JP5481470B2 - Electronic blackboard and computer program - Google Patents

Description

  Embodiments described herein relate generally to an electronic blackboard that captures and outputs characters, figures, and the like drawn on a writing surface as image data and a computer program thereof.

  Conventionally, image data is generated by optically reading characters and figures drawn with a writing instrument such as a marker on the writing surface, and the generated image data is printed on a paper medium by a printer, or USB (Universal Serial Bus). There is an electronic blackboard that outputs by writing to a storage medium such as a memory.

  When a conventional electronic blackboard reads the writing surface and generates image data (monochrome image) binarized in black and white and outputs it, the characters and figures on the writing surface are drawn In this case, the whole or part of the portion that is drowned in the output image data is lost, and it is easy to cause a situation that the portion becomes difficult to read. In order to cope with such a situation, an electronic blackboard provided with a button for adjusting the density of image capture (threshold used for binarization) so that the user can capture characters and figures on the writing surface at a desired density There is also.

JP 2008-131499 A

  Even if it is an extremely drowned portion, it is possible to obtain image data that allows the portion to be visually recognized by adjusting the darkness as described above. However, if the density of image capture is too high, part of the writing surface on which characters or figures are not drawn, dark lines on the writing surface, etc. are captured in black, and the visibility of the entire image data deteriorates. There is.

  In addition, when image data is written to a storage medium such as a USB memory instead of being printed by a printer, the contents of the image data cannot often be confirmed on the spot. Therefore, even though the image data content is so bad that it cannot recognize characters, etc., there is a concern that the characters and figures on the writing surface will be erased by the cleaner and the drawn content will not be understood. Is done.

  The problem to be solved by the present invention is that, when outputting image data generated by reading characters or figures drawn on the writing surface, the lack of writing content is maintained while maintaining good visibility of the image data. An electronic blackboard that can be prevented, and a computer program for the electronic blackboard.

An electronic blackboard according to an embodiment reads a writing surface, an attaching / detaching unit to which a storage medium can be attached and detached, information read on the writing surface, and multi-tone image data in which each pixel is expressed in multi-tones. The number of generations is determined according to the reading unit to be generated and the free storage capacity of the storage medium attached to the detachable unit, and each pixel included in the multi-tone image data generated by the reading unit is related to the gradation value. Two-tone image data obtained by binarization with a predetermined threshold value is generated by the image generation unit which generates the same number of generations by changing the threshold value, and the image generation unit on a storage medium attached to the attachment / detachment unit An output control unit for writing the plurality of two-tone image data.

1 is an external perspective view of an electronic blackboard according to an embodiment. The figure which shows the power switch and USB port with which the electronic blackboard is equipped. The top view which shows roughly the internal structure of the electronic blackboard. The front view which shows roughly the internal structure of the electronic blackboard. The block diagram which shows the control circuit of the electronic blackboard. The flowchart which shows the operation | movement at the time of the electronic blackboard outputting image data. The figure for supplementarily explaining a part of operation | movement of the electronic blackboard.

Hereinafter, an embodiment will be described with reference to the drawings.
In the following description, the same components are denoted by the same reference numerals, and redundant description will be given only when necessary.

[Appearance configuration]
FIG. 1 is an external perspective view of an electronic blackboard 1 in the present embodiment.
The electronic blackboard 1 is configured by supporting a frame 3 having a rectangular frame shape by a pair of stands 2a and 2b. The frame 3 houses an annular sheet 4 made of, for example, polyethylene. A portion of the sheet 4 exposed to the outside from the opening on the front side of the frame 3 becomes a writing surface 4a on which characters, figures, and the like are drawn by a writing tool such as a marker pen. An ink jet printer 5 for printing and issuing an image read by the CCD line sensor 15 (see FIGS. 4 and 5) on a print medium is provided below the frame 3 on the stand 2b side.

  A lower shelf 6 that protrudes toward the front side is provided at the lower edge of the frame 3. The lower shelf 6 is provided with a cleaner or the like that erases characters drawn on the writing surface 4a by a sliding operation with a writing instrument such as a marker pen.

  An operation panel 7 having various operation keys for operating the electronic blackboard 1 is provided on the edge of the frame 3 on the stand 2b side.

