JP2005114878A - Image display system, method and program for generating display image data - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the display ability of a display device having limited number of display colors by efficiently generating display image data with small number of colors from image data. <P>SOLUTION: A program for making a computer generate display image data from the original image data comprises an original display image pixel data acquisition step, a division determining step, and a display image pixel data generation step. The display image pixel data generation step includes a step to generate a first display image, and a step to generate a second display image pixel data. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image display system, a display image data generation method, and a program, and more particularly, to an image display system and a display image that can be applied to a display device that displays fewer colors than the number of colors that can be expressed by image data. The present invention relates to a data generation method and a program.

  With the development of information technology and communication technology, research on displays such as liquid crystal display devices and organic EL display devices has been actively conducted. For example, liquid crystal display devices are used in personal computers, TV receivers, etc. instead of CRT (Cathode Ray Tube), and in addition to paper, electronic shelf labels, electronic price tags, electronic advertisements, electronic bulletin boards Etc. are also used.

  Display devices having various sizes and display capabilities have been developed in accordance with such usage forms. The resolution, which is one index of display capability, is represented by the number of pixels (pixels) as a display unit. For example, a display device such as 640 × 480 pixels, 800 × 600 pixels, 1024 × 768 pixels, 1280 × 1024 pixels, etc. It has been known.

  The colors that can be expressed by the display device differ depending on the number of bits of color information assigned to one pixel, 256 colors when 8 bits are assigned to one pixel, 65,000 colors when 16 bits are assigned, and 16.77 million when 24 bits are assigned. Color can be expressed. One pixel is called a full pixel, and this full pixel is formed of three sub-pixels. The three subpixels indicate R (red), G (green), and B (blue), respectively.

  For example, in a liquid crystal display device having a color filter, image data in a bitmap format having RGB values for each sub-pixel is generated in a computer, and the liquid crystal display device is passed through a color filter corresponding to each sub-pixel. The image data is displayed in full color.

  On the other hand, in a display device composed of two chiral nematic liquid crystal display elements, a technique for performing color display using a color due to cell reflection and a color due to a colored layer is known. For example, when each cell develops blue and orange and the colored layer develops black, the display device can display four colors, which are white by combining blue and orange. However, since the number of colors that can be displayed by such a display device is limited to four colors, there is a restriction in the representation of image display.

As a method for increasing the display color in a liquid crystal display device having RGB color filters, a technique using dithering (see Patent Document 1) is known.
JP 2001-282190 A

  As described above, for example, a display device constituted by two conventional chiral nematic liquid crystal display elements can display only four colors, and there is a problem that the display capability of color images is limited. there were.

  The present invention has been made in view of the above technical background, and one object of the present invention is to improve the display capability of a display device with a limited number of display colors. Another object of the present invention is to efficiently generate display image data with a small number of colors from the image data and improve the display capability of a display device with a limited number of display colors. Another object of the present invention is to improve the image quality of display image data in a process of generating display image data with a small number of colors from image data. Another object of the present invention is to improve the display capability of a display device composed of a plurality of chiral nematic liquid crystal display elements.

  According to a first aspect of the present invention, there is provided a program for causing a computer to execute a process of generating display image data having a smaller number of colors than the original image data from the original image data, the process comprising: An original image pixel data obtaining step for obtaining original image pixel data capable of displaying a first number of colors, the pixel data being divided into colors that can be displayed by the original image pixel data A division determination step for determining a division to which a color of the acquired original image pixel data belongs, and a division to which the color of the original image pixel data belongs. Generating display image pixel data for dithering representation capable of displaying a second number of colors that is less than one color number; and The display image pixel data generation step includes a step of generating a first display image pixel data for displaying a first color and a second color for displaying a second color different from the first color. Generating display image pixel data. As a result, the display capability of a display device with a limited number of colors can be improved, and display image data generation processing can be performed efficiently.

  The original image pixel data acquisition step acquires a plurality of original image pixel data, and when a predetermined number or more of the acquired plurality of original image pixel data are the same color, the display image pixel data Preferably, a data generation step is performed. Furthermore, it is preferable that the display image pixel data generation step is executed when all of the acquired plurality of original image pixel data have the same color. This can improve the image quality.

  And generating a display image pixel data corresponding to each of the plurality of original image pixel data when a predetermined number or more of the plurality of original image pixel data obtained is not the same color, The image pixel data generation step includes a plurality of different colors corresponding to the plurality of original image pixel data when the predetermined number or more of the acquired plurality of original image pixel data is the same color. Preferably, display image pixel data is generated. This can improve the image quality.

  The number of sections is preferably larger than the number of colors that can be displayed by dithering. As a result, it is possible to display effectively by dithering expression.

