JP2013187828A - Display device and display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make density of a portion having a chromatic color darker when a color image is converted into a monochrome image.SOLUTION: An image processing part 6 rasterizes color image data to develop a raster image to a VRAM 4. The color of pixels which constitute the raster image is displayed in three colors of RGB. The image processing part 6 calculates an average value of a gradation value of the RGB for each pixel, and performs correction to lower the gradation value for a color having the gradation value larger than the average value. After converting the color image in which the gradation value is corrected into a gray scale image, the image processing part 6 performs a gamma correction to the gray scale image, and performs a binarization processing to the gamma-corrected image. A controller 2 controls a display part 1 in accordance with the binarization-processed image to display the monochrome image on the display part 1.

Description

  The present invention relates to a technique for converting a color image into a monochrome image.

As an image processing apparatus that converts a color image into a monochrome image, for example, there are image processing apparatuses disclosed in Patent Documents 1 and 2.
The image processing apparatus disclosed in Patent Document 1 determines whether a color drawing command or a monochrome drawing command for each drawing type such as text or line. When the drawing command is monochrome and the data of the object to be drawn is color data, the color of the image to be drawn is set to a predetermined default color. Here, the default color is, for example, an achromatic gray having R = 30, G = 30, and B = 30 in which the gradation values of red, green, and blue are the same. For example, if a color image in which black characters and red characters are mixed is drawn in monochrome, the black character is converted to black and the red character is converted to gray in the monochrome image. Even after drawing, it is possible to distinguish a portion that was a black character from a portion that was a red character.
Further, the image processing apparatus disclosed in Patent Document 2 can adjust the density when a color selected by the user is converted into a monochrome image with a user interface. According to this apparatus, for example, when red is adjusted, the red color of the red mark in the color original can be made darker in the monochrome image.

JP 2006-25229 A JP 2011-45052 A

  In the image processing apparatus of Patent Document 1, when a color image is drawn as a monochrome image, colors other than black are converted to gray of the same gradation. For this reason, for example, even if there are characters written in red and emphasized in a color image, there is a problem that the characters are drawn with gray characters and become inconspicuous. With regard to this point, according to the image processing apparatus of Patent Document 2, the density of red characters can be increased in a monochrome image, so that it can be conspicuous in a monochrome image. However, the image processing apparatus disclosed in Patent Document 2 has a problem that the user must specify a color for increasing the density, and the density cannot be increased unless it is set appropriately.

  The present invention has been made in view of the above-described circumstances, and one of its purposes is to increase the density of a chromatic portion when a color image is converted into a monochrome image. is there.

In order to achieve the above object, the display device according to the present invention, for each of the chromatic colors in the color image representing the color using the gradation values of the first color component, the second color component, and the third color component, A color component having the highest density in the chromatic color is specified based on the gradation values of the first color component, the second color component, and the third color component, and at least one of the color components other than the specified color component Correction means for correcting the tone value of the color component so as to increase the density; first conversion means for converting the color image corrected by the correction means into a first monochrome image of gray scale; The second conversion means for converting one monochrome image into a second monochrome image having a predetermined number of gradations with a smaller number of gradations than the first monochrome image; and the display means for displaying the image with the predetermined number of gradations. Display control to display 2 monochrome images And a stage.
According to the present invention, for a chromatic color having a color component with a higher density than the other color components, the gradation value of at least one color component other than the color component with the highest density is corrected so as to have a higher density. Therefore, the color becomes darker than the original color. Then, since it is converted to a monochrome image in a darker state than the original, the density is higher in the monochrome image, and chromatic color lines and characters are converted into monochrome after comparison with the case without this configuration. It becomes conspicuous, and even when binarized, the line is difficult to break.

In the present invention, the correction means obtains an average of gradation values of the first color component, the second color component, and the third color component for the chromatic color, and has a lower density than the average gradation value. The tone value may be corrected so that the density of the color component of the tone value is increased.
According to this configuration, the density of the chromatic color component having a low density is increased, resulting in a darker color than the original color, and the density is increased when converted to a monochrome image. Compared with the case where it does not, it becomes conspicuous after converting the chromatic color to monochrome.

In the present invention, the correction unit may correct the gradation values of color components other than the specified color component so that the density becomes high.
According to this configuration, the color components other than the color component having the highest density among the chromatic color components are increased in density, so that the color becomes darker than the original color, and the density increases when converted to a monochrome image. As compared with the case where this configuration is not provided, the chromatic color becomes conspicuous after being converted to monochrome.

In the present invention, the correction means may include an average of gradation values of the first color component, the second color component, and the third color component of the chromatic color, and a gradation of the specified color component. An intermediate gradation value with respect to the value may be obtained, and the gradation value of the color component having a lower gradation value than the intermediate gradation value in the chromatic color may be corrected so as to increase the density.
According to this configuration, the density of the chromatic color component having a low density is increased, resulting in a darker color than the original color, and the density is increased when converted to a monochrome image. Compared to the case of not, it becomes noticeable after the chromatic color is converted to monochrome.

The display device according to the present invention also includes a first conversion that converts a color image representing a color using a gradation value of the first color component, the second color component, and the third color component into a grayscale first monochrome image. And when there is a difference in gradation values of each color component of the chromatic color in the color image, the color component having the highest density in the chromatic color is determined as the first color component, the second color component, and the third color. The tone value of the first monochrome image obtained by the first conversion means is specified based on the tone value of the component, and is set to the tone value of at least one color component other than the specified color component. A correction unit that performs correction so as to increase the density based on the first monochrome image after the correction by the correction unit is converted into a second monochrome image having a predetermined number of gradations that has a smaller number of gradations than the monochrome image; Second conversion means for displaying the image with the predetermined number of gradations. And a display control means for displaying the second monochromatic image display means for.
According to this configuration, when there is a difference in gradation values of each color component of the chromatic color in the color image, in the monochrome image obtained by converting the color image, the density obtained by converting the chromatic color is obtained. Since the density of the monochrome image after correction is increased so that the density is high, the chromatic color becomes conspicuous after the chromatic color is converted to monochrome as compared with the case without this configuration.

In the present invention, an edge portion may be detected in the color image, and the correction unit may correct the detected edge portion.
According to the present invention, since the edge portion is corrected so as to have a higher density, the portion that was the edge portion of the chromatic color after the chromatic color is converted to monochrome becomes conspicuous.

