WO2014007104A1 - Image display device and gradation change method - Google Patents

Image display device and gradation change method Download PDF

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Publication number
WO2014007104A1
WO2014007104A1 PCT/JP2013/067329 JP2013067329W WO2014007104A1 WO 2014007104 A1 WO2014007104 A1 WO 2014007104A1 JP 2013067329 W JP2013067329 W JP 2013067329W WO 2014007104 A1 WO2014007104 A1 WO 2014007104A1
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WO
WIPO (PCT)
Prior art keywords
gradation
image
value
gradation value
watermark
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Application number
PCT/JP2013/067329
Other languages
French (fr)
Japanese (ja)
Inventor
孝洋 河野
竜太郎 今井
憲市 香川
大地 藤本
謙次 平木
純一郎 冨田
孝典 亀井
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Eizo株式会社
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Publication of WO2014007104A1 publication Critical patent/WO2014007104A1/en

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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T5/00—Image enhancement or restoration
    • G06T5/90—Dynamic range modification of images or parts thereof
    • G06T5/92—Dynamic range modification of images or parts thereof based on global image properties
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10004—Still image; Photographic image
    • G06T2207/10008—Still image; Photographic image from scanner, fax or copier
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10024—Color image

Definitions

  • the present invention relates to an image display apparatus and a gradation conversion method that make watermark display in an electronic document, an image, etc. inconspicuous.
  • Image display devices are used not only in offices and homes, but also in various specialized fields such as graphic design and medical care.
  • the image display device is mainly used by being connected to a personal computer (PC), and displays various electronic data such as an electronic document and an image.
  • PC personal computer
  • Electronic documents such as electronic documents and images (hereinafter referred to as electronic documents, etc.) are in word format (Word is a Microsoft product name), PDF format (Portable Document Format developed by Adobe Systems), TIFF format (Microsoft and Created in various data file formats such as Tagged Image File Format developed and advocated by Adobe Systems.
  • word format is a Microsoft product name
  • PDF format Portable Document Format developed by Adobe Systems
  • TIFF format Microsoft and Created in various data file formats such as Tagged Image File Format developed and advocated by Adobe Systems.
  • FIG. 7 exemplifies an electronic document 201 with a watermark display.
  • a “sample” character is overlaid on a character in the document to form a watermark display 301.
  • this watermark display may be referred to as a stamp display.
  • a display overlaid on characters in a document is generally referred to as a watermark display.
  • the watermark display 301 When the electronic document 201 is printed, the watermark display 301 is usually lifted, emphasized, and displayed darkly. On the other hand, when an electronic document or the like is displayed as an image on a known image display device, it often happens that it is difficult to read the character 401 where the watermark display 301 overlaps.
  • the background color of the background 501 of the electronic document 201 is white (255 gradation) and the character color of the character 401 of the electronic document 201 is black (0 gradation)
  • the color of the character 401 and the color of the watermark display 301 are made different so that the character color of the watermark display 301 is red.
  • an electronic document 201 with a watermark display as shown in FIG. 7 is displayed on a known image display device (monitor)
  • the image quality adjustment for changing the display gradation is performed on the monitor side, the watermark display is performed.
  • the gradation difference between the gradation of 301 and the gradation of the character 401 becomes small, and conversely to the intention (intention to make the character easy to see), a situation may occur where the character 401 becomes extremely unclear.
  • Patent Documents 1-3 are known as image processing apparatuses that process document images.
  • Patent Document 1 relates to a color copying machine, in order to improve the reproducibility of the background color of an original image (white of the original paper), prescan a color original to be read, input R, G, B signals, and perform histogram counting.
  • the circuit counts the appearance frequency of the input R, G, B signals, extracts a combination of RGB values having the maximum appearance frequency from the histogram, and based on the extracted R, G, B values, R, G of the color document , B signal is described as non-linear transformation.
  • Patent Document 2 relates to a color copying machine, and in order to improve the reproducibility of the background color of the original image (white of the original paper) when the characters are thinned to reduce the show-through of the original, the color image that is input
  • the document describes that the density distribution of the document is calculated based on the data, the background density level of the document is calculated based on the data, the density conversion table is created, and the image density of the input color image data is converted.
  • Patent Document 3 relates to a color copying machine, in order to reduce the show-through of an original, obtains a gradation range of an unnecessary image portion for each color component from gradation data of all pixels of an input image, and based on this gradation range.
  • the removal gradation condition for each color component is set, and for each pixel of the input image, a pixel satisfying this removal gradation condition for all color components is determined as the removal pixel, and the gradation of the removal pixel is zero (original paper In white).
  • Patent Documents 1-3 the gradation of unnecessary parts such as show-through is set to zero (white of the original paper) in order to make the original easy to see and copy.
  • the image display apparatus performs image quality adjustment such as gamma correction ( ⁇ correction), and the gradation 255 of the original image may be smaller than 255 in the display image. For this reason, in the case of a copying machine, “show-through” can be removed by setting the gradation to zero, but it cannot be sufficiently removed by a monitor in a state where image quality adjustment such as ⁇ correction is performed.
  • the monitor is used in connection with a PC, and various electronic data such as electronic documents and images may be displayed in a so-called multi-window, and if a predetermined gradation or less is uniformly converted as in the prior art. This may affect electronic documents and images of windows that are not originally related, and may cause a bad effect of deteriorating appearance.
  • the watermark display usually has a color such as red, and the image quality is different from the show-through of the document.
  • an object of the present invention is to reduce the watermark display without falsifying the electronic document or the like when displaying the electronic document or image or the like with a watermark display on the image display device.
  • a display device and a gradation conversion method are provided.
  • An image display apparatus includes a gradation conversion unit capable of converting an input gradation of an image input signal into an output gradation value different for each input gradation value, and an input gradation value in the gradation conversion unit.
  • a control circuit for rewriting the output gradation value is provided, and an output gradation value associated with an input gradation equal to one set gradation value among two or more gradation values set in the control circuit is acquired.
  • the output gradation associated with the input gradation equal to the other set gradation value is replaced with a value that is the same as or close to the acquired output gradation value.
  • the image is a document image
  • the one set gradation value is a gradation for displaying a background of the document image
  • the other set gradation value is a floor for displaying the background of the document image.
  • the gradation value is within the range of the gradation and the gradation for displaying the character. According to the present invention, it is possible to suppress the influence on other regions and windows as much as possible while reducing unnecessary display without falsifying an electronic document or the like.
  • the image is a document image including a watermark image
  • the one set gradation value is a gradation for displaying a background of the document image
  • the other set gradation value is a watermark image.
  • the gradation value is within the range of the gradation to be displayed. According to the present invention, it is possible to suppress the influence on other regions and windows as much as possible while reducing watermark display without falsifying an electronic document or the like.
  • the gradation converting means is a mechanism capable of converting the input gradation of the image input signal into different output gradation values for each input gradation value, and more specifically, uses a lookup table (LUT).
  • LUT is an abbreviation of LookLup Table, and is an output tone allocation table for input tones.
  • the LUT has 256 data storage numbers for 256 gradations.
  • an output gradation for each input gradation is created in advance, and gradation conversion is performed by referring to the LUT. For example, data that can be calculated in advance is calculated in advance, and the value is stored in the LUT.
  • the fact that the output gradation value associated with the watermark gradation value of the gradation converting means is the same as or close to the background output gradation value is the background of the electronic document or the like. Points to the correct value. For example, if the background of the electronic document or the like is white, if the gradation value is 255, the background output gradation value is the same value. For example, if the gradation value is set to a value within the range of 200 to 254, the value is close to the background output gradation value.
  • the background gradation value as the background of the electronic document or the like uses a fixed value set in advance, or is calculated by a processing circuit or a processing program in the image display device, or the user visually recognizes the display screen. Then, it is determined by operating an operation menu on the display screen or an operation button of the image display device.
  • a preset fixed value is used, or it is calculated by a processing circuit or a processing program in the image display device, or the user visually recognizes the display screen. Then, it is determined by operating an operation menu on the display screen or an operation button of the image display device.
  • the background gradation value is set within a predetermined range.
  • the pinpoint value include a gradation value that can be easily used as a watermark display.
  • an output gradation value associated with the watermark gradation value can be set as a fixed value.
  • the fixed value include 205, 210, 215, 220, 225, 230, and the like.
  • the control circuit when the watermark gradation value, the background gradation value, and the output gradation value associated with the watermark gradation value are input to the control circuit, the control circuit It is preferable to replace the output tone value associated with the value with the background output tone value.
  • a watermark gradation value that is a watermark display of the electronic document or the like is automatically acquired without bothering the user, which is easy to use.
  • a window area for displaying the electronic document or the like is designated, and the gradation conversion of the present invention is performed only in that area.
  • the gradation conversion method of the present invention is a gradation conversion method for an image display device provided with gradation conversion means capable of converting an input gradation of an image input signal into an output gradation value that differs for each input gradation value.
  • gradation conversion means capable of converting an input gradation of an image input signal into an output gradation value that differs for each input gradation value.
  • an output gradation value associated with an input gradation equal to one set gradation value is obtained, and an input gradation equal to another set gradation value is obtained.
  • the attached output gradation is replaced with a value that is the same as or close to the acquired output gradation value.
  • gradation conversion can be performed only for gradations to be removed by using a computer connected to an existing image display device or using a built-in computer, it is easy to use.
  • a watermark display reduction program to which the gradation conversion method of the present invention is applied is installed in a control circuit having a computer function in the image display device or a peripheral mechanical unit having a computer function, or the image display device. It is installed on a computer connected to and used.
  • the display reduction program is installed via a medium such as a USB memory or a CD-ROM, or is downloaded and installed using a network line such as the Internet or an intranet.
  • the program indicates a programmed command and includes software and firmware.
  • the image display device to which the present invention is applied only needs to have an image display panel or an image display unit such as a cathode ray tube or a CRT.
  • the image display panel include a liquid crystal display panel, an organic electroluminescence display panel, and a plasma display panel.
  • the gradation converting means is provided before the image quality adjustment circuit that adjusts the image quality such as contrast, brightness, brightness, and gamma correction, or after the image quality adjustment circuit.
  • the image display device is characterized in that the gradation converting means is provided in a preceding stage of an image quality adjustment circuit for adjusting image quality such as contrast, brightness, brightness, and gamma correction.
