Patent Publication Number: US-2018041564-A1

Title: Electronic blackboard system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of International Application No. PCT/JP2016/002243, filed Apr. 28, 2016, which claims priority to Japanese Patent Application No. 2015-095597, filed May 8, 2015, and Japanese Patent Application No. 2016-079799, filed Apr. 12, 2016. The contents of these applications are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electronic blackboard system. 
     2. Description of the Related Art 
     In recent years, electronic blackboards such as electronic whiteboards (interactive whiteboards: IWBs) have been widely used as display apparatuses. Such an electronic blackboard has a configuration combining an image display device that includes a flat panel such as a liquid crystal panel, a coordinate detection device such as a touch panel that detects coordinates of a position on a display surface of the image display device where an object used for input such as an input pen or a finger touches, and a control device that causes an image including various images, text, numbers, and figures written on the display surface of the image display device to be displayed based on coordinate data output from the coordinate detection device. With this electronic blackboard, conference material or any other material can be enlarged and displayed, and an input pen or a finger can be used to write on the display surface. 
     As display systems, electronic blackboard systems that each connect an electronic blackboard as described above and communication terminals (client terminals) such as personal computers (PCs) and tablet computers via a network such as an in-house LAN, exist. The electronic blackboard system can compress an image displayed on or a written video drawn on the electronic blackboard and distribute the compressed image or written video to a communication terminal, so that the image on the electronic blackboard can be viewed from the communication terminal. 
     Japanese Laid-open Patent Publication No. 2014-199650 describes a technique to transmit image data of content generated by an electronic blackboard to a communication terminal. The technique includes cutting out part of the image data, converting the cut-out image data into transmission data, and transmitting the converted data to the communication terminal. 
     The typical electronic blackboard system known to the inventor, however, basically distributes all images generated by the electronic blackboard, and therefore an image including an area that should not be distributed is distributed as it is to the communication terminal. The area of the image undesirable for distribution can be trimmed out before the image is distributed; however, if the area to exclude is transparent, an image displayed under the trimmed image is missing from the distributed image. Also, the area to exclude may dynamically change depending on the status of the display apparatus, and in this case, the area is difficult to specify. 
     The technique described in Japanese Laid-open Patent Publication No. 2014-199650 that cuts out part of image data does not solve the problems of missing of a generated image and the difficulty in specifying a variable area to exclude. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, an electronic blackboard system includes an electronic blackboard, and at least one communication terminal connected to the electronic blackboard via a communication network. The electronic blackboard includes an image generation unit and a distribution module. The image generation unit is configured to superimpose layers to be displayed in the electric black board, to generate a display imag, and generate a distribution image that does not include an operation panel display layer for displaying an operation panel. The distribution module is configured to transmit the distribution image to the at least one communication terminal. Each of the at least one communication terminal includes a communication control unit and an image display unit. The communication control unit is configured to receive the distribution image transmitted from the electronic blackboard. The image display unit is configured to display the distribution image that is received by the communication control unit and in which the operation panel display layer is excluded. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating a configuration of an electronic blackboard system according to a first embodiment and a second embodiment of the present invention; 
         FIG. 2  is a configuration diagram illustrating a hardware configuration of an electronic blackboard used for the electronic blackboard system according to the first embodiment of the present invention; 
         FIG. 3  is a functional block diagram of the electronic blackboard used for the electronic blackboard system; 
         FIG. 4  is a view illustrating a display screen on the electronic blackboard; 
         FIG. 5  is a view illustrating layers of the display screen on the electronic blackboard; 
         FIG. 6  is a functional block diagram of a communication terminal used for the electronic blackboard system; 
         FIG. 7  is a diagram illustrating a procedure for generating and distributing a distribution image in the electronic blackboard system; 
         FIG. 8  is a view illustrating a display screen on a communication terminal according to a modification of the first embodiment; 
         FIG. 9  is a functional block diagram of an electronic blackboard used for the electronic blackboard system according to the second embodiment; 
         FIG. 10  is a view illustrating a display screen on the electronic blackboard according to the second embodiment; 
         FIG. 11  is a view illustrating a display screen on the electronic blackboard and display screens on communication terminals according to the second embodiment; 
         FIG. 12  is a view illustrating selection of a temporary distribution image in the electronic blackboard system; 
         FIG. 13  is a view illustrating display screens on an electronic blackboard and the communication terminals when the temporary distribution image is distributed in the electronic blackboard system; 
         FIG. 14  is a diagram illustrating a procedure for distributing the temporary distribution image in the electronic blackboard system; and 
         FIG. 15  is a flowchart illustrating a procedure in which a frame output unit of the electronic blackboard acquires a distribution image. 