  The segment determining step preferably includes a step of determining a color segment to which each sub pixel data belongs for each of the sub pixel data constituting the original image pixel data. Thereby, the color classification can be determined more effectively.

  According to a second aspect of the present invention, there is provided a program for causing a computer to execute a process of generating display image data having fewer colors than the original image data from the original image data. Obtaining a plurality of original image pixel data capable of being displayed with a first number of colors, and pixels of the display image data according to the colors of the plurality of original image pixel data A step of determining a generation mode of display image pixel data which is data, and colors of the plurality of original image pixel data obtained when it is determined to generate data in the dithering mode in the determining step In response to display image pixel data capable of displaying a second number of colors less than the first number of colors for dithering representation. And the step of generating the display image pixel data includes generating a first display image pixel data for displaying a first color, and a second different from the first color. Generating second display image pixel data for displaying the colors of the image. Thereby, the display capability of the display device with a limited number of colors can be improved. Furthermore, it is preferable that the step of determining the generation mode determines data generation by the dithering mode when the plurality of original image pixel data have the same color. Thereby, the image quality can be improved.

  According to a third aspect of the present invention, there is provided a display image data generation method for generating display image data for a display device that displays a number of colors smaller than the number of colors that can be represented by image data, Obtaining image data; and converting the image data by dithering to generate display image data having the number of colors that can be displayed by the display device, and generating the display image data Obtains data corresponding to a predetermined number of pixels of the image data, converts the predetermined number of pixels by dithering when the predetermined number of pixels have the same color, and the predetermined number of pixels are different colors. In this case, conversion is performed for each pixel. Thereby, the display capability of the display device with a limited number of colors can be improved.

  According to a fourth aspect of the present invention, there is provided a display image data generation method for generating display image data for a display device that displays a number of colors smaller than the number of colors that can be represented by image data, Obtaining image data; and converting the image data by dithering to generate display image data having the number of colors that can be displayed by the display device. The data is subjected to gradation conversion to a color with fewer gradations than the image data, and the gradation-converted color is converted into a color that can be expressed by dithering. Thereby, the display capability of the display device with a limited number of colors can be improved. Further, it is preferable that the gradation conversion is performed so that the number of colors is greater than the number of colors that can be expressed by dithering. As a result, it is possible to display effectively by dithering expression.

  According to a fifth aspect of the present invention, there is provided a display device in which a plurality of display panels that display different colors are stacked, and the display device displays a color number smaller than the number of colors that can be represented by image data. A program for causing a computer to generate display image data, wherein the processing includes: storing image data; and generating display image data for display by the display device from the image data. And generating the display image data comprises: obtaining pixel data of the image data; and converting the pixel data of the image data into pixel data of a color that can be displayed by the pixels of the display device. Converting, and converting pixel data of the image data by dithering. Thereby, the display capability of the display device with a limited number of colors can be improved.

  According to a sixth aspect of the present invention, there is provided a display device in which a plurality of display panels that display different colors are stacked, and the display device displays a color having a smaller number of colors than can be represented by image data, A control device for the display device, the control device storing means for storing image data, means for generating display image data for display by the display device from the image data, and the generated display Means for transmitting image data for display to the display device, means for generating the display image data, means for acquiring pixel data of the image data, and pixel data of the image data, Means for converting the pixel of the display device into pixel data of a color that can be displayed, and means for converting the pixel data of the image data by dithering. Thereby, the display capability of the display device with a limited number of colors can be improved.

  According to the present invention, the display capability of a display device with a limited number of colors can be improved.

  Hereinafter, embodiments to which the present invention can be applied will be described. The following description is to describe the embodiment of the present invention, and the present invention is not limited to the following embodiment. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. Moreover, those skilled in the art can easily change, add, and convert each element of the following embodiments within the scope of the present invention.

  FIG. 1 shows an example of a basic configuration of an image display system 100 according to the present embodiment. The image display system 100 includes a display device 110 and a control device 120 that controls the display device 110. The display device 110 may include one or a plurality of display areas. In FIG. 1, the display device 110 includes one display area as an example, and displays a menu in the display area. The display device 110 is installed at an entrance of a restaurant, a wall surface in the store, or the like, and can present information such as a menu corresponding to the day and the time to the user. Since the display device 110 can easily change the display content electrically, the display device 110 can efficiently change the menu according to the time as compared with a menu printed on a plastic, wooden board, or paper. Can respond. Note that the image displayed on the display device 110 is not limited to the menu, and may be an arbitrary one such as a shelf label, a price tag, an advertisement, a signboard, a bulletin board, a timetable, a destination display board, and the like.