  • the watermark display of the electronic document or the like is image-processed without being affected by the image quality adjustment circuit, there is no possibility that the gradation difference between the watermark display and the character in the electronic document or the like is eliminated. And there is no worry of affecting the electronic document, image, etc. of the window which is not related originally.
  • the output gradation value associated with the watermark gradation value is set as a pinpoint or within a predetermined range.
  • the pinpoint value include a gradation value that can be easily used as a watermark display, and an output gradation value associated with the watermark gradation value can be set as a fixed value in advance.
  • the fixed value include 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 254, and 255.
  • the watermark display may include a plurality of gradations.
  • the image display device of the present invention assumes that the watermark gradation value is a gradation value having a predetermined width, and the output gradation value associated with the watermark gradation value is the same as or close to the background output gradation value. It is good also as a structure replaced with a value. According to this configuration, even when the watermark display includes a plurality of gradations, or even if there is a reading error in the output gradation value associated with the watermark gradation value, the watermark display is It will reduce more reliably.
  • the gradation value of the predetermined width is an output gradation value associated with the watermark gradation value, and uses a preset fixed value, or by a processing circuit or a processing program in the image display device. It is calculated or determined by the user viewing the display screen and operating an operation menu on the display screen or an operation button of the image display device. For example, a user may operate a slider or a knob on the display screen while visually recognizing the display screen, or the user may specify an area using a mouse.
  • the gradation value of the predetermined width a value in a predetermined range including a gradation value that is easily used as a watermark display can be adopted, and a predetermined width can be set.
  • the fixed width value include 200 to 210, 205 to 225, 210 to 230, 220 to 240, 225 to 250, 225 to 254, and 225 to 255.
  • the output gradation value associated with the watermark gradation value is set to 1 or more and 254 or less.
  • the output gradation value associated with the watermark gradation value is set to 1 or more and 254 or less so that it does not overlap with the black of the zero gradation and the white of 255 gradations. Therefore, it is difficult to cause a sense of incongruity so that the watermark display of the electronic document can be completely seen through.
  • a histogram of an input image is calculated from the electronic document as an output gradation value associated with the watermark gradation value, and a gradation value estimated based on the calculated histogram is used. it can.
  • the present invention can calculate a histogram of an input image from the electronic document or the like, and estimate an output gradation value associated with the watermark gradation value based on the calculated histogram.
  • a window region for displaying the electronic document or the like is designated, and it is easy to deal with multi-windows such as performing gradation conversion of the present invention only in that region.
  • the output tone value associated with the watermark tone value among the output tone values of the tone converting means is replaced with a value that is the same as or close to the background output tone value, and the signal output Since it is displayed on the screen, gradation conversion can be performed only for the gradation to be removed. Therefore, it is possible to suppress the influence on other regions and windows as much as possible while reducing the watermark display without falsifying the electronic document or the like.
  • the watermark gradation value that is the watermark display of the electronic document or the like is automatically acquired without bothering the user, which is easy to use.
  • a window area for displaying the electronic document or the like may be designated, and gradation conversion of the present invention may be performed only within that area.
  • the watermark display of the electronic document or the like is image-processed without being affected by the image quality adjustment circuit, there is no possibility that the gradation difference between the watermark display and the character in the electronic document or the like is eliminated.
  • the watermark display is more reliably reduced.
  • the output gradation value associated with the watermark gradation value is 1 or more and 254 or less, it does not overlap with the black of the zero gradation on the screen and overlaps with the white of the 255 gradation. Therefore, it is difficult to cause an uncomfortable feeling that the watermark display of the electronic document is completely transparent on the screen and the background can be seen. Further, since the electronic document or the like has not been altered, the watermark is displayed on the printed paper.
  • gradation conversion can be performed only for gradations to be removed by using a computer connected to an existing image display device or using a built-in computer, it is easy to use.
  • FIG. 1 is a block diagram illustrating an image display device with a watermark display reduction function according to an embodiment to which the present invention is applied.
  • the image display apparatus 1 includes a gradation conversion unit 2 that can convert an input gradation of an image input signal into an output gradation value that differs for each input gradation value, and a control circuit 7 that controls various signals.
  • the image is output from the gradation converting means 2, and the image quality adjustment circuit 51 adjusts the image quality such as contrast, brightness, brightness, and gamma correction, and the image is displayed on the image display panel 52.
  • the gradation converting means 2 is provided in the preceding stage of an image quality adjustment circuit 51 for adjusting image quality such as contrast, brightness, brightness, and gamma correction.
  • Examples of the image display panel 52 include a liquid crystal display panel, an organic electroluminescence display panel, and a plasma display panel.
  • FIG. 7 shows an example of an electronic document 201 with a watermark display.
  • a “sample” character is overlaid on a character 401 in the document to form a watermark display 301.
  • FIG. 3 is a graph illustrating the relationship between the input gradation and output gradation of each of R, G, and B in a conventional image processing apparatus.
  • the horizontal axis of the graph is the input gray scale, and the vertical axis is the output gray scale, which is 0 to 255 gradations, respectively.
  • the character 401 in the document in the electronic document 201 is generally black or a color scheme close to black. If the character 401 is black, the gradation is 0. If the character 401 has a color scheme close to black, the gradation is close to 0.
  • the background 501 in the electronic document 201 is generally white or a color scheme close to white. If the background 501 is white, there are 255 gradations.
  • the watermark display (“sample” character) 301 in the electronic document 201 has a gradation represented by the symbol C2.
  • the color scheme of the gradation value C2 is often a light color scheme such as gray or red, and the gradation value C2 that can be easily used as the watermark display 301 is, for example, 205, 210, 215, 220, 225, 230. Etc.
  • image display devices have been subjected to image quality adjustment such as gamma correction ( ⁇ correction), and there are cases in which a gradation that is smaller in a display image than in an original image occurs (see FIG. 3). That is, the 255 gradation of the background 501 and the gradation value C2 of the watermark display 301 may be smaller than the 255 gradation or the gradation value C2 in the output gradation.
  • image quality adjustment such as gamma correction ( ⁇ correction)
  • ⁇ correction gamma correction
  • the gradation converting means 2 is a mechanism capable of converting the input gradation of the image input signal into different output gradation values for each input gradation value, and more specifically uses a look-up table (LUT). (FIG. 1). An output gradation for each input gradation is created in advance in the LUT, and gradation conversion is performed by referring to the LUT.
  • LUT look-up table
  • the background gradation value (input gradation Z) is input to the control circuit 7 by the background gradation value setting means 3, and the watermark gradation value (input gradation C) is input by the watermark gradation value setting means 4.
  • an output gradation value (output gradation value Z) previously associated with the watermark gradation value is input to the control circuit 7 by the output gradation acquisition means 5.
  • the control circuit 7 obtains an output gradation value (output gradation C) previously associated with the set watermark gradation value (input gradation C) to the output gradation changing means 6. Further, replacement with the output gradation value Z is executed.
  • the output signal from the gradation converting means 2 is input to an image quality adjustment circuit 51 that adjusts image quality such as contrast, brightness, brightness, and gamma correction, and an image is displayed on the image display panel 52 by the output signal from the image quality adjustment circuit 51. Is displayed.
  • the watermark gradation value corresponding to the watermark display 301 of the electronic document 201 is automatically acquired without bothering the user, which is convenient.
  • FIG. 4 is an example of a graph illustrating the relationship between the input gradation and the output gradation when the gradation conversion of the present invention is performed.
  • the watermark display (“sample” character) 301 in the electronic document 201 has a gradation represented by the symbol C2.
  • the watermark gradation value C2 is pinpointed and replaced with a value that is the same as or close to the background output gradation value. Examples of the pinpoint value include 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 254, and 255.
  • the watermark gradation value C2 is set as the background gradation value at a pinpoint, the influence on the characters 401 other than the watermark display 301 in the electronic document 201 can be suppressed as much as possible.
  • FIG. 5 is another example of a graph illustrating the relationship between the input gradation and the output gradation when the gradation conversion of the present invention is performed.
  • the watermark display (“CONFIDENTIAL” character) 301 in the electronic document 201 has a gradation represented by reference numeral C2, but the watermark display may include a plurality of gradations due to the color scheme.
  • the output gradation values associated with the watermark gradation values C1 to C3 are assumed to be gradation values having a predetermined width from the gradation values C1 to C3 across the watermark gradation value C2. Is replaced with a value that is the same as or close to the background output gradation value.
  • Examples of the gradation value having the predetermined width include 200 to 210, 205 to 225, 210 to 230, 220 to 240, 225 to 250, 225 to 254, and 225 to 255. According to the present embodiment, even if the watermark display 301 includes a plurality of gradations, the watermark display 301 is more reliably reduced.
  • FIG. 6 is a diagram illustrating an electronic document when the gradation conversion of the present invention is performed.
  • the watermark display (“sample” character) 302 in the electronic document 202 after gradation conversion is replaced with a value that is the same as or close to the background output gradation value of the background 501.
  • the background 501 is white
  • the watermark display 302 is replaced with the same white color, cream color or light yellow color. Therefore, the watermark display 302 is in a state close to the background 501, and the characters 401 in the area where the watermark display 302 overlaps are easy to read.
  • a window area for displaying the electronic document or the like is specified, and the gradation conversion of the present invention is performed only in that area. Since the electronic document, the image, etc. are not altered at all, the watermark 301 is displayed on the printed paper.
  • FIG. 2 is a block diagram illustrating an image display apparatus using a watermark display reduction program according to an embodiment to which the present invention is applied.
  • the watermark display reduction program according to the present embodiment is represented by reference numeral 18 in FIG.
  • the watermark display reduction program 18 is used in the image display apparatus 101 provided with the gradation conversion means 2 capable of converting the input gradation of the image input signal into different output gradation values for each input gradation value. This is used when displaying an image with reduced watermark display.
  • the gradation converting means 2 is provided in the preceding stage of an image quality adjustment circuit 51 that adjusts image quality such as contrast, brightness, brightness, and gamma correction.
  • an image input signal is input to the image display device 101 from the computer 17 connected to the existing image display device 101.
  • the watermark display reduction program 18 when the watermark display reduction program 18 is started on the computer 17, the output gradation value associated with the watermark gradation value among the output gradation values of the gradation converting means 2 is output to the background. Replace with a value that is the same as or close to the gradation value.
