JP2009260473A - Color processing method and apparatus, program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to perform smoothing processing considering characteristics of respective color processing for a color conversion table which is made by combining a plurality of color processes. <P>SOLUTION: A color processing apparatus is provided with: a first color conversion means which converts an input color signal to a first color signal; a second color conversion means which converts the first color signal converted by the first color conversion means to a second color signal; a detection means which detects tone characteristics of the first color signal converted by the first conversion means; a table generation means which generates a table which specifies the corresponding relation of the input color signal and the second color signal converted by the second color conversion means; and a smoothing means which performs smoothing processing for the second color signal of the table generated by the generation means based on the tone characteristics. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a color processing method and apparatus, a control program, and a storage medium in color matching.

  Since the range of colors that can be reproduced varies depending on devices such as digital cameras, monitors, and printers, so-called color matching processing is required to match colors between devices. For example, as a color matching process for matching the colors of a monitor and a printer, a color processing method is known in which an interpolation operation is performed with reference to a color conversion table that takes into account the color characteristics of the monitor and the printer.

  An example of a method for creating the above color conversion table is given below. First, the monitor RGB values are converted into XYZ values and Lab values, which are color spaces independent of the device, using the color characteristic data of the monitor that is the input device. Next, the device-independent color values are subjected to color gamut compression within the color reproduction range of the printer so that the printer can reproduce them. Further, the compressed device-independent color value is converted into a printer CMYK value using the color characteristic data of the printer as the output device. Using the converted CMYK values, a color conversion table for converting monitor RGB values into printer CMYK values is created.

  Here, the color conversion accuracy of the created color conversion table decreases due to various factors. For example, color characteristic data of a printer is generally obtained by measuring a color patch printed out by a printer with a colorimeter. Therefore, the accuracy of the color conversion table is affected by the measurement accuracy during this color measurement. Another factor that decreases the accuracy is a quantization error when the calculation processing result is quantized. Due to the above-mentioned factors, the table value may not change smoothly. As a result, the gradation change is not smooth in the image after color conversion, and a pseudo contour or the like is likely to occur.

Therefore, conventionally, a smoothing process has been performed on the color conversion table in order to smooth the change in the value of the color conversion table. As this smoothing process, a method is known in which smoothing processing is performed by setting a table value variation allowable amount by smoothing for a plurality of positions in a color space (Patent Document 1).
JP 2006-033245 A

  However, in the method of Patent Document 1, since smoothing is performed using only a color conversion table in which input and output colors are associated, for example, color characteristics of an input device and color reproduction in color gamut compression processing are performed at the time of smoothing. Characteristics were not considered. As a result, for example, when an exceptional gradation characteristic such as gradation inversion is included in the color characteristic of the input device, this characteristic may be lost due to smoothing. This is a problem when it is desirable to preserve gradation characteristics including exceptional gradation characteristics, such as faithful color matching.

  In addition, there is a problem that the gradation reproduction that is intentionally crushed in the color gamut compression process may be lost by the smoothing process.

  FIG. 17 shows an example when smoothing is performed on a one-dimensional table. In the data before smoothing, gradation inversion occurs in Grid5. However, when a smoothing process that does not consider the characteristics is applied, the gradation inversion characteristics of Grid5 are lost after smoothing.

  Therefore, in order to solve the above-described problem, an object of the present invention is to make it possible to perform a smoothing process in consideration of the characteristics of each color process on a color conversion table created by combining a plurality of color processes. And

  The present invention has the following configuration as one means for achieving the above object.

  The color processing apparatus according to the present invention includes a first conversion unit that converts an input color signal into a first color signal, and the first color signal converted by the first conversion unit into a second color signal. Second conversion means for conversion, detection means for detecting gradation characteristics of the first color signal converted by the first conversion means, and the input color signal and the second conversion means Table generating means for generating a table for defining the correspondence relationship with the second color signal, and smoothing processing is performed on the second color signal of the table generated by the generating means based on the gradation characteristics And smoothing means.