  By transmitting display data corresponding to the display content from the control device 120 to the display device 110, the display content of the display device 110 can be changed. Preferably, the control device 120 and the display device 110 include a wireless communication unit, and the display device 110 is controlled by the control device 120 by wireless communication using Bluetooth (registered commercial). By controlling the display content of the display device 110 using wireless communication, it is possible to cope with various installation locations, and to easily change the display content when the display device 110 is installed. Can do. When controlling the display device 110 by wireless communication, it is preferable to implement a security mechanism such as access control by authentication processing in order to prevent an arbitrary device from accessing the display device 110 and changing the display contents. Note that the communication between the display device 110 and the control device 120 may be wired communication such as RS232C, and may use radio waves in bands other than infrared or Bluetooth (registered trademark).

  The display device 110 preferably includes a plurality of memory areas for storing display data. By storing display data in each memory area, the display screen can be maintained and changed efficiently. Particularly, by providing a plurality of memory areas corresponding to one display area, a plurality of display screens can be selectively displayed. As a power supply means of the display device 110, it is preferable to incorporate a primary battery or a secondary battery. Alternatively, it is preferable to use a solar cell in combination. It is preferable to be able to operate without being connected by wiring from the outside and receiving power supply. Increased system operational benefits.

  The display device 110 preferably uses a memory type display panel. A memory-type display panel is a display having a property that display information can be held without being driven continuously or in a state where the drive voltage is substantially 0V. For the memory type display panel, it is preferable to use a chiral nematic liquid crystal display element capable of reducing power consumption and capable of color display. The chiral nematic liquid crystal display element has a phase transition type operation. The phase transition type is stable in at least two states of a planar state in which a part of incident light is selectively reflected and a focal conic state in which incident light is scattered or transmitted, and a liquid crystal is applied by applying a predetermined voltage between the electrodes. Can be transferred to the planar state or the focal conic state.

  FIG. 2 schematically shows an example of a cross-sectional structure of a two-layered chiral nematic liquid crystal display panel 200 using a chiral nematic liquid crystal display element. The chiral nematic liquid crystal panel operates in a phase transition type and is stable in at least two phases of a planar state in which a part of incident light is selectively reflected and a focal conic state in which incident light is scattered. By applying a predetermined voltage between the electrodes, the liquid crystal can be transferred to the planar state or the focal conic state. The chiral nematic liquid crystal display panel 200 can perform multi-color display by stacking a plurality of cells as in this embodiment and selectively reflecting different colors in each cell.

  As shown in FIG. 2, in this embodiment, two chiral nematic liquid crystal display cells 232 and 233 having the same cell structure are stacked. The first substrate 234 and the second substrate 236 are arranged so that the electrode surfaces of the row electrode 235 formed on the first substrate 234 and the column electrodes 237 formed on the second substrate 236 are orthogonal to each other. The first substrate 234 and the second substrate 236 are fixed by a peripheral sealing material 238, and a cell space is formed between the two substrates. A chiral nematic liquid crystal layer 239 is sealed inside the cell space. The chiral nematic liquid crystal display panel 200 is preferably driven by a simple matrix method.

  A colored layer 240 of black matte paint is formed on the back surface side of the first substrate of the second cell 233. An adhesive layer 241 is formed between the first cell 232 and the second cell 233. At this time, the two cells are arranged and bonded so that the respective pixels spatially coincide. The chiral nematic liquid crystal layer 239 is driven by a voltage applied between the row electrode 235 and the column electrode 237 arranged to face each other, and the transition of the phase state is controlled to perform display. Since the chiral nematic liquid crystal display panel 200 does not use a polarizing plate, bright display with a wide viewing angle can be performed. The selective reflection characteristics of the first cell 232 and the second cell 233 are changed to perform different color development, so that a plurality of colors can be displayed. Typically, the main wavelength of selective reflection can be adjusted by adjusting the helical pitch by adjusting the ratio between the chiral agent and the liquid crystal material, and adjusting it along with the refractive index of the liquid crystal material used. it can.

  The color of the colored layer 240 can be set to other than black, and can be set as appropriate in combination with the selective reflection color of the chiral nematic liquid crystal display element. For example, two-color display of “white-blue” can be displayed by combining selective reflection of orange and a blue colored layer. In addition, the chiral nematic liquid crystal display element may have a single layer or a three-layer structure to display more colors. In addition, the chiral nematic liquid crystal display panel 200 is preferably formed by stacking two layers of cells because it is difficult to align each cell in the manufacturing process when three or more layers of cells are stacked. Any number of cells may be stacked.

  In the present embodiment, the chiral nematic liquid crystal display panel 200 is used in which the first cell 232 is colored blue, the second cell 233 is colored orange, and the colored layer 240 is black. That is, the display device 110 according to the present embodiment can display four colors of blue, orange, black, and white by a combination of blue and orange. Further, since the intersection of the row electrode 235 and the column electrode 237 corresponds to a pixel, these four colors can be displayed independently for each pixel.

