JP2011223509A - Color correction system, program and color correction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display an appropriate image irrespective of an installation environment of a display unit by correcting a display image.SOLUTION: A color collection system includes surrounding color acquisition means 10 to acquire surrounding color information 110, which is color information around a display unit, and parameter calculation means 12 to calculate a parameter 112 needed for correcting display color of input image data based on the surrounding color information. The parameter calculation means performs parameter calculation to calculate a parameter on predetermined image pixels of input image data 100 for each element in a predetermined color space. The parameter calculation determines a calculation target range within an area around the display unit; acquires background color information that is color information of background points, which are image elements within the calculation target range, from the surrounding color information; calculates background point distance which is the distance between the predetermined image pixels and the background points; calculates a background point correction value based on the background color information and the background point distance; and defines the total sum of the background correction value on all the background points included in the calculation target range as a parameter.

Description

  The present invention relates to a color correction system, a program, a color correction method, and the like.

  As physiological functions of human eyes, there are chromatic adaptation and light / dark adaptation. For example, an object that looks white under sunlight (color temperature is about 5500K) is initially reddish when viewed under light bulb-colored illumination light (color temperature is about 3000K), but appears white over time. become. This is an example of chromatic adaptation. For example, when you enter a dark movie theater, you can't see your feet at first, but gradually you can see the surroundings. This is an example of light and dark adaptation.

  In consideration of such a physiological function of the eye, a system that corrects the color of the display image in the previous stage of the display unit (display device) (hereinafter also referred to as a color correction system) may be used. For example, some recent televisions (an example of a display unit and a color correction system) have a timer that determines whether it is daytime or evening, and a luminance sensor that determines a change in illuminance. The invention of Patent Document 2 performs color correction in consideration of ambient illumination light.

JP 2006-3332908 A Japanese Patent Application No. 2007-512803 JP 2001-292333 A

  However, in addition to the illumination color and illuminance, there are other factors that affect the physiological function of the human eye and affect the image viewed by the user. For example, not only chromatic adaptation occurs in the display image due to the color of the wall as the background, but also the influence of brightness contrast may occur. Further, in an image display device such as a television receiver, there is a possibility that the display image may be influenced by brightness contrast due to the outer frame. Here, lightness contrast means that when two colors having different lightness are arranged, a bright color looks brighter and a dark color looks darker.

  For example, in the test image 1000 of FIG. 11A, three sets of four squares of the same color are arranged on a background with gradation (black on the left and white on the right). The first set is four white squares, which are arranged in a horizontal row at the top of the test image 1000. The second set is light gray and is also arranged in a horizontal row in the middle. The third set is dark gray and is arranged in a horizontal row at the bottom. For example, when the leftmost square in the second group (middle stage) is compared with the rightmost square, the color of the rightmost square is felt dark even though they are the same color. In the first set (upper stage), the leftmost square appears whiter, and in the third set (lower stage), the rightmost square gray appears darker. This is an example of brightness contrast.

  In addition, since the display unit does not always have a wall as a background, the surrounding color of the display unit (hereinafter referred to as ambient color) may not be uniform. For example, although it is placed in a room with a white wall, the display unit is placed in front of the black light-shielding curtain, and the display unit, black curtain, and white wall may all enter the user's field of view. obtain. In this case, it is the surrounding color that is closer to the display unit that causes a strong brightness contrast.

  For example, test images 1001 to 1003 in FIG. 11B are for confirming the appearance of dark gray squares as in FIG. The square colors (dark gray) of the test images 1001 to 1003 are all the same color. However, when the test image 1001 and the test image 1003 are compared, the square gray of the test image 1003 appears darker due to the influence of brightness contrast. Here, in the test image 1002, the surrounding color close to the dark gray square is black and the outer surrounding color is white. At this time, the gray square of the test image 1002 appears to have a darkness different from that of the test image 1003 and similar to that of the test image 1001. That is, the surrounding color of the test image 1002 includes white, but black, which is a closer surrounding color, has an influence.

  Based on the above, when the surrounding color of the display unit is not uniform, it is impossible to convey the color intended by the photographer unless correction is performed in consideration of the influence of the closer surrounding color. Here, the inventions of Patent Document 1 and Patent Document 3 are not color correction considering the periphery of the display unit. Further, the invention of Patent Document 2 is limited to color correction with respect to the ambient ambient light level. For this reason, the correction methods proposed by the inventions of Patent Documents 1 to 3 are not sufficient for correcting the contrast phenomenon.

  The present invention has been made in view of such problems. According to some aspects of the present invention, the image processing apparatus includes a unit that acquires a surrounding color of the screen, performs an operation in consideration of the position of an object arranged around the screen, and directly or indirectly displays a display image based on the result. Provided is a color correction system that automatically corrects. An appropriate image can be displayed regardless of the installation environment of the display unit.

  (1) The present invention is a color correction system for causing an image based on correction data obtained by correcting the display color of input image data to be displayed on a display unit, and is a surrounding color which is color information of an image around the display unit Ambient color acquisition means for acquiring information, and parameter calculation means for calculating parameters necessary for correcting the display color of the input image data based on the ambient color information, wherein the parameter calculation means is the input image For a given pixel of data, a parameter calculation for obtaining the parameter is performed based on the position information of the pixel and the surrounding color information.

  According to the present invention, it is provided with means for acquiring the surrounding color of the screen (ambient color acquiring means), performs calculation (parameter calculation) in consideration of the position of an object placed in the periphery, and displays a display image based on the result. Correct directly or indirectly. Therefore, it is possible to display an appropriate image regardless of the installation environment of the display unit.