     
    
    
     The accompanying drawings are intended to depict exemplary embodiments of the present invention and should not be interpreted to limit the scope thereof. Identical or similar reference numerals designate identical or similar components throughout the various drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     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 describing preferred embodiments illustrated in the drawings, specific terminology may be employed for the sake of clarity. However, the disclosure of this patent 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 the same function, operate in a similar manner, and achieve a similar result. 
     An embodiment has an object to generate a distribution image with a specific image undesirable for distribution being excluded, enabling easy and suitable viewing at a communication terminal. 
     The following describes in detail the present invention by way of embodiments illustrated in the drawings. The present invention includes the following configurations for easily and suitably distributing a desired image to a communication terminal, with a specific image undesirable for distribution being excluded. In the embodiments below, a display apparatus is exemplified by an electronic blackboard, and a display system is exemplified by an electronic blackboard system in which the electronic blackboard and communication terminals are connected via a communication network. 
     First Embodiment 
     First, the following describes an electronic blackboard according to a first embodiment of the present invention. 
       FIG. 1  is a block diagram illustrating a configuration of an electronic blackboard system according to the first embodiment of the present invention. An electronic blackboard system  1  according to the present embodiment includes an electronic blackboard  10  and a plurality of communication terminals  20  ( 20 - 1 ,  20 - 2 , . . . ,  20 - n ) connected to the electronic blackboard  10  via a wireless local area network (LAN). The wireless LAN is used for an intra-company network, for example. The electronic blackboard  10  can be connected to the communication terminals  20  via various wired or wireless communication networks such as a wired LAN and the Internet, not limited to the wireless LAN. 
     The electronic blackboard  10  includes an application  100 , a video distribution service  200 , and an image display device  50 . 
     The communication terminals  20  are notebook-type personal computers, tablet computers, and other devices, and operate on various operating systems (OSs) such as iOS, Android (registered trademark), Windows (registered trademark), and Mac OS (registered trademark). The communication terminals  20  each include an image display unit. 
       FIG. 2  is a configuration diagram illustrating a hardware configuration of the electronic blackboard used for the electronic blackboard system according to the first embodiment of the present invention. 
     The electronic blackboard  10  includes a central processing unit (CPU)  501 , a read only memory (ROM)  502 , a random access memory (RAM)  503 , a hard disc drive (HDD)  504 , a hard disk controller (HDC)  505 , a media drive  507 , an image display interface (I/F) device  508 , an interface (I/F)  509 , a keyboard  511 , a mouse  512 , a microphone  513 , a speaker  514 , a graphics processing unit (GPU)  515 , and a touch panel  519 , which are connected via an extension bus line  520 . 
     The CPU  501  controls the entire operation of the electronic blackboard  10 . The ROM  502  stores therein a computer program, such as an initial program loader (IPL), used for driving the CPU  501 . The RAM  503  is used as a work area for the CPU  501 . The HDD  504  stores therein various pieces of data such as a computer program. The HDC  505  controls reading and writing of various pieces of data from and to the HDD  504  under the control of the CPU  501 . The media drive  507  controls reading and writing (storing) of data from and to a recording medium  506  such as a flash memory. The image display interface  508  is used for connecting to the image display device  50  that displays various pieces of information. The I/F  509  is used for transmitting data via a communication network or for connecting a dongle. The GPU  515  is connected to a ROM  516  storing therein a computer program used for driving the GPU  515 , and a RAM  517  used as a work area for the GPU  515 . The extension bus line  520  includes an address bus, a data bus, and other lines for electrically connecting the components described above. The touch panel  519  detects coordinates of a position on the image display device  50  where an input pen or a finger touches. 