  The chiral nematic liquid crystal display panel 200 exhibits a memory property, and when the voltage is set to a predetermined display state by applying a voltage to the column electrode 237 of the second substrate 236, the display state in the state where the applied voltage is set to 0V. Is maintained. By applying a predetermined signal voltage again, the maintained display state can be transferred to another display state. Typically, the color of selective reflection is displayed by setting the entire display surface to the planar state, and the surface of the colored layer 240 (black paint) on the back side is changed to the faintly scattered state by setting the focal conic state. indicate.

  The control device 120 can be configured by a hardware configuration, or by hardware and software executed on the hardware. In this embodiment, an example in which a software program is executed on a general-purpose computer is shown. FIG. 3 shows an example of the hardware configuration of the control device 120. The control device 120 can use a typical computer system, and includes a central processing unit (CPU) 301 and a memory 304.

  The CPU 301 and the memory 304 are connected to a hard disk device 313 as an auxiliary storage device via a bus. Storage medium drive devices such as the flexible disk device 320, the hard disk device 313, and the CD-ROM drive 326 are connected to the bus via various controllers such as a flexible disk controller 319 and an IDE controller 325. A portable storage medium such as a flexible disk is inserted into a storage medium driving device such as the flexible disk device 320.

  The storage medium can store a computer program for giving a command to the CPU 301 or the like in cooperation with the operating system and for executing the function of the control device 120 of the present embodiment. The computer program is executed by being loaded into the memory 304. The computer program can be compressed or divided into a plurality of pieces and stored in a storage medium. The hardware configuration typically comprises user interface hardware.

  The user interface hardware includes, for example, a display device 311 such as a pointing device (mouse 307, joystick, etc.) and a keyboard 306 for inputting, or a liquid crystal display for presenting visual data to the user. . The control device 120 can communicate with the display device 110 via the wireless communication adapter 318. In addition, the said structure can be abbreviate | omitted as needed.

  FIG. 4 is a block diagram illustrating an example of a logical configuration of the image display system 100. Each block is configured by hardware or software executed on the hardware. As shown in FIG. 4, the control device 120 includes an input unit 401 that functions as an interface for data input by a user, and a display unit 402 that performs processing for displaying a display screen on the display device 311 of the control device 120. ing. Further, reference numeral 403 denotes an external storage device, which stores image data of a preset portion on a display screen displayed on the display device 110. A communication unit 404 transmits display data and commands to the display device 110.

  Reference numeral 405 denotes an image data generation unit, which can display the display area size of the display device 110 or displayable colors from image data stored in advance in the external storage device 403 or data input by the user via the input unit 401. The image data matched to is generated. Each functional block of the control device 120 can be configured by deploying a software program on the memory 304, the CPU 301 performing processing according to the software program, and cooperating with other hardware configurations.

  The display device 110 includes a communication unit 406 for communicating with the control device 120, a plurality of memory areas 407 corresponding to the display areas, a display panel 408 for displaying an image, and a control unit 409 for controlling the operation of the display device 110. It has. The image data transmitted from the control device 120 is received by the communication unit 406 and stored in the memory area 407 by the control unit 409. The display panel 408 displays an image according to the image data stored in the memory area 407.

  FIG. 5 is a flowchart showing processing for displaying user-desired image data on the display device 110 (S501 to S504). These processes are executed by a predetermined application program in the control device 120, for example. In addition, these processes may be triggered by a user operation, or the control device 120 may be provided with a timer function and may be operated at a predetermined time.

  First, image data prepared in advance by a user is acquired (S501), original image data that the user wants to display on the display device 110 is generated from the image data (S502), and can be displayed on the display device 110 based on the original image data. The converted image data of four colors (blue, orange, black, white) is generated (S503), and the converted image data is transmitted to the display device 110 (S504). Hereinafter, each step will be described in detail.

  First, in step S <b> 501, the image data generation unit 405 acquires the image data in order to perform processing on image data prepared in advance by the user. In this process, for example, image data stored in the storage device 403 in advance may be acquired, or stored in the storage device 403 via the input unit 401 from a scanner, a digital camera, or the like to acquire image data. Also good. In addition, the image data may be displayed on the display unit 402 so that the user can check the acquired image data.

  Next, in S502, the image data generation unit 405 generates original image data that the user wants to display on the display device 110 (S502). In this process, for example, the image data acquired in S501 may be used as it is without changing the original image data, or any text may be synthesized or various image processes may be performed according to the user's operation. May be generated. In addition, the original image data may be displayed on the display unit 402 so that the user can check the generated original image data.