  The color processing method according to the present invention includes a first conversion step of converting an input color signal into a first color signal, and the first color signal converted by the first conversion step into a second color signal. A second conversion step for conversion, a detection step for detecting gradation characteristics of the first color signal converted by the first conversion step, and a conversion step by the input color signal and the second conversion step. A table generation step for generating a table that defines the correspondence relationship with the second color signal, and a smoothing process is performed on the second color signal of the table generated by the generation step based on the gradation characteristics And a smoothing step.

  As described above, according to the present invention, it is possible to perform a smoothing process in consideration of the characteristics of each color process in a color conversion table created by combining a plurality of color processes.

  Hereinafter, the image processing apparatus of the present embodiment will be described with reference to the drawings. Note that the numbers in parentheses following each component correspond to the reference numerals of the components in the drawings.

<First Embodiment>
FIG. 1 is a block diagram illustrating a configuration example of an image processing apparatus that is a color processing apparatus according to the first embodiment.

  In FIG. 1, a CPU (101) governs the operation of the entire apparatus according to programs stored in a ROM (102) and a hard disk (HD) (107). At that time, the RAM (103) is used as a work memory to execute various processes including the color process according to the present embodiment. The input interface (104) is an interface for connecting the input device (105). The hard disk interface (106) is an interface for connecting the HD (107) and the video interface (108) for connecting the video device (109). The output interface (110) is an interface for connecting the output device (111).

  Note that the input devices targeted by the present embodiment include various image input devices such as a photographing device such as a digital still camera and a digital video camera, and an image reader such as an image scanner and a film scanner. Video devices include display devices such as color monitors such as CRTs and LCDs. The output device includes an image output device such as a color printer such as an ink jet printer or an electrophotographic printer.

  A general-purpose interface can be used as the interface. Depending on the application, serial interfaces such as USB and IEEE 1394, and parallel interfaces such as SCSI and Centronics can be used.

  FIG. 2 is a block diagram illustrating a functional configuration example of the color processing apparatus according to the first embodiment.

  The color conversion LUT generation unit (201) generates lattice point data that is data corresponding to the lattice points in the input color space by the input lattice data generation unit (202). Although an example in which the input color space is RGB will be described here, other color spaces such as CMYK may be used as input.

  The generated grid point data of the input color signal RGB is converted into a first color signal which is data in a color space independent of the device by the first color processing unit (203). Here, an example of Lab as a color space that does not depend on a device will be described, but other color spaces such as XYZ and JCh may be used. Further, the lattice point data converted into Lab is associated with the converted Lab and is generated as the first LUT (208). Next, the second color processing unit (204) converts the Lab grid point data into a second color signal that is output color space data, and generates an initial color conversion LUT (207). Although an example in which the output color space is RGB will be described here, other color spaces such as CMYK may be output. The smoothing control unit (205) uses the first LUT (208) output from the first color processing unit (203) to generate a smoothing control parameter for controlling the smoothing process. Details of the smoothing control parameter will be described later. The smoothing processing unit (206) applies the smoothing processing to the initial color conversion LUT (207) using the smoothing control parameter generated by the smoothing control unit (205), and the color conversion LUT (209). ) Is generated. Details of the smoothing process will be described later.

  FIG. 3 is a diagram showing an example of the initial color conversion LUT (207) and the color conversion LUT (209) in the present embodiment.

  The initial color conversion LUT (207) and the color conversion LUT (209) define the correspondence between the input RGB values and the output RGB values after color conversion. Here, the input RGB values are color coordinate data of lattice points regularly arranged in the RGB color space, and each axis of R, G, and B is composed of nine lattice points in a lattice shape. However, the number of grid points is not limited to the above, and the grid point data may be non-uniformly arranged.

  FIG. 4 is a schematic diagram showing the input lattice points of the LUT shown in FIG.

  In FIG. 4, each of the R, G, and B axes is composed of nine grid points, and black (Bk), red (R), blue (B), cyan (C), yellow (Y), and white The RGB value of each grid point such as (W) and the grid coordinates of each grid point by the grid number are described. Corresponding output RGB values are associated with each grid point, and a table storing these associations is shown in FIG. In FIG. 3, in particular, when the color coordinate data of the input RGB value and the grid number are defined and fixed, the input RGB data may be omitted, and the data configuration of only the output RGB value may be used.

