JP2008203527A - Image processing apparatus, image display apparatus, and image output method - Google Patents

Abstract

To smoothly switch the tone of an image.
When an image output mode is switched by a user, a projector 100 rewrites a low-precision LUT and then outputs an image using the low-precision LUT. The high-precision LUT is rewritten while the image is output using the low-precision LUT. When the rewriting of the high precision LUT is completed, the output of the image using the low precision LUT is switched to the output of the image using the high precision LUT.
[Selection] Figure 2

Description

  The present invention relates to a technique for converting a color tone of an image.

  Many image display apparatuses such as a CRT display, a liquid crystal display, a plasma display, and a projector in recent years have a plurality of color tone modes for an image to be displayed. Examples of such a mode include a dynamic mode that enhances luminance and saturation, and a cinema mode that corrects a color tone suitable for viewing a movie.

  As a technique for performing color conversion according to the color tone mode, there is a technique using a three-dimensional lookup table (hereinafter referred to as “3D-LUT”) (see Patent Document 1 below). In the 3D-LUT, a correspondence relationship between the input color and the output color is recorded. The image display apparatus stores the 3D-LUT in a memory, and converts the color tone by referring to the 3D-LUT. The image display apparatus can support various modes by appropriately rewriting the 3D-LUT stored in the memory according to the color tone mode.

Japanese Patent Publication No.58-16180

  As described above, in the 3D-LUT, output colors are recorded in association with each input color, and thus a large amount of memory is consumed. Although it is possible to reduce the amount of data by reducing the number of output colors of the 3D-LUT and performing an interpolation process after color conversion, it is still possible to increase the accuracy of the color conversion. The amount of data will inevitably increase. For this reason, when the color mode of the image display device is switched by the user, it takes time to load the 3D-LUT corresponding to the switched mode into the memory, and the display of the image after the mode change is delayed. There was a case. In addition, the output image may stop or the displayed image may be disturbed until the loading to the memory is completed.

  Considering such problems, the problem to be solved by the present invention is to smoothly switch the color tone of an image.

Based on the above problems, an image processing apparatus which is one embodiment of the present invention is configured as follows. That is,
An image processing apparatus for converting the color tone of an image,
An input unit for inputting an image;
A state setting unit for setting a state of color tone at the time of output of the input image;
A first color conversion table in which a correspondence relationship between an input color and an output color is written according to the set color tone;
A color tone conversion unit that converts the color tone of the input image using the first color conversion table;
A rewriting unit that rewrites the first color conversion table according to the state of the color tone after the change when the state of the color tone is changed by the state setting unit;
Before the rewriting of the first color conversion table is completed by the table rewriting unit, a second color conversion table having a smaller number of colors of the output color than the first color conversion table is changed to the post-change A generation unit that generates the color according to the state of the color tone;
And a change control unit that outputs the image that has been subjected to color tone conversion using the second color conversion table until the rewriting of the first color conversion table is completed by the table rewriting unit. To do.

  In the image processing apparatus of the present invention, when the color tone state (mode) of the output image is changed, the color of the output color is changed before the rewriting of the first color conversion table used for normal color conversion is completed. A second color conversion table with a small number is generated. Until the rewriting of the first color conversion table is completed, the color tone of the image is converted using the second color conversion table. With such a configuration, it is possible to perform color conversion using the second color conversion table without waiting for completion of rewriting of the first color conversion table, so that the mode of image tone can be switched smoothly. It becomes possible to do.

  In the present invention, the correspondence relationship between the input color and the output color is written in both the first color conversion table and the second color conversion table in accordance with the changed color tone state. For this reason, even if color conversion is performed using the second color conversion table, an image is output with a color tone showing the same tendency as when color conversion is performed using the first color conversion table. As a result, it is possible to suppress a sense of incongruity in the output image.

  Further, in the present invention, since the number of colors in the second color conversion table is set to be smaller than that in the first color conversion table, the second color conversion table can be rewritten at high speed. As a result, after changing the color tone mode, it is possible to quickly output an image with the color tone after switching. In addition, since the number of colors in the second color conversion table is set to be smaller than that in the first color conversion table, the capacity of the memory for storing the table can be saved.

  In the image processing apparatus having the above configuration, the rewriting unit may start rewriting of the first color conversion table after the generation of the second color conversion table by the generating unit is completed.

