JP2008235981A - 7-axis color correction device and method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color correction device capable of reducing capacity of a memory in an LUT. <P>SOLUTION: The color correction device includes: a color correction data generating circuit 104 for generating color correction data for correcting each of color components of white, red, green, blue, yellow, sky blue and violet; a lookup table for storing the correcting data generated in the color correction data generating circuit 104. The device has a 7-axis color correction circuit 106 for executing color correction based on the lookup table for an input video signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a color correction apparatus that is mounted on a video device that displays or outputs a video signal and that performs color correction on the video signal so that the color of the video that is displayed or output becomes a designated color.

  Lookup tables (LUT) are often used for color correction of digital video signals. In color correction using an LUT, correction data for converting an input video signal into a target color is written in the LUT, and the input video signal is converted using the LUT. When color correction is performed on video signals of three colors of red (R), green (G), and blue (B), correction data (luminance data) corresponding to each of the R signal, G signal, and B signal is generally stored. A three-dimensional LUT is used.

Patent Document 1 describes a data conversion method using a three-dimensional LUT. In this data conversion method, a three-dimensional (XYZ) color space is divided into cubes made up of a plurality of grid points, and each of the three-dimensional LUTs storing color correction values at each grid point of the cube is used. Interpolates input values at grid points.
JP 2004-341765 A

  However, in the method of performing color correction using the three-dimensional LUT as described above, the three-dimensional LUT is configured to store the color correction value for each lattice point of the cube, and thus requires an enormous memory. To do. For example, when each of the R signal, the G signal, and the B signal is a 10-bit signal, a memory capacity of about 3 G (= 1024 × 1024 × 1024 × 3) bits is required to create a three-dimensional LUT. Thus, since a large-capacity memory is required, the cost of the color correction apparatus increases.

  An object of the present invention is to provide a low-cost color correction apparatus that can solve the above problems and reduce the memory capacity required for the LUT.

In order to achieve the above object, the color correction apparatus of the present invention provides:
A color correction device that receives a video signal including first, second, and third signals indicating red, green, and blue components, respectively, and corrects the color of an image that is generated based on the video signal. ,
Correction data for correcting the white component, yellow component, light blue component, and purple component is generated for each of the first to third signals, and the red component is corrected for the first signal. For the second signal, correction data for correcting the green component is generated, and correction data for correcting the blue component is corrected for the third signal. A color correction data generation circuit to be generated;
A lookup table for storing correction data generated by the color correction data generation circuit, wherein the first to third signals are input, and the lookup for the first to third signals; A 7-axis color correction circuit for performing color correction based on the table,
The color correction data generation circuit generates the white component correction data based on the specified white component value and the characteristic defining the change in brightness of the white component, and the specified white component Create correction data for each color component based on the characteristics defining the change in saturation or hue from the component value to each color of the red component, green component, blue component, yellow component, light blue component and purple component,
The seven-axis color correction circuit is
Performing color correction based on the white component correction data for each of the first to third signals;
For each of the first to third signals subjected to color correction of the white component, color correction is performed based on correction data for the yellow component, light blue component, and purple component,
For the first signal subjected to color correction of the white component, color correction based on the correction data for the red component is performed,
For the second signal subjected to color correction of the white component, color correction based on the correction data of the green component is performed,
For the third signal subjected to color correction of the white component, color correction based on the blue component correction data is performed,
A fourth signal based on the signal corrected for each color of the red component, yellow component and purple component, a fifth signal based on the signal corrected for each color of the green component, yellow component and light blue component, and the blue color A signal including a sixth signal based on a signal subjected to color correction of each of the component, the light blue component, and the purple component is output as the video signal.

  In the present invention, the 7-axis color correction circuit performs color correction based on correction data relating to each color of the white component, red component, green component, blue component, yellow component, light blue component, and purple component, Three-dimensional color correction using a three-dimensional LUT is not performed. In the 7-axis color correction circuit, color correction is performed based on the correction data for each color, so the look-up table (LUT) has a white component, a red component, a green component, a blue component, a yellow component, a light blue component, and a purple component. 7 LUTs (W correction LUT, R correction LUT, G correction LUT, B correction LUT, Y correction LUT, M correction LUT, C correction LUT) each storing correction data for each color of Can be configured.

  Correction data for each color of the white component, yellow component, light blue component, and purple component is created for each of the first signal (R signal), the second signal (G signal), and the third signal (B signal). Accordingly, the W correction LUT, the Y correction LUT, the C correction LUT, and the M correction LUT are all configured by three LUTs.

  Red component correction data is created only for the first signal (R signal), green component correction data is created only for the second signal (G signal), and blue component correction data is the third signal (B signal). Signal R), the R correction LUT, the G correction LUT, and the B correction LUT are all configured by one LUT.

  According to the above configuration, the memory capacity required for the LUT constituting the 7-axis color correction circuit is as follows: W correction LUT, R correction LUT, G correction LUT, B correction LUT, Y correction LUT, M The memory capacities of the correction LUT and the C correction LUT are added. For example, when each RGB signal is 10-bit digital data, the memory capacity of the LUT that constitutes the 7-axis color correction circuit is about 15 kbits. On the other hand, the memory capacity required for the LUT in the case of performing the three-dimensional color correction by the three-dimensional LUT is about 3 Gbits.