In the present invention, a character or line segment in the color image may be detected, and the correction unit may correct the detected character or line segment.
According to the present invention, since the character or line segment is corrected so as to have a high density, the portion that was the chromatic color character or line segment becomes conspicuous after the chromatic color is converted to monochrome. .

In addition, the display method according to the present invention has the highest density for each chromatic color in the color image representing the color using the gradation values of the first color component, the second color component, and the third color component. Is specified based on the gradation values of the first color component, the second color component, and the third color component, and the gradation value of at least one color component other than the specified color component A correction step for correcting the color image so as to increase the density, a first conversion step for converting the color image corrected by the correction step into a first monochrome image in gray scale, and the first monochrome image in the first step. A second conversion step of converting to a second monochrome image having a predetermined number of gradations smaller than the number of gradations of one monochrome image; and displaying the second monochrome image on display means for displaying the image with the predetermined number of gradations. Display control step And a flop.
According to the present invention, for a chromatic color having a color component with a higher density than the other color components, the gradation value of at least one color component other than the color component with the highest density is corrected so as to have a higher density. Therefore, the color becomes darker than the original color. Then, since it is converted to a monochrome image in a darker state than the original, the density is higher in the monochrome image, and chromatic color lines and characters are converted into monochrome after comparison with the case without this configuration. It becomes conspicuous, and even when binarized, the line is difficult to break.

Further, the display method according to the present invention includes a first conversion for converting a color image representing a color using the gradation values of the first color component, the second color component, and the third color component into a first monochrome image of gray scale. If there is a difference in the gradation value of each color component of the chromatic color in the color image, the color component having the highest density in the chromatic color is determined as the first color component, the second color component, and the third color. Specifying the tone value of the first monochrome image obtained in the first conversion step to the tone value of at least one color component other than the specified color component, specified based on the tone value of the component A correction step for performing correction so that the density is increased based on the second monochrome image having a predetermined number of gradations, the number of gradations being smaller than that of the first monochrome image. A second conversion step to convert to And a display control step of displaying the second monochromatic image display means for displaying an image at a predetermined number of gradations.
According to the present invention, when there is a difference in gradation values of each color component of a chromatic color in a color image, in a monochrome image obtained by converting the color image, the density obtained by converting the chromatic color. Since the density of the monochrome image after correction is increased so that the density is high, the chromatic color becomes conspicuous after the chromatic color is converted to monochrome as compared with the case without this configuration.

  Note that the present invention can be conceptualized not only as a display device but also as an electronic apparatus having the display device.

1 is a diagram showing an external appearance of an electronic device according to an embodiment of the present invention. FIG. 3 is a block diagram illustrating a hardware configuration of the electronic apparatus 1000. The figure which showed the cross section of the display part. FIG. 3 is a diagram for explaining a circuit configuration of the display unit 1. FIG. 6 is a diagram for explaining a configuration of a pixel driving circuit 66. FIG. 3 is a block diagram showing a configuration of functions realized in an image processing unit 6. 6 is a flowchart showing a flow of processing performed by the image processing unit 6 according to the first embodiment. 9 is a flowchart showing a flow of processing performed by an image processing unit 6 according to the second embodiment. 10 is a flowchart showing a flow of processing performed by an image processing unit 6 according to the third embodiment. The flowchart which showed the flow of the process which the image process part 6 which concerns on 4th Embodiment performs.

[First Embodiment]
FIG. 1 is a diagram illustrating an appearance of an electronic apparatus 1000 according to an embodiment of the present invention. The electronic device 1000 is a display device that displays an image including characters, lines, figures, photographs, and the like. The electronic device 1000 includes a display unit 1 that displays an image. The electronic apparatus 1000 includes buttons 9A to 9F as operation units operated by the user.

FIG. 2 is a block diagram illustrating a hardware configuration of the electronic device 1000. As shown in FIG. 2, each part of the electronic device 1000 is connected to the bus BUS. Each unit of the electronic device 1000 exchanges data between each unit via the bus BUS.
The display unit 1 includes a display element having a memory property, and is a display device that maintains a displayed image even when no voltage is applied to the display element. In the present embodiment, the display unit 1 includes a display element having electrophoretic particles and displays a monochrome image.

  FIG. 3 is a diagram showing a cross section of the display unit 1. FIG. 4 is a diagram for explaining a circuit configuration of the display unit 1. As shown in FIG. 3, the display unit 1 is roughly composed of a first substrate 10, an electrophoretic layer 20, and a second substrate 30. The first substrate 10 is a substrate in which a circuit layer is formed on an insulating and flexible substrate 11. The substrate 11 is made of polycarbonate in this embodiment. The substrate 11 is not limited to polycarbonate, and a resin material having lightness, flexibility, elasticity, and insulation can be used. Moreover, the board | substrate 11 may be formed with the glass which does not have flexibility. An adhesive layer 11a is provided on the surface of the substrate 11, and a circuit layer 12 is laminated on the surface of the adhesive layer 11a.

  The circuit layer 12 includes a plurality of scanning lines 64 provided in the horizontal direction and a plurality of data lines 65 provided in the vertical direction so as to be electrically insulated from each scanning line. The circuit layer 12 is composed of a pixel electrode 13a (first electrode) and a TFT (Thin Film Transistor) corresponding to each intersection of the m rows of scanning lines 64 and the n columns of data lines 65. And a pixel driving circuit 66.

  The electrophoretic layer 20 includes a binder 22 and a plurality of microcapsules 21 fixed by the binder 22, and is formed on the pixel electrode 13a. Note that an adhesive layer formed of an adhesive may be provided between the microcapsule 21 and the pixel electrode 13a.

  The binder 22 is not particularly limited as long as it has a good affinity with the microcapsule 21, an excellent adhesion with the electrode, and an insulating property. A dispersion medium and electrophoretic particles are stored in the microcapsule 21. As a material constituting the microcapsule 21, it is preferable to use a flexible material such as a gum arabic / gelatin compound or a urethane compound.