  Here, an appropriate image is an image having an image quality (for example, color / image) that the photographer, creator, sender, or provider of the image wants to convey. For example, it is an image that gives a sense of realism, an image that makes a user feel the vividness of a hue as seen with the naked eye, and an image that makes a user feel comfortable. The sensory expression is an image that makes the viewer feel the video / image intended by the photographer, creator, sender, or provider of the image. As another aspect, an appropriate image is an image having an image quality that is easy for a user to see. For example, an image that does not get tired when viewed, an image with a natural hue, and the like. Of course, the image may be an image having all or some of these, and other characteristics (for example, excellent dark part expression, low power consumption by brightness adjustment, long life of the backlight, etc.) May be included.

  (2) In this color correction system, in the parameter calculation, the parameter calculation unit determines a calculation target range for an image around the display unit, and color information about a background point that is a pixel in the calculation target range. The background color information is obtained from the surrounding color information, and for each background point included in the calculation target range, a background point distance that is a distance between the given pixel and the background point and the background color information. A background point correction value may be calculated based on the parameter, and the parameter may be obtained based on a sum of background point correction values for all background points included in the calculation target range.

  According to the present invention, a calculation target range is determined, and a background point correction value is calculated for each background point inside. Since the parameter calculation is performed based on both the color information (background color information) and the distance (background point distance) of each background point, it is possible to display an appropriate image in consideration of the influence of the contrast phenomenon.

  (3) In this color correction system, the parameter calculation means performs the parameter calculation as the given pixel for a representative pixel that is a part of the pixel of the input image data, and calculates the pixel of the input image data. Among the pixels that are not the representative pixels, parameters may be obtained by calculation based on the parameters of the representative pixels.

  (4) In this color correction system, at least one of the number and coordinates of the representative pixels may be determined based on a screen size of the display unit.

  According to the present invention, it is only necessary to perform the parameter calculation for only the representative pixel, so that the calculation time can be shortened. For pixels that are not representative pixels, parameters may be obtained by linear interpolation, for example. In addition, the number and coordinates of the representative pixels may be fixed, but by changing according to the size of the screen, it is possible to perform correction that reflects information around the screen more appropriately.

  (5) In this color correction system, the parameter calculation means may determine the calculation target range for each element of the given color space.

  According to the present invention, since the calculation target range is determined according to the color field of view, it is possible to perform more appropriate correction in consideration of the physiological function of the human eye.

  (6) The color correction system may include color correction means for generating correction data in which the parameter is a correction amount and the correction amount is added to the input image data.

  (7) The color correction system includes a color correction unit that creates the correction data based on the parameter, and the color correction unit adds a correction amount represented by a function of the parameter to the input image data. Correction data may be generated, and the function or the coefficient thereof may be adjusted for each pixel of the input image data based on the color information of the pixel and the background color information.

  (8) The color correction system includes a storage unit that stores specific color information that is information on a color specified in advance, and the color correction unit adjusts the function or its coefficient based on the specific color information. May be.

  (9) In this color correction system, the color correction unit obtains a dispersion value for color information of a part or all of the pixels of the input image data, and the correction amount is reduced when the dispersion value is large. The function or its coefficient may be adjusted, and when the variance value is small, the function or its coefficient may be adjusted so that the correction amount becomes large.

  According to the present invention, the color correction system generates correction data based on the generated parameters including the color correction means. At this time, the parameter value itself may be used as the correction amount, and the correction amount corresponding to the characteristics of the input image data is adjusted by adjusting the coefficient using an N-order polynomial (an example of a function) using the parameter as the correction amount. You may make it obtain. When the parameter value itself is used as the correction amount, the calculation process can be performed quickly. Further, when adjusting the coefficient, it is possible to cope with the case where it is desired to set the correction amount to 0 for specific color information, and the configuration of the color correction system becomes flexible.

(10) In this color correction system, the parameter calculation means may perform the parameter calculation for each element of L ^* , a ^* , b ^{* in} the L ^* a ^* b ^* color system.

According to the present invention, by using the L ^* a ^* b ^* color system having perceptual uniformity, it is possible to approximate a change in numerical values representing color information and a change in human perception. For example, linear interpolation can be performed in parameter calculation and the like, and the amount of calculation can be reduced.

  (11) In this color correction system, in the given color space, the parameter calculation means may perform the parameter calculation for each of Y, U, and V elements in the YUV format.

  According to the present invention, for example, when the input image data is in the YUV format, it is not necessary to convert the color space of the input image data or the correction data. Therefore, the number of calculation steps can be reduced.

  (12) The present invention is a program for performing color correction for causing an image based on correction data obtained by correcting the display color of input image data to be displayed on a display unit, and is color information of an image around the display unit. The parameter calculation unit is configured to function a computer as an ambient color acquisition unit that acquires ambient color information, and a parameter calculation unit that calculates parameters necessary for correcting the display color of the input image data based on the ambient color information. The means performs a parameter calculation for the given pixel of the input image data based on the position information of the pixel and the surrounding color information to obtain the parameter.

  According to the present invention, the surrounding color of the screen is acquired by software, the calculation is performed in consideration of the position of an object placed around the screen, and the display image is corrected directly or indirectly based on the result. Can do. Therefore, it can be applied to various color correction systems using a computer.

  (13) The present invention is a color correction method for causing an image based on correction data obtained by correcting the display color of input image data to be displayed on a display unit, and is a surrounding color which is color information of an image around the display unit An ambient color acquisition step for acquiring information; and a parameter calculation step for calculating a parameter necessary for correcting a display color of the input image data based on the ambient color information, wherein in the parameter calculation step, the input image For a given pixel of data, a parameter calculation for obtaining the parameter is performed based on the position information of the pixel and the surrounding color information.