  • a background gradation value (input gradation Z) is set by the background gradation value setting step 3 and inputted to the computer 17, and a watermark gradation value (input gradation) is set by the watermark gradation value setting step 4.
  • C) is set and input to the computer 17.
  • an output tone value (output tone value Z) previously associated with the watermark tone value is obtained from the tone converting means 2 in the output tone obtaining step 5 and input to the computer 17.
  • an output gradation value (output) associated with the watermark gradation value (input gradation C) in advance is output to the gradation converting means 2 in the output gradation changing step 6.
  • the gradation C) is replaced with the acquired output gradation value Z.
  • the output signal from the gradation converting means 2 is input to an image quality adjustment circuit 51 that adjusts image quality such as contrast, brightness, brightness, and gamma correction, and an image is displayed on the image display panel 52 by the output signal from the image quality adjustment circuit 51. Is displayed.
  • the electronic document 201 can be stored in the computer 17 that is connected to or built in the existing image display apparatus 101 by simply installing the watermark display reduction program 18 without bothering the user 50. Since the watermark display 301 can be reduced, it is easy to use.
  • the user 50 visually recognizes the display screen 52 and operates an operation menu on the display screen or an operation button of the image display device 101.
  • the user 50 may designate the area using the mouse.
  • the output gradation value associated with the watermark gradation value does not necessarily need to be replaced with the output gradation value associated with the background gradation value in advance, but corresponds to the watermark gradation value in advance. It may be executed so as to set a gradation value larger than the attached output gradation value.
  • a histogram of an input image can be calculated from the electronic document 201 as the background gradation value and the watermark gradation value, and the gradation value estimated based on the calculated histogram can be used.
  • a window area for displaying an electronic document, an image, or the like is designated, and multi-window handling such as performing gradation conversion of the present invention only in the area is facilitated.
  • the area may be designated by the user using a mouse or the like, or the window area may be estimated from an edge detected from the input image.
  • the background gradation value as the background of the electronic document or the like uses a fixed value set in advance, or is calculated by a processing circuit or a processing program in the image display device, or the user can display the display screen. Is determined by operating the operation menu on the display screen or the operation button of the image display device.
  • a preset fixed value is used, or it is calculated by a processing circuit or a processing program in the image display device, or the user visually recognizes the display screen. Then, it is determined by operating an operation menu on the display screen or an operation button of the image display device.
  • the gradation converting means has been described as being provided in the preceding stage of an image quality adjustment circuit that adjusts image quality such as contrast, brightness, brightness, and gamma correction, but in conjunction with contrast adjustment and ⁇ value, If the gradation value and the gradation width can be readjusted, it is possible to provide the gradation conversion section after the image quality adjustment circuit.
  • the image quality adjustment circuit may be realized by hardware or may be realized by software.
  • the present invention can be applied to various image display devices such as liquid crystal, organic EL, and plasma. Thus, it goes without saying that the present invention can be modified as appropriate without departing from the spirit of the present invention.
  • 1 image display device of the present invention 2 gradation conversion means, 3 background gradation value acquisition means (background gradation value acquisition step), 4 watermark gradation value acquisition means (watermark gradation value acquisition step), 5 output gradation acquisition means (output gradation acquisition step), 6 Output gradation changing means (output gradation changing step), 7 Control circuit, 17 computer, 18.
  • a watermark display reduction program of the present invention 51 Image quality adjustment circuit, 52 Image display panel, 101 Existing image display device

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Abstract

[Problem] To provide an image display device that, when displaying on a screen an electronic document, image or the like having a watermark display, is capable of reducing the watermark display without altering the electronic document or the like. [Solution] The image display device is provided with a gradation change means (2) capable of changing an input gradation from an image input signal into output gradation values different for each input gradation value, and a control circuit (7) that controls various signals. The image display device is configured so that in order to reduce the watermark display in the electronic document, image or the like and then to display the electronic document, image or the like, the output gradation value corresponding to the watermark gradation value, out of output gradation values for the gradation change means (2), is changed to a value either the same or close to the background output gradation value.

Description

画像表示装置及び階調変換方法Image display apparatus and gradation conversion method
　本発明は、電子文書や画像等における透かし表示を目立たないようにする画像表示装置、及び階調変換方法に関する。 The present invention relates to an image display apparatus and a gradation conversion method that make watermark display in an electronic document, an image, etc. inconspicuous.
　画像表示装置（モニタ）は、オフィスや家庭で使用されるのみならず、グラフィックデザインや医療等の様々な専門的業務の現場でも使用されている。画像表示装置は、主にパーソナルコンピュータ（ＰＣ）と接続されて使用され、電子文書や画像等の各種電子データを表示する。 Image display devices (monitors) are used not only in offices and homes, but also in various specialized fields such as graphic design and medical care. The image display device is mainly used by being connected to a personal computer (PC), and displays various electronic data such as an electronic document and an image.
　電子文書や画像等の各種電子データ（以下、電子文書等という）は、ワード形式（Wordはマイクロソフトの商品名）、ＰＤＦ形式（アドビシステムズが開発し提唱するPortable Document Format）、ＴＩＦＦ形式（マイクロソフトとアドビシステムズが開発し提唱するTagged Image File Format）、などの各種データファイル形式で作成される。 Various electronic data such as electronic documents and images (hereinafter referred to as electronic documents, etc.) are in word format (Word is a Microsoft product name), PDF format (Portable Document Format developed by Adobe Systems), TIFF format (Microsoft and Created in various data file formats such as Tagged Image File Format developed and advocated by Adobe Systems.
　これら電子文書等には、機密扱いなど文書の性質に応じて、“CONFIDENTIAL”、“機密”、“社外秘”、“複写禁止”、“見本”などのスタンプ表記が付与される。そして、このような電子文書は、セキュリティ上の理由から、文書が改ざんされないように、プロテクトされていることが通例である。図７は、透かし表示のある電子文書２０１を例示しており、“見本”の文字が、文書中の文字に重ねて表記され、透かし表示３０１となっている。アプリケーションソフトウェアによっては、この透かし表示をスタンプ表示と称するものもあるが、本明細書では、文書中の文字に重ねて表記された表示を総じて透かし表示と記載する。前記電子文書２０１は、印刷すると、透かし表示３０１が浮き上がって強調され濃く表示されるようになっていることが通例である。その一方で、既知の画像表示装置で電子文書等を画像表示させると、透かし表示３０１が重なった個所の文字４０１が読み取り難いことが、しばしば起こる。 These electronic documents are given a stamp notation such as “CONFIDENTIAL”, “confidential”, “confidential”, “copy prohibited”, “sample”, etc., depending on the nature of the document such as confidentiality. Such electronic documents are usually protected for security reasons so that the documents are not tampered with. FIG. 7 exemplifies an electronic document 201 with a watermark display. A “sample” character is overlaid on a character in the document to form a watermark display 301. Depending on the application software, this watermark display may be referred to as a stamp display. In this specification, a display overlaid on characters in a document is generally referred to as a watermark display. When the electronic document 201 is printed, the watermark display 301 is usually lifted, emphasized, and displayed darkly. On the other hand, when an electronic document or the like is displayed as an image on a known image display device, it often happens that it is difficult to read the character 401 where the watermark display 301 overlaps.
　上記の現象に対する対処方法としては、例えば、電子文書２０１の背景５０１の背景色を白色（２５５階調）とし、電子文書２０１の文字４０１の文字色を黒色（０階調）としたならば、透かし表示３０１の文字色を赤色とするというように、文字４０１の色と、透かし表示３０１の色とを異ならせることが行われている。しかし、文字４０１が読み取り難いことについては、さほど改善されていない。また、図７に示すような、透かし表示のある電子文書２０１を、既知の画像表示装置（モニタ）で表示させる際に、モニタ側で表示階調を変化させる画質調整が行われると、透かし表示３０１の階調と、文字４０１の階調との階調差が小さくなり、その意図（文字を見易くしたいとの意図）とは逆に、文字４０１が著しく不鮮明となってしまう事態も起こり得る。 As a countermeasure against the above phenomenon, for example, if the background color of the background 501 of the electronic document 201 is white (255 gradation) and the character color of the character 401 of the electronic document 201 is black (0 gradation), The color of the character 401 and the color of the watermark display 301 are made different so that the character color of the watermark display 301 is red. However, it is not so much improved that the character 401 is difficult to read. Further, when an electronic document 201 with a watermark display as shown in FIG. 7 is displayed on a known image display device (monitor), if the image quality adjustment for changing the display gradation is performed on the monitor side, the watermark display is performed. The gradation difference between the gradation of 301 and the gradation of the character 401 becomes small, and conversely to the intention (intention to make the character easy to see), a situation may occur where the character 401 becomes extremely unclear.
　文字を見易くするための方策としては、画像処理専用の画像加工用ソフトウエアを用いて、透かし表示３０１自体を加工処理することも不可能ではないが、ユーザの利便性が損なわれるうえ、電子文書２０１を改ざんすることとなってしまうので、現実的ではない。 As a measure for making the characters easy to see, it is not impossible to process the watermark display 301 itself by using image processing software dedicated to image processing. Since 201 will be falsified, it is not realistic.
　原稿画像を処理する画像処理装置としては、例えば、特許文献１－３が文献公知となっている。 For example, Patent Documents 1-3 are known as image processing apparatuses that process document images.
　特許文献１は、カラー複写機に関し、原稿画像の下地色（原稿用紙の白色）の再現性を高めるために、読み取るべきカラー原稿をプリスキャンしてＲ，Ｇ，Ｂ信号を入力し、ヒストグラム計数回路は入力したＲ，Ｇ，Ｂ信号の出現頻度を計数し、ヒストグラムから出現頻度最大となるＲＧＢ値の組合せを抽出し、抽出されたＲ，Ｇ，Ｂ値に基づいてカラー原稿のＲ，Ｇ，Ｂ信号を非線形変換することが記載されている。
　特許文献２は、カラー複写機に関し、原稿の裏写りを軽減するために文字を薄くした場合において、原稿画像の下地色（原稿用紙の白色）の再現性を高めるために、入力されるカラー画像データを基に原稿の濃度分布を算出し、それを基に原稿の下地濃度レベルを算出し、濃度変換テーブルを作成し、入力されるカラー画像データの画像濃度を変換することが記載されている。
　特許文献３は、カラー複写機に関し、原稿の裏写りを軽減するために、入力画像の全画素の階調データから各色成分ごとに不要画像部の階調範囲を求め、この階調範囲に基づいて各色成分ごとの除去階調条件を設定し、入力画像の各画素について、すべての色成分がこの除去階調条件を満たす画素を除去画素として判定し、除去画素の階調をゼロ（原稿用紙の白色）に変換して除去することが記載されている。 Patent Document 1 relates to a color copying machine, in order to improve the reproducibility of the background color of an original image (white of the original paper), prescan a color original to be read, input R, G, B signals, and perform histogram counting. The circuit counts the appearance frequency of the input R, G, B signals, extracts a combination of RGB values having the maximum appearance frequency from the histogram, and based on the extracted R, G, B values, R, G of the color document , B signal is described as non-linear transformation.