  As shown in FIG. 2, a protrusion 3a protruding toward the front is formed at the lower corner of the frame 3 on the stand 2b side, and power supply to the electronic blackboard 1 is turned on / off in the protrusion 3a. For this purpose, a power switch 8 and a USB port 9 to which the USB connector 101 of the USB memory 100 can be attached and detached are provided. In addition to the USB memory, the USB port 9 includes various external storage devices such as an SD card drive having a USB connector, a floppy (registered trademark) disk drive, a CD-R drive, a DVD-R drive, and a hard disk drive. Can be connected.

  The operation panel 7 is an LED display unit that notifies the presence / absence of power supply, out of paper, and the like by lighting the LED, and a sheet feed that gives a sheet feed instruction for feeding the sheet 4 from the stand 2b side to the stand 2a side in FIG. A button, a print button for giving an instruction to print characters drawn on the writing surface 4a, and a USB write button for giving an instruction to output the characters drawn on the writing surface 4a as electronic data from the USB port 9 to the outside Etc.

[Internal configuration]
FIG. 3 is a plan view schematically showing the internal structure of the electronic blackboard 1, and FIG. 4 is a front view schematically showing the internal structure of the electronic blackboard 1.
A pair of rollers 10 a and 10 b that rotate and convey the sheet 4 are provided at both left and right ends in the frame 3. The rollers 10a and 10b have an axis substantially parallel to the left and right edges of the frame 3, and an annular sheet 4 is stretched between the rollers 10a and 10b. A sheet feed (SF) motor 25 (see FIG. 5) is connected to one of the rollers 10a and 10b via a belt transmission mechanism (not shown). When the SF motor 25 is driven, the rollers 10a and 10b are rotated via the belt transmission mechanism, and the sheet 4 is rotated and conveyed in the left-right direction.

  In addition, a writing board 11 is provided immediately behind the writing surface 4a of the sheet 4 in order to ensure good writing properties for the writing surface 4a.

  On the opposite side of the writing surface 4a with the writing board 11 in between, a light source 12 and a mirror 13, a lens 14, and a CCD line sensor 15 that are long in a direction substantially perpendicular to the conveying direction of the sheet 4 are provided. ing. When reading characters or the like drawn on the sheet 4, the light source 12 irradiates the sheet 4 with visible light, and the reflected light from the sheet 4 is sent to the lens 14 via the mirror 13 and received by the CCD line sensor 15. Focused on the surface. At this time, an electrical signal for one line along the longitudinal direction of the mirror 13 is output from the CCD line sensor 15 in accordance with the visible light received by the light receiving surface.

  The light source 12, the mirror 13, the lens 14, the CCD line sensor 15, and an image processing unit 24 (see FIG. 5) described later constitute a reading unit that reads information on the sheet 4 and generates image data.

[Control circuit]
Next, the control circuit of the electronic blackboard 1 will be described.
FIG. 5 is a block diagram showing a control circuit of the electronic blackboard 1.
The control circuit includes a control unit 20, a ROM (Read Only Memory) 21, a RAM (Random Access Memory) 22, a lighting circuit 23, an image processing unit 24, an SF motor 25, a power supply unit 26, the inkjet printer 5, and the operation panel. 7, the power switch 8, the USB port 9, the light source 12, the CCD line sensor 15, and the like.

  The ROM 21 stores fixed data such as an operation program of the electronic blackboard 1 and various default setting values. The RAM 22 forms various working storage areas according to the processing scene of the electronic blackboard 1.

  The lighting circuit 23 energizes the light source 12 when reading characters or the like drawn on the sheet 4 and turns on the light source 12. As described above, when the light source 12 is turned on, the reflected light from the sheet 4 is condensed on the CCD line sensor 15 via the lens 14 and the like, and an electrical signal corresponding to the visible light received by the CCD line sensor 15 is output. .

  The image processing unit 24 amplifies the electric signal for each line output from the CCD line sensor 15, and A / D converts the electric signal amplified by the amplifier into a gradation value corresponding to the intensity to convert the digital data. An A / D converter to be generated, an image processing LSI that generates various multi-tone image data by combining a plurality of lines of digital data generated by the A / D converter, and performs various corrections such as shading correction It is configured. In the present embodiment, it is assumed that the multi-tone image data generated by the image processing unit 24 is 256-scale (8-bit) grayscale image data. Various file formats such as TIFF, JPEG, and BMP can be adopted as specific file formats of the image data.

  The power supply unit 26 takes in the operating power from the external power supply 30 such as a commercial AC power supply in response to the power switch 8 being switched to the power-on state, and supplies it to each part constituting the control circuit.

