JP5029693B2 - Image processing system and image processing apparatus - Google Patents

Description

  The present invention relates to an image processing system and an image processing apparatus for performing image processing for displaying an image, particularly color conversion processing.

  When a color image is output by a printer, a display, or the like, processing for color correction is generally performed in accordance with the color reproduction characteristics of the display device. Hereinafter referred to as color conversion processing.

  The color conversion process is performed in order to reproduce and output the color that looks most natural to the observer by correcting the color reproduction characteristics unique to the apparatus that outputs the image. However, normally, any output device has a limit of the color reproduction range, and it cannot be said that all colors can be output freely. Accordingly, various color conversion techniques have been developed depending on how to appropriately reproduce color display within a limited color reproduction range.

  In such a color conversion process, even if the color space that is generally used is linear, in practice, it tends to be a conversion process that pushes the display color within a limited color reproduction range. In other words, it tends to occur in a non-linear space or the loss of continuity as color expression. In fact, as for a specific color conversion processing method, a LUT (Look Up Table) method using a conversion table is generally used rather than matrix conversion in order to cope with such nonlinearity.

  Therefore, as color reproduction of a color image, color conversion processing is performed in consideration of what color reproduction is required for the image, that is, the color conversion processing is varied depending on the image to be subjected to color conversion processing. Such techniques have been proposed. For example, in a text image mainly composed of characters, contrast is more important than gradation, so color conversion processing that increases contrast is performed, and gradation is emphasized in gradation images such as photographic images. Therefore, color conversion processing is performed so that gradation reproduction is improved.

  Further, a technique has been proposed in which those image areas mixed in one image are discriminated and the color conversion processing is changed for each image area (see, for example, Patent Documents 1 to 3).

  In Patent Document 1, a plurality of LUTs used for color conversion are prepared and used separately for characters and photographic images. In Patent Document 2, a scene is discriminated and a color conversion definition is selected according to the scene. In Patent Document 3, the user designates an object so that a favorite color conversion table can be applied.

  However, the main point is that any of these can be selected according to the nature and type of the image. In other words, the color reproduction range itself for performing color display is not basically characteristic, but the main point of the technology is how to change the emphasis in the color reproduction range.

  That is, in Patent Document 1, memory saving is advocated by preparing a smaller-sized LUT as an option. In Patent Document 2, the usage of K (black) is changed on the premise of conversion to CMYK space. In Patent Document 3, an object is to select a preferred color conversion for each object.

On the other hand, the inventors of the present application have developed a display device having a novel color reproduction range, and have studied an effective use method of these color reproduction characteristics. In other words, for display devices that have both a conventional linear color reproduction range and a non-linear color reproduction range, it is possible to effectively utilize such multiple independent color reproduction ranges, thereby enabling more image types and We have been pursuing technology to perform color conversion processing suitable for the properties.
JP 2003-219191 A JP 2006-163503 A JP 2007-150571 A

  As described above, conventionally, an attempt has been made to select an appropriate color conversion process according to the nature and type of an image. However, the color conversion process does not come from what presupposes output in a limited color reproduction range, such as changing the LUT size, adjusting the addition of K, or adapting to preferences. It was.

  As described above, the inventors of the present application technically change the color reproduction characteristic itself as a color image display device, thereby presenting a new color reproduction range and an appropriate mapping technique using the color reproduction range. Have been considered and considered possible.

  That is, the object of the present invention is to provide a more natural and preferable color according to the type and nature of the image, even for the color reproduction characteristics of a display device having both a conventional linear color reproduction range and a non-linear color reproduction range. An image processing system and an image processing apparatus capable of color conversion processing for achieving reproduction are provided.

  In order to solve the above problems, the present invention has the following features.

  1. Image acquisition means for acquiring an image; image storage means for storing the image acquired by the image acquisition means; image processing means for image processing to display the image stored in the image storage means; An image display system for displaying the image processed by the image processing unit, wherein the image processing unit divides the image into image regions having different requirements for color reproduction. And color conversion means for performing different color conversion processing on each of the image areas divided by the image analysis means, and the color conversion means An image processing system characterized by combining a plurality of independent color spaces in accordance with display characteristics of display means and performing color conversion into different color spaces.

  2. The image display means has a display unit in which pixels composed of a plurality of display cells that display different colors are arranged, and each display cell that displays different colors includes a common black display and a different color display. 2. The image processing system according to 1, wherein the color display can be continuously changed between the common white display and the common white display.

  3. 3. The image processing system according to 2, wherein the plurality of display cells displaying different colors are display cells displaying three colors of red, green, and blue, which are referred to as R, G, and B, respectively. .

  4). 3. The image processing system according to 2, wherein the plurality of display cells that display different colors are display cells that display three colors of cyan, magenta, and yellow, which are referred to as C, M, and Y, respectively. .

  5). The image analysis means includes a first image area that requires color reproduction characteristics with good gradation reproduction, a second image area that requires color reproduction characteristics with good contrast, and a color with high brightness. 4. The image processing system according to 3, wherein the image processing system is divided into a third image area where reproduction characteristics are required and a fourth image area where color reproduction characteristics with high saturation are required.

  6). For the first image area, the color conversion means may change the color between the common black display and the different color displays for any of the display cells displaying R, G, and B colors. 6. The image processing system according to 5, wherein color conversion processing is performed using a range in which display changes as a color reproduction range.

  7). For the second image area, the color conversion means displays a color between a common black display and a common white display for any of the display cells displaying R, G, and B colors. 7. The image processing system according to 5 or 6, wherein color conversion processing is performed using a range in which the color changes as a color reproduction range.