     In the electronic blackboard  10  having the above-described configuration, the CPU  501  executes predetermined image distribution software to implement the application  100  and the video distribution service  200  that distributes, as video, a plurality of images generated by the application  100 . 
     The application  100  detects an operation event that is a stroke of writing with an input pen or a finger or a paging operation on the image display device  50  through the touch panel  519 , and draws a stroke or the like on the image display device  50  based on the operation event detected through the touch panel  519 . The application  100  then outputs an image to be distributed to the communication terminals  20  (distribution image) and an image to be displayed on the image display device  50  (display image), and distributes the distribution image to the video distribution service  200  (Step S 1 ). The video distribution service  200  compresses a plurality of images resulted from the drawing by the application  100  and distributes the images to the communication terminals  20  (Step S 2 ). In this example, the distribution is performed from one electronic blackboard  10  to a plurality of (n) communication terminals  20 - 1 ,  20 - 2 , . . . ,  20 - n  at the same time. 
     Each of the communication terminals  20  displays an image acquired from the electronic blackboard  10 , on the display unit. The communication terminal  20  allows a touch operation or a mouse operation to be performed on the image displayed on the display unit to draw on video. Operation information of the touch operation or the mouse operation, for example, is transmitted to the video distribution service  200  of the electronic blackboard  10  (Step S 3 ), and further transmitted from the video distribution service  200  to the application  100  (Step S 4 ). 
     The following describes a functional configuration of the electronic blackboard  10  in the electronic blackboard system  1 . 
       FIG. 3  is a functional block diagram of the electronic blackboard used for the electronic blackboard system. The electronic blackboard  10  includes the application  100  and the video distribution service  200 . 
     The application  100  provides a user with a function in cooperation with the video distribution service  200 . The application  100  includes: a function execution unit  110 ; an application input/output unit  120 ; a frame output unit  130 ; an image generation unit  140  serving as an image generating unit; an operation reception unit  150 ; and a display control unit  160 . 
     The function execution unit  110  is a module that executes a function specific to the electronic blackboard. The application input/output unit  120  receives data, for example, an operation event, output from a distribution service input/output unit  210 . The function execution unit  110  converts the received data into a format that the function execution unit  110  can process, and distributes the converted data. The function execution unit  110  transmits data regarding service start, service stop, and the like to the distribution service input/output unit  210 . 
     The frame output unit  130  outputs images to be distributed as video to the communication terminals  20 . For example, the frame output unit  130  outputs RGB bitmap images as video compressed in H.264/AVC format. 
     The image generation unit  140  generates a display image to be displayed on the image display device  50  and a distribution image to be distributed to the communication terminals  20 . 
     The operation reception unit  150  receives an operation such as writing based on the coordinates of the input pen or the finger detected through the touch panel  519 . 
     The display control unit  160  causes the image display device  50  to display the display image generated by the image generation unit  140 . Thus, the image display device  50  displays an image of an operation panel and an image of the electronic blackboard in a superimposed manner. 
     An image generated as the distribution image by the image generation unit  140  is output to the frame output unit  130 . The image output by the frame output unit  130  to the video distribution service  200  is captured by a capture unit  270  and distributed to the communication terminals  20 . 
     When an operation is received from one of the communication terminals  20 , operation information from the communication terminal  20  is input to the application input/output unit  120  through the distribution service input/output unit  210  of the video distribution service  200 , transferred to the function execution unit  110 , and processed in the same manner as described above. 
     The video distribution service  200  is a general term for modules of the electronic blackboard  10  in the electronic blackboard system  1 . The video distribution service  200  includes, as illustrated in  FIG. 3 , the distribution service input/output unit  210 , a distribution control unit  220 , a distribution information management unit  230 , a communication control unit  240 , and a video encoder unit  250 . The distribution control unit  220 , the distribution information management unit  230 , and the communication control unit  240  constitute a distribution module  280 , and the video encoder unit  250  constitutes a codec module  290 . 
