b  held by the user  100   b  is connected to the left side of the electronic whiteboard  2 A via the antenna  119   b.    
     The input detecting unit  33   a  detects the connection of one external apparatus to the right side of the electronic whiteboard  2 A via the wired port  117   a  and the connection of another external apparatus to the left side of the electronic whiteboard  2 A via the antenna  119   b . The input detecting unit  33   a  outputs the identification information of each of the wired port  117   a  and the antenna  119   b  to the UI image generating unit  33 . 
     Based on the input identification information, the UI image generating unit  33  generates the UI image A with the camera UI  621   a  and the image UI  622   a  arranged on the right side thereof and the camera UI  621   b  and the image UI  622   b  arranged on the left side thereof. 
     Further, the image acquiring unit  21  acquires the output image C from the laptop PC  6  via the wired port  117   a . Alternatively, the image acquiring unit  21  may acquire the output image C from the smartphone  110   b  via the antenna  119   b.    
     The display superimposing unit  36  outputs, to the image superimposing unit  28 , a superimposed image including the UI image A and the output image C superimposed upon each other. The image superimposing unit  28  displays the input superimposed image on the display surface  301 A of the display  3 A. 
     Normally, a user of an electronic whiteboard makes a presentation, for example, while standing by one side of the electronic whiteboard to avoid blocking the image displayed on the electronic whiteboard. During the presentation, the user may want to perform the UI operation such as inputting an image from an image output apparatus to the electronic whiteboard or setting parameters such as the color and width of the line rendered with an electronic pen, for example. 
     A typical electronic whiteboard displays UIs on one side (e.g., right side) of the electronic whiteboard irrespective of the standing position of the user. Therefore, when the user makes a presentation while standing by the other side (e.g., left side) of the electronic whiteboard, for example, the user may reach out a hand to the displayed UIs while avoiding blocking the display surface of the electronic whiteboard or move to the display position of the UIs to perform the UI operation. Such an electronic whiteboard is inconvenient for the user to perform the UI operation. 
     Although there is an electronic whiteboard enabling the user to change the display position of the UIs by changing user settings, this type of electronic whiteboard causes the user extra work of changing the settings. Further, the user may be unaware of how to change the display position of the UIs. 
     According to the electronic whiteboard  2 A of the present embodiment, on the other hand, when the user stands by the right side of the electronic whiteboard  2 A, data is input to the electronic whiteboard  2 A from the right side thereof near the user. The electronic whiteboard  2 A then displays the UIs such as the camera UI  621   a  and the image UI  622   a  on the right side of the display surface  301 A, i.e., the right side of the electronic whiteboard  2 A to which the data is input. When the user stands by the left side of the electronic whiteboard  2 A, data is input to the electronic whiteboard  2 A from the left side thereof near the user. The electronic whiteboard  2 A then displays the UIs on the left side of the display surface  301 A, i.e., the left side of the electronic whiteboard  2 A to which the data is input. 
     Thereby, the user is able to perform the UI operation on the UIs displayed at a position close to the user. The present embodiment provides a display apparatus (e.g., the electronic whiteboard  2 A) that facilitates the user to perform the UI operation (i.e., input the instruction) without reaching out a hand to the UIs by avoiding blocking the display surface of the display apparatus or without moving to the display position of the UIs. 
     In the present embodiment, the data input devices are disposed on the right and left sides of the display surface  301 A. Alternatively, the data input devices may be disposed on the upper and lower sides of the display surface  301 A. In this case, if data is input to a data input device disposed on the lower side of the display surface  301 A, for example, the UIs are displayed in a lower-central area of the display surface  301 A. Further, if data is input to a data input device disposed on the upper side of the display surface  301 A, the UIs are displayed in an upper-central area of the display surface  301 A. 
     An electronic whiteboard  2 B according to another embodiment of the present invention will be described. Description of the same components as those of the above-described embodiments will be omitted. 
     The electronic whiteboard  2 B of the present embodiment includes a UI for switching between display and non-display of UIs. 
       FIGS. 21A and 21B  are diagrams illustrating exemplary operations of the electronic whiteboard  2 B of the present embodiment.  FIG. 21A  illustrates the electronic whiteboard  2 B with the UIs displayed thereon, and  FIG. 21B  illustrates the electronic whiteboard  2 B with the UIs not displayed thereon. 
     The electronic whiteboard  2 B includes a display  3 B with a display surface  301 B. The display surface  301 B displays a switching UI  630 . The switching UI  630  is an example of a switching instruction receiving section. The switching UI  630  is a user interface for switching between display and non-display of the UIs arranged on the left side of the display surface  301 B. 