  With such a configuration, while the second color conversion table is being generated, the tone conversion can be performed using the first color conversion table before the mode change, so the second color conversion While the table is generated, it is possible to prevent the output image from being stopped or disturbed. As a result, it is possible to smoothly switch the tone mode of the image.

  The image processing apparatus having the above-described configuration may further include an interpolation unit that interpolates the number of colors of the image whose color tone has been converted by the color tone conversion unit or the change control unit. Further, in such a configuration, the interpolation unit has converted the color tone using the second color conversion table rather than the image that has been converted in color tone using the first color conversion table. High-precision interpolation may be performed on the image. With these configurations, it is possible to improve the image quality of the output image even during color conversion using the second color conversion table with a small number of colors.

  In the image processing apparatus having the above configuration, the change control unit causes the color tone conversion unit to output the image obtained by performing color tone conversion using the second color conversion table, and the color tone conversion unit includes: The high-accuracy color conversion unit that converts the color tone of the input image using the first color conversion table, and the color tone of the input image is converted using the second color conversion table. From the low-accuracy color conversion unit, the high-accuracy color conversion unit, and the low-accuracy color conversion unit, the images whose color tones are converted are input in parallel, and the first color conversion table or the second color is input. An output switching unit that selectively switches an image to be output from the two input images according to the rewrite state of the conversion table may be provided.

  In such a configuration, an image is input in parallel from the low-precision color conversion unit and the high-precision color conversion unit to the output switching unit that outputs an image. Therefore, even when the output switching unit switches the output, it is possible to suppress a delay from occurring in the image output before and after the switching. As a result, it is possible to smoothly switch the tone mode of the image.

  In addition to the configuration as the image processing device described above, the present invention may be configured as, for example, an image display device, a projector, an image output method by the image processing device, or a computer program for changing the color tone of the image. it can. This computer program may be recorded on a computer-readable recording medium. As the recording medium, for example, various media such as a flexible disk, a CD-ROM, a DVD-ROM, a magneto-optical disk, a memory card, and a hard disk can be used.

Hereinafter, in order to further clarify the operations and effects of the present invention described above, embodiments of the present invention will be described based on examples in the following order.
A. Projector configuration:
B. Image processing circuit configuration:
C. Mode change processing:
D. Details of color conversion and interpolation:
E. Variation:

A. Projector configuration:
FIG. 1 is an explanatory diagram showing a schematic configuration of a projector 100 as an embodiment of the present invention. As illustrated, the projector 100 according to the present embodiment includes an input interface 170, an image processing circuit 110, a liquid crystal panel drive circuit 130, a liquid crystal panel 140, a light source unit 150, a projection lens 160, and an operation panel 180. It has.

  An external device that outputs an image signal is connected to the input interface 170. The input interface 170 A / D converts an analog image signal input from an external device, and each color of R (red), G (green), and B (blue) is 8 bits, that is, digital having 256 levels of data. A circuit for generating a signal is provided. Examples of external devices connected to the input interface 170 include a DVD player, a video deck, and a personal computer.

  The image processing circuit 110 receives the digital signal output from the input interface 170 and converts the color tone of the image represented by the digital signal. The projector 100 includes a plurality of preset image output modes, and the image processing circuit 110 converts the color tone of the image according to the image output modes. Examples of the image output mode include a “dynamic mode” that enhances contrast and saturation, and a “cinema mode” that converts to a color tone suitable for movie viewing. The image processing circuit 110 has a function of stabilizing an image output when the image output mode is switched. Details of this function will be described later in detail.

  The operation panel 180 includes operation buttons for the user to set the image output mode. The operation panel 180 is connected to the image processing circuit 110. The image processing circuit 110 changes the image output mode in accordance with an operation signal input from the operation panel 180.

  The liquid crystal panel drive circuit 130 inputs the color-converted image output from the image processing circuit 110 as a digital signal. Then, the liquid crystal panel 140 is driven according to the digital signal.

  The liquid crystal panel 140 is a transmissive light valve that forms an image using a liquid crystal element under the control of the liquid crystal panel drive circuit 130. The liquid crystal panel 140 receives light emitted from the light source unit 150, modulates the light, and emits the light to the screen 200 side.