  Dispersion media include water, alcohol solvents (methanol, ethanol, isopropanol, butanol, octanol, methyl cellosolve, etc.), esters (ethyl acetate, butyl acetate, etc.), ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.) , Aliphatic hydrocarbons (pentane, hexane, octane, etc.), alicyclic hydrocarbons (cyclohexane, methylcyclohexane, etc.), aromatic hydrocarbons (benzene, toluene, benzenes with long chain alkyl groups (xylene) Hexylbenzene, hebutylbenzene, octylbenzene, nonylbenzene, decylbenzene, undecylbenzene, dodecylbenzene, tridecylbenzene, tetradecylbenzene)), halogenated hydrocarbons (methylene chloride, chloroform, carbon tetrachloride) 1,2-dichloroethane, etc.), it can be any of such carboxylates, and the dispersion medium may be other oils. These substances can be used alone or in combination as a dispersion medium, and a surfactant or the like may be further blended to form a dispersion medium.

  Electrophoretic particles are particles (polymer or colloid) having the property of moving by an electric field in a dispersion medium. In the present embodiment, white electrophoretic particles and black electrophoretic particles are stored in the microcapsule 21. The black electrophoretic particles are particles made of a black pigment such as aniline black or carbon black, and are positively charged in this embodiment. The white electrophoretic particles are particles made of a white pigment such as titanium dioxide or aluminum oxide, and are negatively charged in this embodiment.

  The second substrate 30 includes a film 31 and a transparent electrode layer 32 (second electrode) formed on the lower surface of the film 31. The film 31 plays a role of sealing and protecting the electrophoretic layer 20 and is, for example, a polyethylene terephthalate film. The film 31 is transparent and has an insulating property. The transparent electrode layer 32 is made of a transparent conductive film such as an indium oxide film (ITO film).

  Next, a circuit included in the display unit 1 will be described. In the display area 55 shown in FIG. 4, a plurality of data lines 65 arranged in parallel along the vertical direction and a plurality of scanning lines 64 arranged in parallel along the horizontal direction are provided. The display area 55 is provided with a pixel driving circuit 66 corresponding to the intersection of the data line 65 and the scanning line 64.

  FIG. 5 is a diagram for explaining the configuration of the pixel driving circuit 66. In the present embodiment, in order to distinguish each scanning line 64, the scanning lines 64 shown in FIG. 4 are called the first, second, third,. You may want to Similarly, in order to distinguish each data line 65, the data lines shown in FIG. 4 are referred to as 1, 2, 3,..., (N−1), nth column in order from the left. There is.

FIG. 5 shows a pixel driving circuit 66 corresponding to the intersection of the scanning line 64 in the first row and the data line 65 in the first column. The same pixel driving circuit 66 is provided at the intersection of the other data line 65 and the scanning line 64. However, since the configuration of each pixel driving circuit 66 is the same, the data in the first row is representatively shown here. The pixel driving circuit 66 corresponding to the intersection of the line and the first scanning line will be described, and the description of the other pixel driving circuits 66 will be omitted.
In the pixel driving circuit 66, the gate of the TFT 61 is connected to the scanning line 64, and the source of the TFT 61 is connected to the data line 65. The drain of the TFT 61 is connected to the pixel electrode 13a. The pixel electrode 13 a faces the transparent electrode layer 32, and the electrophoretic layer 20 is sandwiched between the pixel electrode 13 a and the transparent electrode layer 32. The microcapsule 21 between the one pixel electrode 13 a and the transparent electrode layer 32 becomes one pixel in the display unit 1. In the pixel drive circuit 66, a storage capacitor 63 is connected in parallel with the electrophoretic layer 20. The potential of the transparent electrode layer 32 is set to a predetermined potential Vcom.

  The scanning line driving circuit 53 is connected to each scanning line 64 in the display area 55, and supplies scanning signals Y1, Y2,..., Ym to the scanning lines 64 in the 1, 2,. To do. Specifically, the scanning line driving circuit 53 selects the scanning line 64 in the order of 1, 2,..., M-th row, and selects the voltage of the scanning signal of the selected scanning line 64 as the selection voltage VH (H level). ), And the voltage of the scanning signal of the scanning line that is not selected is the non-selection voltage VL (L level).

The data line driving circuit 54 is connected to each data line in the display area, and supplies data signals X1, X2,..., Xn to the data lines 65 in the 1, 2,. A data signal is supplied from the data line 65 to the pixel driving circuit 66 connected to the scanning line 64 whose potential is the selection voltage VH. Specifically, when the scanning line 64 becomes H level, the TFT 61 whose gate is connected to the scanning line 64 is turned on, and the pixel electrode 13 a is connected to the data line 65. For this reason, when a data signal is supplied to the data line 65 when the scanning line 64 is at the H level, the data signal is applied to the pixel electrode 13a via the TFT 61 that is turned on. When the scanning line 64 becomes L level, the TFT 61 is turned off, but the voltage applied to the pixel electrode 13a by the data signal is accumulated in the storage capacitor 63, and the potential of the pixel electrode 13a and the potential of the transparent electrode layer 32 are stored. Electrophoretic particles move according to the potential difference (voltage).
For example, when the potential of the pixel electrode 13 a is higher than the potential Vcom of the transparent electrode layer 32, the negatively charged white electrophoretic particles move to the pixel electrode 13 a side, and the positively charged black electricity The migrating particles move to the transparent electrode layer 32 side, and the pixel is displayed in black. When the potential of the pixel electrode 13a is lower than the potential Vcom of the transparent electrode layer 32, the positively charged black electrophoretic particles move to the pixel electrode 13a side, and the negatively charged white electricity The migrating particles move to the transparent electrode layer 32 side, and the pixel is displayed in white.

  A period from when the scanning line driving circuit 53 selects the first scanning line to when the selection of the Yth scanning line is completed is referred to as “frame period” or simply “frame”. Each scanning line 64 is selected once per frame, and a data signal is supplied to each pixel driving circuit 66 once per frame.

  Returning to FIG. 2, the control unit 3 is a so-called microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and the electronic device 1000 according to a program stored in the ROM. Control each part. A VRAM (Video RAM) 4 is a memory that stores an image to be displayed on the display unit 1. The storage unit 8 is a nonvolatile memory, and stores image data representing a color image and image data representing a monochrome image. The storage unit 8 can store a plurality of different image data. The controller 2 controls the scanning line driving circuit 53 and the data line driving circuit 54 and displays an image on the display area 55 according to the image stored in the VRAM 4. The communication unit 5 is a communication interface for communicating with other computer devices. The communication unit 5 performs data communication with another computer device by wireless communication or wired communication using a communication cable, and receives image data. The received image data is stored in the storage unit 8.