  In addition, the color correction data generation circuit creates correction data for the white component based on the specified value of the white component and the characteristic that defines the change in brightness of the white component, and the red component ( R), green color component (G), blue color component (B), yellow color component (Y), light blue color component (C) and purple color component (M) based on the characteristics defining the change in saturation or hue to each color, Correction data for each color component is created. As a result, it is possible to perform color correction for each color of RGBCMY based on the change in brightness from all black to all white.

  According to the present invention, it is possible to reduce the memory capacity required for the LUT as compared with the one that performs three-dimensional color correction using a three-dimensional LUT, thereby reducing the cost of the apparatus.

  Next, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing the configuration of the color correction apparatus according to the first embodiment of the present invention.

  Referring to FIG. 1, the color correction apparatus is mounted on a video device that displays or outputs a video signal, and its main parts are a matrix conversion circuit 104, a color correction data generation circuit 105, and a seven-axis color correction. A circuit 106 is provided.

  The three terminals of the input terminal 101 to which the R signal is supplied, the input terminal 102 to which the G signal is supplied, and the input terminal 103 to which the B signal is supplied are the matrix conversion circuit 104 and the 7-axis color correction circuit 106, respectively. Connected to the input. Here, the R signal, the G signal, and the B signal are signals corresponding to the three primary colors (RGB). A video signal is formed by these R, G, and B signals.

  The matrix conversion circuit 104 converts the R signal, the G signal, and the B signal input through the input terminals 101 to 103 into an X signal, a Y signal, and a Z signal representing tristimulus values, respectively.

  In general, RGB signals of the three primary colors can be converted into XYZ signals that are tristimulus values by 3 × 3 matrix conversion (conversion from RGB to XYZ). Usually, the following formula 1 is applied to the conversion from the RGB system to the XYZ system.

When displaying video in sRGB,
R ₁ = 0.412424
R ₂ = 0.212656
R ₃ = 0.0193324
G ₁ = 0.357579
G ₂ = 0.715158
G ₃ = 0.119193
B ₁ = 0.180464
B ₂ = 0.0721856
B ₃ = 0.950444
It is. In this case, X is the red component intensity, Y is the sum of the green component intensity and the luminance component of the video signal, and Z is the blue component intensity.

  Conversely, XYZ signals can be converted into RGB signals of the three primary colors by matrix conversion (conversion from XYZ system to RGB system). Usually, the following formula 2 is applied to the conversion from the XYZ system to the RGB system.

When displaying video in sRGB,
X ₁ = 3.24071
X ₂ = -0.969258
X ₃ = 0.0556352
Y ₁ = -1.53726
Y ₂ = 1.87599
Y ₃ = -0.203996
Z ₁ = -0.498571
Z ₂ = 0.0415557
Z ₃ = 1.05707
It is.

  The X signal, Y signal, and Z signal output from the matrix conversion circuit 104 are supplied to the color correction data generation circuit 105.

  The color correction data generation circuit 105 includes XYZ values for white (W), red (R), green (G), blue (B), yellow (Y), purple (M), and light blue (C). A value (XYZ designated value) designating each value is supplied from the external control unit. The external control unit may be a control unit (CPU) of the video equipment main body or a control unit of an external device (such as a personal computer) connected to the video equipment. For example, when the user sets XYZ values of desired color temperatures for each color of W, R, G, B, Y, M, and C through the operation unit of the video device, the control unit ( CPU) supplies the set value to the color correction data generation circuit 105 as a specified value.

  The color correction data generation circuit 105 has W, R, G, B, Y, M, and C so that the values of the XYZ signals supplied from the matrix conversion circuit 104 are the color temperatures set by the user. Color correction data is generated for each of the colors. Specifically, the color correction data generation circuit 105 creates W correction data based on the W specification value and the characteristics defining the change in brightness of the white component, and R, Correction data for each color component is created on the basis of characteristics defining the saturation or hue change for each color of G, B, Y, M, and C.

  The correction data for each color of W, R, G, B, Y, M, and C is converted into RGB values, and the corresponding data in the look-up table (LUT) that constitutes the seven-axis color correction circuit 106. To the LUT of the color to be used.

  The seven-axis color correction circuit 106 has an LUT for correcting each color of W, R, G, B, Y, M, and C. FIG. 2 shows the configuration of the seven-axis color correction circuit 106.

  Referring to FIG. 2, the 7-axis color correction circuit 106 includes a W correction LUT 204, an R correction LUT 205, a G correction LUT 206, a B correction LUT 207, a Y correction LUT 208, a C correction LUT 209, an M correction LUT 210, adders 211 to 213, and a divider. 214-216.

  The W correction LUT 204 stores W correction data supplied from the color correction data generation circuit 105. The W correction LUT 204 receives R, G, and B signals from the input terminals 101 to 103, and performs color correction based on W correction data for each of the input R, G, and B signals. . The R signal, G signal, and B signal color-corrected by the W correction LUT 204 are supplied to the R correction LUT 205, the G correction LUT 206, and the B correction LUT 207, respectively.

  The R correction LUT 205 stores R correction data supplied from the color correction data generation circuit 105. The R correction LUT 205 performs color correction based on the R correction data for the R signal color-corrected by the W correction LUT 204. The R signal color-corrected by the R correction LUT 205 is supplied to the first input of the adder 211.

  The G correction LUT 206 stores G correction data supplied from the color correction data generation circuit 105. The G correction LUT 206 performs color correction based on the G correction data for the G signal color-corrected by the W correction LUT 204. The G signal color-corrected by the G correction LUT 206 is supplied to the first input of the adder 212.