  The image data handled here is preferably bitmap format data. The bitmap format data is data in which RGB values, which are color data, are expressed as an enumeration for each pixel, and full color is expressed by a combination of RGB values. In addition to the image data itself, this data includes header information indicating the size of the entire image data, the size of the RGB value for each pixel, and the like. As a bitmap image format, PNG, JPEG, GIF, BMP, TIFF, or the like can be used.

  After that, in S503, the image data generation unit 405 generates converted image data having four colors that can be displayed on the display device 110 based on the original image data. This conversion process will be described later. In addition, the converted image data may be displayed on the display unit 402 so that the user can check the converted image data.

  In step S <b> 504, the communication unit 404 transmits the converted image data to the display device 110 in order to display the converted image data on the display device 110. The transmitted image data is stored in one of the memory areas 407 via the communication unit 406 of the display device 110. For example, image data is stored in a specific memory area by designating a memory area from the control device 120, and the image data stored in the specific memory area 407 is displayed on the display panel 408 of the display device 110. Can be made.

  FIG. 6 is a flowchart showing a process for generating converted image data based on the original image data (S601 to S605). These processes are the processes in S503 described above. In these processes, original image data having full-color RGB values for each pixel is converted into four colors that can be displayed on the display device 110 for each pixel. Here, dithering is used as one of the conversion methods. Dithering is to express intermediate colors by combining limited colors, and to increase the number of colors that can be apparently displayed. Thus, the display device 110 can express more than four colors. Further, in dithering, an intermediate color is displayed by a plurality of pixels, and here, as an example, processing is performed in units of 4 pixels of 2 × 2 pixels in length × width, and conversion is performed.

  First, it is determined whether 2 × 2 pixel data exists in the original image data (S601). If there are 2 × 2 pixels in S601, the RGB values of each pixel are acquired (S602), and if there are no 2 × 2 pixels, the converted image data generation process is terminated. Further, after S602, it is determined whether the RGB values of the respective pixels are equal (S603). The control apparatus according to the present embodiment includes a conversion mode using dithering and a conversion mode not using dithering. In S603, if the RGB value of each pixel is equal, conversion using dithering is performed (S604), and if the RGB value of each pixel is different, conversion without dithering is performed (S605). Hereinafter, each step will be described in detail.

  First, in step S601, in order to perform conversion for 2 × 2 pixels, the image data generation unit 405 determines whether there are 2 × 2 pixels in the original image data generated in step S502 described above (S601). In this process, for example, the size of data can be obtained and determined from header information included in the original image data. Further, when the processing of two horizontal rows or two vertical columns is completed, the next processing of two horizontal rows or two vertical columns is performed. If 2 × 2 pixels are present, S602 is performed, and if 2 × 2 pixels are not present, the converted image data generation processing is terminated. Even when there are no 2 × 2 pixels, if there are remaining pixels such as one horizontal row or one vertical row, the conversion in S605 may be performed on the remaining pixels. The 2 × 2 pixels are not limited to this size as long as the size matches the dithering conversion unit, and may be any other size.

  In step S <b> 602, the image data generation unit 405 acquires the RGB value of each pixel in the 2 × 2 pixels. In this processing, for example, the RGB value size in one pixel can be obtained from the header information included in the original image data, and the RGB value can be obtained for each size. For example, if the RGB values are 8 bits each, values from 0 to 255 are acquired.

  In step S603, the image data generation unit 405 determines whether the RGB values of the pixels are equal to determine whether to perform conversion using dithering. This processing is preferably equal when, for example, the RGB values of the four pixels are completely the same, but the present invention is not limited to this and may be equal even if there is a certain difference in the RGB values. Of the pixels, two or three pixels may have the same RGB value as long as they are the same. Alternatively, the conversion using the dithering in S604 may be performed without performing this process.

  If it is determined in S603 that the RGB values of each pixel are equal, in S604, the image data generation unit 405 converts the 2 × 2 pixels using dithering. Here, full color pixels are converted into nine colors (blue, orange, black, white, light blue, dark blue, light orange, dark orange, gray) by using dithering. This conversion process will be described later.

  If it is determined in S603 that the RGB values of each pixel are different, in S605, the image data generation unit 405 converts 2 × 2 pixels without using dithering. The display device 110 converts the color into four colors that can be displayed by one pixel. Here, the RGB value is determined for each of the four pixels, and the display device 110 converts the RGB values into four colors that can be displayed by one pixel.