The operation unit 9 includes buttons 9A to 9F illustrated in FIG. When this button is operated, a signal indicating the operated button is sent to the control unit 3. The control unit 3 acquires the signal sent from the operation unit 9 and identifies the operated button. The control unit 3 specifies an instruction from the user according to the specified button, and executes a process corresponding to the specified instruction.
In this embodiment, the image processing unit 6 is an ASIC (Application Specific Integrated Circuit), and performs processing for converting a color image into a monochrome binary image. The image processing unit 6 acquires image data, and converts an image represented by the acquired image data into a monochrome binary image when the image is a color image.

  FIG. 6 is a block diagram illustrating a configuration of functions related to processing for converting a color image into a monochrome image in the image processing unit 6. The expansion unit 6 a acquires image data, rasterizes the image data, and expands the raster image into the VRAM 4. The expansion unit 6 a expands the color raster image in the VRAM 4 when the color image data is acquired. The density correction unit 6 b corrects the chromatic gradation of the color raster image developed in the VRAM 4. The first converter 6c converts the color raster image developed in the VRAM 4 into a grayscale monochrome image. The gamma correction unit 6 d performs gamma correction on the gray scale raster image developed in the VRAM 4. The second conversion unit 6e performs binarization processing on the raster image that has been subjected to gamma correction.

  Next, an operation when the electronic device 1000 converts a color image into a monochrome image and displays it will be described. In the following description, image data representing a color image has colors R (Red: R component (first color component)), G (Green: G component (second color component)), B (Blue: B component). (Third color component)), and the operation will be described by taking as an example a case where each gradation can specify 256 gradations from 0 to 255. In the present embodiment, black is obtained when all the R, G, and B gradation values are 0, and white when each gradation value is 255. In this embodiment, the gradation value of the color image is the darkest when the value is 0, and the lightest when the value is 255.

FIG. 7 is a flowchart showing a flow of processing performed when the image processing unit 6 converts a color image into a monochrome image. Hereinafter, the operation of the image processing unit 6 will be described with reference to FIG.
First, when the operation unit 9 performs an operation to instruct display of image data stored in the storage unit 8, the control unit 3 reads the image data from the storage unit 8, and performs image processing on the read image data. Send to part 6. When the image processing unit 6 (developing unit 6a) acquires the image data sent from the control unit 3, the image processing unit 6 rasterizes the acquired image data and develops the raster image obtained by the rasterization in the VRAM 4 (step SA1). Here, in the VRAM 4, gradation values of R, G, and B colors are stored for each pixel constituting the raster image.

Next, the image processing unit 6 (density correction unit 6b) calculates, for each pixel of the raster image, an average value of the gradation values of the three colors R, G, and B that specify the color of the pixel (step SA2). When this average value is mean_RGB, the red gradation value of the pixel is R1, the green gradation value of the pixel is G1, and the blue gradation value of the pixel is B1, the average value mean_RGB is the following (1) It is calculated by the following formula.
mean_RGB = (R1 + G1 + B1) / 3 (1)

After calculating mean_RGB for each pixel, the image processing unit 6 (density correction unit 6b) calculates the difference between the tone value of each color and mean_RGB for each pixel (step SA3). If the difference between the red tone value and mean_RGB is diff_R, the difference between the green tone value and mean_RGB is diff_G, and the difference between the blue tone value and mean_RGB is diff_B, diff_R, diff_G and diff_B are: It is calculated by the following formulas (2) to (4).
diff_R = R1-mean_RGB (2)
diff_G = G1-mean_RGB (3)
diff_B = B1-mean_RGB (4)

When the processing in step SA3 is completed, the image processing unit 6 (density correction unit 6b) corrects the gradation values of the R, G, and B colors that specify the pixel color (step SA4). Specifically, it is determined for each pixel whether the calculation result of the expressions (2) to (4) is a positive value. Then, for the color whose calculation result is a positive value, the gradation value of each color is corrected using the following equations (5) to (7). Further, when the calculation result is 0 or a negative value, correction according to the following expression is not performed. The following α1 to α3 can be arbitrarily selected from values of 0 or more and 1 or less. When the value is 0, there is no correction, and when the value is 1, the correction amount is Maximum.
R1 = R1-diff_R × α1 (5)
G1 = G1-diff_G × α2 (6)
B1 = B1-diff_B × α3 (7)

For example, when diff_R becomes a positive value for the pixel in the first row and the first column, the red gradation value is corrected using the equation (5). When the value of diff_G for the pixel in the first row and first column is 0, the green gradation value is not corrected, and the value of diff_B for the pixel in the first row and first column is a negative value. In this case, the gradation value of B is not corrected.
In addition, when R1 = G1 = B1, that is, when the color is achromatic, all the values calculated by the expressions (2) to (4) are 0, so that correction is not performed. On the other hand, when the gradation values of R, G, and B are not the same, that is, in the case of a chromatic color, correction is performed.

When the process of step SA4 ends, the image processing unit 6 (first conversion unit 6c) converts the raster image into a grayscale image whose pixel gradation value ranges from 0 to 255 (step SA5). Here, assuming that the gradation value of each pixel is Y, Y is calculated using the following equation (8).
Y = R1 × β1 + G1 × β2 + B1 × β3 (8)
β1 to β3 are coefficients for converting a color image into a grayscale image, and the sum of β1 to β3 is preferably 1. For example, when a Y value corresponding to lightness of the XYZ color system is obtained from a color image of the CIE RGB color system, and this is used as a gradation value of a monochrome pixel, β1 = 0.769, β2 = 0. 8124 and β3 = 0.0107. Similarly, when the color image is an sRGB color space, β1 = 0.22989, β2 = 0.5866, and β3 = 0.1144. Note that the values of β1 to β3 are not limited to these values. For example, when it is not necessary to accurately reproduce the lightness, each coefficient may be simplified such that β1 = 3/8, β2 = 4/8, and β3 = 1/8.

  When the processing in step SA5 is completed, the image processing unit 6 (gamma correction unit 6d) performs gamma correction on the gradation value Y in accordance with the characteristics of the display unit 1 (step SA6). In the present embodiment, gamma correction is performed using a one-dimensional lookup table.