  The light source unit 150 is a light source that emits light to the liquid crystal panel 140. The light source unit 150 mainly includes a lamp 151 that emits light and a lens 152 that emits light generated from the lamp to a liquid crystal panel.

  The projection lens 160 is a lens that magnifies and projects the modulated light emitted from the liquid crystal panel 140 toward the screen 200 side.

  In the projector 100 configured as described above, the color tone of the image input by the input interface 170 can be converted by the image processing circuit 110, and the color-tone-converted image can be projected on the screen 200.

B. Image processing circuit configuration:
FIG. 2 is a block diagram showing a specific configuration of the image processing circuit 110 shown in FIG. As illustrated, the image processing circuit 110 includes a high-accuracy color conversion unit 10, a low-accuracy color conversion unit 20, an output switching circuit 30, and a control unit 40.

  The high-precision color conversion unit 10 has a function of inputting RGB data from the input interface 170 and converting the color tone of the RGB data with reference to the 3D-LUT. The high-precision color conversion unit 10 includes a first address calculation unit 12, a high-precision LUT 14, and a first interpolation calculation unit 16 in order to realize this function.

  The high accuracy LUT 14 is a memory circuit that stores a 3D-LUT for performing color conversion with high accuracy. The high-precision LUT 14 is configured by storing RGB data after color conversion represented by 17 color depths at 4913 (= 17 * 17 * 17) addresses. When the high-accuracy LUT 14 is accessed by designating an address from the first address calculation unit 12, it outputs RGB data after color conversion corresponding to the address to a first interpolation calculation unit 16 described later. The RGB data after color conversion output to the first interpolation calculation unit 16 in this way is hereinafter referred to as “K data”. The high-precision LUT 14 outputs three types of RGB data adjacent to the K data to the first interpolation calculation unit 16 in the 3D space in addition to the K data. These data are referred to as “W data”, “S data”, and “T data”, respectively. These data are subjected to RGB data interpolation processing in the first interpolation calculation unit 16. Details of this interpolation processing will be described later.

  The first address calculation unit 12 obtains an address for accessing the high-precision LUT 14 based on the RGB data represented by the 256-step (8 bits) color depth input from the input interface 170. Specifically, the upper 4 bits of data are extracted from the input 8-bit RGB data, and an address for accessing the high-precision LUT 14 is obtained using the extracted 4 bits of data.

  FIG. 3 is an explanatory diagram showing the correspondence between 256-stage RGB data and the address of the high-precision LUT 14. When the first 4-bit data is extracted for each of R, G, and B by the first address calculation unit 12 in 256 steps of RGB data, each 4-bit data is set to a value from 0 to 15 for each of R, G, and B. Will be converted. Therefore, the first address calculation unit 12 associates addresses for accessing the high-precision LUT 14 in advance with all combinations of the 4-bit data. By doing so, the address of the high-precision LUT 14 can be easily obtained. However, when the original RGB data is “255”, an address that cannot be obtained by only the upper 4 bits of data is prepared in order to suppress an error in interpolation calculation by the first interpolation calculation unit 16 described later. Among the addresses shown in FIG. 3, those corresponding to this special address are addresses “17”, “288”, and “4912”. That is, when the value of any of R, G, and B is “255” in the input original RGB data, the first address calculation unit 12 is a combination of R, G, and B having that value. The special address described above is obtained according to the above, and in other cases, the address is obtained using the upper 4 bits of data.

  The first interpolation calculation unit 16 inputs “K data” having a color depth of 17 levels from the high-precision LUT 14 and performs a process of interpolating the data to a color depth of 256 levels. In this interpolation process, lower 4 bit data output from the first address calculation unit 12 and “W data”, “S data”, and “T data” output from the high-precision LUT 14 are used. Details of the interpolation processing will be described at the end of this embodiment.

  In the present embodiment, the high-accuracy color conversion unit 10 converts RGB data having 256 levels of color depth input from the input interface 170 into RGB data having 17 levels of color depth using the high-precision LUT 14. . Then, the colors thinned out by this conversion are interpolated by the first interpolation calculation unit, and finally, RGB data in which each color has 256 levels of values is output. Originally, when RGB data having a color depth of 256 levels is color-converted at the same color depth, one set of R data for each combination of input R data, G data, and B data. , G data and B data need to be prepared. In this case, 16.77 million (= 256 * 256 * 256) addresses and data are required for the 3D-LUT. However, as in this embodiment, assuming that RGB data after color conversion is interpolated later, RGB data having a color depth of 256 levels is once converted into RGB data having a color depth of 17 levels. , 4912 (= 17 * 17 * 17) can be used to convert the color tone.