  8). For the third image region, the color conversion means may display different colors and a common white display for one or more of the display cells that display R, G, and B colors. The image processing system according to any one of 5 to 7, wherein color conversion processing is performed using a range in which color display changes between the two as a color reproduction range.

  9. For the fourth image area, the color conversion means may display a common black display and a different color display for one or more of the display cells that display R, G, and B colors. The image processing system according to any one of 5 to 8, wherein color conversion processing is performed using a range in which color display changes between the two as a color reproduction range.

  10. 10. The image processing according to any one of 5 to 9, wherein the color conversion unit performs color conversion processing into a different color space using a Look Up Table according to each of the image regions. system.

  11. Image acquisition means for acquiring an image; image storage means for storing the image acquired by the image acquisition means; image processing means for image processing to display the image stored in the image storage means; An image output unit that outputs the image processed by the image processing unit to an external display unit, wherein the image processing unit converts the image into an image area having different requirements for color reproduction. Image analysis means for dividing, and color conversion means for performing different color conversion processing on each of the image regions divided by the image analysis means, wherein the color conversion means is a display of the external display means Holding information on characteristics, and in accordance with each of the image areas, a plurality of independent color spaces combined with the display characteristics of the external display means, The image processing apparatus characterized by performing color conversion to the color space of.

  12 The information relating to the display characteristics of the external display means held by the color conversion means is a plurality of displays for displaying three colors of red, green, and blue, respectively referred to as R, G, and B, which the external display means has. 11. The color reproduction range in which the color display continuously changes between a common black display, a different color display, and a common white display for each of the cells is included. Image processing device.

  13. 13. The image processing according to 12, wherein the plurality of display cells included in the external display unit are display cells displaying three colors of cyan, magenta, and yellow, which are referred to as C, M, and Y, respectively. apparatus.

  14 The image analysis means includes a first image area that requires color reproduction characteristics with good gradation reproduction, a second image area that requires color reproduction characteristics with good contrast, and a color with high brightness. 13. The image processing apparatus according to 12, wherein the image processing apparatus is divided into a third image area in which reproduction characteristics are required and a fourth image area in which color reproduction characteristics with high saturation are required.

  15. For the first image area, the color conversion means may change the color between the common black display and the different color displays for any of the display cells displaying R, G, and B colors. 15. The image processing apparatus according to 14, wherein color conversion processing is performed using a range in which display changes as a color reproduction range.

  16. For the second image area, the color conversion means displays a color between a common black display and a common white display for any of the display cells displaying R, G, and B colors. 16. The image processing apparatus according to item 14 or 15, wherein color conversion processing is performed using a range in which the color changes as a color reproduction range.

  17. For the third image region, the color conversion means may display different colors and a common white display for one or more of the display cells that display R, G, and B colors. The image processing apparatus according to any one of claims 14 to 16, wherein color conversion processing is performed using a range in which color display changes between the two as a color reproduction range.

  18. For the fourth image area, the color conversion means may display a common black display and a different color display for one or more of the display cells that display R, G, and B colors. The image processing apparatus according to any one of claims 14 to 17, wherein color conversion processing is performed using a range in which color display changes between the two as a color reproduction range.

  19. The information on the display characteristics of the external display means held by the color conversion means is held as a Look Up Table used for color conversion processing for each of the image areas, according to any one of 14 to 18, Image processing apparatus.

  According to the image processing system and the image processing apparatus according to the present invention, even the color reproduction characteristics of a display device having a conventional linear color reproduction range and a non-linear color reproduction range can be reproduced. By combining the characteristics, it is possible to create a plurality of color spaces more suitable for the type and nature of the image. Since color conversion processing corresponding to each image can be performed using these color spaces, more natural and preferable color reproduction suitable for each image can be achieved.

1 is a block diagram illustrating a schematic configuration example of an image processing system according to an embodiment. It is a block diagram which shows the example of schematic structure of the image processing apparatus which concerns on this embodiment. It is a block diagram which shows the basic structural example of the display device which has the linear color reproduction range used by this embodiment, and the non-linear color reproduction range. It is a figure which shows the state of the color display by the conventional display cell, (b) The state of the color display by the display cell (display element A) used by this embodiment. It is a figure which shows the state of the color display by another display cell (display element B) used by this embodiment. It is a figure which shows typically the color reproduction range in Lab color space about the display device (display element A) used by this embodiment. It is a figure which shows typically the color reproduction range in Lab color space about the display device (display element B) used by this embodiment. It is a figure for demonstrating the correspondence of an image area | region and the color reproduction area used for color conversion. It is a flowchart which shows the procedure which performs the image process of a display image according to the display characteristic of a display device. It is a figure which shows the example of the display image by which area | region splitting and color conversion are carried out. It is a figure which shows the example of LUT1. It is a figure which shows the example of LUT2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image processing system 2 Image processing apparatus 3 External display apparatus 11 Application 12 Image acquisition part 13 Image storage part 14 Image output part 15 Temporary data memory part 16 Communication IF part 30 Image processing part 31 Image analysis part 32 Color conversion part 40 Image display Unit 41 display unit 42 display driver 43 drawing processing unit 44 temporary data memory unit 50a, 60a color reproduction of each display cell 50b, 60b color reproduction as pixel 51-53, 61-65 color display output state 71 display on display device Images 72a to 72d First to fourth image areas 73a to 73d LUT1 to 4
80 Display characteristics of display device 81 Linear color reproduction range 82 Non-linear color reproduction range 83a to 83d Color reproduction range 1 to 4
90 Display Image 91 Photo Image Area 92 Text Image Area 93 Marker Area 94 Illustration Area 95 Other Area 95

  Embodiments of an image processing system and an image processing apparatus according to the present invention will be described below with reference to the drawings.