  FIG. 5 is a diagram showing an example of the first LUT (208) in the present embodiment.

  The first LUT (208) defines a correspondence relationship between an input RGB value converted by the first color processing unit and an output Lab value after conversion. Here, the input RGB values are the same data as in FIG. 3, and are color coordinate data of lattice points regularly arranged in the RGB color space, and each of the R, G, and B axes is 9 lattice points. It is configured. Further, as in FIG. 3, the input RGB data may be omitted, and a data configuration having only output RGB values may be used.

  FIG. 6 is a flowchart illustrating a processing flow of the color processing apparatus according to the first embodiment.

  First, in step S601, input grid data is generated by the input grid generation unit (202). Here, in accordance with the above description, it is assumed that the input RGB value is regular grid point data with 9 grid points on each of the R, G, and B axes.

  Next, in step S602, the first color processing unit (203) converts the input RGB values into Lab values according to the characteristics of the input device by the first conversion. Also, the first LUT (208) is generated.

  Next, in step S603, the second color processing unit (204) converts the Lab values into RGB values according to the characteristics of the output device by the second conversion, and generates an initial color conversion LUT (207).

  Next, in step S604, it is determined whether or not smoothing processing is performed on the initial color conversion LUT (207). The smoothing process may be set to always be executed, or the control may be switched by an external designation. When the smoothing process is performed, the process proceeds to step S605. When the smoothing process is not performed, the initial color conversion LUT (207) is output as the color conversion LUT (209), and the process ends.

  In step S605, a control parameter for controlling the smoothing process is generated based on the first LUT (208). Details of the generation of the smoothing control parameter will be described later.

  Next, in step S606, the initial color conversion LUT (207) is smoothed based on the smoothing control parameter, and is output as the color conversion LUT (209), and the process ends. Details of the smoothing process will be described later.

  Hereinafter, the smoothing process control parameter generation method in step S605 and the smoothing process method in step S606 will be described in detail.

  For example, when performing faithful color matching, even if the color characteristics of the input device include exceptional gradation characteristics such as gradation inversion, the gradation characteristics including the exceptional gradation are preserved. May be desirable. As in the prior art, the smoothing process performed on the output value of the initial color conversion LUT (207) storing the input RGB value and the R′G′B ′ value after the second conversion is performed is as follows. The value is smoothed so that the gradation of the value becomes smooth. However, since this output value is a value after the first conversion and the second conversion, it is impossible to determine which conversion characteristic reflects the output value alone. . In other words, the smoothing process performed on the output value smoothes only the gradation of the output value. For example, the smoothing is selectively smoothed according to the characteristics (gradation) of either conversion. You can't do it. As a result, in the conventional smoothing process, the smoothing process ignoring the characteristics of the first conversion may be performed. Therefore, in this embodiment, in order to detect the exceptional gradation of the input device from the first LUT (208) and to preserve the gradation characteristics including the exceptional gradation even after smoothing, the exceptional gradation is used. A method of processing that does not smooth a portion where a tone is generated will be described.

  FIG. 15 is a flowchart illustrating the flow of the smoothing process control parameter generation in step S605 and the smoothing process flow in step S606. Steps S1501 to S1503 correspond to the smoothing control parameter generation process (step S605), and steps S1504 to S1508 correspond to the smoothing process (step S606).

  First, in step S1501, an exceptional gradation for the target lattice point in the first LUT (208) is detected.

  An exceptional gradation is detected in a tetrahedron as shown in FIG. 7 based on the volume V of the tetrahedron defined by the following equation (1).

Here, x represents an outer product of vectors, and · represents an inner product of vectors. The gradation of the tetrahedron is classified as follows according to the value of V.
・ V> 0: Normal gradation ・ V = 0: Exceptional gradation (collapse)
V <0: exceptional gradation (inversion)

  FIG. 8 shows an example in which a hexahedron composed of a certain reference grid point (Grid (i, j, k)) and 7 neighboring grid points is divided into tetrahedrons. The seven grid points in the vicinity are Grid (i + 1, j, k), Grid (i, j + 1, k), Grid (i, j, k + 1), Grid (i + 1, j + 1, k), Grid (i + 1, j). , K + 1), Grid (i, j + 1, k + 1), and Grid (i + 1, j + 1, k + 1). As shown in FIG. 8, the tetrahedron is divided into six from Tetra1 to Tetra6. For these tetrahedrons with lattice points as vertices, vectors based on the reference lattice points as shown in FIG.