  The low-precision color conversion unit 20 illustrated in FIG. 2 includes a second address calculation unit 22, a low-precision LUT 24, and a second interpolation calculation unit 26. The configuration of the low-precision color conversion unit 20 is almost the same as the configuration of the high-precision color conversion unit 10 described above. However, the high-accuracy LUT 14 stores RGB data with 17 levels of color depth, whereas the low-accuracy LUT 24 differs greatly in that it stores RGB data with 5 levels of color depth. Specifically, in the low-precision LUT 24, combinations of R data, G data, and B data after color conversion represented by five levels of color depth are stored in 125 (= 5 * 5 * 5) addresses. Is made up of. That is, in the color conversion by the low-accuracy color conversion unit 20, the number of colors after color conversion is small compared to the color conversion by the high-precision color conversion unit 10, and color conversion is performed with low accuracy. The second address calculation unit 22 uses the upper 2 bits of the RGB data input from the input interface 170 in order to obtain 125 addresses. The remaining lower 6-bit data is output to the second interpolation calculation unit 26 for use in interpolation processing. FIG. 4 shows the correspondence between 256 levels of RGB data and the address of the low-precision LUT 24.

  The first interpolation calculation unit 16 of the high-precision color conversion unit 10 and the second interpolation calculation unit 26 of the low-precision color conversion unit 20 are connected to the output switching circuit 30 in parallel. The output switching circuit 30 outputs RGB data to be output to the liquid crystal panel drive circuit 130 in response to an instruction from the control unit 40 described later, from the high-precision color conversion unit 10 and from the low-precision color conversion unit 20. Selectively switch to one of the outputs.

  The control unit 40 is a unit that performs overall control of the projector 100. The control unit 40 includes a CPU, a ROM, and a RAM. The CPU controls the projector 100 by loading a control program stored in the ROM into the RAM and executing it. The control unit 40 corresponds to the “rewriting unit”, “generation unit”, and “change control unit” of the present application.

  In addition to the control program, the ROM stores the 3D-LUT data stored in the high-precision LUT 14 and the low-precision LUT 24 in a nonvolatile manner. Two types of 3D-LUT data are prepared for the high-precision LUT 14 and the low-precision LUT 24 for one image output mode. The CPU reads 3D-LUT data corresponding to the image output mode designated by the user from the ROM, and writes it in the high-precision LUT 14 and the low-precision LUT 24. By doing so, the high-accuracy color conversion unit 10 and the low-accuracy color conversion unit 20 can perform color tone conversion according to the image output mode. Note that the ROM can store the 3D-LUT data in a compressed form. In this case, the CPU performs a process of expanding the compressed 3D-LUT when writing the 3D-LUT to the high-precision LUT 14 or the low-precision LUT 24. By doing so, the storage capacity of the ROM can be reduced.

C. Mode change processing:
FIG. 5 is a flowchart of the mode change process executed by the control unit 40. This process is executed when the control unit 40 detects through the operation panel 180 that the user has performed an operation of switching the image output mode. In this embodiment, for convenience of explanation, as a premise that this processing is executed, a 3D-LUT corresponding to one of the image output modes is written in advance in the high-precision LUT 14 and the low-precision LUT 24. It is assumed that the output switching circuit 30 outputs the RGB data input from the high-accuracy color conversion unit 10 to the liquid crystal panel drive circuit 130.

  When this mode change process is executed, the control unit 40 first reads out the 3D-LUT data for the low-precision LUT 24 corresponding to the image processing mode after switching designated by the user from the ROM. Then, the contents of the low-precision LUT 24 are rewritten to the read data (step S10). Since the 3D-LUT to be rewritten has only 125 addresses, this processing is completed almost instantaneously.

  When the contents of the low-precision LUT 24 are rewritten, the control unit 40 gives an instruction to the output switching circuit 30 and switches the output of RGB data from the high-precision color conversion unit 10 side to the low-precision color conversion unit 20 side (step S20). . By doing so, the projector 100 temporarily outputs an image that has been color-converted with low accuracy.