  When the USB connector 101 of the USB memory 100 is connected to the USB port 9, operating power is supplied to the USB memory 100 from the power supply unit 26 via the USB port 9. The USB memory 100 receives this operating power and writes and reads data to and from the internal memory. Also, the USB port 9 monitors the presence or absence of power supply to the USB memory 100, notifies the control unit 20 of the status of no connection when power is not supplied, and is connected when power is supplied. Has a function of notifying the control unit 20 of the status.

The control unit 20 realizes a monochrome image generation function 201 and an output control function 202 as characteristic functions in the present embodiment, in addition to the function of controlling the basic operation of each unit constituting the control circuit.
The monochrome image generation function 201 converts monochrome image data (binarized image data) obtained by binarizing each pixel included in the grayscale image data generated by the image processing unit 24 with a predetermined threshold relating to the gradation value. This is a function for generating a plurality of different thresholds.

  The output control function 202 is either grayscale or monochrome for the grayscale image data generated by the image processing unit 24 or the monochrome image data generated by the monochrome image generation function 201, or is monochrome Is a function that gives a name that can be recognized to what level the gradation value (density) as a binarization threshold is, and outputs it to the USB memory 100 or the like attached to the USB port 9. .

[Operation]
A specific operation of the electronic blackboard 1 configured as described above will be described.
When the power switch 8 is switched to the power-on state and the print button of the operation panel 7 is operated in a state where the operating power is supplied from the power supply unit 26, the control unit 20 causes the characters drawn on the writing surface 4a, etc. As image data. Specifically, the light circuit 12 is turned on in the lamp circuit 23, the SF motor 25 is rotated to convey the sheet 4, and the image processing unit 24 is instructed to generate image data. Upon receiving this instruction, the image processing unit 24 converts the electric signal for each line output from the CCD line sensor 15 into digital data. The SF motor 25 rotates until the image processing unit 24 finishes obtaining digital data corresponding to the last line of the writing surface 4a at the time when the print button is operated. Then, the image processing unit 24 generates a single grayscale image data by combining all the digital data acquired until the SF motor 25 is stopped in the line order, and outputs the grayscale image data to the control unit 20. The control unit 20 stores the gray scale image data thus captured in the RAM 22. Then, the control unit 20 binarizes the grayscale image data stored in the RAM 22 with, for example, a gradation threshold corresponding to a preset density, generates monochrome image data, and outputs the monochrome image data to the inkjet printer 5. The inkjet printer 5 prints the input monochrome image data on a paper medium and discharges it to the outside.

  Further, when the power switch 8 is switched to the power-on state and the USB writing button on the operation panel 7 is operated with the operating power supplied from the power supply unit 26, the control unit 20 is stored in the ROM 21. The operation program is read and executed, and operates according to the flowchart shown in FIG.

  That is, first, similarly to the above-described operation of the print button, the control unit 20 captures characters drawn on the writing surface 4a as grayscale image data and stores them in the RAM 22 (step S1).

  Next, the control unit 20 determines whether or not the USB memory 100 is connected to the USB port 9 (step S2). When the status of no connection is notified from the USB port 9, the control unit 20 determines that the USB memory 100 is not connected to the USB port 9 (No in step S2), and an error is caused by the LED display unit of the operation panel. And the process shown in the flowchart is terminated.

  On the other hand, when the connection status is notified from the USB port 9, the control unit 20 determines that the USB memory 100 is connected to the USB port 9 (Yes in step S2), and accesses the USB memory 100. The free storage capacity E (byte) is specified (step S3). For example, if the format of the USB memory 100 corresponds to a FAT (File Allocation Table) file system such as FAT16 or FAT32, the free storage capacity E is known by referring to the FSInfo sector included in the format. May be specified.

  After specifying the free storage capacity E, the control unit 20 compares the free storage capacity E with the file size GS (byte) of the grayscale image data stored in the RAM 22 in step S1, and determines the grayscale image data. It is determined whether or not data can be stored in the USB memory 100 (step S4).

  As a result, if the free storage capacity E is larger than the file size GS of the grayscale image data, the control unit 20 determines that the grayscale image data can be stored in the USB memory 100 (Yes in step S4). ), And writes the gray scale image data in an empty area of the USB memory 100 (step S5). At this time, the control unit 20 can identify from the file name that the file is grayscale image data by adding a file name such as “grayscale.extension” to the grayscale image data. Thus, the data is written into the USB memory 100. When the writing is completed, the processing shown in the flowchart is terminated.