And calculate the volume of each tetrahedron according to equation (1).

  Here, focusing on Grid (i, j, k), which is the reference grid point, that the gradation of Grid (i, j, k) is normal means that Grid (i, j, k) is included. The case where V> 0 in the tetrahedron. Conversely, the gradation of Grid (i, j, k) is an exceptional gradation means that at least one tetrahedron among all tetrahedrons including Grid (i, j, k) is V. = 0 or V <0.

  Next, in step S1502, the exceptional gradation information detected in step S1501 is stored in a smoothing control parameter storage LUT as shown in FIG. The LUT in FIG. 10 stores exceptional gradation information so as to correspond to each grid point of input RGB. 0 is stored when the gradation of the grid point is normal, and 1 is stored when the gradation is exceptional. Further, as in FIG. 3, the input RGB data may be omitted, and a data configuration with only exceptional gradation information may be used.

  Next, in step S1503, it is determined whether the process has been applied to all grid points of the first LUT (208). If there is an unprocessed grid point, the process returns to step S1501.

  Next, in step S1504, the value of the smoothing control parameter stored in the smoothing control parameter storage LUT is referred to. In step S1505, if the value referred to in step S1504 is 1 (in the case of an exceptional gradation), the process proceeds to step S1507, and if not (in the case where the gradation is normal), the process proceeds to step S1506.

  In step S1506, since the target lattice point is a normal gradation, the lattice point of the initial color conversion LUT (207) is smoothed. The smoothing method may be, for example, a method of averaging the output RGB values for the grid points adjacent in the RGB respective axis directions of the input of the initial color conversion LUT (207), or other general smoothing such as Gaussian smoothing. It may be a crystallization process.

  In step S1507, the smoothing processing result (the value of the initial conversion LUT when the target lattice point is an exceptional gradation) is stored in the color conversion LUT (209).

  In step S1508, it is determined whether processing has been applied to all grid points of the initial color conversion LUT (207). If there are unprocessed grid points, the process returns to step S1504. When processing has been performed for all grid points, the color conversion LUT (208) is output and the processing ends.

  Through the above processing, smoothing can be performed while preserving the gradation characteristics of the input device including exceptional gradations.

  FIG. 18 shows an effect of applying the smoothing of the present embodiment as an example of a one-dimensional table. In the data before smoothing, gradation inversion occurs in Grid5. By performing smoothing using the information of the exceptional gradation characteristics, the exceptional gradation characteristics of Grid5 (after smoothing) It can be seen that (gradation inversion) is stored.

  Although the smoothing process control method in this embodiment is a method in which exceptional tone information is used as a parameter and lattice points of exceptional tone are not smoothed, the present invention is not limited to this. . For example, a weighting smoothing method is also conceivable in which weights are calculated based on exceptional tone information, and smoothing results of exceptional tone grid points and surrounding grid points become smooth. Alternatively, a method may be used in which data before and after smoothing are mixed by weights based on exceptional gradation information. Further, in these methods, as described in Japanese Patent Application Laid-Open No. 2006-033245, the allowable variation amount due to smoothing may be set based on exceptional gradation information.

  As described above, according to the present embodiment, it is possible to perform a smoothing process in consideration of the gradation characteristics of the first color process in a color conversion table created by combining a plurality of color processes.

<Second Embodiment>
A second embodiment will be described. In the present embodiment, only the parts different from the first embodiment will be described, and description of overlapping parts will be omitted.

  In the second embodiment, for example, a description will be given of a process in a case where a gradation reproduction that is intentionally crushed in a color gamut compression process is lost by the smoothing process.

  FIG. 11 is a block diagram illustrating a functional configuration example of the color processing apparatus according to the second embodiment.