  When the process of step SA6 ends, the image processing unit 6 (second conversion unit 6e) performs a binarization process on the grayscale image in the VRAM 4 (step SA7). Here, as the binarization process, a systematic dither method using a dither mask having a regular repeating pattern as a binarization threshold, a blue noise mask method using a dither mask having a blue noise characteristic with no regularity, and processing are: A well-known method such as a complex but high-quality error diffusion method may be employed, but the present invention is not limited to these methods, and other known methods may be employed. By this binarization processing, a raster image in which 0 is black and 1 is white is obtained.

  When the process of step SA7 ends, the image processing unit 6 notifies the controller 2 that the conversion process to the monochrome image has ended. Upon receiving this notification, the controller 2 controls the display unit 1 based on the raster image stored in the VRAM 4 and causes the display unit 1 to display an image represented by the raster image.

According to the present embodiment, in the pixel of the raster image, for the color having a larger gradation value than other colors in RGB, the gradation value is lowered by the process of step SA4, so that the pixel is more than the original color. It becomes a dark color. And since it is converted into a monochrome image in a darker state than the original, the gradation is dark in the monochrome image. In other words, a pixel with a high saturation color is a dark pixel in a monochrome image, so that it does not become inconspicuous after conversion to a monochrome image.
Further, in the present embodiment, a pixel having a high saturation is not limited to a specific color, and is a pixel having a high density in a monochrome image. Characters and lines can stand out in a monochrome image. In addition, since the correction amount changes smoothly according to the RGB gradation values, instead of correcting only a specific color, even if applied to image data such as a photograph, natural emphasis is achieved without producing a pseudo contour. Is possible.

Further, in a display device that displays an image in binary of white and black, a monochrome image having a halftone is binarized and displayed. However, the image is converted to gray scale by the image processing device described in the background art, and further half-colored. When binarization is performed by tone processing, if the gray density is low, the result is that the dots are thinned out from the characters and lines, the fine lines appear to be broken, and the characters are difficult to discriminate. There is a problem.
On the other hand, in the present embodiment, when the image is converted into a grayscale image by the process of step SA5, the density does not become lighter and the image becomes darker even if the binarization process is performed. It is less likely to cause image quality degradation.

  In the present embodiment, the gradation is corrected for a color component having a positive value in the calculation results of the expressions (2) to (4). However, the color component having a positive value and the largest value is used. It is also possible to correct the gradation only for.

Further, in the present embodiment, the color of the pixel may be specified by another color system that can be mutually converted into RGB. For example, the gradation values of R, G, and B are complementary colors C (Cyan (first color component)), M (Magenta (second color component)), and Y (Yellow (third color component)). It is also possible to express by a subtractive color system that becomes darker as the gradation value increases.
In the simplest example, conversion can be performed with C = 255-R, M = 255-G, and Y = 255-B. Also, the black component Bk (Black) is set in the range of 0 ≦ Bk ≦ Min (C, M, Y), and C = 255−R−Bk, M = 255−G−Bk, Y = 255−B−Bk. May be expressed by four color components of C, M, Y, and Bk.
When C, M, Y or C, M, Y, Bk is used, in this embodiment, the average value is calculated by the following equation (1 ′).
mean_CMY = (C + M + Y) / 3 (1 ′)
Further, the difference between the average value and each color is calculated by the following formulas (2 ′) to (4 ′).
diff_C = mean_CMY-C (2 ′)
diff_M = mean_CMY-M (3 ′)
diff_Y = mean_CMY-Y (4 ′)
If diff_C is positive, an operation using the following equation (5 ′) is performed.
C = C + diff_R × α1 (5 ′)
If diff_M is positive, an operation using the following equation (6 ′) is performed.
M = M + diff_G × α2 (6 ′)
If diff_Y is positive, an operation using the following equation (7 ′) is performed.
Y = Y + diff_B × α3 (7 ′)
Compared with the case represented by RGB, the magnitude relationship of gradation is reversed, but is logically equivalent. Then, a gray scale image is generated from the C, M, and Y thus obtained, and the gray scale image is binarized.

[Second Embodiment]
Next, an electronic apparatus 1000 according to the second embodiment of the present invention will be described. The electronic apparatus 1000 according to the second embodiment has the same hardware configuration as that of the first embodiment. The electronic device 1000 according to the second embodiment is different from the electronic device 1000 according to the first embodiment in processing performed by the image processing unit 6. Therefore, in the following, this different processing will be mainly described.

  FIG. 8 is a flowchart showing a flow of processing performed when the image processing unit 6 according to the second embodiment converts a color image into a monochrome image. Note that the processing of steps SB1 to SB3 is the same as the processing of steps SA1 to SA3 of the first embodiment. When the processing of step SB3 is completed, the image processing unit 6 (first conversion unit 6c) uses the above equation (8) to convert the raster image to a gray scale whose pixel gradation value ranges from 0 to 255. (Step SB4).

When the processing in step SB4 is completed, the image processing unit 6 (density correction unit 6b) corrects the gradation value calculated in step SB4 (step SB5). Specifically, first, the image processing unit 6 determines whether the value of diff_R calculated in step SB3 is positive. Here, when the value of diff_R is positive, the gradation value of the pixel calculated in step SB4 is corrected using the following equation (9).
Y1 = Y-diff_R × α11 (9)
If the value of diff_R is 0 or a negative value, Y1 = Y. Α11 is set to α11 = α1 × β1.

Next, the image processing unit 6 (density correction unit 6b) determines whether the value of diff_G calculated in step SB3 is positive. Here, when the value of diff_G is positive, the gradation value of the pixel is corrected using the following equation (10).
Y2 = Y1-diff_G × α12 (10)
If the value of diff_G is 0 or a negative value, Y2 = Y1. Α12 is set to α12 = α2 × β2.

Next, the image processing unit 6 (density correction unit 6b) determines whether the value of diff_B calculated in step SB3 is positive. Here, when the value of diff_B is positive, the gradation value of the pixel is corrected using the following equation (11).
Y3 = Y2-diff_B × α13 (11)
If the value of diff_B is 0 or a negative value, Y3 = Y2. Α13 is set to α13 = α3 × β3.
Also in this embodiment, when R1 = G1 = B1, that is, when the color is achromatic, diff_R, diff_G, and diff_B calculated by the equations (2) to (4) are all 0, and correction is performed. Will not be done. On the other hand, when the gradation values of R, G, and B are not the same, that is, in the case of a chromatic color, correction is performed.