Patent Document 2 relates to a color copying machine, and in order to improve the reproducibility of the background color of the original image (white of the original paper) when the characters are thinned to reduce the show-through of the original, the color image that is input The document describes that the density distribution of the document is calculated based on the data, the background density level of the document is calculated based on the data, the density conversion table is created, and the image density of the input color image data is converted. .
Patent Document 3 relates to a color copying machine, in order to reduce the show-through of an original, obtains a gradation range of an unnecessary image portion for each color component from gradation data of all pixels of an input image, and based on this gradation range. The removal gradation condition for each color component is set, and for each pixel of the input image, a pixel satisfying this removal gradation condition for all color components is determined as the removal pixel, and the gradation of the removal pixel is zero (original paper In white).
　つまり、特許文献１－３では、原稿を見易く複写するために、裏写りなどの不要部分の階調をゼロ（原稿用紙の白色）としている。 In other words, in Patent Documents 1-3, the gradation of unnecessary parts such as show-through is set to zero (white of the original paper) in order to make the original easy to see and copy.
特開平０５－０６３９６８号公報Japanese Patent Laid-Open No. 05-063968 特開平１１－１８７２６６号公報Japanese Patent Laid-Open No. 11-187266 特開２００１－０９４８０４号公報JP 2001-094804 A
　しかしながら、上述のように、画像表示装置（モニタ）では、ガンマ補正（γ補正）などの画質調整を行っており、原画像の階調２５５が、表示画像では２５５よりも小さくなる場合がある。このため、複写機であれば階調ゼロとすれば”裏写り”を除去できるところ、γ補正などの画質調整を行っている状態のモニタでは十分に除去しきれない。 However, as described above, the image display apparatus (monitor) performs image quality adjustment such as gamma correction (γ correction), and the gradation 255 of the original image may be smaller than 255 in the display image. For this reason, in the case of a copying machine, “show-through” can be removed by setting the gradation to zero, but it cannot be sufficiently removed by a monitor in a state where image quality adjustment such as γ correction is performed.
　また、モニタは、ＰＣと接続されて使用され、電子文書や画像等の各種電子データを、いわゆるマルチウィンドウ表示することがあり、先行技術のように所定階調以下を一律に変換してしまうと、本来関係のないウィンドウの電子文書や画像等にも影響を与え、見栄えを悪くするという弊害を招く虞がある。そして、透かし表示は、赤色などの色が付いていることが通例であり、原稿の裏写りとは画質が異なっている。 In addition, the monitor is used in connection with a PC, and various electronic data such as electronic documents and images may be displayed in a so-called multi-window, and if a predetermined gradation or less is uniformly converted as in the prior art. This may affect electronic documents and images of windows that are not originally related, and may cause a bad effect of deteriorating appearance. The watermark display usually has a color such as red, and the image quality is different from the show-through of the document.
　そこで、本発明の目的は、透かし表示のある電子文書や画像等を、画像表示装置にて画面表示するに際し、前記電子文書等を改ざんすることなく、透かし表示を低減することが可能な、画像表示装置、及び階調変換方法を提供することにある。 Accordingly, an object of the present invention is to reduce the watermark display without falsifying the electronic document or the like when displaying the electronic document or image or the like with a watermark display on the image display device. A display device and a gradation conversion method are provided.
　本発明の画像表示装置は、画像入力信号の入力階調を各入力階調値毎に異なる出力階調値に変換可能な階調変換手段と、前記階調変換手段にある入力階調値と出力階調値を書き換える制御回路を備え、前記制御回路に設定された２以上の階調値のうち、一の設定階調値と等しい入力階調に対応づけられた出力階調値を取得し、他の設定階調値と等しい入力階調に対応づけられた出力階調を、前記取得した出力階調値と同じか近い値に置き換えることを特徴とする。 An image display apparatus according to the present invention includes a gradation conversion unit capable of converting an input gradation of an image input signal into an output gradation value different for each input gradation value, and an input gradation value in the gradation conversion unit. A control circuit for rewriting the output gradation value is provided, and an output gradation value associated with an input gradation equal to one set gradation value among two or more gradation values set in the control circuit is acquired. The output gradation associated with the input gradation equal to the other set gradation value is replaced with a value that is the same as or close to the acquired output gradation value.
　本発明によれば、除去したい階調に限定して階調変換することが可能となる。 According to the present invention, it is possible to perform gradation conversion limited to the gradation to be removed.
　本発明は、例えば、前記画像は文書画像であって、前記一の設定階調値は文書画像の下地を表示する階調であり前記他の設定階調値は文書画像の下地を表示する階調と文字を表示する階調との範囲内にある階調値である。本発明によれば、電子文書等を改ざんすることなく、不要な表示を低減しつつ、他の領域やウィンドウへの影響を極力抑えることができる。 In the present invention, for example, the image is a document image, the one set gradation value is a gradation for displaying a background of the document image, and the other set gradation value is a floor for displaying the background of the document image. The gradation value is within the range of the gradation and the gradation for displaying the character. According to the present invention, it is possible to suppress the influence on other regions and windows as much as possible while reducing unnecessary display without falsifying an electronic document or the like.
　本発明は、例えば、　前記画像は透かし画像を含む文書画像であって、前記一の設定階調値は文書画像の下地を表示する階調であり、前記他の設定階調値は透かし画像を表示する階調との範囲内にある階調値である。本発明によれば、電子文書等を改ざんすることなく、透かし表示を低減しつつ、他の領域やウィンドウへの影響を極力抑えることができる。 In the present invention, for example, the image is a document image including a watermark image, the one set gradation value is a gradation for displaying a background of the document image, and the other set gradation value is a watermark image. The gradation value is within the range of the gradation to be displayed. According to the present invention, it is possible to suppress the influence on other regions and windows as much as possible while reducing watermark display without falsifying an electronic document or the like.
　前記階調変換手段は、画像入力信号の入力階調を各入力階調値毎に異なる出力階調値に変換可能な仕組みであり、より具体的には、ルックアップテーブル（ＬＵＴ）を用いる。ＬＵＴは、Look up Table の略で、入力階調に対する出力階調の割当テーブルである。ＬＵＴは、例えば２５６階調なら２５６個のデータ格納数を持っている。このＬＵＴに、各入力階調に対する出力階調をあらかじめ作成しておき、ＬＵＴを参照することで階調変換を行う。例えば、あらかじめ先に計算できるデータは計算しておき、その値をＬＵＴに保存しておく。 The gradation converting means is a mechanism capable of converting the input gradation of the image input signal into different output gradation values for each input gradation value, and more specifically, uses a lookup table (LUT). LUT is an abbreviation of LookLup Table, and is an output tone allocation table for input tones. For example, the LUT has 256 data storage numbers for 256 gradations. In this LUT, an output gradation for each input gradation is created in advance, and gradation conversion is performed by referring to the LUT. For example, data that can be calculated in advance is calculated in advance, and the value is stored in the LUT.
　ここで、前記階調変換手段の前記透かし階調値に対応付けされた出力階調値が、前記背景出力階調値と同じか近い値であるとは、前記電子文書等の背景となるような値を指している。例えば、前記電子文書等の背景が白色であれば、階調値を２５５とすれば、前記背景出力階調値と同じ値となる。例えば、階調値を２００から２５４の範囲内の値とすれば、前記背景出力階調値と近い値となる。 Here, the fact that the output gradation value associated with the watermark gradation value of the gradation converting means is the same as or close to the background output gradation value is the background of the electronic document or the like. Points to the correct value. For example, if the background of the electronic document or the like is white, if the gradation value is 255, the background output gradation value is the same value. For example, if the gradation value is set to a value within the range of 200 to 254, the value is close to the background output gradation value.
　前記電子文書等の背景となる背景階調値は、予め設定された固定値を用いるか、または、画像表示装置内の処理回路や処理プログラムによって算出されるか、若しくは、ユーザが表示画面を視認して表示画面上の操作メニューや画像表示装置の操作ボタンを操作することで決定される。透かし表示となる透かし階調値についても、同様に、予め設定された固定値を用いるか、または、画像表示装置内の処理回路や処理プログラムによって算出されるか、若しくは、ユーザが表示画面を視認して表示画面上の操作メニューや画像表示装置の操作ボタンを操作することで決定される。 The background gradation value as the background of the electronic document or the like uses a fixed value set in advance, or is calculated by a processing circuit or a processing program in the image display device, or the user visually recognizes the display screen. Then, it is determined by operating an operation menu on the display screen or an operation button of the image display device. Similarly, for the watermark gradation value to be displayed as a watermark, a preset fixed value is used, or it is calculated by a processing circuit or a processing program in the image display device, or the user visually recognizes the display screen. Then, it is determined by operating an operation menu on the display screen or an operation button of the image display device.
　前記背景階調値は、所定の範囲内で設定される。前記ピンポイントの値としては、透かし表示として用いられ易い階調値が挙げられ、例えば、前記透かし階調値に対応付けされた出力階調値を固定値としておくことができる。前記固定値としては、例えば、２０５、２１０、２１５、２２０、２２５、２３０等が挙げられる。 The background gradation value is set within a predetermined range. Examples of the pinpoint value include a gradation value that can be easily used as a watermark display. For example, an output gradation value associated with the watermark gradation value can be set as a fixed value. Examples of the fixed value include 205, 210, 215, 220, 225, 230, and the like.