  The B correction LUT 207 stores B correction data supplied from the color correction data generation circuit 105. The B correction LUT 207 performs color correction based on the B correction data for the B signal color-corrected by the W correction LUT 204. The B signal color-corrected by the B correction LUT 207 is supplied to the first input of the adder 213.

  The Y correction LUT 208 stores Y correction data supplied from the color correction data generation circuit 105. The Y correction LUT 208 receives the R signal, the G signal, and the B signal color-corrected by the W correction LUT 204, respectively, and performs color correction based on Y correction data for the input R signal, G signal, and B signal. I do. The signal whose color has been corrected by the Y correction LUT 208 is supplied to the third input of the adder 211 and the second input of the adder 212, respectively.

  The C correction LUT 209 stores C correction data supplied from the color correction data generation circuit 105. The C correction LUT 209 receives the R signal, G signal, and B signal color-corrected by the W correction LUT 204, and performs color correction based on C correction data for the input R signal, G signal, and B signal. I do. The signal color-corrected by the C correction LUT 209 is supplied to the third input of the adder 212 and the second input of the adder 213, respectively.

  The M correction LUT 210 stores M correction data supplied from the color correction data generation circuit 105. The M correction LUT 210 receives the R signal, the G signal, and the B signal color-corrected by the W correction LUT 204, and performs color correction based on the M correction data for the input R signal, G signal, and B signal. I do. The signal whose color has been corrected by the M correction LUT 210 is supplied to the second input of the adder 211 and the third input of the adder 213, respectively.

  Each of the adders 211 to 213 adds the first to third inputs. The divider 214 outputs a value obtained by dividing the output value of the adder 211 by 3. The divider 215 outputs a value obtained by dividing the output value of the adder 212 by 3. The divider 216 outputs a value obtained by dividing the output value of the adder 213 by 3. The output signal of the divider 214 is an R signal after color correction. The output signal of the divider 215 is a G signal after color correction. The output signal of the divider 216 is a B signal after color correction.

  Next, the operation of the color correction apparatus of this embodiment will be specifically described.

[Set XYZ values]
First, a procedure for setting XYZ designated values by the user will be described.

  FIG. 3 shows a system including the color correction apparatus shown in FIG. 1 and an external control unit. Referring to FIG. 3, the control unit 10 is an external control unit. An input unit 11 such as a keyboard (or operation panel), a display unit 12 such as an LCD, and a storage unit 13 that stores programs and data are connected to the control unit 10.

  The control unit 10 displays the chromaticity diagram on the display unit 12 based on the chromaticity diagram information stored in the storage unit 13, and based on the XYZ signals supplied from the color correction data generation circuit 105. The obtained chromaticity coordinates (or chromaticity points) are developed on the chromaticity diagram. A chromaticity diagram distribution is obtained by developing chromaticity coordinates on a chromaticity diagram. Here, the chromaticity coordinates are given by a ratio between the respective values of X, Y, and Z and the total value (sum) of X, Y, and Z. The chromaticity diagram is a two-dimensional coordinate system by x and y.

  FIG. 4 shows an example of an input image, and FIG. 5 shows an example of a chromaticity diagram distribution obtained based on the input image.

  Referring to FIG. 4, an image 401 is an image that has the highest saturation on the left side in the drawing and gradually changes to white as it goes to the right side. In the image 401, BK (black), R, G, B, Y, M, and C are arranged in order from the upper side, and each color changes to white.

  When an R signal, a G signal, and a B signal related to the image 401 are input to the matrix conversion circuit 104, the matrix conversion circuit 104 performs matrix conversion on the input R signal, G signal, and B signal to generate an X signal and a Y signal. , Z signal is output.

  The X signal, Y signal, and Z signal relating to the image 401 output from the matrix conversion circuit 104 are supplied to the control unit 10 via the color correction data generation circuit 105. The control unit 10 develops the chromaticity coordinates obtained based on the X signal, the Y signal, and the Z signal regarding the image 401 on the chromaticity diagram displayed on the display unit 12.

  The chromaticity diagram distribution of the image 401 thus obtained is the chromaticity diagram distribution shown in FIG. In FIG. 5, a chromaticity diagram 508 is a chromaticity diagram of a known two-dimensional coordinate system in which chromaticity coordinates are indicated by x and y (the ratio of tristimulus values X, Y, and Z is quantified as chromaticity x and y). 2 is a Yxy chromaticity diagram plotted on a two-dimensional coordinate system. A point 504 is positioned on a region showing white (gray) color near the center of the chromaticity diagram 508, and extends radially from the point 504 toward a region showing each color of G, Y, R, C, B, and M. Points 501, 502, 503, 505, 506 and 507 are located on the line, respectively. Here, points 501, 502, 503, 504, 505, 506, and 507 are chromaticity coordinate points (chromaticity points) indicating G, Y, R, W, C, B, and M, respectively.

  The G point 501, Y point 502, R point 503, W point 504, C point 505, B point 506, and M point 507 in the chromaticity diagram distribution shown in FIG. By moving each of these points, an x value and a y value for obtaining a desired color temperature are designated for each color of W, R, G, B, Y, M, and C.

  The user moves the point up / down / left / right on the chromaticity diagram 508 through the input unit 11. An instruction signal corresponding to the point movement is supplied from the input unit 11 to the control unit 10, and the control unit 10 moves a corresponding point on the chromaticity diagram displayed on the display unit 10 according to the instruction signal. By this operation, the user can move the point freely and specify the x value and the y value so as to obtain a desired color temperature for each color of W, R, G, B, Y, M, and C. can do.