  When the processing in step SB5 is completed, the image processing unit 6 (gamma correction unit 6d) performs gamma correction on the finally obtained pixel gradation value Y3 in the same manner as in step SA6 in the first embodiment. (Step SB6). Then, the image processing unit 6 (second conversion unit 6e) performs binarization processing on the grayscale raster image after the gamma correction (step SB7).

  Also in the present embodiment, as in the first embodiment, a pixel having a high saturation is a pixel having a high density in a monochrome image, so that it does not become inconspicuous after being converted into a monochrome image.

[Third Embodiment]
Next, an electronic apparatus 1000 according to a third embodiment of the present invention will be described. The electronic apparatus 1000 according to the third embodiment has the same hardware configuration as that of the first embodiment. The electronic device 1000 according to the third embodiment is different from the electronic device 1000 according to the first embodiment in processing performed by the image processing unit 6. Therefore, in the following, this different processing will be mainly described.

  FIG. 9 is a flowchart showing a flow of processing performed when the image processing unit 6 according to the third embodiment converts a color image into a monochrome image. Note that the process of step SC1 is the same as the process of step SA1, and therefore the description thereof is omitted. The image processing unit 6 (density correction unit 6b) specifies, for each pixel of the raster image, the minimum value of R, G, and B gradation values that specify the pixel color as min_RGB (step SC2). For example, when the R gradation value is minimum for a certain pixel, this gradation value is set to min_RGB.

When min_RGB is specified for each pixel, the image processing unit 6 (density correction unit 6b) calculates the difference between the tone value of each color and min_RGB for each pixel (step SC3). Note that if the difference between red gradation value R1 and min_RGB is diff_R, the difference between green gradation value G1 and min_RGB is diff_G, and the difference between blue gradation value B1 and min_RGB is diff_B, diff_R , Diff_G and diff_B are calculated by the following equations (12) to (14).
diff_R = R1-min_RGB (12)
diff_G = G1-min_RGB (13)
diff_B = B1-min_RGB (14)

When the process of step SC3 ends, the image processing unit 6 (density correction unit 6b) corrects the gradation values of the R, G, and B colors that specify the pixel color (step SC4). Specifically, the gradation value of each color is corrected for each pixel using the following equations (15) to (17). The following α21 to α23 can be arbitrarily selected from values of 0 or more and 1 or less.
R1 = R1-diff_R × α21 (15)
G1 = G1-diff_G × α22 (16)
B1 = B1-diff_B × α23 (17)
When R1 = G1 = B1, that is, when the color is achromatic, all the values calculated by the equations (12) to (14) are 0, and no correction is made. On the other hand, when the gradation values of R, G, and B are not the same, that is, in the case of a chromatic color, correction is performed.

  When the process of step SC4 ends, the image processing unit 6 (first conversion unit 6c) converts the raster image into a grayscale image whose pixel gradation value ranges from 0 to 255, similar to the process of step SA5. Conversion is performed (step SC5). Here, assuming that the gradation value of each pixel is Y, Y is calculated using the above equation (8). Note that the processing of steps SC6 and SC7 performed thereafter is the same as the processing of steps SA6 and SA7 of the first embodiment. Therefore, the description of steps SC6 and SC7 is omitted.

  According to the present embodiment, the colors R, G, and B are corrected in the darkening direction, and then converted into a grayscale image. Therefore, compared with the first embodiment, even if the same color is 2 When it is converted into a value, it will be displayed in a darker color.

In the present embodiment, after the process of step SC3 is performed, the process of step SC5 may be performed to obtain a grayscale image. Then, the image processing unit 6 may correct the grayscale of the grayscale image based on diff_R, diff_G, and diff_B.
Specifically, the image processing unit 6 determines whether the value of diff_R is positive. Here, when the value of diff_R is positive, the gradation value of the grayscale pixel is corrected using the following equation.
Y1 = Y-diff_R × α24
If the value of diff_R is 0 or a negative value, Y1 = Y. Α24 is set to α24 = α21 × β1.

Next, the image processing unit 6 determines whether the value of diff_G is positive. Here, when the value of diff_G is positive, the gradation value of the pixel is corrected using the following equation.
Y2 = Y1-diff_G × α25
If the value of diff_G is 0 or a negative value, Y2 = Y1. Α25 is set to α25 = α22 × β2.

Next, the image processing unit 6 determines whether the value of diff_B is positive. Here, when the value of diff_B is positive, the gradation value of the pixel is corrected using the following equation.
Y3 = Y2-diff_B × α26
If the value of diff_B is 0 or a negative value, Y3 = Y2. Α26 is set to α26 = α23 × β3.

[Fourth Embodiment]
Next, an electronic apparatus 1000 according to a fourth embodiment of the present invention will be described. The electronic apparatus 1000 according to the fourth embodiment has the same hardware configuration as that of the first embodiment. The electronic device 1000 according to the fourth embodiment differs from the electronic device 1000 according to the first embodiment in processing performed by the image processing unit 6. Therefore, in the following, this difference will be mainly described.

  FIG. 10 is a flowchart showing a flow of processing performed when the image processing unit 6 according to the fourth embodiment converts a color image into a monochrome image. In addition, since the process of step SD1, SD2 is the same as the process of step SA1, SA2 of 1st Embodiment, the description is abbreviate | omitted. When the processing of step SD2 is completed, the image processing unit 6 (density correction unit 6b) specifies R, G, and B for specifying the pixel color for each pixel of the raster image, as in step SC2 of the third embodiment. The minimum value of the gradation values of the three colors is specified as min_RGB (step SD3).

Next, the image processing unit 6 (density correction unit 6b) calculates an intermediate value (average value) between the average value calculated in step SD2 and the minimum value specified in step SD3 for each pixel of the raster image. (Step SD4). When this intermediate value is min_mean_RGB, the intermediate value min_mean_RGB is calculated by the following equation (18).
min_mean_RGB = (min_RGB + mean_RGB) / 2 (18)
The formula for obtaining the intermediate value is not limited to the above formula. For example, a value obtained by an expression in which a divisor when dividing (min_RGB + mean_RGB) is a number exceeding 1 may be used as an intermediate value.