  Specifically, an arbitrary threshold value is set for each color of RGB values (R, G, and B each of 8 bits), and the set threshold value is compared with the intensity of RGB. Thereby, the color classification of each color of the RGB value is determined by binarizing each RGB colorant from 0 to 255 to 0 and 1. The binarized data is converted into 8 colors (black, blue, green, cyan, red, magenta, yellow, white), and these 8 colors are converted into the nearest 4 colors (black, blue, orange, white). To do. Convert from “green to orange”, “cyan to white”, “red to black”, and “magenta to blue”. For example, when RGB is (128, 128, 128) gray and the threshold is set to 128 or less, RGB is binarized to (0, 0, 0) and converted to black, and the threshold is set to 128 or more. Then, RGB is binarized to (1, 1, 1) and converted to white. As a method for converting the data of each pixel into four colors, for example, it is disclosed in Japanese Patent Application No. 2002-119041, which includes the present applicant as the applicant.

  After S604 or S605, the processing from S601 to S605 is further performed until there is no 2 × 2 pixel data in the original image data, and all the original image data is converted.

  In this way, converted image data can be generated. Also, dithering conversion is performed when the RGB values of four pixels are equal, and dithering conversion is not performed when the RGB values are different. Since the part that is present is converted while being mixed, it can be converted in a more natural state. In particular, when characters are included in the image data, the dithering conversion is not performed at the boundary portions of the characters, so that the characters can be clearly expressed. That is, a line thinner than 2 × 2 pixels can be expressed more naturally.

  FIG. 7 is a flowchart illustrating a process of converting an image using dithering (S701 to S703). These processes are the processes in S604 described above. In these processes, 2 × 2 pixels of original image data composed of full-color RGB values are converted into nine dithering expression colors using dithering.

  First, the RGB values in the range from 0 to 255 are each ternarized and converted into 27 colors (S710), a dithering expression color corresponding to the converted 27 colors is acquired (S702), and each pixel is converted into the dither. The color is converted into a ring expression color (S703). Hereinafter, each step will be described in detail.

  First, in S701, for 2 × 2 pixels, the color classification to which the pixels belong is determined. Specifically, the image data generation unit 405 converts the RGB value of an arbitrary pixel out of the 2 × 2 pixels acquired in S602 described above into a ternary value using a predetermined threshold value. Thereby, the division to which the pixel belongs can be determined. Since these four pixels have the same RGB value as determined in S603, the RGB value of any pixel may be used. When the RGB values of the four pixels are not the same, the average value of the four pixels may be used. When the RGB value is from 0 to 255, for example, it is ternarized by setting 0 to 85 as “L”, 86 to 170 as “M”, and 171 to 255 as “H”. The threshold value is not limited to this, and may be another value.

  By ternizing each of RGB, each division of RGB is determined. 27 colors are combined with RGB. Here, by dividing one color and associating it with three sections, it is possible to assign nine colors by dithering expression in S702. Thus, although it is preferable to divide into more colors than the color to allocate, you may divide | segment by other arbitrary numbers. Furthermore, you may divide | segment into another number by RGB. For example, colors that can be expressed in detail may be divided by a larger number, and colors that cannot be expressed in detail may be divided by a smaller number. Further, S702 may be performed as it is without converting the RGB values into three values. In the case of not ternarizing, if the RGB value is from 0 to 255, nine colors are assigned to 16.77 million colors, and it is necessary to secure an area in the storage device 403 for this conversion information.

  In step S <b> 702, the image data generation unit 405 acquires dithering expression colors corresponding to 27 colors obtained by ternarization. For example, information indicating the correspondence between ternarized colors and dithering expression colors, which will be described later in Table 1, is stored in advance in the storage device 403 as dithering conversion information, and the dithering conversion information is referred to. In addition, the corresponding color can be acquired.

表１は、ＲＧＢをディザリング表現に変換する例を示す表である。この例は、上述したように、ＲＧＢをそれぞれＬ、Ｍ、Ｈに３値化した場合の例である。ここで、ディザリング表現で用いる色は、ディザリングしない４色（青、橙、黒、白）と、ディザリングした５色（薄青、濃青、薄橙、濃橙、灰色）の計９色である。これらの色は、図８で後述する方法で表示される。 In step S <b> 703, the image data generation unit 405 converts each pixel of 2 × 2 pixels into the dithering expression color acquired in step S <b> 702. For example, if the dithering expression color is light blue, the pixel mapping is performed by associating the dithering expression color with the 4 pixel color so that 2 pixels out of 2 × 2 pixels are blue and the other 2 pixels are white. Information can be stored in the storage device 403 in advance, and each pixel can be converted by referring to the pixel conversion information. The correspondence between the dithering expression color and each pixel will be described later.

Table 1 is a table showing an example of converting RGB into a dithering expression. In this example, as described above, RGB is ternarized into L, M, and H, respectively. Here, the colors used in the dithering expression are a total of 9 colors: 4 colors that are not dithered (blue, orange, black, white) and 5 colors that are dithered (light blue, dark blue, light orange, dark orange, gray). Color. These colors are displayed by the method described later in FIG.