[Create color correction data]
Next, a procedure for creating color correction data by the color correction data generation circuit 105 will be described.

  When the user designates a chromaticity coordinate point (x, y) that obtains a desired color temperature for each color of W, R, G, B, Y, M, and C, the control unit 10 designates the designated value of each color. (Chromaticity coordinate point) is supplied to the color correction data generation circuit 105. The color correction data generation circuit 105 generates color correction data for each color of W, R, G, B, Y, M, and C based on the specified value supplied from the control unit 10. Chromaticity coordinate points (chromaticity x, y) can be converted into tristimulus values X, Y, Z according to a known conversion formula.

  FIG. 6 is a diagram for explaining the relationship between the specified color value and the color correction data. In FIG. 6, a chromaticity diagram 608 corresponds to the chromaticity diagram 508 shown in FIG. G point 601, Y point 602, R point 603, W point 604, C point 605, B point 606, and M point 607 are chromaticity coordinate points designated by the user. The color correction data generation circuit 105 is based on the G point 601, the Y point 602, the R point 603, the W point 604, the C point 605, the B point 606, and the M point 607. The correction data stored in is created.

  Here, the configuration of the LUT constituting the seven-axis color correction circuit 106 will be described. FIG. 7 shows an example of an LUT that constitutes the seven-axis color correction circuit 106 when the video signal is 10-bit width digital data.

  Referring to FIG. 7, the LUT 301 is a memory in which an address input is a video input and an output is a data output. The address ranges from “0” to “1023”, and correction data is stored for each address. According to the LUT 301, the video signal (digital data) is converted according to the correction data. For example, when correction data “0” is stored for address “0”, when “0” is input to the address input, the output is “0”. When correction data “2” is stored for address “1”, when “1” is input to the address input, the output is “2”. When correction data “4” is stored for address “2”, when “2” is input to the address input, the output data is “4”.

  In the seven-axis color correction circuit 106 shown in FIG. 2, the W correction LUT 204, the Y correction LUT 208, the C correction LUT 209, and the M correction LUT 210 all have three RGB inputs. With the LUT shown. That is, each of these LUTs 204 and 208 to 209 includes three LUTs for the R input system, the G input system, and the B input system. On the other hand, the R correction LUT 205, the G correction LUT 206, and the B correction LUT 207 all have one system, and therefore have one LUT shown in FIG.

  Based on the G point 601, the Y point 602, the R point 603, the W point 604, the C point 605, the B point 606, and the M point 607, the color correction data generation circuit 105 performs W, R, G, B, Y, Data for correcting each color of M and C is created.

(1) W correction data:
The W correction data is created based on the value (specified value) of the chromaticity coordinate point (x, y) of the W point 604. Specifically, since the W correction LUT 204 includes three LUTs for the R input system, the G input system, and the B input system, the W correction data is created for each LUT.

  A procedure for creating correction data stored in the R input system LUT will be described below.

  First, an X value, a Y value, and a Z value are obtained from the value of the chromaticity coordinate point (x, y) of the W point 604. The X value is used as stored data at the address “1023”. The stored data of addresses “0” to “1022” is determined based on characteristic data that prescribes a change from black to white.

  For conversion from chromaticity x, y to tristimulus values X, Y, Z (conversion in Yxy chromaticity diagram), the following equations 3 and 4 are applied.

The characteristic data is characteristic data obtained by preliminarily defining the magnitude of the change from black to white in the image 401 shown in FIG. The upper limit value (white) of this characteristic data, that is, the stored data at the address “1023” is the X value obtained from the W point 604, and the stored data from the address “0” to the address “1022” which is the lower limit value (black). calculate. The correction data calculated in this way is converted into correction data relating to the R value by the above-described equation 2.

  The correction data stored in the G input system LUT and the B input system LUT are also created in the same procedure as the correction data stored in the R input system LUT. However, the correction data of the G input system LUT is created as the Y value obtained from the stored data at the address “1023” from the W point 604. The correction data of the B input system LUT is created as the Z value obtained from the stored data at the address “1023” from the W point 604.

  In this way, calculation is performed from brightness 0 to 1023 so as to conform to the XYZ specified value, the XYZ value at resolution 1024 is calculated, and the calculated value is converted into the RGB value using the above-described equation 2. By converting, correction data relating to each value of RGB is created.

(2) R correction data:
The R correction data is created based on the W point 604 and the R point 603. Since the R correction LUT 205 includes one LUT shown in FIG. 7, R correction data is created for one LUT.

  A procedure for creating R correction data will be described below.

  First, an X value, a Y value, and a Z value are obtained from the value of the chromaticity coordinate point (x, y) of the W point 604. Further, the X value, the Y value, and the Z value are obtained from the value of the chromaticity coordinate point (x, y) of the R point 603. The X value is used as stored data at the address “1023”. The stored data of addresses “0” to “1022” is determined based on characteristic data that prescribes a change from red to white.

  The characteristic data is characteristic data obtained by preliminarily specifying the magnitude of the change from red to white in the image 401 shown in FIG. 4 with an X value. More specifically, the characteristic data is the chromaticity shown in FIG. This is characteristic data defining a straight line (or a curve) connecting the W point 604 and the R point 603 on the diagram distribution. The upper limit value (white) of this characteristic data, that is, the stored data at the address “1023” is the X value obtained from the W point 604, and the lower limit value (red), that is, the stored data at the address “0” is obtained from the R point 603. The stored data from the address “1” to the address “1022” is calculated using the obtained X value. Here, the stored data from address “1” to address “1022” is located on a straight line (or curve) connecting W point 604 and R point 603. The correction data calculated in this way is converted into correction data relating to the R value using the above-described equation 2.