     The distribution service input/output unit  210  receives data (for example, data regarding service start and service stop) output from the application input/output unit  120 . The distribution service input/output unit  210  transmits data such as an operation event to the application input/output unit  120 . The distribution information management unit  230  manages a video encode setting related to image distribution, and information on the communication terminals  20  that are being connected. The communication control unit  240  serving as a communicating unit performs overall control of the image distribution and issues instructions to start and end the codec module  290 . 
     The video encoder unit  250  acquires and compresses an image from the capture unit  270  to generate compressed data. The capture unit  270  acquires a frame image output from the frame output unit  130  of the application  100 . 
     The following describes the display image and the distribution image generated by the image generation unit  140 . 
       FIG. 4  is a view illustrating a display screen on the electronic blackboard. The image display device  50  of the electronic blackboard  10  displays, other than an acquired image or a handwritten image  60 , an operation panel  70  at the side of the image. The handwritten image  60  includes a stroke image  61  and text  62  being “Whiteboard Application” that have been drawn. The operation panel  70  includes a plurality of icons. When the operation reception unit  150  detects selection of a pen icon  71  with an input pen, the function execution unit  110  changes colors used for writing. 
     In this configuration, when an image including the handwritten image  60  and the operation panel  70  is distributed to and displayed on each communication terminal  20 , a user of the communication terminal  20  misunderstands that the user can operate the handwritten image  60  with the displayed operation panel  70 . 
     In the present embodiment, the electronic blackboard  10  generates an image with the operation panel  70  being excluded, and distributes only the handwritten image  60  to the communication terminals  20 . Not only the operation panel  70  but also a thumbnail or other item displayed on the lower part of the image display device  50  can be a target of exclusion. The target of exclusion can be defined by the specification or other setting of the communication terminals  20 . 
       FIG. 5  is a view illustrating layers of the display screen on the electronic blackboard. 
     As illustrated in  FIG. 5 , the operation panel  70  is displayed on an operation panel display layer  81 , the stroke image  61  on a handwritten image layer  82 , and the text  62  on a handwritten image layer  83 . Not limited to the two handwritten image layers, a desired handwritten image layer may be selected and superimposed. The operation panel  70  displayed on the image display device  50  is a specific image, and the operation panel display layer  81  is a specific layer. The stroke image  61  and the text  62  are images other than the specific image. The handwritten image layers  82  and  83  are other layers. 
     The display image is generated from the operation panel display layer  81  and the handwritten image layers  82  and  83  superimposed by the image generation unit  140 . The distribution image is generated from the handwritten image layers  82  and  83  superimposed by the image generation unit  140 . In other words, the distribution image is an image obtained by excluding the operation panel display layer  81  from the display image. 
     When a plurality of handwritten image layers are present, the image generation unit  140  can superimpose a specified desired handwritten image layer to generate an image. 
     Each layer may be assigned with metadata or an ID that identifies the layer, so that whether the layer is to be included in a distribution image can be determined. 
     The following describes the communication terminals  20 . 
       FIG. 6  is a functional block diagram of an electronic processing terminal used for an image processing system. The communication terminals  20  each include a graphical user interface (GUI) unit  310 , a communication information management unit  320 , an overall control unit  330 , a communication control unit  340 , a reproduction control unit  350 , a video decoder unit  360 , and an image display unit  370 . 
     The GUI unit  310  causes the image display unit  370  of the communication terminal  20  to display a user interface (UI). The overall control unit  330  performs overall control such as issuing instructions to start and disconnect communication. The communication information management unit  320  holds information on distribution, for example, a video encode setting. The communication control unit  340  controls communication with the electronic blackboard  10 , and transmits and receives data to and from the video distribution service  200  of the electronic blackboard  10 . The reproduction control unit  350  inputs compressed data to the video decoder unit  360 . The video decoder unit  360  decodes the compressed data and causes the image display unit  370  to display an image. The image display unit  370  includes a liquid-crystal image display panel and displays a GUI based on an image output from the GUI unit  310  and a distribution image based on the image from the video decoder unit  360 . 
     The following describes a flow of processing performed in the electronic blackboard system  1 .  FIG. 7  is a diagram illustrating a procedure for generating and distributing a distribution image in the electronic blackboard system. 