  In this case, the above nine colors are assigned to 27 colors based on ternary RGB. Of the 27 colors, when 9 colors correspond as they are, they are assigned as they are without being changed. However, when there are no colors corresponding to 9 colors, they are assigned as close colors. A close color is a color that does not change the feeling of contrast or color difference so much.

  As an example in which the color is not changed, RGB is “LLL” is black, “HHH” is white, “MMM” between black and white is gray, “LLH” is blue, and “LLM” is between blue and black. "Is dark blue. As an example of changing the color, RGB “LHH” is originally cyan but white, and “HLH” is originally magenta but blue. “HHL” is originally yellow, but this is orange, and “HHM” between orange and white is light orange. Note that the present invention is not limited to this example, and other colors may be assigned. For example, “LHH” may be blue instead of white, and “HLH” may be orange instead of blue.

  FIG. 8 is a diagram illustrating an example of dithering conversion of 2 × 2 pixels. In the original image data, as shown in FIG. 8A, each pixel is expressed in RGB. For example, when blue is displayed on the display device 110, each pixel is displayed in blue as shown in FIG. 8B. When displaying light blue, as shown in FIG. 8C, the upper left and lower right are displayed in blue, and the lower left and upper right are displayed in white. Thus, by looking at a certain distance from the display device 110, light blue, which is an intermediate color between blue and white, can be recognized. When dark blue is displayed, as shown in FIG. 8D, the upper left and lower right are displayed in blue, and the lower left and upper right are displayed in black. Thereby, it is possible to recognize dark blue, which is between blue and black. Similarly, light orange can be displayed by orange and white, dark orange by orange and black, and gray by black and white.

  For example, in FIG. 8C, the upper two pixels may be blue, the lower two pixels may be white, the left two pixels may be blue, and the right two pixels may be white. Furthermore, 3 pixels out of 4 pixels are blue, 1 pixel is white, 2 pixels are blue, 1 pixel is white, 1 pixel is black, etc. Variations may be increased. If blue and orange are set every two pixels, the color becomes white. However, by using a combination of 3 pixels and 1 pixel, a further intermediate color can be expressed. In addition, here, 2 × 2 pixels are taken as an example, but the present invention is not limited to this, and may be a square shape having an arbitrary size such as 3 × 3 pixels, or an arbitrary size such as 2 × 3 pixels. It may be rectangular.

  FIG. 9 is a diagram illustrating an example of an original image before conversion according to the present embodiment. That is, the original image data generated in S502 described above. FIG. 10 is a diagram illustrating an example of a converted image after conversion according to the present embodiment. That is, the converted image data generated in S503 described above.

  In this way, in the chiral nematic liquid crystal display device that can display only four colors, nine colors including intermediate colors can be displayed by using the dithering expression, so that the display capability can be improved.

  Although this embodiment is described as displaying four colors of black, blue, orange, and white in one pixel of the display device 110, the present invention is not limited to this, and other four colors (for example, black, green, Red, white). The number of colors that can be displayed by one pixel is preferably four colors, but may be any other number of colors as long as it is smaller than the number of colors that can be expressed by bitmap format image data. Furthermore, although the display device 110 has been described as a four-color display chiral nematic liquid crystal display device, any display device with a limited number of colors may be used.

  In this embodiment, an example is described in which one display device 110 is controlled by the control device 120 by wireless communication. For example, a plurality of display devices are connected via a network, and an address is assigned to each display device. It is possible to construct a system that centrally controls each display device by a central control device. This makes it possible to efficiently control a plurality of display devices installed at various places. By associating the display images of the respective display devices, more efficient control can be performed.

It is a figure which shows the basic composition of the information display system which concerns on this Embodiment. It is sectional drawing which shows schematic structure of the chiral nematic liquid crystal display panel as an example of the display apparatus which concerns on this Embodiment. It is a block diagram which shows an example of the hardware constitutions of the control apparatus which concerns on this Embodiment. It is a block diagram which shows the logical structure of the information display system which concerns on this Embodiment. It is a flowchart which shows the image conversion process which concerns on this Embodiment. It is a flowchart which shows the image conversion process which concerns on this Embodiment. It is a flowchart which shows the image conversion process which concerns on this Embodiment. It is a figure which shows an example of the image conversion which concerns on this Embodiment. It is a figure which shows an example of the original image before the conversion which concerns on this Embodiment. It is a figure which shows an example of the converted image after the conversion which concerns on this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Information display system 110 Display apparatus 120 Control apparatus 232 Chiral nematic liquid crystal display cell 233 Chiral nematic liquid crystal display cell 234 1st board | substrate 235 Row electrode 236 2nd board | substrate 237 Column electrode 238 Peripheral sealing material 239 Chiral nematic liquid crystal layer 240 Colored layer