　本発明は、前記透かし階調値、前記背景階調値、及び前記透かし階調値に対応付けされた出力階調値が前記制御回路に入力されると、前記制御回路が、前記透かし階調値に対応付けされた出力階調値を、前記背景出力階調値に置き換えることが好ましい。
　本発明によれば、ユーザの手を煩わせることなく、前記電子文書等の透かし表示となる透かし階調値が自動的に取得されることとなり、使い勝手が良い。マルチウィンドウへの対応としては、前記電子文書等を表示するウィンドウ領域を指定し、その領域内のみ本発明の階調変換を施せばよい。 In the present invention, when the watermark gradation value, the background gradation value, and the output gradation value associated with the watermark gradation value are input to the control circuit, the control circuit It is preferable to replace the output tone value associated with the value with the background output tone value.
According to the present invention, a watermark gradation value that is a watermark display of the electronic document or the like is automatically acquired without bothering the user, which is easy to use. In order to cope with the multi-window, a window area for displaying the electronic document or the like is designated, and the gradation conversion of the present invention is performed only in that area.
　本発明の階調変換方法は、画像入力信号の入力階調を各入力階調値毎に異なる出力階調値に変換可能な階調変換手段が備わっている画像表示装置の階調変換方法において、設定された２以上の階調値のうち、一の設定階調値と等しい入力階調に対応づけられた出力階調値を取得し、他の設定階調値と等しい入力階調に対応づけられた出力階調を、前記取得した出力階調値と同じか近い値に置き換えることを特徴とする。 The gradation conversion method of the present invention is a gradation conversion method for an image display device provided with gradation conversion means capable of converting an input gradation of an image input signal into an output gradation value that differs for each input gradation value. Of the two or more set gradation values, an output gradation value associated with an input gradation equal to one set gradation value is obtained, and an input gradation equal to another set gradation value is obtained. The attached output gradation is replaced with a value that is the same as or close to the acquired output gradation value.
　本発明によれば、既存の画像表示装置に接続されるか内蔵されたコンピュータを利用するなどして、除去したい階調に限定して階調変換することが出来るので、使い勝手が良い。 According to the present invention, since gradation conversion can be performed only for gradations to be removed by using a computer connected to an existing image display device or using a built-in computer, it is easy to use.
　本発明の階調変換方法を適用した透かし表示低減プログラムは、前記画像表示装置内のコンピュータ機能を有する制御回路やその周辺のコンピュータ機能を有する機構部にインストールされるか、または、前記画像表示装置と接続されたコンピュータにインストールされて利用される。前記表示低減プログラムは、例えば、ＵＳＢメモリやＣＤ－ＲＯＭなどの媒体を介してインストールされるか、インターネットやイントラネットなどのネットワーク回線を利用してダウンロードされ、インストールされる。ここで、プログラムは、プログラミングされた指令を指し、ソフトウエア、ファームウエアを含む。 A watermark display reduction program to which the gradation conversion method of the present invention is applied is installed in a control circuit having a computer function in the image display device or a peripheral mechanical unit having a computer function, or the image display device. It is installed on a computer connected to and used. For example, the display reduction program is installed via a medium such as a USB memory or a CD-ROM, or is downloaded and installed using a network line such as the Internet or an intranet. Here, the program indicates a programmed command and includes software and firmware.
　本発明が適用される画像表示装置としては、画像表示パネル若しくはブラウン管やＣＲＴ等の画像表示部を有していればよい。前記画像表示パネルとしては、液晶表示ディスプレイパネル、有機エレクトロルミネッセンスディスプレイパネル、プラズマディスプレイパネル等が挙げられる。 The image display device to which the present invention is applied only needs to have an image display panel or an image display unit such as a cathode ray tube or a CRT. Examples of the image display panel include a liquid crystal display panel, an organic electroluminescence display panel, and a plasma display panel.
　前記階調変換手段は、コントラスト、輝度、明度、ガンマ補正等の画質を調整する画質調整回路の前段に設けられるか、または、前記画質調整回路の後段に設けられる。 The gradation converting means is provided before the image quality adjustment circuit that adjusts the image quality such as contrast, brightness, brightness, and gamma correction, or after the image quality adjustment circuit.
　本発明の画像表示装置は、前記階調変換手段が、コントラスト、輝度、明度、ガンマ補正等の画質を調整する画質調整回路の前段に設けられていることを特徴とする。 The image display device according to the present invention is characterized in that the gradation converting means is provided in a preceding stage of an image quality adjustment circuit for adjusting image quality such as contrast, brightness, brightness, and gamma correction.
　本発明によれば、前記画質調整回路の影響を受けない状態で前記電子文書等の透かし表示を画像処理するので、前記電子文書等における透かし表示と文字との階調差がなくなる虞がない。そして、本来関係のないウィンドウの電子文書や画像等に影響を与える心配がない。 According to the present invention, since the watermark display of the electronic document or the like is image-processed without being affected by the image quality adjustment circuit, there is no possibility that the gradation difference between the watermark display and the character in the electronic document or the like is eliminated. And there is no worry of affecting the electronic document, image, etc. of the window which is not related originally.
　前記透かし階調値に対応付けされた出力階調値は、ピンポイントで設定されるか、または、所定幅の範囲内で設定される。前記ピンポイントの値としては、透かし表示として用いられ易い階調値が挙げられ、前記透かし階調値に対応付けされた出力階調値を予め固定値としておくことができる。前記固定値としては、例えば、２０５、２１０、２１５、２２０、２２５、２３０、２３５、２４０、２４５、２５０、２５４、２５５等が挙げられる。 The output gradation value associated with the watermark gradation value is set as a pinpoint or within a predetermined range. Examples of the pinpoint value include a gradation value that can be easily used as a watermark display, and an output gradation value associated with the watermark gradation value can be set as a fixed value in advance. Examples of the fixed value include 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 254, and 255.
　例えば、紙の書類に朱肉で“社外秘”とスタンプし、その後、スキャナ等でスキャンして変換した電子書類などでは、朱色の濃淡や滲みや色むらが生じて前記透かし表示に複数の階調が含まれることとなる。また、電子書類を作成する際の、スキャン条件等によっては、前記透かし表示に複数の階調が含まれることがある。 For example, in an electronic document that is stamped on paper paper as “confidential” with vermilion, and then scanned and converted with a scanner or the like, vermilion shades, blurring, and uneven color occur, resulting in multiple gradations in the watermark display. Will be included. Further, depending on the scanning conditions when creating the electronic document, the watermark display may include a plurality of gradations.
　本発明の画像表示装置は、前記透かし階調値が所定幅の階調値であるとして、前記透かし階調値に対応付けされた出力階調値を、前記背景出力階調値と同じか近い値に置き換える構成としてもよい。この構成によれば、前記透かし表示に複数の階調が含まれている場合や、前記透かし階調値に対応付けされた出力階調値に読み取り誤差があったとしても、前記透かし表示を、より確実に低減することとなる。 The image display device of the present invention assumes that the watermark gradation value is a gradation value having a predetermined width, and the output gradation value associated with the watermark gradation value is the same as or close to the background output gradation value. It is good also as a structure replaced with a value. According to this configuration, even when the watermark display includes a plurality of gradations, or even if there is a reading error in the output gradation value associated with the watermark gradation value, the watermark display is It will reduce more reliably.
　前記所定幅の階調値は、前記透かし階調値に対応付けされた出力階調値であって、予め設定された固定値を用いるか、または、画像表示装置内の処理回路や処理プログラムによって算出されるか、若しくは、ユーザが表示画面を視認して表示画面上の操作メニューや画像表示装置の操作ボタンを操作することで決定される。例えば、ユーザが表示画面を視認しながら表示画面上のスライダやつまみを操作するようにしてもよく、また、ユーザがマウスを用いて領域指定するようにしてもよい。 The gradation value of the predetermined width is an output gradation value associated with the watermark gradation value, and uses a preset fixed value, or by a processing circuit or a processing program in the image display device. It is calculated or determined by the user viewing the display screen and operating an operation menu on the display screen or an operation button of the image display device. For example, a user may operate a slider or a knob on the display screen while visually recognizing the display screen, or the user may specify an area using a mouse.
　前記所定幅の階調値は、透かし表示として用いられ易い階調値を含む所定範囲の値を採用することができ、予め固定された幅としておくことができる。前記固定された幅の値としては、例えば、２００～２１０、２０５～２２５、２１０～２３０、２２０～２４０、２２５～２５０、２２５～２５４、２２５～２５５等が挙げられる。 As the gradation value of the predetermined width, a value in a predetermined range including a gradation value that is easily used as a watermark display can be adopted, and a predetermined width can be set. Examples of the fixed width value include 200 to 210, 205 to 225, 210 to 230, 220 to 240, 225 to 250, 225 to 254, and 225 to 255.
　本発明の画像表示装置は、例えば、前記透かし階調値に対応付けされた出力階調値が、１以上２５４以下に設定される。この構成によれば、前記透かし階調値に対応付けされた出力階調値を、１以上２５４以下に設定することで、ゼロ階調の黒色と重なることがなく、かつ、２５５階調の白色と重なることもないので、前記電子文書の透かし表示が完全に透けて見えるような違和感が生じ難い。 In the image display device of the present invention, for example, the output gradation value associated with the watermark gradation value is set to 1 or more and 254 or less. According to this configuration, the output gradation value associated with the watermark gradation value is set to 1 or more and 254 or less so that it does not overlap with the black of the zero gradation and the white of 255 gradations. Therefore, it is difficult to cause a sense of incongruity so that the watermark display of the electronic document can be completely seen through.
　本発明は、前記透かし階調値に対応付けされた出力階調値として、前記電子文書から入力画像のヒストグラムを演算し、演算された前記ヒストグラムに基づいて推定された階調値を用いることができる。換言すると、本発明は、前記電子文書等から入力画像のヒストグラムを演算し、演算された前記ヒストグラムに基づいて前記透かし階調値に対応付けされた出力階調値を推定することができる。本発明によれば、例えば、前記電子文書等を表示するウィンドウ領域を指定し、その領域内のみ本発明の階調変換を施すなどのマルチウィンドウへの対応が容易となる。 In the present invention, a histogram of an input image is calculated from the electronic document as an output gradation value associated with the watermark gradation value, and a gradation value estimated based on the calculated histogram is used. it can. In other words, the present invention can calculate a histogram of an input image from the electronic document or the like, and estimate an output gradation value associated with the watermark gradation value based on the calculated histogram. According to the present invention, for example, a window region for displaying the electronic document or the like is designated, and it is easy to deal with multi-windows such as performing gradation conversion of the present invention only in that region.