(3) G correction data:
The G correction data is created based on the W point 604 and the G point 601. The G correction data is also created in the same procedure as the R correction data, but characteristic data defining a straight line (or a curve) connecting the W point 604 and the G point 601 is used as the characteristic data. Then, the storage data at the address “1023” that is the upper limit (white) is the Y value obtained from the W point 604, and the storage data at the address “0” that is the lower limit (green) is obtained from the G point 601. As the Y value, the storage data from the address “1” to the address “1022” is calculated. Here, the stored data from address “1” to address “1022” is located on a straight line (or curve) connecting W point 604 and G point 601. The correction data calculated in this way is converted into correction data relating to the G value using the above-described equation 2.

(4) B correction data:
B correction data is created based on the W point 604 and the B point 606. The B correction data is also created in the same procedure as the R correction data, but characteristic data defining a straight line (or a curve) connecting the W point 604 and the B point 606 is used as the characteristic data. The storage data at the address “1023” that is the upper limit (white) is taken as the Z value obtained from the W point 604, and the storage data at the address “0” that is the lower limit (blue) is obtained from the B point 606. As the Z value, the storage data from the address “1” to the address “1022” is calculated. Here, the stored data from address “1” to address “1022” is located on a straight line (or curve) connecting W point 604 and B point 606. The correction data calculated in this way is converted into correction data relating to the B value using the above-described equation 2.

(5) Y correction data:
The Y correction data is created based on the W point 604 and the Y point 602. The Y correction data is also created in the same procedure as the W correction data described above, but characteristic data defining a straight line (or a curve) connecting the W point 604 and the Y point 602 is used as the characteristic data.

  The correction data stored in the R input system LUT is stored in the address “1023” that is the upper limit value (white) of the characteristic data is the X value obtained from the W point 604, and is the address that is the lower limit value (yellow). Using the stored data “0” as the X value obtained from the Y point 602, the stored data from the address “1” to the address “1022” is calculated. Here, the stored data from address “1” to address “1022” is located on a straight line (or curve) connecting W point 604 and Y point 602. The correction data calculated in this way is converted into correction data relating to the R value using the above-described equation 2.

  The correction data stored in the G input system LUT and the B input system LUT are also created in the same procedure as the correction data stored in the R input system LUT. However, the correction data of the G input system LUT is created with the stored data at the address “1023” as the Y value obtained from the W point 604 and the stored data at the address “0” as the Y value obtained from the Y point 602. Is done. The correction data of the B input system LUT is created using the storage data at the address “1023” as the Z value obtained from the W point 604 and the storage data at the address “0” as the Z value obtained from the Y point 602. .

(6) M correction data:
The M correction data is created based on the W point 604 and the M point 607. The M correction data is also created in the same procedure as the Y correction data, but characteristic data defining a straight line (or a curve) connecting the W point 604 and the M point 607 is used as the characteristic data.

(7) C correction data:
The C correction data is created based on the W point 604 and the C point 605. The C correction data is also created in the same procedure as the Y correction data, but characteristic data defining a straight line (or a curve) connecting the W point 604 and the C point 605 is used as the characteristic data.

  As described above, by creating correction data stored in each LUT constituting the seven-axis color correction circuit 106, color management by XYZ from all black to all white becomes possible.

[Color correction processing]
Next, the procedure of color correction processing by the seven-axis color correction circuit 106 will be described.

  When the video signal is input to the 7-axis color correction circuit 106, the 7-axis color correction circuit 106 first performs color correction based on the W correction data in the W correction LUT 204. Specifically, the R input system LUT, the G input system LUT, and the B input system LUT constituting the W correction LUT 204 respectively convert the R signal, the G signal, and the B signal supplied as video signals into color correction data. Color correction is performed in accordance with the correction data stored by the generation circuit 105.

  The R signal color-corrected by the R input system LUT of the W correction LUT 204 is supplied to the R correction LUT 205, the Y correction LUT 208, the C correction LUT 209, and the M correction LUT 210. The G signal color-corrected by the G input system LUT of the W correction LUT 204 is supplied to the G correction LUT 206, Y correction LUT 208, C correction LUT 209, and M correction LUT 210. The B signal color-corrected by the B input system LUT of the W correction LUT 204 is supplied to the B correction LUT 207, the Y correction LUT 208, the C correction LUT 209, and the M correction LUT 210.

  Next, the R correction LUT 205, the G correction LUT 206, the B correction LUT 207, the Y correction LUT 208, the C correction LUT 209, and the M correction LUT 210 perform color correction on the RGB signals supplied from the W correction LUT 204.

  The R correction LUT 205 performs color correction based on the correction data stored by the color correction data generation circuit 105 on the R signal supplied from the W correction LUT 204. The R signal subjected to color correction by the R correction LUT 205 is supplied to the first input of the adder 211.

  In the G correction LUT 206, color correction based on the correction data stored by the color correction data generation circuit 105 is performed on the G signal supplied from the W correction LUT 204. The G signal that has undergone color correction by the G correction LUT 206 is supplied to the first input of the adder 212.

  The B correction LUT 207 performs color correction based on the correction data stored by the color correction data generation circuit 105 on the B signal supplied from the W correction LUT 204. The B signal that has undergone color correction by the B correction LUT 207 is supplied to the first input of the adder 213.