  The color conversion LUT generation unit (1101) generates grid point data in the input color space by the input grid data generation unit (1102). Although an example in which the input color space is RGB will be described here, other color spaces such as CMYK may be used as input.

  The generated RGB grid data is converted into device-independent color space data by the first color processing unit (1103). Here, an example of Lab as a color space that does not depend on a device will be described, but other color spaces such as XYZ and JCh may be used. The grid point data converted to Lab is output as the first LUT (1109). Next, the second color processing unit (1104) converts the Lab grid data into another Lab data. For example, the second color processing unit includes color gamut compression processing. The converted Lab grid point data is output as a second LUT (1110). Next, the third color processing unit (1105) converts the Lab data into a third color signal, which is data in the output color space, and generates an initial color conversion LUT (1108). Although an example in which the output color space is RGB will be described here, other color spaces such as CMYK may be output. The smoothing control unit (1106) includes a first LUT (1109) output from the first color processing unit (1103) and a second LUT (1110) output from the second color processing unit (1104). Is used to generate a smoothing control parameter for controlling the smoothing process. The smoothing processing unit (1107) applies the smoothing process to the initial color conversion LUT (1108) using the smoothing control parameter generated by the smoothing control unit (1106), and the color conversion LUT (1111). ) Is generated.

  FIG. 12 is a flowchart showing the flow of the color processing apparatus according to the second embodiment of the present invention.

  First, in step S1201, the input grid generation unit (1102) generates input grid data. Here, as in the first embodiment, it is assumed that the input RGB value is regular grid point data with 9 grid points on each of the R, G, and B axes.

  In step S1202, the first color processing unit (1103) converts the input RGB values into Lab values according to the characteristics of the input device. Also, the first LUT (1109) is generated.

  Next, in step S1203, the Lab value is subjected to color gamut compression processing by the second color processing unit (1104), and converted to a Lab value within the color reproduction range of the output device. Also, a correspondence relationship between the input RGB value converted by the first color processing unit (1103) and the Lab value after color gamut compression processing is defined, and a second LUT (1110) storing each value is defined. Generate.

  Next, in step S1204, the third color processing unit (1105) converts the Lab value converted in step S1203 into an RGB value by the third conversion according to the characteristics of the output device, and an initial color conversion LUT ( 1108).

  Next, in step S1205, it is determined whether smoothing processing is performed on the initial color conversion LUT (1108). The smoothing process may be set to always be executed, or the control may be switched by an external designation. If the smoothing process is performed, the process proceeds to step S1206. If the smoothing process is not performed, the initial color conversion LUT (1108) is output as the color conversion LUT (1111), and the process ends.

  In step S1206, control parameters for controlling the smoothing process are generated based on the first LUT (1109) and the second LUT (1110). Details of the generation of the smoothing control parameter will be described later.

  In step S1207, the initial color conversion LUT (1108) is smoothed based on the smoothing control parameter, and is output as the color conversion LUT (1111), and the process ends. Details of the smoothing process will be described later.

  Hereinafter, the smoothing process control parameter generation method in step S1206 and the smoothing process method in step 1207 will be described in detail.

  For example, it is conceivable to create gradation reproduction such as intentionally crushing gradation in the second color processing, that is, color gamut compression processing, but color creation at the time of color gamut compression is saved even in the final result. Things are desirable. Therefore, in the present embodiment, color creation in color gamut compression is determined from the first LUT (1109) and the second LUT (1110) using parameters based on the distance between grid points. In order to save the determination result as much as possible after smoothing, a method for reducing the influence of the smoothing process on the result will be described with respect to the location where the color creation has an influence.

  FIG. 16 is a flowchart showing the flow of the smoothing process control parameter generation in step S1206 and the smoothing process flow in step S1207. Steps S1601 to S1603 correspond to the smoothing control parameter generation process (step S1206), and steps S1604 to S1607 correspond to the smoothing process (step S1207).

  First, in step S1601, the lattice distance ratio at the target lattice point is calculated for each of the first LUT (1109) and the second LUT (1110). Since the lattice distance ratio is calculated from the average distance between lattice points, a method for calculating the average distance will be described first.