     The image generation unit  140  of the application  100  superimposes all layers including the operation panel display layer  81  to be displayed on the image display device  50  of the electronic blackboard  10 , to generate a display image. The image generation unit  140  transmits the display image to the display control unit  160  (Step S 11 ). 
     At the same time, the image generation unit  140  generates a distribution image that does not include the operation panel display layer  81  and outputs the distribution image to the frame output unit  130  (Step S 12 ). 
     The capture unit  270  of the video distribution service  200  captures and acquires the image output to the frame output unit  130  (Step S 13 ). The captured image is transmitted to the codec module  290  (Step S 14 ). In the codec module  290 , the video encoder unit  250  compresses the image to generate compressed data and transmits the compressed data to the distribution module  280  (Step S 15 ). 
     The distribution module  280  transmits the compressed data to the communication terminals  20  (Step S 16 ). In each of the communication terminals  20 , the video decoder unit  360  decodes the compressed data and the GUI unit  310  displays the distribution image with the operation panel being excluded. 
     By the above-described processing, the communication terminals  20  each displays the distribution image including the handwritten image layers  82  and  83 , with the operation panel display layer  81  being excluded. 
     The distribution image may be formed with desired layers selected from a plurality of handwritten image layers such as the layers  82  and  83 , and distributed. 
     In this manner, the operation panel is excluded from the distribution image distributed to each communication terminal  20  in order to prevent a user of the communication terminal  20  from misunderstanding that the user can operate the blackboard from the operation panel. 
     The following describes a modification of the first embodiment. 
       FIG. 8  is a view illustrating a display screen on a communication terminal in the electronic blackboard system according to the modification of the first embodiment. 
     If each communication terminal  20  allows only viewing, the image display unit  370  of the communication terminal  20  may display only a handwritten image without an operation panel. However, some communication terminals desirably provide a number of functions such as changing colors of handwriting and enlarging display. 
     Thus, in the present modification, the communication terminals  20  can each display a unique operation panel  30 . For example, the operation panel  30  may include a pen writing icon  31 , an enlarged-display icon  32 , and a text input icon  33 . 
     As described above, displaying the unique operation panel  30  on each of the communication terminals  20  enables provision of an appropriate operation panel depending on the type of the communication terminal  20 . For example, when one of the communication terminals  20  includes a keyboard, the text input icon  33  may be specified so as to facilitate text input to the display unit. 
     Second Embodiment 
     The following describes an electronic blackboard system according to a second embodiment of the present invention. 
     An electronic blackboard system  1 A according to the second embodiment includes, as illustrated in  FIG. 1 , an electronic blackboard  10 A and the communication terminals  20 . 
     In the electronic blackboard system  1 A according to the present embodiment, the electronic blackboard  10 A can select, as an image to be transmitted to the communication terminals  20 , a predetermined image other than a handwritten image according to an external instruction such as an instruction from an operator of the electronic blackboard  10 A. The predetermined image is distributed as a distribution image to the communication terminals  20 . 
     As illustrated in  FIG. 1 , the electronic blackboard system  1 A includes the electronic blackboard  10 A and the communication terminals  20  ( 20 - 1 ,  20 - 2 , . . . ,  20 - n ) connected to the electronic blackboard  10 A via a wireless LAN. The wireless LAN is used for an in-house network, for example. 
     The electronic blackboard  10 A includes an application  100 A, the video distribution service  200 , and the image display device  50 . The communication terminals  20  are the same as the first embodiment. The electronic blackboard  10 A has the same hardware configuration as the electronic blackboard  10  according to the first embodiment, which is illustrated in  FIG. 2 . 
       FIG. 9  is a functional block diagram of the electronic blackboard used for the electronic blackboard system according to the second embodiment. The electronic blackboard  10 A includes the application  100 A and the video distribution service  200 . 
     The application  100 A has the same configuration as the application  100  of the first embodiment except that the application  100 A includes a nonvolatile memory unit  170  serving as an image storing unit. That is, the application  100 A includes, other than the nonvolatile memory unit  170 , the function execution unit  110 , the application input/output unit  120 , the frame output unit  130 , the image generation unit  140 , the operation reception unit  150 , and the display control unit  160 . The nonvolatile memory unit  170  preliminarily stores therein one or more distribution layers selectable as other layers. 