  According to the present invention, the method includes the step of acquiring the surrounding color of the screen, performs a calculation in consideration of the position of an object placed around the screen, and corrects the display image directly or indirectly based on the result. Therefore, it is possible to display an appropriate image regardless of the installation environment of the display unit.

1 is a block diagram of a color correction system in a first embodiment. FIG. 2A is a diagram showing a use environment of a television which is a specific example of the first embodiment. FIG. 2B shows an example of ambient color information. FIG. 3 is a diagram illustrating an example of a method for determining a calculation target range. FIG. 4 is a diagram showing the background point distance. FIG. 3 is a diagram illustrating a color correction method according to the first embodiment. The figure which shows the subroutine of FIG. The block diagram of the color correction system in 2nd Embodiment. FIG. 8A to FIG. 8B are diagrams for explaining the interpolation processing. The figure which shows the color correction method in 2nd Embodiment. The figure which shows the subroutine of FIG. FIG. 11A to FIG. 11B are diagrams of brightness contrast test images.

  Embodiments of the present invention will be described below with reference to the drawings.

  The color correction system according to the present invention is not limited to the specific examples in the following embodiments. The color correction system according to the present invention may be a part of various electronic devices such as a television, a portable small terminal, an electronic book, and an electronic poster. Furthermore, the display unit may be any display unit that can reflect the color information corrected by the color correction system according to the present invention until the display image is finally visually recognized by the user. Therefore, the display unit should be interpreted in a broad sense without being limited to electronic display devices such as televisions and displays. For example, a projector image displayed on a wall and an image of a paper medium printed by a printer may be included in the display unit. That is, the color correction system according to the present invention may be a part of a projector or a printer.

  Further, the information processing in the color correction system according to the present invention may be software processing specifically realized using a CPU or the like. That is, information processing in the color correction system according to the present invention may be performed by a program that causes a computer to function as ambient color acquisition means, parameter calculation means, color correction means, and the like.

1. First Embodiment A first embodiment of the present invention will be described with reference to FIGS.

1.1. Configuration of Color Correction System FIG. 1 is a block diagram of a color correction system 1 according to this embodiment. The color correction system 1 is a system for displaying an image obtained by correcting the display color of the input image data 100 on the display unit 2. The color correction system 1 includes an ambient color acquisition unit 10 and a parameter calculation unit 12. The color correction system 1 according to the present embodiment outputs the parameter 112 generated by the parameter calculation unit 12.

  In the present embodiment, the parameter 112 output from the color correction system 1 is input to the color correction unit 20. The color correction unit 20 generates correction data 120 obtained by adding a correction amount based on the parameter 112 to the input image data 100. The display unit 2 displays the contents of the correction data 120. The color correction unit 20 and the display unit 2 may be included in the color correction system 1.

  The ambient color acquisition unit 10 is included in the color correction system 1 of the present embodiment, and acquires ambient color information 110 that is color information around the display unit 2. Here, the surroundings refer to images other than the display unit 2 that enter the visual field when the display unit 2 is viewed from the user. That is, the surroundings refer to the background of the display unit 2 viewed from the user (hereinafter, used as a broad background including the foreground). The ambient color refers to the color of the background of the display unit 2. The ambient color acquisition unit 10 may be, for example, a camera provided in a remote controller of the display unit 2. At this time, the ambient color information 110 may be color still image data taken from a position where the user views the display unit 2 (image viewing point) (see FIG. 2B). When the display unit 2 includes a component such as a frame or a leg in addition to the screen that displays the display image, the area other than the screen may be the periphery.

  The parameter calculation unit 12 calculates a parameter 112 necessary for correction performed by the color correction unit 20 based on the ambient color information 110. The parameter calculation means 12 may be a calculation circuit, for example. At this time, the parameter 112 is a numerical value having a correlation with the correction amount, and may be handled as the correction amount itself in the color correction unit 20 or may be handled as the correction amount after processing such as weighting.

Here, the parameter 112 is generated for each element according to the expression format of the image data handled by the parameter calculation unit 12. For example, when the parameter calculation means 12 performs calculation by handling the ambient color information 110 in the YUV format, parameters 112 are generated and output for each of the Y component, U component, and V component. In this embodiment, the parameter calculation means 12 handles the ambient color information 110 in the L ^* a ^* b ^* (Elster / Aster / Beester) color system. Accordingly, the parameter 112 is generated for each element of L ^* , a ^* , b ^* . Specific calculation will be described later.

  Here, a specific example of the color correction system 1 is a television receiver (hereinafter referred to as a television). The television includes the color correction system 1 that receives input image data 100 such as a program and outputs a parameter 112 therein, and the correction data 120 generated by the color correction unit 20 based on the parameter 112 is a liquid crystal or the like. Display unit 2 displays. Hereinafter, the color correction system 1 of the present embodiment will be described as being part of a television.

1.2. Acquisition of Ambient Color FIG. 2A is a diagram illustrating an environment in which the television 810 including the color correction system 1 of the present embodiment is used. The installation environment of the television is not uniform, and the television 810 may be disposed in front of the wall 811, the window 812, or the curtain 813. In addition, an indoor light 814 or a houseplant 815 may be placed. These surrounding objects may affect the image displayed on the television 810 due to the physiological function of the human eye. For example, when the influence of the red curtain 813 is strongly influenced, the display image of the screen 30 becomes a greenish color, and when the influence of the yellow wall 811 is strongly influenced, the display image of the screen 30 becomes a bluish color.