  In the Y correction LUT 208, the R input system LUT, the G input system LUT, and the B input system LUT are supplied from the W correction LUT 204 by the color correction data generation circuit 105. Color correction is performed according to the stored correction data. The Y correction LUT 208 outputs a signal obtained by adding the R signal, G signal, and B signal subjected to color correction in the R input system LUT, the G input system LUT, and the B input system LUT. The output of the Y correction LUT 208 is supplied to the third input of the adder 211 and the second input of the adder 212.

  In the C correction LUT 209, the R input system LUT, the G input system LUT, and the B input system LUT are supplied from the W correction LUT 204 by the color correction data generation circuit 105. Color correction is performed according to the stored correction data. The C correction LUT 209 outputs a signal obtained by adding the R signal, the G signal, and the B signal subjected to color correction by the R input system LUT, the G input system LUT, and the B input system LUT. The output of the C correction LUT 209 is supplied to the third input of the adder 212 and the second input of the adder 213.

  In the M correction LUT 210, the R input system LUT, the G input system LUT, and the B input system LUT respectively receive the R signal, the G signal, and the B signal supplied from the W correction LUT 204 by the color correction data generation circuit 105. Color correction is performed according to the stored correction data. The M correction LUT 210 outputs a signal obtained by adding the R signal, the G signal, and the B signal subjected to color correction by the L input system LUT, the G input system LUT, and the B input system LUT. The output of the C correction LUT 210 is supplied to the third input of the adder 213 and the second input of the adder 211.

  Next, each of the adders 211 to 213 adds the signals supplied to the first to third inputs. Addition processing by the adders 211 to 213 is based on the following principle.

  The color points next to the R point 603 are the Y point 602 and the M point 607. Therefore, in order to correct the color of the R signal, the YM color adjacent to the R color is referred to. For the same reason, the color of the CY adjacent to the G color is referred to correct the color of the G signal, and the color of the MC adjacent to the B color is referred to correct the color of the B signal. Based on this principle, correction for each color of RGBCMY becomes possible.

  The output of the adder 211 is supplied to the divider 214, the output of the adder 212 is supplied to the divider 215, and the output of the adder 213 is supplied to the divider 216.

  Finally, the dividers 214 to 216 perform 1/3 processing on the outputs of the adders 211 to 213. The outputs of the dividers 214 to 216 are RGB signals after color correction.

  The color correction apparatus according to the present embodiment is configured to perform correction related to W (gray), which is a white component, in advance, and then correct each color of RGBCMY. With this configuration, it is possible to correct each color of RGBCMY from all black to all white.

  According to the color correction apparatus of the present embodiment, for example, when each RGB signal is 10-bit digital data, the memory capacity of the LUT constituting the seven-axis color correction circuit 106 is about 15 kbits. . Here, the memory capacities of the W correction LUT 204, the Y correction LUT 208, the C correction LUT 209, and the M correction LUT 210 are 3072 (= 1024 × 3) bits, respectively. Each of the R correction LUT 205, the G correction LUT 206, and the B correction LUT 207 has a memory capacity of 1024 bits. On the other hand, the memory capacity when performing three-dimensional color correction with a three-dimensional LUT is about 3 Gbits. Therefore, the memory can be reduced by about 1/200000.

  Further, the correction data for each color of RGBCMY is created based on characteristics defining a straight line or a curve connecting the designated coordinate point of each color component to the designated coordinate point of the white component. In this case, the user can make settings for color correction by a simple operation such as designating coordinate points of each color of RGBCMY on the chromaticity diagram.

  Further, the user can easily imagine a color improvement effect from the relationship between the designated coordinate point of the white component and the designated coordinate point of each color component in the color correction setting.

  In addition, since the user can freely set the saturation and hue change for each color from W to RGBCMY, it is possible to perform finer color correction.

  Also, for Y (yellow), which is the most important color for the skin color that is the most memorized color (memory color) for humans, a line connecting the W point 604 and the Y point 602 is shown as shown in FIG. It is desirable to make it a curve. By doing so, the skin color can be made closer to the human memory color. In addition, when setting as shown in FIG. 6 is performed, an intermediate point of saturation becomes reddish for Y (yellow).

  The color correction apparatus of the present embodiment described above is an example of the present invention, and the configuration and operation thereof can be changed as appropriate without departing from the spirit of the invention.

  For example, the seven-axis color correction circuit 106 may be configured as shown in FIG. Referring to FIG. 8, the 7-axis color correction circuit 106 includes adders 711 to 713 and 717 to 719 and dividers 714 to 716 and 720 to 722 instead of the adders 211 to 213 and the dividers 214 to 126. However, this point is different from the configuration shown in FIG.

  The adder 711 adds the output of the R correction LUT 205 and the output of the Y correction LUT 208. The adder 711 adds the output of the G correction LUT 206 and the output of the C correction LUT 209. The adder 713 adds the output of the B correction LUT 207 and the output of the M correction LUT 210.

  The divider 714 outputs a value obtained by dividing the output of the adder 711 by 2. The divider 715 outputs a value obtained by dividing the output of the adder 712 by 2. The divider 716 outputs a value obtained by dividing the output of the adder 713 by 2.

  The adder 717 adds the output of the M correction LUT 210 and the output of the divider 714. The adder 718 adds the output of the Y correction LUT 208 and the output of the divider 715. The adder 719 adds the output of the C correction LUT 209 and the output of the divider 716.