     The communication terminals  20  used in the electronic blackboard system  1 A each have the same configuration as the communication terminals  20  used in the electronic blackboard system  1  according to the first embodiment (refer to  FIG. 6 ). 
       FIG. 10  is a view illustrating a display screen on the electronic blackboard according to the second embodiment. The image display device  50  in the electronic blackboard system  1 A displays an operation panel  70 A and the handwritten image  60  including the stroke image  61  and the text  62 , for example. The configuration of the handwritten image  60  is the same as the configuration of the handwritten image  60  in the first embodiment. 
     The operation panel  70 A includes a plurality of function icons. In the present embodiment, the operation panel  70 A includes a message distribution icon  72  for distributing, as a distribution image, a layer specified from one or more distribution layers displaying respective messages stored in the nonvolatile memory unit  170 . 
       FIG. 11  is a view illustrating a display screen on the electronic blackboard and display screens on the communication terminals according to the second embodiment. In  FIG. 11 , the image display device  50  of the electronic blackboard  10 A displays the handwritten image  60  and the operation panel  70 A. The handwritten image  60  is distributed as the distribution image to the communication terminals  20  ( 20 - 1  to  20 - 4 ) and displayed on the respective image display units. This state is the same as the display in the first embodiment. The procedure for distributing the handwritten image  60  is the same as the first embodiment, which is illustrated in  FIG. 7 . 
     The following describes the distribution of an image stored as a distribution image in the nonvolatile memory unit  170  to the communication terminals  20 . 
     It is assumed that the electronic blackboard system  1 A is used in an educational field. A teacher performs writing or presents material on the electronic blackboard  10 A to give explanation. Students use the communication terminals  20  such as tablet terminals. Each student views an image of the electronic blackboard on the screen of the student&#39;s communication terminal  20 , and inputs handwritten information from the communication terminal  20  as needed. 
     Each student can view the handwritten image  60  on the screen of the communication terminal  20  and thus the student&#39;s attention is on the communication terminal  20 . When the teacher needs the students to look up and give attention to the teacher, it is desirable that a desired message or image be displayed on each communication terminal  20  without changing the image that has been displayed on the image display device  50  of the electronic blackboard  10 A. 
     In the present embodiment, specifying the message distribution icon  72  on the operation panel  70 A of the electronic blackboard  10 A enables selection of a necessary image from images stored in the nonvolatile memory unit  170  and transmission of the image to the communication terminals  20 . 
       FIG. 12  is a view illustrating selection of a temporary distribution image in the electronic blackboard system.  FIG. 13  is a view illustrating display screens on the electronic blackboard and the communication terminals when the temporary distribution image is distributed in the electronic blackboard system. 
     These diagrams illustrate an example screen displayed on the communication terminals  20 . Selecting the message distribution icon  72  displays a list  90  of the temporary distribution images that can be distributed to the communication terminals  20 , as illustrated in  FIG. 12 . 
     In this example, four images are selectably displayed, which are an image  91  indicating “Look Forward!”, an image  92  indicating “Attention!”, an image  93  indicating “Working”, and an image  94  indicating “Break until 16:00”. One of the four temporary distribution images is selected. These temporary distribution images are stored as temporary distribution layers in the nonvolatile memory unit  170 . From the temporary distribution layers, a layer is selected by the function execution unit  110  serving as a selecting unit, formed as a distribution image by the image generation unit  140 , and distributed to the communication terminals  20 . 
     When the temporary distribution image is distributed, all the communication terminals  20  ( 20 - 1  to  20 - 4 ) display the selected temporary distribution image (in this example, the image  91  of “Look Forward!”) in place of the handwritten image  60 , as illustrated in  FIG. 13 . The nonvolatile memory unit  170  is set to be capable of storing therein a temporary image freely added from the electronic blackboard. 