  When the control unit 40 switches the output from the output switching circuit 30 to the low-accuracy color conversion unit 20 side, the control unit 40 subsequently reads 3D-LUT data for the high-precision LUT 14 corresponding to the mode designated by the user from the ROM. Then, the contents of the high-precision LUT 14 are rewritten with the data read from the ROM (step S30). Since the 3D-LUT data written to the high-precision LUT 14 has 4913 addresses, the data capacity is larger than the 3D-LUT data written to the low-precision LUT 24 (about 40 times). Therefore, the time required for rewriting the high accuracy LUT 14 is longer than the time required for rewriting the low accuracy LUT 24. Specifically, the time required for rewriting the high-precision LUT 14 is about 0.3 to 1 second. During the rewriting of the high-precision LUT 14, the RGB data that has been color-converted by the low-precision color conversion unit 20 is output from the projector 100 by the process of step S 20.

  When the rewriting of data to the high-precision LUT 14 is completed, the control unit 40 gives an instruction to the output switching circuit 30 to switch the output of RGB data from the low-precision color conversion unit 20 side to the high-precision color conversion unit 10 side (step) S40). By doing so, the projector 100 outputs an image that has been subjected to color tone conversion with high accuracy.

  The projector 100 according to the present embodiment described above temporarily outputs an image after color tone conversion from the low-accuracy color conversion unit 20 when the image output mode is switched by the user. In the meantime, the high-precision LUT 14 is rewritten. When the rewriting of the high precision LUT 14 is completed, the projector 100 switches the image output to the output from the high precision color conversion unit 10 side. Therefore, even if it takes some time to rewrite the high-precision LUT 14, only an image with low color conversion accuracy is output, and the image does not stop and outputs a stable image with good response. be able to. In the present embodiment, the second interpolation calculation unit 26 also performs interpolation processing on an image with low color conversion accuracy that is output when the high-precision LUT 14 is rewritten, so that an image displayed during rewriting of the high-precision LUT 14 is also performed. It does not cause much image quality degradation.

  Further, in this embodiment, two types of circuits that perform color conversion, the high-precision color conversion unit 10 and the low-precision color conversion unit 20, are connected to the output switching circuit 30 in parallel. Therefore, even when the output switching circuit 30 switches the output target, there is no delay in the displayed image. As a result, the output image can be switched without a sense of incongruity.

D. Details of color conversion and interpolation:
Details of color conversion and interpolation processing by the image processing circuit 110 will be described below. The high-accuracy color conversion unit 10 and the low-accuracy color conversion unit 20 perform substantially the same processing, and therefore, the processing performed by the high-accuracy color conversion unit 10 will be described below as a representative example.

  As illustrated in FIG. 2, the high-precision color conversion unit 10 includes a first address calculation unit 12, a high-precision LUT 14, and a first interpolation calculation unit 16.

  The first address calculation unit 12 divides the RGB data input from the input interface 170 into upper 4 bits and lower 4 bits for each of R data, G data, and B data. The first address calculation unit 12 accesses the high-precision LUT 14 by specifying an address calculated based on the upper 4 bits of data.

  As described above, 17 * 17 * 17 addresses are prepared in the high-precision LUT 14, and "K data" is stored in each. In other words, the high-precision LUT 14 divides the three-dimensional color space into 17 * 17 * 17 cube areas, and considers that “K data” is associated with the lattice points of each cube area. Can do. K data is data representing a combination of R data, G data, and B data after color conversion. The address calculated based on the upper 4 bits of data described above specifies one cube area to be used in the following interpolation calculation from 17 * 17 * 17 cube areas. The length of one side of the cubic region is “E”. The value of “E” depends on the number of upper bits used by the first address calculation unit 12 for address calculation. That is, when the address is calculated with the upper 4 bits of data, as shown in FIG. 3, the original RGB data takes values every 16th, so the value of E is “16”. Become. Further, when the address is calculated with the upper 2 bits of data as in the low-precision color conversion unit 20, the original RGB data takes values every 64th as shown in FIG. Therefore, the value of E is “64”.