(Schematic configuration example of image processing system)
FIG. 1 is a block diagram illustrating a schematic configuration example of an image processing system according to the present embodiment. A schematic configuration example of the image processing system will be described with reference to FIG.

  In FIG. 1, the image processing system 1 includes a main body part that mainly functions as the image processing apparatus 2 and an image display unit 40. These may be integrated as hardware, or may be a system in which individual devices are connected by wired or wireless communication. In FIG. 1, it is assumed that both are connected by a communication IF (interface) unit 16 so as to be able to transmit and receive each other.

  An information processing apparatus such as a personal computer (hereinafter referred to as a PC) is generally used as the hardware of the main body functioning as the image processing apparatus 2. In addition, a printer, a scanner, and other various peripheral devices may be connected in accordance with a general PC usage pattern. The configuration may be such that data can be input and output by communicating with various devices via a network or the like.

  The hardware of the image display unit 40 is generally a wide variety of display devices. A CRT, a liquid crystal display, a plasma display, an LED display device, or any other display device is used. These usually display the image as a two-dimensional array of pixels. In the case of a color image, each pixel constituting the image display is generally composed of a combination of display elements for displaying a plurality of unit colors (for example, usually R (red) G (green) B (blue)).

  Details of a display device having both a linear color reproduction range and a non-linear color reproduction range used in this embodiment will be described later.

  The internal functional configuration of the main body portion that functions as the image processing apparatus 2 will be described. Only the part related to the function of displaying an image on the image display unit 40 is shown.

  Each process for displaying an image is performed by causing an appropriate application 11 to operate as a program and execute the following functional parts.

  The image acquisition unit 12 functions as an image acquisition unit and acquires image data. The acquisition destination of the image data is arbitrary. As set by the application, it may be acquired via a storage device, an external device, various input devices, or a network.

  The image storage unit 13 functions as an image storage unit and stores acquired image data. The hardware is a storage device, and may be a device outside the main body of the image processing device 2 as necessary. Further, it may be an external storage medium that can be mounted.

  The image processing unit 30 performs image processing for image display, and mainly includes an image analysis unit 31 and a color conversion unit 32. The image processing unit 30 functions as an image processing unit.

  The image analysis unit 31 functions as an image analysis unit. That is, when displaying the acquired and stored image data, first, the properties as an image are analyzed, and the image is divided into a plurality of image areas as necessary. The property as an image is a requirement for an image whose text reproduction method should be changed according to whether it is a text-based image or a gradation image. That is, the purpose of dividing the image accordingly is to change the color conversion method according to these requirements.

  The color conversion unit 32 functions as a color conversion unit. That is, color conversion processing corresponding to each image area divided by the image analysis unit 31 is performed. In order to perform processing according to the requirements for each image region, the color conversion unit 32 holds information on the display characteristics of the image display unit 40, that is, the color reproduction range and the gradation reproduction characteristics in the color reproduction range. There is a need. Usually, it is held as an LUT of the image display unit 40.

  Details of the processing in the image processing unit 30 will be described later.

  The image data subjected to image processing toward the image display unit 40 is stored in the temporary data memory unit 15 and transferred to the temporary data memory unit 44 of the image display unit 40 by the communication IF unit 16.

  The image display unit 40 functions as an image display unit. The internal functional configuration of the image display unit 40 will be described.

  The drawing processing unit 43 performs drawing processing on the image data in the temporary data memory unit 44, and converts the image data into a display format. Based on the image data on which the display driver 42 has drawn, the display driver 42 sends a signal to the display unit 41, which is a display device, to drive it. The display unit 41 is an array of pixels composed of display cells as described above, and each pixel performs a color display in accordance with a signal to perform image display.

  Note that the external display device used in the present embodiment is a display device having both a linear color reproduction range and a non-linear color reproduction range, which will be described later.

(Schematic configuration example of image processing apparatus)
In FIG. 1, the schematic configuration example of the image processing system has been described. The embodiment according to the present invention may be an image processing apparatus. The image display unit shown in FIG. 1 is not necessarily required. For display, an external display device may be connected to output image data. The display characteristics of the external display device are necessary, but they may be held in advance or acquired when connected for display output.

  FIG. 2 is a block diagram illustrating a schematic configuration example of the image processing apparatus according to the present embodiment. A schematic configuration example of the image processing apparatus will be described with reference to FIG. However, blocks having the same functions as those in FIG.

  In FIG. 2, the image processing apparatus 2 functions in the same manner as the main body portion of FIG. The image is output to the external display device 3 for display. The external display device 3 functions in the same manner as the image display unit 40 in FIG. These are connected by wired or wireless communication at the time of image display output.

  As the hardware of the image processing apparatus 2, an information processing apparatus similar to that shown in FIG. 1 is generally used. Similarly, each process for displaying an image is performed by causing an appropriate application 11 to operate as a program and execute the following functional parts.

  The image acquisition unit 12 functions as an image acquisition unit, and the image storage unit 13 functions as an image storage unit, as in the image processing system of FIG.

  Similarly, the image processing unit 30 functions as an image processing unit. That is, it is a part that performs image processing for image display, and includes the following image analysis unit 31 and color conversion unit 32.

  The image analysis unit 31 functions as an image analysis unit, and when displaying image data, first, the property as an image is analyzed, and the image is divided into a plurality of image regions as necessary. The property as an image is a requirement for an image whose text reproduction method should be changed according to whether it is a text-based image or a gradation image. That is, the purpose of dividing the image accordingly is to change the color conversion method according to these requirements.