  The divider 720 outputs a value obtained by dividing the output of the adder 717 by 2. The divider 721 outputs a value obtained by dividing the output of the adder 718 by 2. The divider 722 outputs a value obtained by dividing the output of the adder 719 by 2.

According to the above configuration, since each of the dividers is a circuit that performs 1/2 processing, it can be configured by a shift type divider (1 bit shift circuit) that performs 1 bit shift. Here, the shift type divider performs a 1/2 process by shifting the bits to the right by one bit. For example, in the case of 8-bit data,
Before shift: 10000000
After the shift: 01000000
Such shift processing is performed. The value after the shift is a value obtained by performing 1/2 processing. Since such a shift type divider is suitable for a digital circuit and has a simple circuit configuration, the circuit scale can be reduced as compared with the case of using a divider that performs 1/3 processing.

  In the configuration illustrated in FIG. 1, the color correction data generation circuit 105 may have a function realized by a control unit such as a CPU. In this case, the control unit may be a control unit (for example, the control unit 10 shown in FIG. 3) of the video equipment main body.

  As the chromaticity diagram, various chromaticity diagrams such as a chromaticity diagram in which a three-dimensional color space of the CIE XYZ color system is expressed as an area on two-dimensional coordinates can be applied.

  The color correction apparatus of the present invention is applied to all video equipment that performs image processing based on image data, such as projectors, display devices such as liquid crystal displays and plasma displays, output devices such as color printers and color copiers, and electronic cameras. be able to.

  As an example, a display device including the color correction device of the present invention will be described below.

  FIG. 9 shows a configuration of a display device to which the color correction apparatus of the present invention is applied. Referring to FIG. 9, the display device includes a display device 144 that is illuminated with a light beam from a lamp 143, a lens 145 for projecting image light formed by the display device 144 on a screen (not shown), and an input. A video signal processing circuit 140 that performs video signal processing on the signal, a color correction circuit 141, and a display device drive circuit 142 for driving the display device 144 are included. The color correction circuit 141 is the color correction apparatus according to the present invention, and other configurations are existing.

  In this display device, a video signal is supplied from the video signal processing circuit 140 to the color correction circuit 141, and the color correction circuit 141 performs color correction processing on the input video signal. Then, the display device drive circuit 142 drives the display device 144 based on the video signal subjected to the color correction from the color correction circuit 141.

  The present invention is applied to all video equipment that displays or outputs video data, such as a projector, a display device such as a liquid crystal display or a plasma display, an imaging device such as a camera or a video camera, and a device that records or plays back or records video. be able to.

1 is a block diagram illustrating a configuration of a color correction apparatus according to a first embodiment of the present invention. FIG. 2 is a block diagram illustrating an example of a 7-axis color correction circuit illustrated in FIG. 1. It is a block diagram which shows an example of the system containing the color correction apparatus and external control part which are shown in FIG. It is a schematic diagram which shows an example of an input image. It is a schematic diagram which shows an example of chromaticity diagram distribution obtained based on the input image shown in FIG. It is a figure for demonstrating the relationship between the designated value of color and the data for color correction. It is a schematic diagram which shows an example of LUT which comprises the 7 axis | shaft color correction circuit shown in FIG. FIG. 6 is a block diagram illustrating another example of the 7-axis color correction circuit illustrated in FIG. 1. It is a block diagram which shows the structure of the display apparatus to which the color correction apparatus of this invention is applied.

Explanation of symbols

104 matrix conversion circuit 105 color correction data generation circuit 106 7-axis color correction circuit

Claims (6)