　本発明によれば、前記階調変換手段の出力階調値のうち、透かし階調値に対応付けされた出力階調値が、背景出力階調値と同じか近い値に置き換えられて信号出力され画面表示されるので、除去したい階調に限定して階調変換することが可能となる。よって、電子文書等を改ざんすることなく、透かし表示を低減しつつ、他の領域やウィンドウへの影響を極力抑えることができる。そして、本発明によれば、ユーザの手を煩わせることなく、前記電子文書等の透かし表示となる透かし階調値が自動的に取得されることとなり、使い勝手が良い。マルチウィンドウへの対応としては、前記電子文書等を表示するウィンドウ領域を指定し、その領域内のみ本発明の階調変換を施せばよい。また、前記画質調整回路の影響を受けない状態で前記電子文書等の透かし表示を画像処理するので、前記電子文書等における透かし表示と文字との階調差がなくなる虞がない。 According to the present invention, the output tone value associated with the watermark tone value among the output tone values of the tone converting means is replaced with a value that is the same as or close to the background output tone value, and the signal output Since it is displayed on the screen, gradation conversion can be performed only for the gradation to be removed. Therefore, it is possible to suppress the influence on other regions and windows as much as possible while reducing the watermark display without falsifying the electronic document or the like. According to the present invention, the watermark gradation value that is the watermark display of the electronic document or the like is automatically acquired without bothering the user, which is easy to use. In order to deal with multi-windows, a window area for displaying the electronic document or the like may be designated, and gradation conversion of the present invention may be performed only within that area. In addition, since the watermark display of the electronic document or the like is image-processed without being affected by the image quality adjustment circuit, there is no possibility that the gradation difference between the watermark display and the character in the electronic document or the like is eliminated.
　本発明によれば、本来関係のないウィンドウの電子文書や画像等に影響を与える心配がない。そして、前記透かし表示に複数の階調が含まれていたとしても、前記透かし表示を、より確実に低減することとなる。前記透かし階調値に対応付けされた出力階調値を、１以上２５４以下に設定することで、画面上ではゼロ階調の黒色と重なることがなく、かつ、２５５階調の白色と重なることもないので、画面上では前記電子文書の透かし表示が完全に透けて背景が見えるような違和感が生じ難い。また、前記電子文書等は何ら改変されていないので、プリントアウトした紙には前記透かしが表示されることとなる。 According to the present invention, there is no concern of affecting electronic documents or images of windows that are not originally related. And even if a plurality of gradations are included in the watermark display, the watermark display is more reliably reduced. By setting the output gradation value associated with the watermark gradation value to 1 or more and 254 or less, it does not overlap with the black of the zero gradation on the screen and overlaps with the white of the 255 gradation. Therefore, it is difficult to cause an uncomfortable feeling that the watermark display of the electronic document is completely transparent on the screen and the background can be seen. Further, since the electronic document or the like has not been altered, the watermark is displayed on the printed paper.
　本発明によれば、既存の画像表示装置に接続されるか内蔵されたコンピュータを利用するなどして、除去したい階調に限定して階調変換することが出来るので、使い勝手が良い。 According to the present invention, since gradation conversion can be performed only for gradations to be removed by using a computer connected to an existing image display device or using a built-in computer, it is easy to use.
本発明の実施形態の透かし表示低減機能付き画像表示装置を例示するブロック構成図である。It is a block block diagram which illustrates the image display apparatus with a watermark display reduction function of embodiment of this invention. 本発明の実施形態の透かし表示低減プログラムを用いた画像表示装置を例示するブロック構成図である。It is a block block diagram which illustrates the image display apparatus using the watermark display reduction program of embodiment of this invention. 従来の入力階調と出力階調との関係を例示するグラフ図である。It is a graph which illustrates the relationship between the conventional input gradation and output gradation. 本発明の階調変換を行ったときの入力階調と出力階調との関係を例示するグラフ図である。It is a graph which illustrates the relationship between the input gradation and output gradation when performing the gradation conversion of this invention. 本発明の階調変換を行ったときの入力階調と出力階調との関係を例示するグラフ図である。It is a graph which illustrates the relationship between the input gradation and output gradation when performing the gradation conversion of this invention. 本発明の階調変換を行ったときの電子文書を例示する図である。It is a figure which illustrates the electronic document when performing the gradation conversion of this invention. 従来の電子文書を例示する図である。It is a figure which illustrates the conventional electronic document.
　以下、本発明を実施するための具体的な形態について図面を用いて説明する。 Hereinafter, specific modes for carrying out the present invention will be described with reference to the drawings.
（本発明の画像表示装置）
　図１は、本発明を適用した実施形態の透かし表示低減機能付き画像表示装置を例示するブロック構成図である。本実施形態の画像表示装置１は、画像入力信号の入力階調を各入力階調値毎に異なる出力階調値に変換可能な階調変換手段２と、各種信号を制御する制御回路７を備え、前記階調変換手段２から信号出力され、画質調整回路５１にてコントラスト、輝度、明度、ガンマ補正等の画質が調整され、画像表示パネル５２にて画像表示される。図１に示す構成では、前記階調変換手段２は、コントラスト、輝度、明度、ガンマ補正等の画質を調整する画質調整回路５１の前段に設けられている。 (Image display device of the present invention)
FIG. 1 is a block diagram illustrating an image display device with a watermark display reduction function according to an embodiment to which the present invention is applied. The image display apparatus 1 according to the present embodiment includes a gradation conversion unit 2 that can convert an input gradation of an image input signal into an output gradation value that differs for each input gradation value, and a control circuit 7 that controls various signals. The image is output from the gradation converting means 2, and the image quality adjustment circuit 51 adjusts the image quality such as contrast, brightness, brightness, and gamma correction, and the image is displayed on the image display panel 52. In the configuration shown in FIG. 1, the gradation converting means 2 is provided in the preceding stage of an image quality adjustment circuit 51 for adjusting image quality such as contrast, brightness, brightness, and gamma correction.
　前記画像表示パネル５２としては、液晶表示ディスプレイパネル、有機エレクトロルミネッセンスディスプレイパネル、プラズマディスプレイパネル等が挙げられる。 Examples of the image display panel 52 include a liquid crystal display panel, an organic electroluminescence display panel, and a plasma display panel.
　図７は、透かし表示のある電子文書２０１を例示しており、“見本”の文字が、文書中の文字４０１に重ねて表記され、透かし表示３０１となっている。 FIG. 7 shows an example of an electronic document 201 with a watermark display. A “sample” character is overlaid on a character 401 in the document to form a watermark display 301.
　図３は、従来の画像処理装置におけるＲ，Ｇ，Ｂそれぞれの入力階調と出力階調との関係を例示するグラフ図である。グラフの横軸は入力階調であり、縦軸は出力階調であって、それぞれ０階調～２５５階調である。電子文書２０１における文書中の文字４０１は黒色か黒色に近い配色が一般的である。文字４０１が黒色であれば、０階調となる。文字４０１が黒色に近い配色であれば、０に近い階調となる。電子文書２０１における背景５０１は白色か白色に近い配色が一般的である。背景５０１が白色であれば、２５５階調となる。背景５０１が白色に近い配色であれば、２５５に近い階調となる。電子文書２０１における透かし表示（“見本”の文字）３０１は、符号Ｃ２で表す階調となる。階調値Ｃ２の配色は、グレーや赤色などで薄めの配色であることが多く、前記透かし表示３０１として用いられ易い階調値Ｃ２としては、例えば、２０５、２１０、２１５、２２０、２２５、２３０等が挙げられる。 FIG. 3 is a graph illustrating the relationship between the input gradation and output gradation of each of R, G, and B in a conventional image processing apparatus. The horizontal axis of the graph is the input gray scale, and the vertical axis is the output gray scale, which is 0 to 255 gradations, respectively. The character 401 in the document in the electronic document 201 is generally black or a color scheme close to black. If the character 401 is black, the gradation is 0. If the character 401 has a color scheme close to black, the gradation is close to 0. The background 501 in the electronic document 201 is generally white or a color scheme close to white. If the background 501 is white, there are 255 gradations. If the background 501 has a color scheme close to white, the gradation is close to 255. The watermark display (“sample” character) 301 in the electronic document 201 has a gradation represented by the symbol C2. The color scheme of the gradation value C2 is often a light color scheme such as gray or red, and the gradation value C2 that can be easily used as the watermark display 301 is, for example, 205, 210, 215, 220, 225, 230. Etc.
　従来から、画像表示装置（モニタ）では、ガンマ補正（γ補正）などの画質調整を行っており、原画像に比べ、表示画像では小さくなる階調が生じる場合がある（図３を参照）。すなわち、前記背景５０１の２５５階調や前記透かし表示３０１の階調値Ｃ２が、出力階調では２５５階調、あるいは階調値Ｃ２より小さくなる場合がある。 Conventionally, image display devices (monitors) have been subjected to image quality adjustment such as gamma correction (γ correction), and there are cases in which a gradation that is smaller in a display image than in an original image occurs (see FIG. 3). That is, the 255 gradation of the background 501 and the gradation value C2 of the watermark display 301 may be smaller than the 255 gradation or the gradation value C2 in the output gradation.
　前記階調変換手段２は、画像入力信号の入力階調を各入力階調値毎に異なる出力階調値に変換可能な仕組みであり、より具体的には、ルックアップテーブル（ＬＵＴ）を用いる（図１）。そして、ＬＵＴに、各入力階調に対する出力階調をあらかじめ作成しておき、ＬＵＴを参照することで階調変換を行う。 The gradation converting means 2 is a mechanism capable of converting the input gradation of the image input signal into different output gradation values for each input gradation value, and more specifically uses a look-up table (LUT). (FIG. 1). An output gradation for each input gradation is created in advance in the LUT, and gradation conversion is performed by referring to the LUT.