  The color conversion unit 32 functions as a color conversion unit, and performs color conversion processing corresponding to each image region divided by the image analysis unit 31. In order to perform processing according to the requirements for each image region, the color conversion unit 32 holds information on the display characteristics of the external display device 3, that is, the color reproduction range and the gradation reproduction characteristics in the color reproduction range. There is a need. Normally, it is held as the LUT of the external display device 3.

  As described above, the LUT of the external display device 3 may be held in advance, or may be acquired or generated each time an image is output.

  The image data subjected to the image processing toward the external display device 3 is output to the connected external display device 3 by the image output unit 14 functioning as an image output unit. After that, the external display device 3 performs display processing and displays. The process is the same as the process in the image display unit 40 of FIG.

(About display devices)
In this embodiment, when displaying an image, color conversion processing is performed in accordance with the display characteristics of the display device. In addition, effective color conversion processing is performed for display on a display device having both a normal linear color reproduction range and a non-linear color reproduction range as its display characteristics.

  A display device having both a linear color reproduction range and a non-linear color reproduction range and color display on the display device will be described below.

  In this embodiment, a display device that performs color display using three display cells called R, G, and B is used. However, other three color display cells such as C, M, and Y are used. Also in the display device, a display device having the same display characteristics, that is, a normal linear color reproduction range and a non-linear color reproduction range can be configured, and a similar color conversion process can be applied.

  FIG. 3 is a schematic cross-sectional view showing a basic configuration example of a display element (display cell) in the display device according to the present embodiment. With reference to FIG. 3, a configuration example of a display element (the inventors of the present application called SECD) having both a normal linear color reproduction range and a non-linear color reproduction range will be described.

  SECD (Silver electrical color device) is a display method as follows.

  As a reflective display element, an SDD system is known in which a change in white and black is expressed by a change in transparent silver ions and blackened silver (Ag) by exchanging charges of silver ions (Ag +). On the other hand, an EC method is known in which a change between a transparent state and a colored state is caused by redox of an electrochromic material (such as a conductive polymer).

  The SECD method is a display method in which the function of the SDD method and the function of the EC method are combined into one display cell. As a result, the display element has both a linear color reproduction range and a non-linear color reproduction range.

  That is, by generating the black change due to silver deposition described above at a negative potential and the redox color change at a positive potential. This is a reflective display element that can be changed into three states of transparent, black, and each color.

  The display element shown in FIG. 3 holds an electrolyte 21 between a transparent ITO electrode 22 and a silver electrode 20. In the example shown in FIG. 3, a current source 23 is connected to the ITO electrode 22 and the silver electrode 20. When a current i is applied from the current source 23 to the silver electrode 20 in the direction of the arrow in the drawing, a precipitation reaction of silver contained in the electrolyte 21 occurs. The deposited silver absorbs light, and the concentration of the display element viewed from the ITO electrode 22 increases.

  On the other hand, when a current i is applied from the current source 23 to the silver electrode 20 in the direction opposite to the arrow in the figure, a dissolution reaction of silver contained in the electrolyte 21 occurs. The precipitated silver dissolves and turns transparent. The SECD electrolyte 21 contains white scatterers (such as titanium oxide), and light is reflected by the white scatterers, so that it looks white from the outside. Therefore, when the current i is applied in a direction opposite to the arrow in the figure for a certain period of time, the density and color of the display element A viewed from the ITO electrode 22 becomes white in the initial state.

  In SECD, since the electrolyte 21 containing an electrochromic compound is used in addition to the above silver ions, the color develops according to the applied current i, and a colored state other than black is produced in addition to the black and white gradation described above. Color development can be R, G, B, Y, M, or C by changing substituents.

  As the electrochromic compound, any compound may be used as long as it exhibits a phenomenon (electrochromism) in which the property of optical absorption (color and light transmittance) of the substance is reversibly changed by electrochemical redox. Examples of the display element A using polypyridine as the electrochromic compound and the display element B using imidazole leuco will be described below.

<First Display Element Example A>
The relationship between the writing operation and the display gradation of the display element A using polypyridine as the electrochromic compound will be described.

  In the display element A of the present embodiment, when a constant write current is applied, the deposition amount increases in proportion to the write time, and the display of the display element A changes from the first display state to the second display state. Then, the state changes to the third display state.

  That is, it is displayed white in the first display state, colored in a state other than black (R, G, B) in the second intermediate display state, and black in the maximum third display state. Is displayed. Or, depending on the direction of current application, the reverse change occurs.

  In this way, the display element A has a color reproduction range in which the color display continuously changes between a common black display, different color displays, and a common white display, that is, a linear color. A reproduction range (black to R, G, B) and a non-linear color reproduction range (R, G, B to white) are combined.

<Second display element example B>
Next, unlike the display element A described above, a configuration example of the display element B using imidazole leuco as an electrochromic compound will be described.

  An example of display characteristics of the display element B will be described. In the display element B, when a writing current having a constant current is applied, the deposition amount changes in proportion to the writing time, and like the display element A, the display state of the display element B changes from the first display state to the second display state. The state changes to the third display state.

  That is, in the first display state, a colored state other than black (R, G, B) is displayed, in the intermediate second display state, it is displayed in white, and in the third display state, it is displayed in black. The Moreover, if a current is applied in the reverse direction, the current can be changed in the reverse order.

  In this way, the display element B has a color reproduction range in which the color display continuously changes between the different color displays, the common black display, and the common white display, that is, the display element A. And a linear color reproduction range (black to white) and a non-linear color reproduction range (white to R, G, B) in a different order.