FIG. 2B is a diagram illustrating an example of the ambient color information 110 according to the present embodiment. In this embodiment, in order to grasp which of the objects around the display unit 2 has a strong influence on the display image on the screen 30, an image taken from the image appreciation point is set as the ambient color information 110. Ambient color information 110 is a color image, and has values of elements of L ^* , a ^* , and b ^* for each pixel. Here, the image size of the ambient color information 110 is sufficient even with a small resolution such as VGA. For example, the ambient color acquisition unit may be configured by a VGA-size image sensor and a peripheral circuit mounted on a remote controller that operates the display unit 2. According to this example, when a user views a television, an image from an image appreciation point can be taken without using another device.

  In the surrounding color information 110 of the present embodiment, it is possible to grasp the distance between the screen 30 and surrounding objects. Objects arranged near the screen 30 have a stronger influence on the display screen of the screen 30 than objects far away. Therefore, the parameter calculation means 12 determines parameters based on the color of surrounding objects and the distance from the screen 30.

  Here, the color at a location away from the screen 30 does not significantly affect the display image on the screen 30. That is, it does not cause a contrast phenomenon. Therefore, in order to effectively correct and reduce the amount of calculation in the parameter calculation means 12 to increase the processing speed, the range from the center C (see FIG. 3) of the screen 30 to a certain distance in the surrounding color information 110 is set. The target of calculation. This range is set as a calculation target range 40 (see FIG. 4).

  FIG. 3 is a diagram illustrating one method for determining the radius of the calculation target range 40. FIG. 3 is a top view of the room in FIG. The trial listening distance of the television receiver 810 is set to be three times or five times the height of the screen 30. Here, it is exemplified as 5 times. In this case, let D be the point at which a line that forms an angle of 30 ° with the straight line connecting the image viewing point 820 and the center C of the screen 30 reaches the position of the television receiver. At this time, the radius (the constant distance) of the calculation target range 40 is a distance between CD.

  For example, in a 40-inch television receiver 810, the image viewing point 820 is located 2.5 m away from the television receiver 810. Then, the point D that defines the radius of the calculation target range 40 is about 1.4 m away from the center C of the screen 30. In consideration of the user's field of view, the correction can be effectively performed if the range within 1.4 m from the center C of the screen 30 is taken into consideration.

  Then, the surrounding color acquisition unit 10 may acquire an image including the calculation target range 40. At this time, such an image can be obtained without using an imaging device having a wide-angle lens. Therefore, problems such as an increase in cost do not occur.

1.3. Parameter calculation 1.3.1. Setting of Calculation Target Range FIG. 4 is a diagram showing the background point distance. Black circles (P, P ₁ , P ₂ ) and squares (E _{1 to} E ₅ ) in FIG. 4 are pixels of the ambient color information 110 that is an image taken from the image viewing point 820. The Cartesian coordinates XY are used to specify the positions of these pixels.

The parameter calculation means 12 of this embodiment defines the calculation target range 40 in the ambient color information 110. It is the pixels included in the calculation target range 40 that the parameter calculation means 12 sets as calculation targets. Therefore, the pixels E _{1 to} E ₅ represented by squares are excluded from the calculation target, and the pixels (for example, P, P ₁ , P ₂ ) indicated by the black circles in FIG. 4 are the calculation target. A black circle pixel to be calculated is called a background point.

Here, the calculation target range 40 may be the same for each element of L ^* , a ^* , and b ^* , but the range may be adjusted in consideration of the color field of view. The color field is the range that can be seen without moving the line of sight. When the color field is wide, it is necessary to consider a background point farther away. In general, the color field of view becomes narrower in the order of blue, yellow, red, and green. In addition, white has the widest color field of view, whether chromatic or achromatic. Therefore, for L ^* representing lightness (white-black), the calculation target range 40 is expanded to obtain a large number of background points. Conversely, for a ^* representing red and green chromaticity, the calculation target range 40 is narrowed to obtain a background point. You may take less. As described above, since the parameter is calculated for each element (L ^* , a ^* , b ^* ), an independent calculation target range 40 can be set.

1.3.2. Acquisition of background color information The parameter calculation means 12 acquires background color information which is color information of a background point from the surrounding color information 110. Here, the background point P is taken as an example. The parameter calculation means 12 obtains L ^* _P , a ^* _P , and b ^* _P as background color information of the background point P. These are the values of the elements L ^* , a ^* , b ^* , respectively.

The parameter calculation means 12 may determine one color as a reference color in advance and perform standardization to obtain a difference between the background color information and the color information (reference value) of the reference color. For example, the reference color may be gray, which takes an intermediate value in all elements of L ^* , a ^* , and b ^* . Here, the reference values are L ^* ₀ , a ^* ₀ , and b ^* ₀ . For example, the background color information standardized for L ^* refers to L ^* _P- L ^* ₀ . In this embodiment, standardized background color information is used for calculating background point correction values dL ^* , da ^* , and db ^* , which will be described later.

The parameter calculation means 12 similarly obtains background color information for other background points (for example, P ₁ and P ₂ ) and performs standardization.

1.3.3. Background Point Distance Calculation The parameter calculation means 12 obtains a background point distance, which is the distance between a given pixel Q in the display image on the screen 30 and the background point. Here, the background point P (X _P , Y _P ) in FIG. 4 is taken as an example. The coordinates of the pixel Q are (X _Q , Y _Q ). The background point distance D _PQ between the pixel Q and the background point P is obtained by _Equation 1.