  The first address calculation unit 12 sets the lower 4 bits of R data as “xf data”, the lower 4 bits of G data as “yf data”, and the lower 4 bits of B data as “zf data”. The result is output to the interpolation calculation unit 16. Also, the first address calculation unit 12 refers to the magnitude relationship between these data (xf, yf, zf), so that one of the six tetrahedrons obtained by dividing the cubic region used for the interpolation calculation can be obtained. Select a tetrahedron. The shape of the tetrahedron selected here determines the calculation formula for the interpolation calculation by the first interpolation calculation unit 16.

  FIG. 6 is an explanatory diagram showing six tetrahedrons obtained by dividing a cubic region. As shown in the figure, six tetrahedrons are obtained by dividing a cubic region by three planes represented by three types of formulas x = y, y = z, and z = x. Therefore, the regions of the six tetrahedrons T1 to T6 are expressed by the following six conditional expressions. That is, Formula (1) is the first tetrahedron T1, Formula (2) is the second tetrahedron T2, Formula (3) is the third tetrahedron T3, and Formula (4) is the fourth tetrahedron. The body T4, the equation (5) represents the fifth tetrahedron T5, and the equation (6) represents the sixth tetrahedron T6.

x ≧ z ≧ y (1)
x ≧ y> z (2)
y> x ≧ z (3)
y>z> x (4)
z ≧ y> x (5)
z> x ≧ y (6)

  FIG. 7 is an explanatory diagram conceptually showing how the tetrahedron is selected by the first address calculation unit 12. As shown in the figure, if the coordinate determined by the xf data, yf data, and zf data is A, the first address calculation unit 12 can determine which four sides of the coordinate A by examining the magnitude relationship between the xf data, yf data, and zf data. It can be determined whether it exists in the body. In the example shown in FIG. 7, the coordinate A (xf, yf, zf) satisfies the condition of the above formula (2), so the second tetrahedron T2 is selected by the first address calculation unit 12.

  When the tetrahedron is selected as described above, the first address calculation unit 12 addresses the “W data”, “S data”, and “T data” stored in the high-precision LUT 14 based on the shape of the tetrahedron. Is determined as follows.

  The origin in the xyz coordinates shown in FIG. 7 corresponds to the lattice point (hereinafter referred to as “K point”) where the “K data” described above is located. Here, among the eight vertices of the cubic region shown in FIG. This point W is a point representing the color closest to white in the cubic region used for the interpolation calculation. The first address calculation unit 12 accesses the address of the high-precision LUT 14 where this W point exists. Then, “W data” is output from the high-precision LUT 14 to the first interpolation calculation unit 16. This W point exists at the same position as the “K point” of the cube adjacent to the upper right direction in front of the cube shown in FIG. Therefore, by accessing the address corresponding to the K point of the adjacent cube, “K data” stored in the address is output to the first interpolation calculation unit 16 as “W data”.

  In the present embodiment, among the two points other than the K point and the W point constituting the second tetrahedron T2, the point closer to the K point is set as the S point. The remaining one point was designated as T point. The first address calculation unit 12 accesses the address of the high-precision LUT 14 where these S point and T point exist. Then, “S data” and “T data” are output from the high-precision LUT 14 to the first interpolation calculation unit 16. That is, “K data” corresponding to the K point of the tetrahedron adjacent to the near side of the cube shown in FIG. 7 is output as “S data” and corresponds to the K point of the tetrahedron adjacent to the oblique front side. “K data” is output as “T data”. In this embodiment, the tetrahedron selected by the first address calculation unit 12 is any tetrahedron, and the K point among the two points other than the K point and the W point constituting the tetrahedron. The point on the near side is designated as S point, and the remaining one point is designated as T point.

  The first interpolation calculation unit 16 inputs xf data, yf data, and zf data from the first address calculation unit 12 and also receives a signal for identifying the selected tetrahedron. Further, the first interpolation calculation unit 16 inputs K data, W data, S data, and T data from the high-precision LUT 14. And the 1st interpolation calculating part 16 performs the calculation which interpolates K data using these data. When K data after interpolation is expressed as KK, this KK can be calculated by the following equation (7). The first interpolation calculation unit 16 performs this calculation for all of the R data, G data, and B data constituting the K data, so that the output switching circuit 30 is subjected to the interpolation process for 256 color depths. Can be output. Details of such an interpolation operation using a tetrahedron are described in detail in Japanese Patent Publication No. 58-16180. If the following equation (7) is adopted, the number of multipliers can be reduced as compared with the case where the equation described in this publication is adopted, so that the circuit scale can be reduced.