     Displaying such temporary distribution image can bring the students&#39; attention to the electronic blackboard  10 A instead of the respective communication terminals  20 . Under this state, which is regarded as the state of distributing the temporary distribution image, operation from the communication terminals can be prohibited. Reselecting the message icon on the operation panel  70 A on the electronic blackboard  10 A ends the state of distributing the temporary distribution image, and redistributes the handwritten image  60  to the communication terminals  20 . 
     The following describes a procedure for distributing the temporary distribution image. 
       FIG. 14  is a diagram illustrating a procedure for distributing the temporary distribution image in the electronic blackboard system. The image generation unit  140  of the application  100 A generates a display image to be displayed on the image display device  50  of the electronic blackboard  10 A, and transmits the display image to the display control unit  160  (Step S 21 ). The frame output unit  130  acquires a temporary distribution image selected from the nonvolatile memory unit  170  (Step S 22 ). The distribution information management unit  230  then transmits the temporary distribution image to the capture unit  270  (Step S 23 ). The capture unit  270  transmits the temporary distribution image to the codec module  290  (Step S 24 ). The codec module  290  compresses the temporary distribution image and transmits the compressed temporary data to the distribution module  280  (Step S 25 ). The distribution module  280  distributes the compressed temporary data to the communication terminals  20  (Step S 26 ). In the video distribution service  200 , the video decoder unit  360  decodes the compressed temporary data and the image display unit  370  displays a temporary display image. 
     The following describes a procedure in which the frame output unit  130  of the electronic blackboard  10 A acquires a distribution image and a temporary distribution image.  FIG. 15  is a flowchart illustrating a procedure in which the frame output unit of the electronic blackboard acquires a distribution image. 
     The frame output unit  130  determines whether a temporary distribution image is being distributed (Step S 31 ). In a normal state of distributing no temporary distribution image (No at Step S 31 ), the handwritten image  60  is acquired as a distribution image from the image generation unit  140  (Step S 32 ) and transmitted to the frame output unit  130  (step S 34 ). 
     If a temporary distribution image is being distributed (Yes at Step S 31 ), the temporary distribution image selected from the nonvolatile memory unit  170  is acquired (Step S 33 ). 
     As described above, the electronic blackboard system  1 A according to the second embodiment can distribute a temporary distribution image to the communication terminals  20  as needed. 
     Each of the electronic blackboards  10  and  10 A may include a web server unit. This configuration enables each communication terminal  20  to use a web browser to view an image from the frame output unit  130 . 
     Configurations, Actions, and Effects of Aspects of Present Invention 
     First Aspect 
     The electronic blackboard  10  of the present aspect generates an image viewable by the communication terminal  20  and includes the image generation unit  140 . The image generation unit  140  generates a display image in which the operation panel display layer  81  for displaying the operation panel  70  and the handwritten image layers  82  and  83  for displaying respective images other than the operation panel  70 are overlapped, and a distribution image in which the operation panel display layer  81  is excluded and only the other layers are overlapped. 
     According to the present aspect, the image generation unit  140  generates the display image generated from the operation panel display layer  81  and the handwritten image layers  82  and  83 , and the distribution image generated from the handwritten image layers  82  and  83 . Thus, the distribution image is generated with a specific image undesirable for distribution being excluded, enabling easy and suitable viewing at the communication terminal  20 . 
     Second Aspect 
     In the present aspect, the image generation unit  140  of the electronic blackboard  10  superimposes a desired layer among the the handwritten image layers  82  and  83 , to form the distribution image. 
     According to the present aspect, the image generation unit  140  generates the display image from the operation panel display layer  81  and the handwritten image layers  82  and  83 . Thus, the distribution image is generated with a specific image undesirable for distribution being excluded, enabling easy and suitable viewing at the communication terminal  20 . 
     Third Aspect 
     The present aspect includes: the nonvolatile memory unit  170  that preliminarily stores therein one or more temporary distribution layers selectable as the other layers, and a selecting unit that selects, as the other layers, any one of the one or more distribution layers stored in the nonvolatile memory unit  170 , according to an instruction from the message distribution icon  72  on the operation panel  70 A. 