Note that the pixel Q may be an arbitrary pixel in the display image on the screen 30, or may be one of representative pixels described later. Parameter computation unit 12 calculates the background point distance for other background point P ₁ and P _2. For example, in _order to obtain the background point distance D _P1Q of the background point P ₁ , X _P1 and Y _P1 are substituted for X _P and Y _P in the equation (1), respectively.

1.3.4. Calculation of background point correction value The parameter calculation means 12 calculates a background point correction value for the pixel Q and each of the background points. The background point correction value is a component of the parameter of the pixel Q and is a value at one background point. At this time, standardized background color information and background point distance are used. Here, assuming that the total number of background points is S, the background point correction values dL ^* _PQ , da ^* _PQ , and db ^* _PQ of the pixel Q and the background point P are expressed by the following equation ⁽ 2).

In Expression (2), (L ^* _P− L ^* ₀ ) / S indicates the degree of deviation of the background point P from the reference color without depending on the position of the pixel Q. When the deviation from the reference color is large, a contrast phenomenon is likely to occur in the pixel Q. 1 / D _PQ is the reciprocal of the background point distance between the pixel Q and the background point P. When the background point distance is short, a contrast phenomenon is likely to occur in the pixel Q. The background point correction value dL ^* _PQ can be multiplied to evaluate both the magnitude of deviation from the reference color and the proximity of the background point distance. The same applies to Expression (3) and Expression (4).

  If it is desired to greatly evaluate the influence of the background point distance, the nth power of the background point distance (n = 2, 3,...) May be used. For example, when n = 2, the background point correction value is expressed by Equation 3.

  When the influence of the background point distance is further evaluated, the background point distance may be a power index. The base A may be a suitable real number. At this time, the background point correction value is expressed by Equation 4.

Any of Equations 2 to 4 gives a background point correction value, but Equation 2 is used in this embodiment. Parameter computation unit 12, background corrections the same way for other background points _{P 1} and ^{_{P 2 {dL * P1Q, da}} * P1Q, db * P1Q}, {dL * P2Q, da * P2Q, db * P2Q } Is performed. For example, dL ^* _P1Q is expressed by _Equation 5.

1.3.5. In calculating this embodiment parameters Parameter ^{_{δL * Q, δa * Q,}} δb * Q for a pixel Q is (in Fig. 4, all black circles) all background point obtained by the sum of the background point correction value in . The parameter calculation means 12 calculates a parameter for the pixel Q using Equation 6.

  In Equation 6, i indicates a background point included in the calculation target range 40.

The parameter calculation unit 12 may calculate the parameter for another pixel in the display image on the screen 30 after calculating the parameter for the pixel Q. For example, parameters may be calculated for all pixels of the display image. However, depending on the number of pixels of the display image, the calculation amount of the parameter calculation means 12 increases, and there is a possibility that the processing takes time. Therefore, in the present embodiment, representative pixels are provided in the central portion and the peripheral portion of the display image (see Q _{1 to} Q _{9 in} FIG. 8A), and parameters are calculated only for the representative pixels. The parameters of the other pixels are obtained by calculation by interpolation processing based on the parameters of the representative pixels in the color correction unit 20. Note that the number of representative pixels is not limited to nine, and may be 16, for example, on a screen 30 larger than 40 inches. Conversely, for example, a small screen 30 of about 20 inches may be provided one at each of the four corners. In addition to the number, the position of the representative pixel may be changed according to the screen size. And it is not always necessary that the representative pixels are placed at regular intervals. In this embodiment, it is assumed that there are nine representative pixels Q _{1 to} Q ₉ as shown in FIG.

The color correction system 1 of this embodiment outputs the parameter 112 to the color correction unit 20 for each element of L ^* , a ^* , and b ^* for each of the representative pixels Q _{1 to} Q ₉ and finishes the process.

1.3.6. Modified Example of Calculation of Background Point Correction Value As a modified example, when the size of the screen 30 is large, the background point may be selected according to the positions of the representative pixels Q _{1 to} Q ₉ . For example, the influence of the background point P ₁ (see FIG. 4) located above the screen 30 should be considered in the representative pixel Q ₂ (see FIG. 8A) located at the upper end of the screen 30, The representative pixel Q ₈ (see FIG. 8A) located at the lower end of 30 has a large background point distance, so there is no need to consider it. Therefore, an upper limit value _Dt of the background point distance is provided, and when the background point distance exceeds _Dt , the calculation of the background point correction value is not performed, and the calculation according to Equation 7 is performed only when the upper limit value _Dt is not exceeded. May be performed.

Instead of the total number S of background points, the number of background points S ₁ (Equation (15)), S ₂ (Equation (16)), S, used for each element of L ^* , a ^* , b ^* ₃ (Formula (17)) may be used.

Further, in consideration of the color field, weighting C ₁ , C ₂ , and C ₃ (C _{1 to} C ₃ are constants) may be performed for each element of L ^* , a ^* , and b ^* as shown in Equation 8.

Similarly, considering the color field of view, upper limit values D _t1 , D _t2 , D _t3 of background point distances are provided for each element of L ^* , a ^* , b ^* , and the background point distances are upper limit values D _{t1 to} D _{t. When t3} is exceeded, the background point correction value is not calculated, and the calculation may be performed according to Equation 2 only when the upper limit value is not exceeded. In these modified examples, the method for calculating the parameters follows Equation 6.

1.4. Color correction method (parameter calculation procedure)
FIG. 5 is a diagram illustrating a color correction method according to the first embodiment. The procedure until the parameter 112 is calculated by the above calculation is shown.