  On the other hand, as a result of the determination in step S4, if the free storage capacity E is smaller than the file size GS of the grayscale image data, the control unit 20 stores a plurality of monochrome image data having different densities in the USB memory 100. Process. That is, first, the control unit 20 sets the generation number N (integer) of monochrome image data to be written to the USB memory 100 (step S6).

  The generation number N may be a number obtained by dividing the free storage capacity E specified in step S3 by the file size MS (byte) of one monochrome image data and rounding off the decimal part. However, in order to avoid the image data number N from becoming unnecessarily large, the maximum value Nmax of the generation number is set in advance to about “5”, for example, and when the calculated generation number N> the maximum value Nmax, The generation number N may be the maximum value Nmax.

  After step S6, the control unit 20 specifies the maximum value Pmax and the minimum value Pmin of the gradation values indicated by each pixel included in the grayscale image data stored in the RAM 22 in step S1 (step S7). For example, each pixel of the gray scale image data is represented by a bit string defined as an intermediate color that changes from “0” to pure white, “255” to pure black, and “1” to “254” from pure white to pure black. In step S7, the largest value (value close to pure black) among the values indicated by the bit string corresponding to each pixel of the grayscale image data is set as the maximum value Pmax, and the smallest value (pure white) is determined in step S7. (Value close to) is defined as the minimum value Pmin. However, the minimum value Pmin is set to “0” in advance in consideration of the fact that the image processing unit 24 normally generates grayscale image data so that the gradation value of the ground color of the writing surface 4a becomes “0” (pure white). It may be set to.

  After step S7, the control unit 20 generates the same number of gradation values εn (n; integer, n = 1 to N) as the number of generations N that equally divides the gradation value range between the maximum value Pmax and the minimum value Pmin. Set (step S8). For example, when N = 3, the maximum value Pmax is “120”, and the minimum value Pmin is “0”, three gradation values ε1 (= “90”), ε2 (= “60”), as shown in FIG. ε3 (= “30”) is set.

  After step S8, the control unit 20 sets two pixels included in the grayscale image data stored in the RAM 22 in step S1 using one of the set gradation values εn (n = 1 to N) as a threshold value. The process of generating monochrome image data by performing the conversion is performed for each gradation value εn (n = 1 to N) to obtain N pieces of monochrome image data (step S9). The obtained N monochrome image data are stored in the RAM 22.

  The monochrome image data generated here is, for example, image data in a format in which “0” is pure white and “1” is pure black, and each pixel is expressed by 1 bit. In step S9, for example, when the gradation values ε1 to ε3 are set as in the example of FIG. 7, the gradation value is determined among the pixels included in the grayscale image data stored in the RAM 22 in step S1. A monochrome image in which all the gradation values of pixels below the threshold ε1 (= “90”) are all “0” (pure white) and all gradation values of pixels whose gradation value is the threshold ε1 or more are all “1” (pure black). All the gradation values of the data and pixels whose gradation value is less than the threshold ε2 (= “60”) are “0” (pure white), and all the gradation values of the pixels whose gradation value is the threshold ε2 or more are “1” ( Monochrome image data set to pure black) and gradation values of pixels whose gradation value is less than the threshold value ε3 (= “30”) are all “0” (pure white), and gradation values of the pixel whose gradation value is the threshold value ε3 or more. Monochrome image data whose values are all “1” (pure black) are generated.

  After step S9, the control unit 20 determines a file name assigned to the generated N pieces of monochrome image data (step S10). The file name assigned to each monochrome image data is determined using a format such as “capture density X.extension” (X = 1 to N), for example. When this format is used, for example, in step S8, gradation values ε1 to ε3 are set as in the example of FIG. 7, and in step S9, the three monochrome values are binarized using the gradation values ε1 to ε3 as threshold values. When the image data is generated, the monochrome image data binarized with the gradation value ε1 as a threshold value is “monochrome that has been binarized with“ capture density 1. extension ”and the gradation value ε2 as a threshold value. The file names of “capture density 2. extension” are determined for the image data, and “capture density 3. extension” is determined for the monochrome image data binarized using the gradation value ε3 as a threshold. If the file name is determined in this way, the density (threshold used for binarization) of each monochrome image data can be determined from the file name.