     In  FIG. 21A , when the user  100   b  holding the smartphone  110   b  stands by the left side of the electronic whiteboard  2 B, the smartphone  110   b  is connected to the electronic whiteboard  2 B via the antenna  119   b.    
     The image superimposing unit  28  displays, on the display surface  301 B, a superimposed image including the UI image A with the camera UI  621   b  and the image UI  622   b  arranged on the left side thereof. The UI image A is generated by the UI image generating unit  33  based on the identification information of the data input device detected to be connected to the smartphone  110   b  by the input detecting unit  33   a.    
     The camera UI  621   b  and the image UI  622   b  are displayed on the left side of the display surface  301 B. When the user performs the UI operation on the switching UI  630  in this state, the camera UI  621   b  and the image UI  622   b  are switched to an undisplayed state. The camera UI  621   b , the image UI  622   b , and the switching UI  630  are an example of a plurality of instruction receiving sections. 
     As a result of the UI operation, the camera UI  621   b  and the image UI  622   b  on the display surface  301 B are brought into the undisplayed state, as illustrated in  FIG. 21B . If many UIs are displayed on the display surface  301 B, it may be difficult for a viewer to clearly see a diagram drawn with the electronic pen  4  or the user&#39;s hand H or the output image displayed on the display surface  301 B, for example. Such difficulty in seeing the diagram or image due to the display of the UIs is removed by bringing the UIs displayed on the display surface  301 B into the undisplayed state. 
     When the user performs the UI operation on the switching UI  630  in the state of  FIG. 21B , the camera UI  621   b  and the image UI  622   b  are displayed to return to the state of  FIG. 21A . 
     In the state of  FIG. 21B , the camera UI  621   b  and the image UI  622   b  are not displayed; the user is unable to perform the UI operation thereon. By returning the camera UI  621   b  and the image UI  622   b  to the state of  FIG. 21A , the user is again able to perform the UI operation on the camera UI  621   b  and the image UI  622   b.    
     As described above, the electronic whiteboard  2 B of the present embodiment includes the switching UI  630  to switch between display and non-display of the UIs on the display surface  301 B. Thereby, the difficulty in seeing the diagram or image, for example, due to the display of the UIs is removed, thereby facilitating communication using the electronic whiteboard  2 B. As well as this effect, the above-described effects of the foregoing embodiments are also provided by the present embodiment. 
     The electronic whiteboard  2  according to one of the foregoing embodiments is connected to the laptop PC  6  by wire. Alternatively, the electronic whiteboard  2  may be wirelessly connected to the laptop PC  6  to input the image from the laptop PC  6  to the electronic whiteboard  2 . In this case, whether the image is input to the electronic whiteboard  2  is determined based on whether the image is received by a communication device for a wireless network such as a wireless LAN. 
     The embodiment is applicable not only to one-to-one connection or communication between the laptop PC  6  and the electronic whiteboard  2  but also to communication therebetween via a wired or wireless network. 
     In the configuration examples illustrated in  FIG. 3  and other drawings, the processing units are divided in accordance with major functions of the electronic whiteboard  2  to facilitate the understanding of the processing of the electronic whiteboard  2 . The present invention, however, is not limited by how the processing units are divided or the names of the processing units. The processing of the electronic whiteboard  2  may be divided into a larger number of processing units depending on processes to be performed. Further, a processing unit of the electronic whiteboard  2  may be sub-divided to include more processes. 
     Each of the display apparatuses of the above-described embodiments may be implemented by a device memory storing one or more programs and one or more processors. The one or more processors may execute the one or more programs to execute the processes described above in the embodiments. For example, with the device memory and the one or more processors, the functions described above in the embodiments may be implemented. The device memory and the one or more processors may be implemented by the hardware components described above in the embodiments, for example. Further, one or more programs for causing a computer such as a display apparatus to execute processes may be stored in a nonvolatile recording medium. 
     According to another embodiment of the present invention, a display method is provided. For example, the display method is executed by a display apparatus including a display with a display surface and at least two data input devices. The display method includes detecting, from the at least two data input devices, a data input device to which data is input, generating an instruction receiving image including an instruction receiving section to receive an instruction from a user, and displaying the instruction receiving image on the display surface. The instruction receiving section is arranged at a position according to a result of the detecting. 
     The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention. 
     Each of the functions of the described embodiments may be implemented by one or more processing circuits or circuitry. Circuitry includes a programmed processor, as a processor includes circuitry. A processing circuit also includes devices such as an application specific integrated circuit (ASIC), digital signal processor (DSP), section programmable gate array (FPGA), and conventional circuit components arranged to perform the recited functions. Further, the above-described steps are not limited to the order disclosed herein.