KK = K + (W−K) · h / E− (WT) · (h−n) / E
-(TS). (Hm) / E (7)

  Note that any one of xf data, yf data, and zf data is assigned to h, m, and n in the above formula according to the type of the tetrahedron selected by the first address calculator 12. Specifically, it is as follows.

(A) When the first tetrahedron T1 is selected, h = xf, m = zf, n = yf
(B) When the second tetrahedron T2 is selected, h = xf, m = yf, n = zf
(C) When the third tetrahedron T3 is selected, h = yf, m = xf, n = zf
(D) When the fourth tetrahedron T4 is selected, h = yf, m = zf, n = xf
(E) When the fifth tetrahedron T5 is selected, h = zf, m = yf, n = xf
(F) When the sixth tetrahedron T6 is selected, h = zf, m = xf, n = yf

  Further, as described above, the parameter “E” indicating the length of one side of the cubic region is “16” in the interpolation processing by the high-precision color conversion unit 10, and “64” in the interpolation processing by the low-precision color conversion unit 20. " As a result, the interpolation processing by the low-accuracy color conversion unit 20 performs detailed interpolation processing with higher accuracy than the interpolation processing by the high-accuracy color conversion unit 10.

E. Variation:
Although various embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and it goes without saying that various configurations can be adopted without departing from the spirit of the present invention. For example, a function realized by hardware may be realized by software. Of course, the reverse is also possible. In addition, the following modifications are possible.

E1. Modification 1:
In the above embodiment, the high-accuracy color conversion unit 10 performs color conversion at a color depth of 17 levels, and the low-accuracy color conversion unit 20 performs color conversion at a color depth of 5 levels. However, the color depth is not limited to these stages. For example, the high-accuracy color conversion unit 10 may perform color conversion at a color depth of 33 levels, and the low-accuracy color conversion unit 20 may perform color conversion at a color depth of 9 levels. That is, the high-accuracy color conversion unit 10 only needs to have a greater color depth stage than the low-accuracy color conversion unit 20.

E2. Modification 2:
In the above embodiment, the above equation (7) is adopted as an equation for performing the interpolation calculation. On the other hand, the following formulas (8) and (9) that are equivalent to the formula (7) may be adopted.

KK = K. (1-h / E) + S. ((Hm) / E)
+ T · ((mn) / E) + W · n / E (8)

KK = K + (SK) .h / E + (TS) .m / E
+ (WT) · n / E (9)

E3. Modification 3:
In the above embodiment, the liquid crystal panel 140 is used as a light valve that modulates light emitted from the light source unit 150. On the other hand, an element such as DMD (Digital Micromirror Device) or LCOS (Liquid Crystal On Silicon) may be used as the light valve. Further, an image may be projected onto a screen using a CRT. “DMD” is a trademark of Texas Instruments Incorporated.

E4. Modification 4:
In the above embodiment, the mode change process described above is performed when the projector 100 switches the image output mode. On the other hand, a similar mode change process may be performed in a direct-view display device such as a liquid crystal display, a plasma display, or a CRT display. The same mode change process may be performed in an image output apparatus such as a DVD player, DVD recorder, video deck, or personal computer. Further, the aspect of the projector 100 may be a front projector or a rear projector.

E5. Modification 5:
In the above-described embodiment, the high-precision color conversion unit 10 and the low-precision color conversion unit 20 are connected in parallel to the output switching circuit 30, and the output switching circuit 30 selectively outputs an image input therefrom. It was. On the other hand, for example, by connecting the high-precision color conversion unit 10 and the low-precision color conversion unit 20 in series, two-stage color conversion can be performed.

FIG. 2 is an explanatory diagram illustrating a schematic configuration of a projector. 2 is a block diagram showing a specific configuration of an image processing circuit 110. FIG. It is explanatory drawing which shows the correspondence of the RGB data of 256 steps, and the address of the high precision LUT14. It is explanatory drawing which shows the correspondence of 256 steps | paragraphs of RGB data and the address of the low precision LUT24. It is a flowchart of a mode change process. It is explanatory drawing which shows six tetrahedrons obtained by dividing | segmenting a cube area | region. It is explanatory drawing which shows notably the mode of selection of a tetrahedron.