The color correction system 1 acquires the ambient color information 110 by the ambient color acquisition unit 10. Specifically, an image including the background of the display unit 2 is acquired and output (S2). Then, the color correction system 1 performs a parameter calculation step for calculating the parameter 112 based on the ambient color information 110 (S4). The color correction system 1 outputs the parameters of the elements of L ^* , a ^* , and b ^* for all the representative pixels Q _{1 to} Q ₉ (see FIG. 8A) and ends the process (S20).

In the parameter calculation step S4, first, which representative pixel is to be calculated is set (S6). Then, which element is to be calculated is set (S8). Then, the parameter calculation S10 is performed for the set element of the set representative pixel. Parameter calculation S10, all the elements ^{(L *, a *, b} *) is performed on (S12), is performed for all the representative pixel _Q 1 ~Q ₉ (S14). For example, the representative pixel _{Q 1,} if ^{the b *} parameter calculation S10 is not running (S12N), performs parameter calculation S10 in ^{b *} returns to S8. Then, the representative pixel Q _1, in the case (S12Y) where the parameters of all elements obtained, if the representative pixels not been calculated yet parameter performs a parameter calculation S10 (S14n), otherwise if parameter calculating step The process of S4 is terminated (S14Y).

FIG. 6 is a diagram illustrating a procedure of the parameter calculation S10. In the parameter calculation S10, a parameter of one element (L ^* , a ^* , or b ^* ) of the set representative pixel Q is calculated. First, the parameter calculation means 12 sets the calculation target range 40 according to the element (S102). The calculation target range 40 may be changed for each element in consideration of the color field of view, or may be common to all elements.

  The parameter calculation means 12 sets one background point to be calculated and acquires background color information (S104). Then, the distance between the background point and the set representative pixel (background point distance) is calculated by Equation 1 (S106). The parameter calculation means 12 calculates a background point correction value by calculation based on the background color information and the background point distance (S108). Here, Equation 2 is used.

  This calculation is performed for all background points (S110). If there is a background point for which no background point correction value has been obtained, the process returns to S104 and the calculation is repeated (S110N). When background point correction values are obtained for all background points (S110Y), parameters are calculated according to Equation 6 (S112).

2. Second Embodiment A second embodiment of the present invention will be described with reference to FIGS.

2.1. Configuration of Color Correction System FIG. 7 is a block diagram of a color correction system 1A according to this embodiment. The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

Unlike the color correction system 1 of FIG. 1, the color correction system 1 </ b> A includes color correction means 20 and outputs correction data 120. The color correction system 1A may include a storage unit 14 as in the present embodiment. The storage unit 14 stores specific color information 114 relating to colors for which the color correction unit 20 performs exceptional processing. The color correction unit 20 generates correction data 120 obtained by adding a correction amount based on the parameter 112 to the input image data 100. At this time, the correction amount may be adjusted based on the specific color information 114. The parameter calculation means 12 of this embodiment also outputs the parameters 112 for the representative pixels Q _{1 to} Q ₉ to the color correction means 20 as in the first embodiment. The process up to the calculation of the parameter 112 is the same as in the first embodiment, and a description thereof will be omitted.

2.2. Color Correction Unit The color correction unit 20 corrects each pixel of the input image data 100. In this embodiment, parameters are obtained for the elements of L ^* , a ^* , b ^* . Therefore, for example, the input image data 100 input in the YUV format is converted into an expression in the L ^* a ^* b ^* color system. Then, after the color correction unit 20 calculates the correction amount and performs the calculation process, it is converted again into correction data 120 such as YUV format and then output to the display unit 2.

2.2.1. Parameter Interpolation Processing The color correction unit 20 acquires the parameters 112 for the representative pixels Q _{1 to} Q ₉ . Of the input image data 100, parameters of pixels other than the representative pixels Q _{1 to} Q ₉ are created from these parameters by interpolation processing. The L ^* a ^* b ^* color system has perceptual uniformity and approximates human vision. In other words, when the value changes, the change is equal to the visual change felt by humans. Therefore, the color correction unit 20 of the present embodiment performs linear interpolation to calculate parameters for arbitrary pixels of the input image data 100.

FIG. 8A to FIG. 8B are diagrams for explaining the interpolation processing. FIG. 8A illustrates representative pixels Q _{1 to} Q _{9 on} the screen 30 and a pixel q for which the color correction unit 20 is to obtain a parameter. The Cartesian coordinates xy are used to specify the positions of these pixels. In order to distinguish from the orthogonal coordinates used for the ambient color information 110 in the description of the parameter calculation, lowercase letters x and y are used.

In FIG. 8A, the pixel q is included in an area formed by the representative pixels Q ₅ , Q ₆ , Q ₉ , and Q ₈ , and the coordinates are represented by (x _q , y _q ). In this embodiment, linear interpolation is performed by using the nearest four representative pixels. Therefore, the representative pixels used for calculating the parameter of the pixel q are Q ₅ , Q ₆ , Q ₈ , and Q ₉ . A rectangular area formed by the four representative pixels is expressed as a divided area. In the example of FIG. 8A, the screen 30 includes four divided areas.

  The color correction unit 20 represents the position of the pixel q in the divided area as a ratio in each of the x direction and the y direction as shown in FIG. That is, u and v in FIG.

Then, using the parameters in the representative pixels Q ₅ , Q ₆ , Q ₈ , and Q ₉ , the parameters δL ^* _q , δa ^* _q , and δb ^* _q of the pixel q are calculated as in Expression 10.