　図１では、背景階調値設定手段３によって背景階調値（入力階調Ｚ）が制御回路７に入力され、また、透かし階調値設定手段４によって透かし階調値（入力階調Ｃ）が制御回路７に入力される。それとともに、出力階調取得手段５によって前記透かし階調値にあらかじめ対応付けされた出力階調値（出力階調値Ｚ）が制御回路７に入力される。その後、制御回路７は出力階調変更手段６に対して、設定された前記透かし階調値（入力階調Ｃ）にあらかじめ対応付けされた出力階調値（出力階調Ｃ）を、取得された前記出力階調値Ｚに置き換えを実行する。そして、階調変換手段２からの出力信号が、コントラスト、輝度、明度、ガンマ補正等の画質を調整する画質調整回路５１に入力され、画質調整回路５１からの出力信号によって画像表示パネル５２に画像表示される。本実施形態によれば、ユーザの手を煩わせることなく、電子文書２０１の透かし表示３０１と対応する透かし階調値が自動的に取得されることとなり、使い勝手が良い。 In FIG. 1, the background gradation value (input gradation Z) is input to the control circuit 7 by the background gradation value setting means 3, and the watermark gradation value (input gradation C) is input by the watermark gradation value setting means 4. Is input to the control circuit 7. At the same time, an output gradation value (output gradation value Z) previously associated with the watermark gradation value is input to the control circuit 7 by the output gradation acquisition means 5. Thereafter, the control circuit 7 obtains an output gradation value (output gradation C) previously associated with the set watermark gradation value (input gradation C) to the output gradation changing means 6. Further, replacement with the output gradation value Z is executed. The output signal from the gradation converting means 2 is input to an image quality adjustment circuit 51 that adjusts image quality such as contrast, brightness, brightness, and gamma correction, and an image is displayed on the image display panel 52 by the output signal from the image quality adjustment circuit 51. Is displayed. According to this embodiment, the watermark gradation value corresponding to the watermark display 301 of the electronic document 201 is automatically acquired without bothering the user, which is convenient.
　図４は、本発明の階調変換を行ったときの入力階調と出力階調との関係を例示するグラフ図の一例である。電子文書２０１における透かし表示（“見本”の文字）３０１は、符号Ｃ２で表す階調となる。図４に示す例では、透かし階調値Ｃ２をピンポイントで、前記背景出力階調値と同じか近い値に置き換えている。前記ピンポイントの値としては、例えば、２０５、２１０、２１５、２２０、２２５、２３０、２３５、２４０、２４５、２５０、２５４、２５５等が挙げられる。本実施例によれば、透かし階調値Ｃ２をピンポイントで、前記背景階調値として、設定しているので、前記電子文書２０１における透かし表示３０１以外の文字４０１への影響を極力抑えられる。 FIG. 4 is an example of a graph illustrating the relationship between the input gradation and the output gradation when the gradation conversion of the present invention is performed. The watermark display (“sample” character) 301 in the electronic document 201 has a gradation represented by the symbol C2. In the example shown in FIG. 4, the watermark gradation value C2 is pinpointed and replaced with a value that is the same as or close to the background output gradation value. Examples of the pinpoint value include 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 254, and 255. According to the present embodiment, since the watermark gradation value C2 is set as the background gradation value at a pinpoint, the influence on the characters 401 other than the watermark display 301 in the electronic document 201 can be suppressed as much as possible.
　図５は、本発明の階調変換を行ったときの入力階調と出力階調との関係を例示するグラフ図の他の例である。電子文書２０１における透かし表示（“CONFIDENTIAL”の文字）３０１は、符号Ｃ２で表す階調となるが、配色の関係で前記透かし表示に複数の階調が含まれることがある。図５に示す例では、透かし階調値Ｃ２を挟んで階調値Ｃ１～Ｃ３までの所定幅の階調値であるとして、前記透かし階調値Ｃ１～Ｃ３に対応付けされた出力階調値を、前記背景出力階調値と同じか近い値に置き換えている。前記所定幅の階調値としては、例えば、２００～２１０、２０５～２２５、２１０～２３０、２２０～２４０、２２５～２５０、２２５～２５４、２２５～２５５等が挙げられる。本実施例によれば、透かし表示３０１に複数の階調が含まれていたとしても、前記透かし表示３０１を、より確実に低減することとなる。 FIG. 5 is another example of a graph illustrating the relationship between the input gradation and the output gradation when the gradation conversion of the present invention is performed. The watermark display (“CONFIDENTIAL” character) 301 in the electronic document 201 has a gradation represented by reference numeral C2, but the watermark display may include a plurality of gradations due to the color scheme. In the example shown in FIG. 5, the output gradation values associated with the watermark gradation values C1 to C3 are assumed to be gradation values having a predetermined width from the gradation values C1 to C3 across the watermark gradation value C2. Is replaced with a value that is the same as or close to the background output gradation value. Examples of the gradation value having the predetermined width include 200 to 210, 205 to 225, 210 to 230, 220 to 240, 225 to 250, 225 to 254, and 225 to 255. According to the present embodiment, even if the watermark display 301 includes a plurality of gradations, the watermark display 301 is more reliably reduced.
　図６は、本発明の階調変換を行ったときの電子文書を例示する図である。階調変換後の電子文書２０２における透かし表示（“見本”の文字）３０２は、背景５０１の背景出力階調値と同じか近い値に置き換えられている。例えば、背景５０１が白色であるとすると、透かし表示３０２は、同色の白色か、クリーム色や薄黄色などに置き換えられる。よって、透かし表示３０２は、背景５０１に近い状態となって、透かし表示３０２が重なっている領域の文字４０１が読み易くなる。本実施形態によれば、電子文書や画像等を改ざんすることなく、透かし表示を低減しつつ、他の領域やウィンドウへの影響を極力抑えることができる。そして、マルチウィンドウへの対応としては、例えば、前記電子文書等を表示するウィンドウ領域を指定し、その領域内のみ本発明の階調変換を施せばよい。そして、前記電子文書や画像等は何ら改変されていないので、プリントアウトした紙には前記透かし３０１が表示されることとなる。 FIG. 6 is a diagram illustrating an electronic document when the gradation conversion of the present invention is performed. The watermark display (“sample” character) 302 in the electronic document 202 after gradation conversion is replaced with a value that is the same as or close to the background output gradation value of the background 501. For example, when the background 501 is white, the watermark display 302 is replaced with the same white color, cream color or light yellow color. Therefore, the watermark display 302 is in a state close to the background 501, and the characters 401 in the area where the watermark display 302 overlaps are easy to read. According to the present embodiment, it is possible to suppress the influence on other regions and windows as much as possible while reducing the watermark display without falsifying an electronic document or an image. In order to cope with the multi-window, for example, a window area for displaying the electronic document or the like is specified, and the gradation conversion of the present invention is performed only in that area. Since the electronic document, the image, etc. are not altered at all, the watermark 301 is displayed on the printed paper.
（本発明の透かし表示低減プログラム）
　図２は、本発明を適用した実施形態の透かし表示低減プログラムを用いた画像表示装置を例示するブロック構成図である。ここで、同じ符号は同じ機能を指しており、その説明を適宜省略する。本実施形態の透かし表示低減プログラムは、図２のうち、一点鎖線で囲んだ符号１８で表される。透かし表示低減プログラム１８は、画像入力信号の入力階調を各入力階調値毎に異なる出力階調値に変換可能な階調変換手段２が備わっている画像表示装置１０１において、電子文書や画像等における透かし表示を低減させて画像表示するに際し使用される。図２に示す構成では、前記階調変換手段２は、コントラスト、輝度、明度、ガンマ補正等の画質を調整する画質調整回路５１の前段に設けられている。 (Watermark display reduction program of the present invention)
FIG. 2 is a block diagram illustrating an image display apparatus using a watermark display reduction program according to an embodiment to which the present invention is applied. Here, the same reference numerals indicate the same functions, and description thereof will be omitted as appropriate. The watermark display reduction program according to the present embodiment is represented by reference numeral 18 in FIG. The watermark display reduction program 18 is used in the image display apparatus 101 provided with the gradation conversion means 2 capable of converting the input gradation of the image input signal into different output gradation values for each input gradation value. This is used when displaying an image with reduced watermark display. In the configuration shown in FIG. 2, the gradation converting means 2 is provided in the preceding stage of an image quality adjustment circuit 51 that adjusts image quality such as contrast, brightness, brightness, and gamma correction.
　本実施形態では、既存の画像表示装置１０１に接続されたコンピュータ１７から画像表示装置１０１に画像入力信号が入力される構成となっている。本実施形態では、コンピュータ１７上で、透かし表示低減プログラム１８を起動させると、階調変換手段２の出力階調値のうち、透かし階調値に対応付けされた出力階調値を、背景出力階調値と同じか近い値に置き換える。 In the present embodiment, an image input signal is input to the image display device 101 from the computer 17 connected to the existing image display device 101. In the present embodiment, when the watermark display reduction program 18 is started on the computer 17, the output gradation value associated with the watermark gradation value among the output gradation values of the gradation converting means 2 is output to the background. Replace with a value that is the same as or close to the gradation value.
　図２では、背景階調値設定ステップ３によって背景階調値（入力階調Ｚ）が設定されてコンピュータ１７に入力され、また、透かし階調値設定ステップ４によって透かし階調値（入力階調Ｃ）が設定されてコンピュータ１７に入力される。それとともに、出力階調取得ステップ５によって前記透かし階調値にあらかじめ対応付けされた出力階調値（出力階調値Ｚ）を階調変換手段２から取得しコンピュータ１７に入力される。その後、コンピュータ１７からの指令を受けて出力階調変更ステップ６にて階調変換手段２に対して、前記透かし階調値（入力階調Ｃ）にあらかじめ対応付けされた出力階調値（出力階調Ｃ）を、取得した前記出力階調値Ｚに置き換えを実行する。そして、階調変換手段２からの出力信号が、コントラスト、輝度、明度、ガンマ補正等の画質を調整する画質調整回路５１に入力され、画質調整回路５１からの出力信号によって画像表示パネル５２に画像表示される。本実施形態によれば、既存の画像表示装置１０１に接続されるか内蔵されたコンピュータ１７に、透かし表示低減プログラム１８をインストールするだけで、ユーザ５０の手を煩わせることなく、電子文書２０１の透かし表示３０１を低減させることが出来るので、使い勝手が良い。 In FIG. 2, a background gradation value (input gradation Z) is set by the background gradation value setting step 3 and inputted to the computer 17, and a watermark gradation value (input gradation) is set by the watermark gradation value setting step 4. C) is set and input to the computer 17. At the same time, an output tone value (output tone value Z) previously associated with the watermark tone value is obtained from the tone converting means 2 in the output tone obtaining step 5 and input to the computer 17. Thereafter, in response to a command from the computer 17, an output gradation value (output) associated with the watermark gradation value (input gradation C) in advance is output to the gradation converting means 2 in the output gradation changing step 6. The gradation C) is replaced with the acquired output gradation value Z. The output signal from the gradation converting means 2 is input to an image quality adjustment circuit 51 that adjusts image quality such as contrast, brightness, brightness, and gamma correction, and an image is displayed on the image display panel 52 by the output signal from the image quality adjustment circuit 51. Is displayed. According to the present embodiment, the electronic document 201 can be stored in the computer 17 that is connected to or built in the existing image display apparatus 101 by simply installing the watermark display reduction program 18 without bothering the user 50. Since the watermark display 301 can be reduced, it is easy to use.