(Display cell and color display method)
The color display in each of the R, G, and B display cells using the display element A and the display element B having both a linear color reproduction range and a non-linear color reproduction range will be described below. First, color display in a display cell having a conventional linear color reproduction range will be described, and then color display in R, G, and B display cells using the display element A and display element B will be described.

<Conventional color display>
FIG. 4A shows a state of color display by conventional R, G, B, and three color display cells.

  In the upper 50a, one pixel is composed of three display cells (for example, aa, ab, and ac) called R, G, and B, and their color display is variable like 51, 52, and 53. Indicates. That is, in 51, R, G, and B display cells are all Bk (black), in 52, R, G, and B are dark R, G, and B. Become.

  The lower part 50b shows how one pixel composed of three display cells of R, G, and B looks. That is, at 51, three display cells appear as black (black) as one pixel, at 52, appear gray (gray), and at 53, appear white (white).

  As described above, the color reproduction range of the pixel composed of three conventional display cells of R, G, and B is mixed evenly from black to R, G, and B if the output of the three display cells of R, G, and B is kept uniform. The color changed to white, that is, white. By changing the balance of the output of R, G, and B, the color changes from black to R, G, and B instead of black to white. In this color reproduction range, each color of R, G, and B is linearly reproduced from an achromatic color (black) to each of R, G, and B.

<Color display on display element A>
In the present embodiment, a display device (display element A) having a non-linear color reproduction range in combination with the linear color reproduction range described above is used.

  FIG. 4B shows the state of color display by the display cell in the display device (display element A) used in the present embodiment.

  The upper 60a indicates that one pixel is composed of three display cells (for example, aa, ab, and ac) called R, G, and B, and their color display is variable as 61 to 65. . Of these, 61 to 63 are the same as in FIG. 4A, and a non-linear color reproduction range of 63 to 65 is added thereto.

  In other words, at 63, the three display cells R, G, and B become R, G, and B, respectively, where colors are maximized, but at 64, the color development of R, G, and B decreases, but only the brightness increases, and at 65 In all of R, G, and B, the color finally disappears, but the brightness is maximized.

  The lower row 60b shows how one pixel composed of three display cells of R, G, and B looks. This is also the same as 61 to 63 in FIG. However, due to the increase in brightness after 64, 62 appears dark gray and 63 also appears gray instead of white.

  When a non-linear color reproduction range of 63 to 65 is added to this, 64 is bright gray, and 65 is not white mixed with R, G, B, but bright with all the colors of R, G, B disappeared. White color is reproduced.

  As described above, the change in appearance in achromatic colors has been described on the assumption that R, G, and B are output uniformly, but in reality, color display is performed by changing the balance of the outputs of R, G, and B. As for the tint in this case, the state of 63 has the maximum tint. When approaching 61, it becomes dark and approaches black, and when approaching 65, the tint fades and becomes white.

<Color display on display element B>
In the present embodiment, a display device (display element B) having a non-linear color reproduction range in addition to the linear color reproduction range described above is used.

  FIG. 5 shows the state of color display by display cells in the display device (display element B) used in the present embodiment.

  In the upper 60a, one pixel is composed of three display cells (for example, aa, ab, ac) called R, G, and B, and their color display is variable from 61 to 66 to 63. Indicates. However, as a whole, the same change as in FIG. 4A is shown, but the route on the way is different, and a white display of 65 passes, so that a non-linear color of 65 to 63 is obtained in the color reproduction range of 61 to 65 achromatic gradation. The color reproduction range is added.

  That is, at 65, the three display cells of R, G, and B have not yet developed color, and each has white with the maximum brightness. At 64, however, color development of R, G, and B has started, and saturation has been added. R, G, and B are completely colored and the saturation is maximized.

  The lower row 60b shows how one pixel composed of three display cells of R, G, and B looks. This is also the same as 61 to 65 in FIG. However, the color after 64 is added, and due to the increase in saturation, 64 and 63 appear slightly gray instead of white.

  When a non-linear color reproduction range of 65 to 63 is added in this way, 63 and 64 are light gray, and 65 is not white mixed with R, G, and B, but R, G, and B are all colored. The bright white color with disappeared is reproduced.

  As described above, the change in appearance in achromatic colors has been described on the assumption that R, G, and B are output uniformly, but in reality, color display is performed by changing the balance of the outputs of R, G, and B. As for the color in that case, the state of 63 has the maximum color, and when it approaches 65, the color disappears and approaches white, and when it approaches 61, it becomes black with no color. Become.

(About color reproduction range)
The color reproduction range by the display device using the three types of R, G, and B display cells has been described in comparison with the conventional display cell and the display cell used in the present embodiment. That is, the display device used in this embodiment has both a conventional linear color reproduction range and a non-linear color reproduction range.

  FIG. 6 schematically shows a color reproduction range in the Lab color space for the display device (display element A) used in the present embodiment. FIG. 6A shows a cross section parallel to the La axis, and FIG. 6B shows a cross section parallel to the Lb axis. A linear color reproduction range, a non-linear color reproduction range and a color reproduction range obtained by combining them will be described with reference to FIG.

  FIG. 7 schematically shows the color reproduction range in the Lab color space for the display device (display element B). As described above, since the relationship between the linear color reproduction range and the non-linear color reproduction range is different between the display element A and the display element B, the substantial definitions of the color reproduction areas 1 to 4 are different.

  Hereinafter, the display element A will be mainly described as an example. In the display element B or other display elements having both a linear color reproduction range and a non-linear color reproduction range, a color reproduction range can be defined based on the same concept and can correspond to an image area described later.