When the processing of step SD4 is completed, the image processing unit 6 (density correction unit 6b) calculates the difference between the tone value of each color and min_mean_RGB for each pixel (step SD5). If the difference between the red gradation value and min_mean_RGB is diff_R, the difference between the green gradation value and min_mean_RGB is diff_G, and the difference between the blue gradation value and min_mean_RGB is diff_B, diff_R, diff_G and diff_B are: It is calculated by the following equations (19) to (21).
diff_R = R1-min_mean_RGB (19)
diff_G = G1-min_mean_RGB (20)
diff_B = B1-min_mean_RGB (21)

When the process of step SD5 is completed, the image processing unit 6 (density correction unit 6b) corrects the gradation values of the R, G, and B colors that specify the pixel color (step SD6). Specifically, it is determined for each pixel whether the calculation result of the expressions (19) to (21) is a positive value. For the color whose calculation result is a positive value, the gradation value of each color is corrected using the following equations (22) to (24). Note that the following α31 to α33 can be arbitrarily selected from values of 0 or more and 1 or less.
R1 = R1-diff_R × α31 (22)
G1 = G1-diff_G × α32 (23)
B1 = B1-diff_B × α33 (24)
When R1 = G1 = B1, that is, when the color is achromatic, all the values calculated by the equations (22) to (24) are 0, and no correction is made. On the other hand, when the gradation values of R, G, and B are not the same, that is, in the case of a chromatic color, correction is performed.

When the processing of step SD6 ends, the image processing unit 6 (first conversion unit 6c) converts the raster image into a grayscale image whose pixel gradation value ranges from 0 to 255, similar to the processing of step SA5. Conversion is performed (step SD7). Here, assuming that the gradation value of each pixel is Y, Y is calculated using the above equation (8). Note that the processing of steps SD8 and SD9 performed thereafter is the same as the processing of steps SA6 and SA7 of the first embodiment. Therefore, the description of steps SD8 and SD9 is omitted.
Also in the present embodiment, a pixel having a color with high saturation is a pixel having a high density in a monochrome image, so that it does not become inconspicuous after conversion to a monochrome image.

In the present embodiment, a gray scale image may be obtained by performing the process in step SD7 after performing the process in step SD5. Then, the image processing unit 6 may correct the grayscale of the grayscale image based on diff_R, diff_G, and diff_B.
Specifically, the image processing unit 6 determines whether the value of diff_R is positive. Here, when the value of diff_R is positive, the gradation value of the grayscale pixel is corrected using the following equation.
Y1 = Y-diff_R × α34
If the value of diff_R is 0 or a negative value, Y1 = Y. Α34 is set to α34 = α31 × β1.

Next, the image processing unit 6 determines whether the value of diff_G is positive. Here, when the value of diff_G is positive, the gradation value of the pixel is corrected using the following equation.
Y2 = Y1-diff_G × α35
If the value of diff_G is 0 or a negative value, Y2 = Y1. Α35 is set to α35 = α32 × β2.

Next, the image processing unit 6 determines whether the value of diff_B is positive. Here, when the value of diff_B is positive, the gradation value of the pixel is corrected using the following equation.
Y3 = Y2-diff_B × α36
If the value of diff_B is 0 or a negative value, Y3 = Y2. Α36 is set to α36 = α33 × β3.

[Modification]
As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, It can implement with another various form. For example, the present invention may be implemented by modifying the above-described embodiment as follows. In addition, you may combine each of embodiment mentioned above and the following modifications.

  In the above-described embodiment, a color image is converted into a monochrome image in the electronic device 1000. For example, the processing performed by the image processing unit 6 is executed in a computer device (for example, a personal computer) other than the electronic device 1000 to perform color processing. A monochrome image may be generated from the image, and the generated monochrome image may be transmitted to the electronic device 1000 for display.

  In the embodiment described above, a color image is converted into a monochrome binary image by the image processing unit 6 that is an ASIC, but the function realized by the image processing unit 6 is realized by the control unit 3 by software, and the control unit 3 may convert a color image into a monochrome image.

In the embodiment described above, the range of gradation values is 0 to 255 when performing gamma correction, but the range of gradation values after performing gamma correction may be 0 to 100 or the like. In the above-described embodiment, 0 is black and 255 is white after gamma correction, but 0 may be white and 255 may be black.
In the above-described embodiment, the second conversion unit 6e performs binarization processing on the image after the gamma correction. For example, when the dither method is used, white, gray, and black ternary values are used. You may make it become an image. In this case, the image is not limited to three values, and may be an image having a plurality of gradations such as four values or five values.
In the embodiment described above, the display unit 1 is configured to display two gradations of white and black, but may be configured to display a halftone between white and black.

In the above-described embodiment, the same processing is performed for all the pixels constituting the color raster image, but the present invention is not limited to the configuration for performing the same processing for all the pixels.
For example, the edge portion in the image is specified by performing known edge detection processing in the raster image, and the processing of any of the above-described embodiments is performed for the specified edge portion, and for the other portion, for example, ( A configuration may be adopted in which the image is converted into a monochrome image using the equation (8).
Further, the character in the image is specified by performing a known character detection process in the raster image, the specified character is subjected to any one of the above-described embodiments, and the other part is, for example, the above (8). It is good also as a structure which converts into a monochrome image using the Formula.
In addition, a line segment is specified using a known algorithm such as a Hough transform in a raster image, the specified line segment is subjected to any of the processes of the above-described embodiment, and the other part is, for example, the above (8). It is good also as a structure which converts into a monochrome image using the Formula.

In the above-described embodiment, a color raster image is developed on the VRAM 4 and then the color image is converted to a monochrome image. However, the configuration for converting to a monochrome image is not limited to this configuration.
For example, when the image data is in a vector format, the above-described color-to-monochrome conversion processing may be performed for each object to be drawn, and a raster image may be generated from the vector-format monochrome image and binarization processing may be performed. .

  In each of the above-described embodiments and modifications, the gradation may not be corrected for the B color component. In the configuration in which the gradation of the gray scale image is corrected based on the gradation of each color component after being converted into the gray scale image, the gradation is not corrected based on the B color component. Also good.