Even when the pixel q is the representative pixels Q _{1 to} Q ₉ , the parameter follows Formula 10. For example, when the pixel q is _{Q 9} is ^{u = v = 1, δL *} q = δL * Q9, δa * q = δa * Q9, δb * q = δb * Q9 is obtained.

2.2.2. Correction amount coefficient The correction amount of the pixel q is expressed as a function of the obtained parameter. The function is, for example, an Nth order polynomial in which N is a natural number, and a suitable numerical value is selected according to the color space. In this embodiment, an L ^* a ^* b ^* color system having perceptual uniformity is used, and correction amounts ΔL ^* _q , Δa ^* _q , and Δb ^* _q are parameters δL ^* _q , δa ^* _q , and δb ^*. It may be a linear expression of _q . As another example, it is preferable to use a quadratic expression when dealing with a color space in YUV format in which changes in human vision and numerical values are not equal.

The color correction means 20 of the present embodiment uses the correction values L ^* _q ′, a ^* _q ′, b ^* _q ′ according to Equation 11 from the values L ^* _q , a ^* _q , b ^* _q of the input image data 100 of the pixel q. Ask for.

Here, K _1q , K _0q , M _1q , M _0q , N _1q , and N _0q are coefficients of a linear expression representing the correction amount in the pixel q. For example, the initial values may be K _1q = M _1q = N _1q = 1, K _0q = M _0q = N _0q = 0, and adjustment may be performed according to the characteristics of the input image data 100, the characteristics of the pixel q, and the like. Good.

2.2.2.1. Adjustment of Coefficient by Dispersion In this embodiment, if the input image data 100 is a complex image, a small coefficient is set because the influence of the contrast phenomenon is not noticeable. Conversely, if the input image data 100 is a simple image, a large coefficient is set. Specifically, the variance is obtained from all the pixels of the input image data 100 or a part of the sampled pixels. If the average number in the input image data 100 is L ^* _avg and the number of pixels sampled is n, the variance s ² is expressed by Equation 12.

Then, K _1q = M _1q = N _1q = α / s ² . Here, α is an appropriate constant. It is not necessary to adjust other coefficients.

2.2.2.2. Adjustment of coefficient by comparison with background color For example, if the pixel q and the background are exactly the same color, the correction amount may be zero. Therefore, the colors of the pixel q and the background are compared, and if the difference is 0, no correction is performed. This adjustment may be performed element by element (L ^* , a ^* , or b ^* ). Specifically, adjustment by a DoG (Difference of Gaussian) function may be added to each of K _1q , M _1q , and N _1q . The DoG function is defined as DoG (t) = G (t + δt) −G (t) using the Gaussian function G, and the value becomes 0 at t = 0. Therefore, the value may be obtained by assigning the difference to t.

2.2.2.3. Exception Processing Using Specific Color Information When the specific color information 114 stored in the storage unit 14 matches the color information of the pixel q, exception processing without correction may be performed. That is, when the pixel q matches the specific color information _114, and _{K 1q = K 0q = M 1q} = M 0q = N 1q = N 0q = 0. As a psychological effect, the memory color is felt with more emphasized features than the color actually seen. For example, such effects are likely to occur in the face of a person or the color of the sky or the sea. Therefore, it is possible to perform more appropriate image display by registering the assumed memory color in the storage unit 14 in advance and making it an object of such exception processing.

  In the present embodiment, all the adjustments of the above coefficients are performed, but only a part of the adjustments may be performed or the adjustments may not be performed.

2.2.3. Generation of Correction Data The color correction unit 20 of the present embodiment generates original correction data for each element of L ^* , a ^* , and b ^* according to Equation 11 for each pixel of the input image data 100. Then, the correction data 120 obtained by converting the obtained data into the YUV format again is output to the display unit 2.

2.3. Color correction method (correction data generation procedure)
FIG. 9 is a diagram illustrating a color correction method according to the second embodiment. The procedure until the generation of correction data by the above calculation is shown. Note that the procedure (S2, S4) until the parameter 112 is calculated is the same as in the first embodiment, and a description thereof is omitted.

In the color correction system 1A, the correction data generation step S16 is performed after the color correction unit 20 acquires the parameters 112 of the representative pixels Q _{1 to} Q ₉ . Then, the obtained correction data 120 is output to the display unit 2 and the process is terminated (S62).

In the correction data generation step S16, color space conversion processing of input image data is first performed (S30). In this embodiment, input image data input in the YUV format is converted into an L ^* a ^* b ^* color system.

Then, a target pixel for generating correction data is set (S34), and which element is to be calculated is set (S36). Then, correction data for the set element of the set pixel is calculated (S40). The correction data calculation S40 is performed for all elements (L ^* , a ^* , b ^* ) (S42), and is performed for all the pixels of the input image data (S44). For example, when the b ^* correction data calculation S40 is not performed for the pixel q (S42N), the process returns to S36 and the b ^* correction data calculation S40 is performed. Then, when correction data of all the elements is obtained for the pixel q (S42Y), if there is a pixel for which correction data has not yet been calculated, a correction data calculation S40 is performed (S44N), otherwise it is obtained. The color space of the original correction data is converted (S44Y, S60).

FIG. 10 is a diagram showing the procedure of the correction data calculation S40. In the correction data calculation S40, correction data of one element (L ^* , a ^* , or b ^* ) of the set pixel q is generated. First, four representative pixels close to the pixel q are selected and their parameters are acquired (S402). Then, the parameter of the pixel q is calculated by linear interpolation (see FIG. 8B). In the present embodiment, the correction amount is expressed by a linear expression of the parameter (S404).