  After step S10, the control unit 20 writes each monochrome image data stored in the RAM 22 in step S9 to the USB memory 100 with the file name determined in step S10 added (step S11). As a result, the USB memory 100 stores N pieces of image data having different densities (threshold values used for binarization). Thus, the process shown in the flowchart is completed.

  As described above, when writing the image data into the USB memory 100, the electronic blackboard 1 according to the present embodiment first reads the image drawn on the writing surface 4a to generate grayscale image data, and generates the generated grayscale image data. A plurality of monochrome image data obtained by binarizing each pixel included in the image with a threshold value relating to a gradation value are generated with different threshold values, and the generated plurality of monochrome image data are written in the USB memory 100.

  When monochrome image data binarized with a plurality of different threshold values, in other words, monochrome image data generated with a plurality of different densities, is written in the USB memory 100, the user selects monochrome image data with a desired density. And can be used for subsequent processing. Further, even if a drawn character or the like drawn on the writing surface 4a is missing in any monochrome image data due to insufficient density, the density is higher than that of the monochrome image data (in this embodiment, the threshold value εn). In other words, the character or the like may be recognized in the monochrome image data. Therefore, it can be said that the possibility that the character or the like drawn on the writing surface 4a is lost can be reduced. Conversely, in high-density monochrome image data, the ground color of the writing surface on which nothing is drawn, the dark line of the writing surface, etc. are captured in black, and the visibility of characters drawn darkly on the writing surface 4a deteriorates. However, such a darkly drawn character or the like appears well in monochrome image data having a low density (in this embodiment, a large threshold value εn), and may be confirmed using this.

  Further, if the electronic blackboard 1 has a capacity capable of writing the grayscale image data in the USB memory 100, the electronic blackboard 1 writes the grayscale image data in the USB memory 100 instead of the monochrome image data. If the grayscale image data is written in the USB memory 100 in this way, the user can freely change the density of the image data later using a personal computer or the like. Normally, dark lines or the like of the writing surface 4a are displayed in the gray scale image data, but these may be deleted by using a binarization tool possessed by a personal computer or the like.

  The number N of monochrome image data generated is determined according to the free storage capacity E of the USB memory 100. Therefore, even when gray scale image data cannot be written, as many monochrome image data with different densities as possible can be generated and written to the USB memory 100.

  Further, the electronic blackboard 1 obtains N gradation values εn that equally divide the gradation value range between the maximum value Pmax and the minimum value Pmin of the gradation values indicated by each pixel included in the grayscale image data, Monochrome image data is generated using the obtained gradation value εn as a threshold value. If the threshold values are determined in this way, the respective threshold values are appropriately dispersed within the gradation value range.

In addition, the electronic blackboard 1 attaches each of the generated monochrome image data to the USB memory 100 with a file name in a format that can specify the magnitude relation of each threshold used for binarization, that is, the density level relation. Write. If the file name is assigned in this way, when the monochrome image data written in the USB memory 100 is used on a personal computer or the like, the user does not need to open the file of each image data and is indicated by the image data. It becomes possible to recognize the density of the image.
In addition, various suitable effects can be obtained from the configuration of the present embodiment.

[Modification]
The configuration disclosed in the above embodiment can be modified in various ways.
For example, in the above-described embodiment, the case where gray scale image data or monochrome image data is output to the USB memory 100 is illustrated. However, the storage medium that is the output destination of each image is not limited to a USB memory, and may be other media such as an SD card, a floppy (registered trademark) disk, a CD-R, a DVD-R, and a hard disk. In addition, image data may be written in these storage media via a drive for each storage medium connected to a connection unit such as a USB port 9, or a drive for each storage medium is connected to the electronic blackboard 1. And image data may be written via the drive.

  In the above-described embodiment, the case where the multi-gradation image data generated by the image processing unit 24 is 256-color (8-bit) grayscale image data is exemplified. However, the number of gradations of the multi-gradation image data generated by the image processing unit 24 may be smaller or larger, such as 4 bits, 16 bits, or 32 bits, and color instead of grayscale image data. It may be image data.