  In FIG. 6, the color reproduction range 1 is an example of a color reproduction range when the display cells are limited to use only a normal linear color reproduction range for each of the R, G, and B display cells. That is, each of the R, G, and B display cells has an output range of 61 to 63 in FIG. 4B (in the display element B, a range of 61 to 65 in FIG. 5).

  On the other hand, the color gamut 4 is an example of a color gamut when the non-linear color gamut is used for each of the R, G, and B display cells. That is, each of the R, G, and B display cells has an output range of 63 to 65 in FIG. 4B (in the display element B, 65 to 63 in FIG. 5).

  As can be seen from FIG. 6, the color gamut 1 is located in a region with a small L (lightness) in the color space, and the color gamut 4 is in a region with a large L (lightness) in the color space. positioned. That is, the color reproduction area 1 is an area where the color is expressed with gradation, and the color reproduction area 4 is an area where the color is light but suitable for expressing the gradation of brightness.

  The color gamuts 2 and 3 are examples of color reproduction ranges when a linear color reproduction range and a non-linear color reproduction range are selectively used for each of R, G, and B display cells.

  For example, the color gamut 2 is a color gamut when at least one of the R, G, and B display cells is limited to use only a linear color gamut, and for example, the color gamut 3 is At least one of the R, G, and B display cells is a color reproduction range when limited to use only the non-linear color reproduction range (the same applies to the display element B).

  Therefore, the color gamuts 2 and 3 are intermediate color gamuts between the color gamuts 1 and 4, and the color gamut 2 is suitable for the expression that emphasizes the color, that is, the saturation. 3 is suitable for expressions that place a relatively high value on brightness.

  In this way, the display cell has multiple independent color reproduction ranges (linear color reproduction range and non-linear color reproduction range). Color gamut can be set.

(Image discrimination and color space corresponding to it)
In order to take advantage of the characteristics of the color reproduction range of the display device as described above, the image analysis unit 31 in the image processing unit 30 described with reference to FIG. Accordingly, the image is divided into a plurality of image areas. The color conversion unit 32 performs color conversion processing for each divided image area to a color reproduction area suitable for the property of the image area.

  FIG. 8 shows a correspondence relationship between division into image regions as a result of determining an image to be displayed and to which color reproduction region color conversion is performed for each divided image region. The correspondence relationship between the image area and the color reproduction area will be described with reference to FIG.

  Since the definition of the color gamut differs somewhat depending on the display device (for example, display element A and display element B), it is preferable to adjust the correspondence with the image area accordingly. Hereinafter, the display element A will be described as an example.

  In FIG. 8, an image 71 displayed on the display device is divided into, for example, a first image region 72a, a second image region 72b, a third image region 72c, and a fourth image region 72d by the image analysis unit 31. Is done.

  The image area determined to be the first image area 72a is an area formed of an image such as a photograph or a natural image, for which color reproduction characteristics with good color reproduction are required.

  The image area determined to be the second image area 72b is an area made up of an image such as a character image, for example, which is light in color and requires good color reproduction characteristics.

  The image area determined to be the third image area 72c is an area made of an image such as a background portion or a marker that requires a color reproduction characteristic to be reproduced with a light color tone even though the color is light.

  The image area determined to be the fourth image area 72d is an area formed of an image such as an illustration image in which color reproduction characteristics that share color reproduction and appropriate contrast are required.

  In order to perform color conversion processing corresponding to each of the image regions (72a to 72d) divided in this way, the color conversion unit 32 holds LUTs (73a to 73d) corresponding thereto. . Each LUT is a color conversion table for a different color gamut.

  A color gamut to be converted by each LUT will be described.

  As described above, the display characteristic 80 of the display device has a plurality of independent color reproduction ranges (a linear color reproduction range 81 and a non-linear color reproduction range 82). Also. As already described, there is a color reproduction range 1 to 4 (83a to 83d) by combining the two.

  For example, the color reproduction range 1 is a color reproduction range when only a normal linear color reproduction range is used, and the color reproduction range 4 is a color reproduction range when only a non-linear color reproduction range is used.

  For example, at least one of the R, G, and B display cells in the color gamut 2 is only a linear color reproduction range, and at least one of the R, G, and B display cells is in the color gamut 3. This is a color reproduction range when only a non-linear color reproduction range is used.

  In FIG. 8, these relationships are shown by lines connecting the linear color reproduction range, the non-linear color reproduction range (81, 82), and the color reproduction regions 1 to 4 (83a to 83d).

  In addition, lines connecting these color gamuts 1 to 4 (83a to 83d) and LUTs 1 to 4 (73a to 73d) indicate which LUT has color conversion to which color gamut.

  For example, LUT 1 corresponds to color gamut 1. A color conversion process to a linear color reproduction region 1 in which the color tone is expressed with gradation is performed on an image region in which color reproduction characteristics with good tone reproduction are required.

  For example, LUT 2 corresponds to color gamuts 1 and 4. Alternatively, all of the color gamuts 1 to 4 may be supported. A color conversion process to color reproduction regions 1 to 4 in which the lightness reproduction range is the widest regardless of the color is performed on an image region in which a color reproduction characteristic with good contrast even though the color is thin.

  For example, LUT 3 corresponds to color gamut 3. Color conversion processing to color reproduction range 3 with a large non-linear color reproduction range suitable for expressions with relatively high lightness is required for image areas that require color reproduction characteristics that are reproduced with light colors even though the color is light. Done.

  For example, LUT 4 corresponds to color gamut 2. To an image area that requires color reproduction characteristics that share color reproduction and appropriate contrast, to a color reproduction area 2 that has a relatively small non-linear color reproduction range that is suitable for expression that emphasizes color, that is, saturation. The color conversion process is performed.