  In the above-described embodiment, the electronic apparatus 1000 is used as a display device. However, a combination of the display unit 1, the controller 2, and the image processing unit 6 can be defined as a display device. Or the part which put together the display part 1, the controller 2, VRAM4, and the image process part 6 can also be defined as a display apparatus.

In the above-described embodiment, correction is not performed in the case of an achromatic color in which the gradation value of R = the gradation value of G = the gradation value of B, and the gradation value of R = the gradation value of G = B. In the case of a chromatic color that is not the gradation value, correction is performed, but the present invention is not limited to this configuration.
For example, for a color whose difference between the maximum and minimum gradation values of each color component is greater than or equal to a predetermined threshold (eg, 3), the difference between the maximum and minimum gradation values of each color component is less than the threshold. The color may be an achromatic color, and the achromatic color may not be corrected by the density correction unit 6b.
For example, when the gradation value of G = the gradation value of B and the difference between the gradation value of G and the gradation value of R is 2, the correction amount is small. In this case, even if it is corrected and converted to grayscale, compared to the case where it is converted to grayscale without correction, there is no big difference in the gradation that is finally obtained, and the visual impact is small. Become. For this reason, if correction is not performed for a color in which the difference between the maximum and minimum gradation values of each color component is less than a predetermined threshold, the amount of calculation can be reduced, and a monochrome image can be reduced. The conversion process can be speeded up.

  In the embodiment described above, the coefficients (α1 to α3, α11 to α13, α21 to α26, α31 to α36) when correcting the gradation values are fixed, but may be variable. For example, when the difference between the minimum value and the maximum value of the gradation value of each color component is equal to or greater than a predetermined threshold, the first coefficient is used. When the difference is less than the threshold, the second coefficient is smaller than the first coefficient. It is good also as a coefficient of.

DESCRIPTION OF SYMBOLS 1 ... Display part, 2 ... Controller, 3 ... Control part, 4 ... VRAM, 5 ... Communication part, 6 ... Image processing part, 8 ... Memory | storage part, 9 ... Operation part, 9A-9F ... Button, 10 ... 1st board | substrate DESCRIPTION OF SYMBOLS 11 ... Board | substrate, 11a ... Adhesion layer, 12 ... Circuit layer, 13a ... Pixel electrode, 20 ... Electrophoresis layer, 21 ... Microcapsule, 22 ... Binder, 30 ... 2nd board | substrate, 31 ... Film, 32 ... Transparent electrode layer 53 ... Scanning line drive circuit, 54 ... Data line drive circuit, 55 ... Display area, 63 ... Retention capacitor, 64 ... Scanning line, 65 ... Data line, 66 ... Pixel drive circuit, 1000 ... Electronic equipment, BUS ... Bus

Claims (9)

For each chromatic color in the color image representing the color using the gradation values of the first color component, the second color component, and the third color component, the color component having the highest density in the chromatic color is the first color component. , Specifying based on the gradation values of the second color component and the third color component, and correcting the gradation value of at least one color component other than the specified color component so as to increase the density Correction means;
First conversion means for converting the color image corrected by the correction means into a grayscale first monochrome image;
Second conversion means for converting the first monochrome image into a second monochrome image having a predetermined number of gradations that has a smaller number of gradations than the first monochrome image;
A display control unit configured to display the second monochrome image on a display unit that displays an image with the predetermined number of gradations. The correcting means obtains an average of gradation values of the first color component, the second color component, and the third color component for the chromatic color, and a color component having a gradation value whose density is lower than the average gradation value. The display device according to claim 1, wherein the gradation value is corrected so that the density is increased. The display device according to claim 1, wherein the correction unit corrects gradation values of color components other than the specified color component so as to increase a density. The correction means is an intermediate gradation between an average of gradation values of the first color component, the second color component, and the third color component of the chromatic color and a gradation value of the specified color component. The display according to claim 1, wherein a value is obtained and a gradation value of a color component having a gradation value lower than the intermediate gradation value in the chromatic color is corrected so as to increase the density. apparatus. First conversion means for converting a color image representing a color using gradation values of the first color component, the second color component, and the third color component into a first monochrome image of gray scale;
When there is a difference in gradation value of each color component of the chromatic color in the color image, the color component having the highest density in the chromatic color is the color component of the first color component, the second color component, and the third color component. The tone value of the first monochrome image specified by the tone value and obtained by the first conversion means is determined based on the tone value of at least one color component other than the specified color component. Correction means for correcting so as to increase,
Second conversion means for converting the first monochrome image after being corrected by the correction means into a second monochrome image having a predetermined number of gradations with a smaller number of gradations than the first monochrome image;
A display control unit configured to display the second monochrome image on a display unit that displays an image with the predetermined number of gradations. The display device according to claim 1, wherein an edge portion is detected in the color image, and the correction unit corrects the detected edge portion. The display according to claim 1, wherein a character or a line segment in the color image is detected, and the correction unit corrects the detected character or line segment. apparatus. For each chromatic color in the color image representing the color using the gradation values of the first color component, the second color component, and the third color component, the color component having the highest density in the chromatic color is the first color component. , Specifying based on the gradation values of the second color component and the third color component, and correcting the gradation value of at least one color component other than the specified color component so as to increase the density A correction step;
A first conversion step of converting the color image corrected by the correction step into a grayscale first monochrome image;
A second conversion step of converting the first monochrome image into a second monochrome image having a predetermined number of gradations with a smaller number of gradations than the first monochrome image;
A display control step of displaying the second monochrome image on display means for displaying an image with the predetermined number of gradations. A first conversion step of converting a color image representing a color using gradation values of the first color component, the second color component, and the third color component into a first monochrome image of gray scale;
When there is a difference in gradation value of each color component of the chromatic color in the color image, the color component having the highest density in the chromatic color is the color component of the first color component, the second color component, and the third color component. The tone value of the first monochrome image obtained in the first conversion step is specified based on the tone value, and the density value is determined based on the tone value of at least one color component other than the specified color component. A correction step for correcting so as to increase,
A second conversion step of converting the first monochrome image after being corrected in the correction step into a second monochrome image having a predetermined number of gradations with a smaller number of gradations than the first monochrome image;
A display control step of displaying the second monochrome image on display means for displaying an image with the predetermined number of gradations.

Images