  FIG. 13 is a schematic diagram for calculating an average distance between lattice points.

Assume that the following six lattice points are adjacent to a reference lattice point, Grid (i, j, k). Grid (i + 1, j, k), Grid (i-1, j, k), Grid (i, j + 1, k), Grid (i, j-1, k), Grid (i, j, k + 1), Grid (I, j, k-1). L1, L2, M1, M2, N1, and N2 represent distances in the Lab space between Grid (i, j, k) and the above adjacent grid points, respectively. An average distance D (i, j, k) between adjacent grid points in Grid (i, j, k) is defined by the following equation (2).
D (i, j, k) = (L ₁ + L ₂ + M ₁ + M ₂ + N ₁ + N ₂ ) / 6 (2)

Next, a method for calculating the lattice distance ratio R, which is a smoothing control parameter, will be described. When the average distance in the first LUT (1109) is D ₁ (i, j, k) and the average distance in the second LUT (1110) is D ₂ (i, j, k), the lattice distance ratio R Becomes the following equation (3).
R = D ₂ (i, j, k) / D ₁ (i, j, k) (3)
As the R value is smaller than 1, the tendency of color creation to reduce the distance between grid points by color gamut compression becomes stronger. As the R value is larger than 1, the tendency of color creation to increase the grid point spacing. Becomes stronger.

  Next, in step S1602, the lattice distance ratio calculated in step S1501 is stored in a smoothing control parameter storage LUT as shown in FIG. The LUT in FIG. 14 stores a grid distance ratio so as to correspond to each grid point of input RGB. Further, as in FIG. 3, the input RGB data may be omitted, and a data configuration having only a lattice distance ratio may be used.

  Next, in step S1603, it is determined whether or not the processing in step S1602 has been applied to all grid points of the first LUT (1109) and the second LUT (1110), and there are unprocessed grid points. Returns to the process of step S1601.

  Next, in step S1604, the value of the smoothing control parameter storage LUT is referred to.

  Next, in step S1605, smoothing is performed using the value of the smoothing control parameter referred to in step S1604. The smoothing method may be, for example, a method of averaging the output RGB values for the grid points adjacent in the RGB respective axis directions of the input of the initial color conversion LUT (1108), or other general smoothing such as Gaussian smoothing. It may be a crystallization process. The value after smoothing and the value before smoothing are combined based on the combination ratio calculated using the value of the smoothing control parameter (grid distance ratio) to obtain the final smoothing result. For example, when the grid distance ratio is 1, the ratio of the grid point output value after smoothing is 100%. The further the grid distance ratio is away from 1, the smoothing, that is, the initial color conversion LUT (1108). It is calculated by a method that increases the ratio of the grid point output values.

  In step S1606, the final smoothing processing result value obtained in step S11605 is stored in the color conversion LUT (1111).

  In step S1607, it is determined whether processing has been applied to all grid points of the initial color conversion LUT (1108). If there are unprocessed grid points, the process returns to step S1604. When processing has been performed for all grid points, the color conversion LUT (1111) is output, and the processing ends.

  By the above processing, smoothing can be performed while preserving the characteristics of the location where the color is created in the color gamut compression.

  Note that, as a control method of the smoothing process in the present embodiment, a method of setting an allowable variation amount by smoothing as in JP-A-2003-179964 is used, and the allowable variation amount is determined based on the lattice distance ratio. Also good.

  As described above, according to the present embodiment, it is possible to perform a smoothing process in consideration of the characteristics of the second color process in a color conversion table created by combining a plurality of color processes.

<Other embodiments>
Even if the present invention is applied to a system constituted by a plurality of devices (for example, a computer, an interface device, a reader, a printer, etc.), it is applied to an apparatus (for example, a copying machine, a facsimile machine, a control device, etc.) comprising a single device. You may apply.

  Another object of the present invention is to supply a recording medium storing a computer program for realizing the functions of the above embodiments to a system or apparatus, and the computer (CPU or MPU) of the system or apparatus executes the computer program. But it is achieved. In this case, the software read from the recording medium itself realizes the functions of the above embodiments, and the computer program and the computer-readable recording medium storing the computer program constitute the present invention. .