  In this way, the color conversion unit 32 selectively uses the LUTs 1 to 4 held for each of the first to fourth image areas, and performs color conversion to a color reproduction range suitable for each image area. Execute the process.

  This is because different LUTs are used, and multiple independent color spaces (linear color reproduction range and non-linear color reproduction range) that match the display characteristics of the image display device according to each image area with different color reproduction requirements. Are converted to different color spaces (color gamuts 1 to 4 or a combination thereof).

(Example of color conversion processing)
FIG. 9 is a flowchart illustrating a procedure for performing image processing of a display image in accordance with the display characteristics of the display device. A procedure for performing image processing of a display image, that is, image region division and color conversion processing will be described with reference to FIG.

  In FIG. 9, it is assumed that the display image has already been acquired by the image acquisition unit 12 and stored in the image storage unit 13.

  First, in step S11, the image analysis unit 31 determines the display type of the display image.

  In step S12, the region is divided according to the determined drawing type.

  An example of a display image divided into regions is shown in FIG. In FIG. 10, the display image 90 includes a photographic image area 91, a text image area 92, a marker area 93, an illustration area 94, and other areas 95. In these steps S11 and S12, the difference in drawing type is determined, and the region is divided.

  In step S13 and subsequent steps, image processing is executed for each divided image region.

  In step S <b> 13, the image analysis unit 31 selects one image area for performing color conversion processing from unprocessed image areas.

  In step S14, it is determined whether the selected image area is a text area (second image area). If YES, step S18 is executed. If NO, step S15 is executed. In the display image example of FIG. 10, the image area 92 is YES.

  In step S15, it is determined whether the selected image area is a natural image area (first image area). If YES, step S19 is executed. If NO, step S16 is executed. In the display image example of FIG. 10, the image area 91 is YES.

  In step S16, it is determined whether the selected image area is an illustration area (fourth image area). If YES, step S20 is executed. If NO, step S17 is executed. In the display image example of FIG. 10, the image area 94 is YES.

  In step S17, it is determined whether or not the selected image area is a background area (third image area). If YES, step S21 is executed. If NO, step S22 is executed. In the display image example of FIG. 10, the image area 93 is YES.

  In step S18 and subsequent steps, the color conversion unit 32 selects an LUT corresponding to each image area and performs color conversion processing.

  In step S18, since the selected image area corresponds to the second image area, LUT2 is selected.

  In step S19, since the selected image area corresponds to the first image area, LUT1 is selected.

  In step S20, since the selected image area corresponds to the fourth image area, the LUT 4 is selected.

  In step S21, since the selected image area corresponds to the third image area, LUT3 is selected.

  In step S22, since the selected image area corresponds to the other image area, a predetermined appropriate LUT (any of LUTs 1 to 4 may be selected) is selected.

  In step S23, the color conversion unit 32 performs color conversion processing using the LUT selected corresponding to each image area.

  In step S24, it is determined whether or not the color conversion process has been completed for all divided image regions. If YES, step S25 is executed. If NO, the process returns to step S13, and one new image area is selected from the unprocessed image areas, and steps S14 to S24 are repeated until the processing of all the image areas is completed.

  In step S25, since the processing of all the image areas has been completed, the images of all the areas are integrated. This completes the image processing of the display image in accordance with the display characteristics of the display device. Thereafter, the image is sent to the image display unit 40 and displayed on the display unit 41. Alternatively, it is output from the image output unit 14 for display on the external display device 3.

<About LUT>
In addition, as described in the explanation of FIG. 8, the LUTs 1 to 4 are data obtained by mapping the color reproduction areas 1 to 4 or their mapping to the composite area.

  11 and 12 show examples of LUT1 and LUT2, respectively.

  Each LUT tabulates data in the color space before conversion and data in the corresponding color space after conversion. For example, the value of R in the color space before conversion included in R0-001 before conversion is converted to the value of R in the color space after conversion included in R1-001 after conversion. It is.

  The LUT 1 in FIG. 11 is data of 255 gradations for each of R, G, and B before conversion, and data of 156 gradations for each of R, G, and B after conversion. This corresponds to the color reproduction range 1 described above, and the color reproduction range after the conversion extends to a region with low brightness in the color reproduction ranges of all the color reproduction regions 1 to 4 as can be seen from FIG. (The closer to 001, the smaller the lightness and saturation).

  The LUT 1 in FIG. 11 reproduces only the linear color reproduction range as described above, and is used for an image region (first image region) in which color reproduction characteristics with good gradation reproduction are required.

  The LUT2 in FIG. 12 is data of 255 gradations for each of R, G, and B before conversion, and data of 255 gradations for each of R, G, and B after conversion. This is because the color reproduction range after conversion corresponds to the color reproduction ranges 1 to 4 described above, and the color reproduction ranges 1 to 4 indicate all the color reproduction ranges as can be seen from FIG.

  The LUT 2 in FIG. 12 reproduces from a linear color reproduction range to a non-linear color reproduction range as described above, and is used for an image area (second image area) where color reproduction characteristics with good contrast are required.

  In this way, the LUT is prepared in advance and held in the color conversion unit 32 with an appropriate combination of color gamuts so as to satisfy the requirements of each image area. Alternatively, display characteristic information may be acquired from an external display device and the LUT may be corrected or generated accordingly.

  As described above, according to the image processing system and the image processing apparatus according to the present embodiment, the color reproduction characteristics of a display device having both a conventional linear color reproduction range and a non-linear color reproduction range can be obtained. By combining these color reproduction characteristics, it is possible to create a plurality of color spaces that are more suitable for the type and nature of the image. Since color conversion processing corresponding to each image can be performed using these color spaces, more natural and preferable color reproduction suitable for each image can be achieved.