Explanation of symbols

10 ... High-precision color conversion unit 12 ... First address calculation unit 14 ... High-precision LUT
16 ... First interpolation calculation unit 20 ... Low-precision color conversion unit 22 ... Second address calculation unit 24 ... Low-precision LUT
26 ... second interpolation calculation unit 30 ... output switching circuit 40 ... control unit 100 ... projector 110 ... image processing circuit 130 ... liquid crystal panel drive circuit 140 ... liquid crystal panel 150. .. Light source 151 ... Lamp 152 ... Lens 160 ... Projection lens 170 ... Input interface 180 ... Operation panel 200 ... Screen

Claims (8)

An image processing apparatus for converting the color tone of an image,
An input unit for inputting an image;
A state setting unit for setting a state of color tone at the time of output of the input image;
A first color conversion table in which a correspondence relationship between an input color and an output color is written according to the set color tone;
A color tone conversion unit that converts the color tone of the input image using the first color conversion table;
A rewriting unit that rewrites the first color conversion table according to the state of the color tone after the change when the state of the color tone is changed by the state setting unit;
Before the rewriting of the first color conversion table is completed by the table rewriting unit, a second color conversion table having a smaller number of colors of the output color than the first color conversion table is changed to the post-change A generation unit that generates the color according to the state of the color tone;
An image processing apparatus comprising: a change control unit that outputs the image that has been subjected to color tone conversion using the second color conversion table until rewriting of the first color conversion table is completed by the table rewriting unit. The image processing apparatus according to claim 1,
The rewriting unit is an image processing apparatus which starts rewriting the first color conversion table after the generation of the second color conversion table by the generating unit is completed. The image processing apparatus according to claim 1 or 2,
An image processing apparatus further comprising an interpolation unit that interpolates the number of colors of the image whose color tone has been converted by the color tone conversion unit or the change control unit. The image processing apparatus according to claim 3,
The interpolation unit is more accurate with respect to the image that has been converted in color tone using the second color conversion table than the image that has been converted in color tone using the first color conversion table. An image processing device that performs high interpolation. An image processing apparatus according to any one of claims 1 to 4,
The change control unit causes the color tone conversion unit to output the image subjected to color tone conversion using the second color conversion table,
The tone conversion unit
Using the first color conversion table, a high-precision color conversion unit that converts the color tone of the input image;
A low-accuracy color conversion unit that converts the color tone of the input image using the second color conversion table;
From the high-accuracy color conversion unit and the low-accuracy color conversion unit, the images with the converted colors are input in parallel, and the first color conversion table or the second color conversion table is rewritten. And an output switching unit that selectively switches an image to be output from the two input images. An image display device that converts a color tone of an image and displays the image,
An input unit for inputting an image;
A state setting unit for setting a state of color tone at the time of output of the input image;
A first color conversion table in which a correspondence relationship between an input color and an output color is written according to the set color tone;
A color tone conversion unit that converts the color tone of the input image using the first color conversion table;
A display unit for displaying the image whose color tone has been converted by the color tone conversion unit;
A rewriting unit that rewrites the first color conversion table according to the state of the color tone after the change when the state of the color tone is changed by the state setting unit;
Before the rewriting of the first color conversion table is completed by the table rewriting unit, a second color conversion table having a smaller number of colors of the output color than the first color conversion table is changed to the post-change A generation unit that generates the color according to the state of the color tone;
A change control unit that causes the display unit to display the image that has been subjected to color tone conversion using the second color conversion table until the rewriting of the first color conversion table is completed by the table rewriting unit. Image display device.   The image display device according to claim 6 configured as a projector. An image output method by an image processing apparatus,
Enter an image,
Accept the setting of the color tone state when outputting the input image,
According to the set color tone state, the correspondence relationship between the input color and the output color is written in the first color conversion table,
Using the first color conversion table, the color tone of the input image is converted and output,
When the state of the color tone is changed, the first color conversion table is rewritten according to the state of the color tone after the change,
Before the rewriting of the first color conversion table is completed, a second color conversion table having a smaller number of colors of the output color than the first color conversion table is changed according to the color tone state after the change. Generated,
An image output method for converting and outputting a color tone of the input image using the second color conversion table until rewriting of the first color conversion table is completed.

Images