  Then, the coefficient of the linear expression is adjusted. The coefficient may be adjusted depending on whether the image of the input image data 100 is complicated. Therefore, all the pixels or some of the pixels of the input image data 100 are sampled to obtain the variance and make adjustment (S406). If the pixel q and the background are exactly the same color, the correction amount may be zero. Therefore, the coefficient of the linear expression is adjusted based on the color difference value between the pixel q and the background (S408). Then, an exception process may be performed on a memory color in which the feature is emphasized more than the actually viewed color. When the specific color information 114 stored in the storage unit 14 matches the color information of the pixel q, the coefficient is adjusted so that the correction amount becomes 0 (S410). Then, correction data obtained by adding the obtained correction amount to the original data is generated (S412).

  In this way, in the color correction system 1A, the obtained correction data 120 undergoes the color space conversion process (S60) and is output to the display unit 2 (S62), and the process ends. When correction is performed in the YUV format, the color space conversion process is not required (S30, S60), and the correction amount expression of the correction data calculation S40 is expressed by a quadratic expression. Even in this case, the procedure for obtaining correction data by adjusting the coefficient is the same.

  The present invention is not limited to these exemplifications, and includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 1 ... Color correction system, 1A ... Color correction system, 2 ... Display part, 10 ... Ambient color acquisition means, 20 ... Color correction means, 12 ... Parameter calculation means, 14 ... Memory | storage means, 30 ... Screen, 40 ... Calculation object range , 100 ... Input image data, 120 ... Correction data, 112 ... Parameters, 110 ... Ambient color information, 114 ... Specific color information, 810 ... Television receiver, 811 ... Wall, 812 ... Window, 813 ... Curtain, 814 ... Indoor light , 815 ... foliage plant, 820 ... image appreciation point, 1000 ... test image, 1001 ... test image, 1002 ... test image, 1003 ... test image

Claims (13)

A color correction system for displaying an image based on correction data obtained by correcting the display color of input image data on a display unit,
Ambient color acquisition means for acquiring ambient color information that is color information of an image around the display unit;
Parameter calculating means for calculating parameters necessary for correcting the display color of the input image data based on the ambient color information,
The parameter calculation means is
A color correction system for performing a parameter calculation for obtaining the parameter for a given pixel of the input image data based on the position information of the pixel and the surrounding color information. The color correction system according to claim 1.
The parameter calculation means is
In the parameter calculation,
A calculation target range is determined for an image around the display unit,
For background points that are pixels within the calculation target range, obtain background color information that is color information from the surrounding color information,
For each background point included in the calculation target range, calculate a background point correction value based on the background point distance and the background color information, which is the distance between the given pixel and the background point,
The color correction system which calculates | requires the said parameter based on the sum total of the background point correction value about all the background points included in the said calculation object range. The color correction system according to claim 2,
The parameter calculation means is
For representative pixels that are part of the pixels of the input image data, the parameter calculation is performed as the given pixel,
The color correction system which calculates | requires a parameter by the calculation based on the parameter of the said representative pixel about the pixel which is not the said representative pixel among the pixels of the said input image data. The color correction system according to claim 3.
The color correction system, wherein at least one of the number and coordinates of the representative pixels is determined based on a screen size of the display unit. The color correction system according to any one of claims 2 to 4,
The parameter calculation means is
A color correction system that defines the calculation target range for each element of the given color space. The color correction system according to any one of claims 1 to 5,
A color correction system comprising color correction means for generating correction data in which the parameter is a correction amount and the correction amount is added to the input image data. The color correction system according to any one of claims 1 to 5,
Color correction means for creating the correction data based on the parameters,
The color correction means includes
Generating correction data by adding a correction amount represented by a function of the parameter to the input image data;
A color correction system that adjusts the function or its coefficient for each pixel of the input image data based on color information of the pixel and the background color information. The color correction system according to claim 7.
Including storage means for storing specific color information which is information of a color designated in advance;
The color correction means includes
A color correction system that adjusts the function or its coefficient based on the specific color information. The color correction system according to any one of claims 7 to 8,
The color correction means includes
A variance value is obtained for color information of some or all pixels of the input image data,
When the variance value is large, the function or its coefficient is adjusted so that the correction amount is small, and when the variance value is small, the function or its coefficient is adjusted so that the correction amount is large, Color correction system. The color correction system according to any one of claims 1 to 9,
The parameter calculation means is
^{L *} a ^* b ^* L in color system ^*, a *, ^{b *} components performing the parameter calculation for each of the color correction system. The color correction system according to any one of claims 1 to 9,
The given color space is
The parameter calculation means is
A color correction system that performs the parameter calculation for each of Y, U, and V elements in the YUV format. A program for performing color correction for displaying an image based on correction data obtained by correcting the display color of input image data on a display unit,
Ambient color acquisition means for acquiring ambient color information that is color information of an image around the display unit;
A parameter calculation means for calculating parameters necessary for correcting the display color of the input image data based on the ambient color information, and causing the computer to function;
The parameter calculation means is
A program for performing a parameter calculation for a given pixel of the input image data based on position information of the pixel and the surrounding color information to obtain the parameter. A color correction method for displaying an image based on correction data obtained by correcting the display color of input image data on a display unit,
An ambient color acquisition step of acquiring ambient color information that is color information of an image around the display unit;
A parameter calculation step for calculating a parameter necessary for correcting the display color of the input image data based on the ambient color information,
In the parameter calculation step,
A color correction method for performing a parameter calculation for obtaining the parameter for a given pixel of the input image data based on position information of the pixel and the surrounding color information.