  The scope of the present invention is not limited to the above embodiment. Unless it deviates from the meaning of this invention, those changed forms are also included in the range.

Claims (19)

Image acquisition means for acquiring images;
Image storage means for storing the image acquired by the image acquisition means;
Image processing means for image processing to display the image stored in the image storage means;
Image display means for displaying the image processed by the image processing means;
An image processing system comprising:
The image processing means includes
Image analysis means for dividing the image into image regions having different requirements for color reproduction;
Color conversion means for performing different color conversion processing for each of the image regions divided by the image analysis means,
The color conversion means includes
An image processing system characterized in that, according to each of the image regions, color conversion into a different color space is performed by combining a plurality of independent color spaces in accordance with display characteristics of the image display means. The image display means includes
It has a display unit in which pixels composed of a plurality of display cells that display different colors are arranged,
Each display cell displaying different colors can change the color display continuously between a common black display, a different color display, and a common white display. The image processing system according to claim 1. The plurality of display cells that display the different colors are:
3. The image processing system according to claim 2, wherein the image processing system is a display cell that displays three colors of red, green, and blue, which are respectively referred to as R, G, and B. The plurality of display cells that display the different colors are:
3. The image processing system according to claim 2, wherein the image processing system is a display cell that displays three colors of cyan, magenta, and yellow, which are respectively referred to as C, M, and Y. The image analysis means converts the image into
A first image area where color reproduction characteristics with good gradation reproduction are required;
A second image area where color reproduction characteristics with good contrast are required;
A third image region where high color reproduction characteristics are required;
A fourth image area where high color reproduction characteristics are required;
The image processing system according to claim 3, wherein the image processing system is divided into two parts. The color conversion unit is configured to perform the first image area.
For any display cell that displays each color of R, G, and B, color conversion processing is performed using a range in which the color display changes between a common black display and a different color display as a color reproduction range. 6. The image processing system according to claim 5, wherein the image processing system is characterized in that: The color conversion unit is configured to perform the second image area.
For any display cell that displays each color of R, G, and B, color conversion processing is performed using a range in which the color display changes between a common black display and a common white display as a color reproduction range. The image processing system according to claim 5 or 6. The color conversion unit is configured to perform the third image area.
For one or more display cells that display R, G, and B colors, a color conversion process is performed using a range in which the color display changes between a different color display and a common white display as a color reproduction range. The image processing system according to any one of claims 5 to 7, wherein: The color conversion unit is configured to perform the fourth image area.
For one or more display cells that display each color of R, G, and B, color conversion processing is performed using a range in which the color display changes between a common black display and a different color display as a color reproduction range. The image processing system according to any one of claims 5 to 8, wherein: 10. The color conversion unit according to claim 5, wherein the color conversion unit performs a color conversion process to a different color space according to each of the image regions using a Look Up Table. The image processing system according to item 1. Image acquisition means for acquiring images;
Image storage means for storing the image acquired by the image acquisition means;
Image processing means for image processing to display the image stored in the image storage means;
Image output means for outputting the image processed by the image processing means to an external display means;
An image processing apparatus comprising:
The image processing means includes
Image analysis means for dividing the image into image regions having different requirements for color reproduction;
Color conversion means for performing different color conversion processing for each of the image regions divided by the image analysis means,
The color conversion means includes
Holding information on display characteristics of the external display means;
2. An image processing apparatus according to claim 1, wherein a plurality of independent color spaces are combined in accordance with display characteristics of the external display unit, and color conversion into different color spaces is performed according to each of the image regions. Information about the display characteristics of the external display means held by the color conversion means is
A common black display and a different color display for each of the plurality of display cells displaying three colors of red, green and blue, which are respectively referred to as R, G and B, which the external display means has; The image processing apparatus according to claim 11, further comprising a color reproduction range in which the color display continuously changes between the common white display. 13. The display cell according to claim 12, wherein the plurality of display cells of the external display means are display cells for displaying three colors of cyan, magenta, and yellow, which are referred to as C, M, and Y, respectively. An image processing apparatus according to 1. The image analysis means converts the image into
A first image area where color reproduction characteristics with good gradation reproduction are required;
A second image area where color reproduction characteristics with good contrast are required;
A third image region where high color reproduction characteristics are required;
A fourth image area where high color reproduction characteristics are required;
The image processing apparatus according to claim 12, wherein the image processing apparatus is divided into two. The color conversion unit is configured to perform the first image area.
For any display cell that displays each color of R, G, and B, color conversion processing is performed using a range in which the color display changes between a common black display and a different color display as a color reproduction range. The image processing apparatus according to claim 14, wherein the image processing apparatus is characterized in that: The color conversion unit is configured to perform the second image area.
For any display cell that displays each color of R, G, and B, color conversion processing is performed using a range in which the color display changes between a common black display and a common white display as a color reproduction range. The image processing device according to claim 14 or 15. The color conversion unit is configured to perform the third image area.
For one or more display cells that display R, G, and B colors, a color conversion process is performed using a range in which the color display changes between a different color display and a common white display as a color reproduction range. The image processing device according to any one of claims 14 to 16, wherein the image processing device performs the processing. The color conversion unit is configured to perform the fourth image area.
For one or more display cells that display each color of R, G, and B, color conversion processing is performed using a range in which the color display changes between a common black display and a different color display as a color reproduction range. The image processing device according to any one of claims 14 to 17, wherein the image processing device performs the processing. Information about the display characteristics of the external display means held by the color conversion means is
The image processing apparatus according to any one of claims 14 to 18, wherein the image processing apparatus holds a Look Up Table used for a color conversion process for each of the image regions.