  Further, the above functions are not only realized by the execution of the computer program. That is, according to the instruction of the computer program, the operating system (OS) and / or the first, second, third,... This includes the case where the above function is realized.

  The computer program may be written in a memory of a device such as a function expansion card or unit connected to the computer. That is, it includes a case where the CPU of the first, second, third,... Device performs part or all of the actual processing by the instruction of the computer program, thereby realizing the above functions.

  When the present invention is applied to the recording medium, the recording medium stores a computer program corresponding to or related to the flowchart described above.

It is a block diagram which shows the structural example of the image processing apparatus which concerns on this embodiment. It is a block diagram which shows the function structural example of the color processing apparatus which concerns on this embodiment. It is a figure showing an example of a color conversion LUT concerning this embodiment. It is the model showing the input lattice point of the color conversion LUT which concerns on this embodiment. It is the figure which showed the example of the 1st LUT which concerns on this embodiment. 6 is a flowchart illustrating a processing flow of the color processing apparatus according to the present embodiment. It is a schematic diagram showing the tetrahedron which concerns on this embodiment. It is the figure which divided the hexahedron which consists of the input lattice point of the 1st LUT concerning this embodiment into a tetrahedron. It is the figure which allocated the vector to the tetrahedron of FIG. It is the figure which showed the table holding the smoothing control parameter which concerns on this embodiment. It is a block diagram which shows the function structural example of the color processing apparatus which concerns on this embodiment. 6 is a flowchart illustrating a processing flow of the color processing apparatus according to the present embodiment. It is a figure for demonstrating calculation of the average distance between the lattice points which concerns on this embodiment. It is the figure which showed the table holding the smoothing control parameter which concerns on this embodiment. It is a flowchart which shows the flow of the smoothing control parameter production | generation process and smoothing process which concern on this embodiment. It is a flowchart which shows the flow of the smoothing control parameter production | generation process and smoothing process which concern on this embodiment. It is the figure which showed an example of the smoothing process result in the conventional method. It is the figure which showed an example of the smoothing process result which concerns on this embodiment.

Claims (9)

First conversion means for converting an input color signal into a first color signal;
Second conversion means for converting the first color signal converted by the first conversion means into a second color signal;
Detecting means for detecting gradation characteristics of the first color signal converted by the first converting means;
Table generating means for generating a table for defining a correspondence relationship between the input color signal and the second color signal converted by the second converting means;
A color processing apparatus comprising: a smoothing unit that performs a smoothing process on the second color signal of the table generated by the generating unit based on the gradation characteristics.   The first conversion unit converts the input color signal, which is a color signal of an input device, into the first color signal, which is data of a color space independent of the input device. The color processing apparatus as described.   The color processing apparatus according to claim 1, wherein the input color signal corresponds to a grid point arranged in a color space of the input color signal.   The color processing apparatus according to claim 3, wherein the gradation characteristic is calculated based on a volume of a tetrahedron having the lattice points as apexes.   5. The smoothing unit does not perform the smoothing process when the gradation represented by the gradation characteristics is inverted or crushed. 6. The color processing apparatus according to 1. The second conversion means further includes third conversion means for converting the first color signal converted by the first conversion means into a third color signal, and the third conversion means converts the first color signal. Converting the third color signal to the second color signal,
The detection means further detects a gradation characteristic of the third color signal converted by the third conversion means,
6. The smoothing unit further performs a smoothing process based on a gradation characteristic of the first color signal and a gradation characteristic of the third color signal. The color processing device according to item. A first conversion step for converting an input color signal into a first color signal;
A second conversion step of converting the first color signal converted by the first conversion step into a second color signal;
A detection step of detecting a gradation characteristic of the first color signal converted by the first conversion step;
A table generation step of generating a table that defines a correspondence relationship between the input color signal and the second color signal converted by the second conversion step;
And a smoothing step of performing a smoothing process on the second color signal of the table generated by the generating step based on the gradation characteristics.   A computer program for controlling a computer device to function as each unit of the color processing device according to any one of claims 1 to 6.   A computer-readable recording medium on which the program according to claim 8 is recorded.

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