  Further, in the above-described embodiment, the case where only the monochrome image data is stored without storing the grayscale image data when the free storage capacity E of the USB memory 100 is insufficient is illustrated. However, even when the USB memory 100 has a sufficient free storage capacity E, a plurality of monochrome image data generated using a plurality of different threshold values together with the grayscale image data or instead of the grayscale image data is stored in the USB memory 100. You may make it write in the memory 100. FIG.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.
The invention described in the scope of the original claims of the present application will be added below.
[1]
Writing surface,
A detachable part to which the storage medium is detachable;
A reading unit that reads information drawn on the writing surface and generates multi-gradation image data in which each pixel is expressed in multiple gradations;
Image generation for generating a plurality of two-gradation image data obtained by binarizing each pixel included in the multi-gradation image data generated by the reading unit with a predetermined threshold relating to a gradation value by changing the threshold And
An output control unit for writing a plurality of two-tone image data generated by the image generation unit to a storage medium mounted on the detachable unit;
An electronic blackboard characterized by comprising:
[2]
The output control unit writes the multi-gradation image data into the storage medium when the free storage capacity of the storage medium attached to the detachable unit exceeds the file size of the multi-gradation image data. The electronic blackboard according to [1].
[3]
The electronic apparatus according to [1] or [2], wherein the image generation unit determines the number of generations of the two-tone image data according to a free storage capacity of a storage medium attached to the detachable unit. blackboard.
[4]
The image generation unit includes the same number of gradation values as the generation number for equally dividing the gradation value range between the maximum value and the minimum value of the gradation values indicated by each pixel included in the multi-tone image data. The electronic blackboard according to [3], which is used as each threshold value.
[5]
The output control unit attaches and removes each of a plurality of two-tone image data generated by the image generation unit with a file name in a format capable of specifying the magnitude relationship of the threshold values used for binarization. The electronic blackboard according to any one of [1] to [4], wherein the electronic blackboard is written in a storage medium attached to the unit.
[6]
An electronic device comprising: a writing surface; an attaching / detaching portion that can attach and detach a storage medium; and a reading portion that reads information drawn on the writing surface and generates multi-gradation image data in which each pixel is expressed in multiple gradations. Blackboard
Image generation for generating a plurality of two-gradation image data obtained by binarizing each pixel included in the multi-gradation image data generated by the reading unit with a predetermined threshold relating to a gradation value by changing the threshold And
An output control unit for writing a plurality of two-tone image data generated by the image generation unit to a storage medium mounted on the detachable unit;
Computer program to function as.

  DESCRIPTION OF SYMBOLS 1 ... Electronic blackboard, 4 ... Sheet, 4a ... Writing surface, 5 ... Inkjet printer, 7 ... Operation panel, 9 ... USB port, 20 ... Control part, 21 ... ROM, 22 ... RAM, 24 ... Image processing part, 25 ... SF motor, 100 ... USB memory, 201 ... monochrome image generation function, 202 ... output control function

Claims (4)

Writing surface,
A detachable part to which the storage medium is detachable;
A reading unit that reads information drawn on the writing surface and generates multi-gradation image data in which each pixel is expressed in multiple gradations;
The number of generations is determined according to the free storage capacity of the storage medium attached to the detachable unit, and each pixel included in the multi-gradation image data generated by the reading unit is binarized by a predetermined threshold value regarding the gradation value. Two-tone image data obtained by converting the threshold value to different numbers to generate the image generation unit;
An output control unit for writing a plurality of two-tone image data generated by the image generation unit to a storage medium mounted on the detachable unit;
An electronic blackboard characterized by comprising: The image generation unit includes the same number of gradation values as the generation number for equally dividing the gradation value range between the maximum value and the minimum value of the gradation values indicated by each pixel included in the multi-tone image data. The electronic blackboard according to claim 1 , wherein the electronic blackboard is used as each threshold value. The output control unit attaches and removes each of a plurality of two-tone image data generated by the image generation unit with a file name in a format capable of specifying the magnitude relationship of the threshold values used for binarization. electronic blackboard according to claim 1 or 2, characterized in that writing to attached storage medium separate component. An electronic device comprising: a writing surface; an attaching / detaching portion that can attach and detach a storage medium; and a reading portion that reads information drawn on the writing surface and generates multi-gradation image data in which each pixel is expressed in multiple gradations. Blackboard
The number of generations is determined according to the free storage capacity of the storage medium attached to the detachable unit, and each pixel included in the multi-gradation image data generated by the reading unit is binarized by a predetermined threshold value regarding the gradation value. Two-tone image data obtained by converting the threshold value to different numbers to generate the image generation unit;
An output control unit for writing a plurality of two-tone image data generated by the image generation unit to a storage medium mounted on the detachable unit;
Computer program to function as.

Images