     According to the present aspect, the image generation unit  140  selects, according to an external instruction, a layer from the temporary distribution layers stored in the nonvolatile memory unit  170 , to form the distribution image. Thus, the electronic blackboard  10 A can distribute a temporary distribution image to the communication terminal  20  at a desired timing. 
     Fourth Aspect 
     In the present aspect, the electronic blackboard  10  or  10 A includes the video distribution service  200  that distributes the distribution image to the communication terminal  20 . 
     According to the present aspect, the video distribution service  200  can distribute the distribution image from the electronic blackboard  10  or  10 A to the communication terminal  20 . Thus, the communication terminal  20  can display the distribution image from the electronic blackboard  10  or  10 A. 
     Fifth Aspect 
     In the present aspect, the electronic blackboard  10  includes the web server unit that publishes the distribution image. 
     According to the present aspect, the communication terminal  20  can acquire the distribution image from the electronic blackboard  10  through the web server unit using a web browser. Thus, the communication terminal  20  can easily display the distribution image. 
     Sixth Aspect 
     In the present aspect, the electronic blackboard  10 A includes a registering unit that registers an image as the one or more distribution layers, in the nonvolatile memory unit  170 . 
     According to the present aspect, the electronic blackboard  10 A can register an image in the nonvolatile memory unit  170 . Thus, various images can be distributed as a temporary distribution image to the communication terminal  20 . 
     Seventh Aspect 
     In the present aspect, the electronic blackboard system  1  or  1 A includes: the electronic blackboard  10  or  10 A; and the communication terminal  20  that is connected to the electronic blackboard  10  or  10 A via a network, and receives and displays the distribution image. 
     According to the present aspect, the electronic blackboard  10  or  10 A distributes, to the communication terminal  20 , the display image generated from the operation panel display layer  81  and the handwritten image layers  82  and  83 , and the distribution image generated from the handwritten image layers  82  and  83 , the display image and the distribution image being generated by the image generation unit  140 . Thus, the distribution image is generated with the image of the operation panel  70  undesirable for distribution being excluded, enabling easy and suitable viewing at the communication terminal  20 . 
     According to an embodiment, the distribution image is generated with a specific image undesirable for distribution being excluded, enabling easy and suitable viewing at the communication terminal. 
     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, at least one element of different illustrative and exemplary embodiments herein may be combined with each other or substituted for each other within the scope of this disclosure and appended claims. Further, features of components of the embodiments, such as the number, the position, and the shape are not limited the embodiments and thus may be preferably set. It is therefore to be understood that within the scope of the appended claims, the disclosure of the present invention may be practiced otherwise than as specifically described herein. 
     The method steps, processes, or operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance or clearly identified through the context. It is also to be understood that additional or alternative steps may be employed. 
     Further, any of the above-described apparatus, devices or units can be implemented as a hardware apparatus, such as a special-purpose circuit or device, or as a hardware/software combination, such as a processor executing a software program. 
     Further, as described above, any one of the above-described and other methods of the present invention may be embodied in the form of a computer program stored in any kind of storage medium. Examples of storage mediums include, but are not limited to, flexible disk, hard disk, optical discs, magneto-optical discs, magnetic tapes, nonvolatile memory, semiconductor memory, read-only-memory (ROM), etc. 
     Alternatively, any one of the above-described and other methods of the present invention may be implemented by an application specific integrated circuit (ASIC), a digital signal processor (DSP) or a field programmable gate array (FPGA), prepared by interconnecting an appropriate network of conventional component circuits or by a combination thereof with one or more conventional general purpose microprocessors or signal processors programmed accordingly. 
     Each of the functions of the described embodiments may be implemented by one or more processing circuits or circuitry. Processing 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), field programmable gate array (FPGA) and conventional circuit components arranged to perform the recited functions. 
     REFERENCE SIGNS LIST 
     
         
           1 ,  1 A Electronic blackboard system 
           10 ,  10 A Electronic blackboard 
           20  Communication terminal 
           100 ,  100 A Application 
           110  Function execution unit 
           120  Application input/output unit 
           130  Frame output unit 
           140  Image generation unit 
           150  Operation reception unit 
           160  Display control unit 
           170  Nonvolatile memory unit 
           200  Video distribution service