A color correction device that receives a video signal including first, second, and third signals indicating red, green, and blue components, respectively, and corrects the color of an image that is generated based on the video signal. ,
Correction data for correcting the white component, yellow component, light blue component, and purple component is generated for each of the first to third signals, and the red component is corrected for the first signal. For the second signal, correction data for correcting the green component is generated, and correction data for correcting the blue component is corrected for the third signal. A color correction data generation circuit to be generated;
A lookup table for storing correction data generated by the color correction data generation circuit, wherein the first to third signals are input, and the lookup for the first to third signals; A 7-axis color correction circuit for performing color correction based on the table,
The color correction data generation circuit generates the white component correction data based on the specified white component value and the characteristic defining the change in brightness of the white component, and the specified white component Based on the characteristics defining the change in saturation or hue from the component value to each color of the red component, green component, blue component, yellow component, light blue component and purple component, create correction data for each color component,
The seven-axis color correction circuit is
Performing color correction based on the white component correction data for each of the first to third signals;
For each of the first to third signals subjected to color correction of the white component, color correction is performed based on correction data for the yellow component, light blue component, and purple component,
For the first signal subjected to color correction of the white component, color correction based on the correction data for the red component is performed,
For the second signal subjected to color correction of the white component, color correction based on the correction data of the green component is performed,
For the third signal subjected to color correction of the white component, color correction based on the blue component correction data is performed,
A fourth signal based on the signal corrected for each color of the red component, yellow component and purple component, a fifth signal based on the signal corrected for each color of the green component, yellow component and light blue component, and the blue color A color correction apparatus that outputs a signal including a sixth signal based on a signal that has been subjected to color correction of each of a component, a light blue component, and a purple component, as the video signal. The seven-axis color correction circuit is
The white component correction data is stored, the first to third signals are input, and color correction based on the stored white component correction data is performed for each of the first to third signals. A first lookup table;
The red component correction data is stored, the first signal color-corrected by the first look-up table is input, and the first signal is based on the stored red component correction data. A second lookup table for color correction;
The green component correction data is stored, the second signal corrected by the first look-up table is input, and color correction based on the stored green component correction data is performed on the second signal. A third lookup table to perform;
The blue component correction data is stored, the third signal corrected by the first look-up table is input, and color correction based on the stored blue component correction data is performed on the third signal. A fourth lookup table to perform;
The yellow component correction data is stored, the first to third signals corrected by the first look-up table are input, and the stored yellow component is stored for each of the first to third signals. A fifth look-up table that performs color correction based on the correction data and outputs a signal obtained by adding the first to third signals subjected to the color correction;
The correction data of the light blue component is stored, the first to third signals corrected by the first look-up table are input, and the stored light blue component is stored for each of the first to third signals. A sixth look-up table that performs color correction based on the correction data and outputs a signal obtained by adding the first to third signals subjected to the color correction;
The purple component correction data is stored, the first to third signals corrected by the first look-up table are input, and the stored purple component is stored for each of the first to third signals. And a seventh look-up table for performing a color correction based on the correction data and outputting a signal obtained by adding the first to third signals subjected to the color correction. . The seven-axis color correction circuit is
A first adder for adding the outputs of the second, fifth and seventh look-up tables;
A second adder for adding the outputs of the third, fifth and sixth look-up tables;
A third adder for adding the outputs of the fourth, sixth and seventh look-up tables;
A first divider that outputs a value obtained by dividing the output of the first adder by 3 as the fourth signal;
A second divider for outputting a value obtained by dividing the output of the second adder by 3 as the fifth signal;
The color correction apparatus according to claim 2, further comprising: a third divider that outputs a value obtained by dividing the output of the third adder by 3 as the sixth signal. The seven-axis color correction circuit is
A first adder for adding the outputs of the second and fifth look-up tables;
A second adder for adding the outputs of the third and sixth look-up tables;
A third adder for adding the outputs of the fourth and seventh look-up tables;
A first divider for outputting a value obtained by dividing the output of the first adder by 2;
A second divider for outputting a value obtained by dividing the output of the second adder by 2;
A third divider for outputting a value obtained by dividing the output of the third adder by 2;
A fourth adder for adding the output of the seventh look-up table and the output of the first divider;
A fifth adder for adding the output of the fifth lookup table and the output of the second divider;
A sixth adder for adding the output of the sixth lookup table and the output of the third divider;
A fourth divider for outputting a value obtained by dividing the output of the fourth adder by 2 as the fourth signal;
A fifth divider that outputs a value obtained by dividing the output of the fifth adder by 2 as the fifth signal;
The color correction apparatus according to claim 2, further comprising: a sixth divider that outputs a value obtained by dividing the output of the sixth adder by 2 as the sixth signal. The white component correction data is given in advance based on coordinate points designated for the white component on a chromaticity diagram representing a three-dimensional color space of a predetermined color system as a region on two-dimensional coordinates. The data created according to the characteristics indicating the degree of change of the white component,
The correction data for the red component is data created in accordance with characteristics defining a straight line or a curve connecting the coordinate point specified for the red component and the coordinate point specified for the white component on the chromaticity diagram,
The green component correction data is data created according to characteristics defining a straight line or a curve connecting the coordinate point specified for the red component and the coordinate point specified for the white component on the chromaticity diagram,
The blue component correction data is data created according to characteristics defining a straight line or a curve connecting the coordinate point specified for the blue component and the coordinate point specified for the white component on the chromaticity diagram,
The correction data for the yellow component is data created according to characteristics defining a straight line or a curve connecting the coordinate point specified for the yellow component and the coordinate point specified for the white component on the chromaticity diagram,
The correction data of the light blue component is data created according to characteristics defining a straight line or a curve connecting the coordinate point specified for the light blue component and the coordinate point specified for the white component on the chromaticity diagram,
The purple component correction data is data created according to a characteristic defining a straight line or a curve connecting a coordinate point designated for the purple component and a coordinate point designated for the white component on the chromaticity diagram. Item 5. The color correction device according to any one of Items 1 to 4. A color correction method for correcting a color of an image generated based on a video signal including first, second, and third signals respectively indicating a red component, a green component, and a blue component,
Correction data for correcting the white component, yellow component, light blue component, and purple component is generated for each of the first to third signals, and the red component is corrected for the first signal. For the second signal, correction data for correcting the green component is generated, and correction data for correcting the blue component is corrected for the third signal. A first step of generating;
A second step of performing color correction on the first to third signals based on the correction data generated in the first step;
The first step creates correction data for the white component based on the value of the designated white component and a characteristic that defines a change in brightness of the white component, and Creating correction data for each color component based on a characteristic that defines a change in saturation or hue from the value to each color of the red component, green component, blue component, yellow component, light blue component, and purple component ,
The second step includes
Performing color correction based on the white component correction data for each of the first to third signals;
Performing color correction based on each correction data of the yellow component, light blue component and purple component for each of the first to third signals subjected to color correction of the white component;
Performing color correction based on the red component correction data for the first signal on which the color correction of the white component is performed;
Performing color correction based on the green component correction data for the second signal that has been subjected to color correction of the white component;
Performing color correction based on the blue component correction data for the third signal that has been subjected to color correction of the white component;
A fourth signal based on the signal corrected for each color of the red component, yellow component and purple component, a fifth signal based on the signal corrected for each color of the green component, yellow component and light blue component, and the blue color Outputting a signal including a sixth signal based on a signal subjected to color correction of each of the component, the light blue component, and the purple component as the video signal.