　前記透かし表示３０１に複数の階調が含まれている場合には、例えば、ユーザ５０が表示画面５２を視認して表示画面上の操作メニューや画像表示装置１０１の操作ボタンを操作するようにしてもよく、また、ユーザ５０がマウスを用いて領域指定するようにしてもよい。 When the watermark display 301 includes a plurality of gradations, for example, the user 50 visually recognizes the display screen 52 and operates an operation menu on the display screen or an operation button of the image display device 101. Alternatively, the user 50 may designate the area using the mouse.
　本実施形態では、前記透かし階調値に対応付けされた出力階調値を、必ずしも背景階調値にあらかじめ対応づけられた出力階調値に置き換える必要はなく、前記透かし階調値にあらかじめ対応付けされた出力階調値より大きい階調値に設定するように実行すればよい。 In the present embodiment, the output gradation value associated with the watermark gradation value does not necessarily need to be replaced with the output gradation value associated with the background gradation value in advance, but corresponds to the watermark gradation value in advance. It may be executed so as to set a gradation value larger than the attached output gradation value.
　本実施形態では、前記背景階調値や前記透かし階調値として、電子文書２０１から入力画像のヒストグラムを演算し、演算された前記ヒストグラムに基づいて推定された階調値を用いることができる。これにより、ユーザにより両階調値を設定させるという煩わしい作業も解消される。本実施形態によれば、例えば、電子文書や画像等を表示するウィンドウ領域を指定し、その領域内のみ本発明の階調変換を施すなどのマルチウィンドウへの対応が容易となる。領域の指定は、ユーザがマウスなどを用いて指定させてもいいし、入力画像から検出されるエッジからウィンドウエリアを推定するようにしてもよい。 In the present embodiment, a histogram of an input image can be calculated from the electronic document 201 as the background gradation value and the watermark gradation value, and the gradation value estimated based on the calculated histogram can be used. This eliminates the troublesome work of setting both gradation values by the user. According to the present embodiment, for example, a window area for displaying an electronic document, an image, or the like is designated, and multi-window handling such as performing gradation conversion of the present invention only in the area is facilitated. The area may be designated by the user using a mouse or the like, or the window area may be estimated from an edge detected from the input image.
　以上、本発明は、上述した実施の形態に限定されるものではない。例えば、前記電子文書等の背景となる背景階調値は、予め設定された固定値を用いるか、または、画像表示装置内の処理回路や処理プログラムによって算出されるか、若しくは、ユーザが表示画面を視認して表示画面上の操作メニューや画像表示装置の操作ボタンを操作することで決定される。透かし表示となる透かし階調値についても、同様に、予め設定された固定値を用いるか、または、画像表示装置内の処理回路や処理プログラムによって算出されるか、若しくは、ユーザが表示画面を視認して表示画面上の操作メニューや画像表示装置の操作ボタンを操作することで決定される。 As described above, the present invention is not limited to the embodiment described above. For example, the background gradation value as the background of the electronic document or the like uses a fixed value set in advance, or is calculated by a processing circuit or a processing program in the image display device, or the user can display the display screen. Is determined by operating the operation menu on the display screen or the operation button of the image display device. Similarly, for the watermark gradation value to be displayed as a watermark, a preset fixed value is used, or it is calculated by a processing circuit or a processing program in the image display device, or the user visually recognizes the display screen. Then, it is determined by operating an operation menu on the display screen or an operation button of the image display device.
　上述の説明では、前記階調変換手段は、コントラスト、輝度、明度、ガンマ補正等の画質を調整する画質調整回路の前段に設けられるとして説明したが、コントラスト調整やγ値などに連動させて、前記階調値や階調幅を再調整することができれば、前記画質調整回路の後段に前記階調変換部を設けることも可能である。前記画質調整回路は、ハードウエアで実現してもよいし、ソフトウエアで実現させることも可能である。本発明は、液晶、有機ＥＬ、プラズマ等の各種画像表示装置に適用可能である。このように、本発明は、その趣旨を逸脱しない範囲で適宜変更が可能であることはいうまでもない。 In the above description, the gradation converting means has been described as being provided in the preceding stage of an image quality adjustment circuit that adjusts image quality such as contrast, brightness, brightness, and gamma correction, but in conjunction with contrast adjustment and γ value, If the gradation value and the gradation width can be readjusted, it is possible to provide the gradation conversion section after the image quality adjustment circuit. The image quality adjustment circuit may be realized by hardware or may be realized by software. The present invention can be applied to various image display devices such as liquid crystal, organic EL, and plasma. Thus, it goes without saying that the present invention can be modified as appropriate without departing from the spirit of the present invention.
　１　　　　　　本発明の画像表示装置、
　２　　　　　　階調変換手段、
　３　　　　　　背景階調値取得手段（背景階調値取得ステップ）、
　４　　　　　　透かし階調値取得手段（透かし階調値取得ステップ）、
　５　　　　　　出力階調取得手段（出力階調取得ステップ）、
　６　　　　　　出力階調変更手段（出力階調変更ステップ）、
　７　　　　　　制御回路、
　１７　　　　　コンピュータ、
　１８　　　　　本発明の透かし表示低減プログラム、
　５１　　　　　画質調整回路、
　５２　　　　　画像表示パネル、
　１０１　　　　既存の画像表示装置 1 image display device of the present invention,
2 gradation conversion means,
3 background gradation value acquisition means (background gradation value acquisition step),
4 watermark gradation value acquisition means (watermark gradation value acquisition step),
5 output gradation acquisition means (output gradation acquisition step),
6 Output gradation changing means (output gradation changing step),
7 Control circuit,
17 computer,
18. A watermark display reduction program of the present invention,
51 Image quality adjustment circuit,
52 Image display panel,
101 Existing image display device

Claims (6)

  1. 　画像入力信号の入力階調を各入力階調値毎に異なる出力階調値に変換可能な階調変換手段と、前記階調変換手段にある入力階調値と出力階調値を書き換える制御回路を備え、
    　前記制御回路に設定された２以上の階調値のうち、一の設定階調値と等しい入力階調に対応づけられた出力階調値を取得し、他の設定階調値と等しい入力階調に対応づけられた出力階調を、前記取得した出力階調値と同じか近い値に置き換えることを特徴とする画像表示装置。     Gradation conversion means capable of converting the input gradation of the image input signal into different output gradation values for each input gradation value, and a control circuit for rewriting the input gradation value and the output gradation value in the gradation conversion means With
    Out of two or more gradation values set in the control circuit, an output gradation value associated with an input gradation equal to one set gradation value is acquired, and an input level equal to another set gradation value is acquired. An image display device characterized in that an output gradation associated with a tone is replaced with a value that is the same as or close to the acquired output gradation value.
  2. 　前記階調変換手段が、コントラスト、輝度、明度、ガンマ補正等の画質を調整する画質調整回路の前段に設けられていることを特徴とする請求項１記載の画像表示装置。 The image display device according to claim 1, wherein the gradation converting means is provided in a preceding stage of an image quality adjustment circuit for adjusting image quality such as contrast, brightness, brightness, and gamma correction.
  3. 　前記一の設定階調値が所定幅の階調値であるとして、前記所定幅にあるすべての入力階調値に対応付けされた出力階調値を、前記取得した出力階調値と同じか近い値に置き換えることを特徴とする請求項１または２記載の画像表示装置。 Assuming that the one set gradation value is a gradation value having a predetermined width, the output gradation values associated with all the input gradation values having the predetermined width are the same as the acquired output gradation values. The image display device according to claim 1, wherein the image display device is replaced with a close value.
  4. 　前記画像は文書画像であって、前記一の設定階調値は文書画像の下地を表示する階調であり前記他の設定階調値は文書画像の下地を表示する階調と文字を表示する階調との範囲内にある階調値であることを特徴とする請求項１から３のいずれか一項記載の画像表示装置。 The image is a document image, the one set gradation value is a gradation for displaying a background of the document image, and the other set gradation value is for displaying a gradation and a character for displaying the background of the document image. The image display device according to claim 1, wherein the image display device has a gradation value within a range of gradation.
  5. 　前記画像は透かし画像を含む文書画像であって、前記一の設定階調値は文書画像の下地を表示する階調であり、前記他の設定階調値は透かし画像を表示する階調との範囲内にある階調値であることを特徴とする請求項１から４のいずれか一項記載の画像表示装置。 The image is a document image including a watermark image, the one set gradation value is a gradation for displaying a background of the document image, and the other set gradation value is a gradation for displaying a watermark image. 5. The image display device according to claim 1, wherein the gradation value is within a range.
  6. 　画像入力信号の入力階調を各入力階調値毎に異なる出力階調値に変換可能な階調変換手段が備わっている画像表示装置の階調変換方法において、
    　設定された２以上の階調値のうち、一の設定階調値と等しい入力階調に対応づけられた出力階調値を取得し、他の設定階調値と等しい入力階調に対応づけられた出力階調を、前記取得した出力階調値と同じか近い値に置き換えることを特徴とする階調変換方法。     In a gradation conversion method for an image display device provided with gradation conversion means capable of converting an input gradation of an image input signal into an output gradation value different for each input gradation value,
    Out of two or more set gradation values, an output gradation value associated with an input gradation equal to one set gradation value is acquired and associated with an input gradation equal to another set gradation value A gradation conversion method, wherein the output gradation is replaced with a value that is the same as or close to the acquired output gradation value.
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