Claims (13)

A program for causing a computer to execute a process of generating display image data having fewer colors than the original image data from the original image data,
Obtaining original image pixel data that is pixel data of the original image data and capable of displaying a first number of colors; and
A section determining step for determining a section to which the color of the acquired original image pixel data belongs, which is one of a plurality of sections into which colors that can be displayed by the original image pixel data are divided;
Display for generating dithered display image pixel data capable of displaying a second number of colors less than the first number of colors according to the section to which the color of the original image pixel data belongs Image pixel data generation step,
The display image pixel data generation step includes:
Generating first display image pixel data for displaying a first color;
Generating second display image pixel data for displaying a second color different from the first color;
Including programs. The original image pixel data acquisition step acquires a plurality of original image pixel data,
When a predetermined number or more of the acquired plurality of original image pixel data are the same color, the display image pixel data generation step is executed.
The program according to claim 1.   The program according to claim 2, wherein the display image pixel data generation step is executed when all of the acquired plurality of original image pixel data are the same color. If a predetermined number or more of the acquired plurality of original image pixel data is not the same color, the method further comprises the step of generating display image pixel data corresponding to each of the plurality of original image pixel data,
In the display image pixel data generation step, when the predetermined number or more of the acquired plurality of original image pixel data are the same color, different colors corresponding to the plurality of original image pixel data are obtained. Generating a plurality of display image pixel data including,
The program according to claim 1.   The program according to any one of claims 1 to 4, wherein the number of the divisions is greater than the number of colors that can be displayed by dithering expression.   The said division | segmentation determination step includes the step of determining the color division to which each sub pixel data belongs for each of the sub pixel data which comprise the said original image pixel data. The program described in the section. A program for causing a computer to execute a process of generating display image data having fewer colors than the original image data from the original image data,
Obtaining pixel data of the original image data, a plurality of original image pixel data capable of displaying a first number of colors;
Determining a generation mode of display image pixel data that is pixel data of the display image data according to a color of the plurality of original image pixel data;
In the step of determining, when it is determined that the data generation by the dithering mode is determined, a second color that is less than the first color number according to the colors of the acquired plurality of original image pixel data Generating display image pixel data capable of display of a number for dithering representation,
Generating the display image pixel data comprises:
Generating first display image pixel data for displaying a first color;
Generating second display image pixel data for displaying a second color different from the first color;
Including programs.   The program according to claim 7, wherein the step of determining the generation mode determines data generation by a dithering mode when the plurality of original image pixel data have the same color. A display image data generation method for generating display image data for a display device that displays colors having fewer colors than can be represented by image data,
Obtaining image data; and
Converting the image data by dithering, and generating display image data having the number of colors that can be displayed by the display device, and
The step of generating the display image data includes
Obtaining data corresponding to a predetermined number of pixels of the image data;
When the predetermined number of pixels have the same color, the predetermined number of pixels is converted by dithering
When the predetermined number of pixels have different colors, conversion is performed for each pixel.
Display image data generation method. A display image data generation method for generating display image data for a display device that displays colors having fewer colors than can be represented by image data,
Acquiring image data; and
Converting the image data by dithering, and generating display image data having the number of colors that can be displayed by the display device, and
In the conversion by the dithering, the image data is converted into a color having a smaller gradation than that of the image data, and the converted color is converted into a color that can be expressed by dithering.
Display image data generation method.   The display image data generation method according to claim 10, wherein the gradation conversion is performed so that the number of colors is greater than the number of colors that can be expressed by dithering. A display device in which a plurality of display panels for displaying different colors are stacked, and display image data is generated in a computer for a display device that displays a color number smaller than the number of colors that can be represented by the image data. A program for causing the processing to be
Storing image data; and
Generating display image data for display by the display device from the image data;
And the step of generating the display image data comprises:
Obtaining pixel data of the image data;
Converting the pixel data of the image data into pixel data of a color that can be displayed by pixels of the display device;
Converting the pixel data of the image data by dithering;
A program comprising: A display device in which a plurality of display panels that display different colors are stacked, and a display device that displays colors with fewer colors than can be represented by image data;
A control device for the display device,
The control device includes:
Means for storing image data;
Means for generating display image data for display by the display device from the image data;
Means for transmitting the generated image data for display to the display device;
The means for generating the display image data comprises:
Means for obtaining pixel data of the image data;
Means for converting the pixel data of the image data into pixel data of a color that can be displayed by pixels of the display device;
Means for converting pixel data of the image data by dithering;
An image display system comprising:

Images