JP2006345111A - Image processor and processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent correction in placing amount of color material of main color from becoming larger than required by utilizing the relation between a specific main color and its complementary color when the placing amount is corrected in order to control the placing amount of ink in formation of a color separation table. <P>SOLUTION: In color correction processing, difference in placing amount of main color corresponding to the correction amount of main color obtained through correction of the placing amount is distributed to complementary color components. Distribution is carried out at a ratio dependent on the difference in hue angle between each main color and the color of complementary color component. Color separation amount of main color is returned to that before correction of the placing amount. Since drastic correction in color separation amount of main color is avoided, reduction in amount of main color used due to correction of the placing amount can be prevented. Consequently, color gamut can be enlarged sufficiently using features while sustaining color reproducibility and suppressing the placing amount of ink below a predetermined level. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing apparatus and an image processing method, and more particularly to creation of a color separation table used when converting an image signal into a signal of a color material amount such as ink or toner.

  This type of color separation table obtains lattice point data (color separation data) based on the colorimetric values of patches for lattice points on a predetermined line connecting the vertices of a cube in the RGB space, for example. These other lattice points not on the line can be obtained by interpolation using the lattice point data of the lattice points on the line. The interpolation by this method is, for example, divided into six tetrahedrons each having a predetermined line of a cube in the RGB space as the sides, and further divided each tetrahedron into a plurality of triangles. Lattice point data of lattice points is obtained.

  In this method, generally, after interpolation processing, smoothing processing is performed on lattice point data in order to reduce adverse effects such as discontinuity of lattice point data at the boundary of the interpolation region. By performing printing based on the grid point data of the color separation table created by performing such processing, it is possible to suppress the occurrence of a pseudo contour due to the above discontinuity in the printed image. it can.

  As described above, the color separation table is created by obtaining grid point data based on the colorimetric values of the patch. Further, the grid point data is determined in consideration of the adhesion characteristics of the color material to the print medium such as paper. It is done. For example, when the color material is ink, lattice point data is determined in order to control the amount of the color material in consideration of its absorbability. That is, the maximum amount of ink that can be absorbed by the print medium of a predetermined area is obtained in advance, and the color material amount correction processing for each color is performed so as not to exceed this amount.

  Here, when the color material amount correction process is performed without considering the smoothing process at all, the result of the smoothing process is impaired by the color material amount correction process, and this causes a problem such as a noticeable false contour in the printed image. There is. In addition, the amount of color material is not sufficiently limited, and for example, ink bleeding may occur in a printed image.

  Conventionally, in order to suppress such an obstacle, color material amount correction considering smoothing is known (Patent Document 1).

  FIG. 13 is a flowchart illustrating an example of conventional color material amount correction in consideration of smoothing. In step S13-0, creation of a color separation table is started. In step S13-1, a driving amount correction rate k (n) used for driving amount correction is initialized to k (0) = 1.0. Also, a correction coefficient α is set. Next, in step S13-2, each of WK, MR, RY, YG, GC, CB, and BM, which are predetermined lines of the cube constituting the table. A color separation table is created for each line and each line of WC, M, Y, R, G, and BK. Next, in step S13-3, internal interpolation is performed to obtain grid point data of grid points other than the grid points on the line. The driving amount correction process in step S13-4 performs correction using the correction rate k, but the correction rate k is changed according to the result of the driving amount overcheck in step S13-6. That is, for a color separation table, when there is a grid point having grid point data that is determined to exceed the placement amount, the grid point data is corrected by multiplying the values of all grid point data in the table by the correction factor k. Do. Here, the driving amount correction rate k (n) varies depending on the number of loops n. As a result, the grid points in the color separation table that are overprinting amounts are corrected little by little, and finally the color separation table does not exceed the implantation amount. Then, the smoothing process of step S13-5 is performed on the color separation table subjected to the driving amount correction process of step S13-4. In step S13-6, for the table after the smoothing process, the lattice point data of the entire table is compared with the maximum placement amount of the print medium, and there is a lattice point having lattice point data that exceeds the placement amount. Check whether or not.

  As described above, with respect to the grid point data of the color separation table, the place where the driving amount is over is corrected little by little, and the influence on the smoothing process in step S13-5 is minimized. In addition to performing the driving amount correction process, it is possible to suppress the occurrence of pseudo contours.

JP 2003-1116016 A

  However, in the above-described driving amount correction processing, the driving amount correction rate k is corrected uniformly regardless of the color of the color material. For this reason, there is a problem that some color materials cannot sufficiently contribute to the reproduction of the color gamut. That is, many spot color inks are used to expand the color gamut. However, since the shot amount correction rate is uniform, the spot color ink with a large amount of use is corrected relatively large. As a result, there is a problem that the amount of the special color ink used is reduced and the color reproduction range cannot be sufficiently expanded.

  The present invention has been made from such a viewpoint, and when performing the shot amount correction, the shot amount correction amount is set for the color material whose color is desired to be suppressed for the purpose of expanding the color gamut. An object of the present invention is to provide an image processing apparatus and an image processing method capable of creating a color separation table capable of suppressing color reproduction with high accuracy.

  Therefore, in the present invention, a color separation table used for processing for converting an image signal into a color material signal used in a printing apparatus, and a grid as the color material signal corresponding to a grid point defined by the image signal. In an image processing apparatus for creating a color separation table storing point data, table data creation means for obtaining grid point data for grid points constituting the color separation table, and grid data obtained by the table data creation means Means for correcting lattice point data whose value exceeds a predetermined value for which the color material applied to the print medium in the printing apparatus is determined to be excessive with respect to the print medium, to reduce the value; The correction amount calculated by the correction means for the color material of the main color selected from the color materials is the previous color of the color material other than the main color. Colors that can generate colors close to the main color are generated according to the ratio of the difference in hue angle between the main color and the color material other than the main color, and the colors close to the main color are generated. Color correction means for assigning to possible colors and reducing the calculated correction amount of the main color is provided.

  Also, a color separation table used for processing of converting an image signal into a color material signal used in a printing apparatus, and storing grid point data as the color material signal in association with a grid point defined by the image signal In the image processing method for creating the color separation table, a table data creation step for obtaining grid point data for grid points constituting the color separation table, and among the grid point data obtained by the table data creation means, Correcting lattice point data whose value exceeds a predetermined value that is determined to be excessive with respect to the print medium in which the color material applied to the print medium in the printing apparatus is reduced, and The correction amount calculated by the correction means for the color material of the main color selected from the color materials is set to the main color among the color material colors other than the main color. A color that can generate a color close to each of the main colors according to the ratio of the hue angle difference between the main color and the color material other than the main color in the correction amount of the color that can generate And a color correction step of reducing the calculated correction amount of the main color.

  According to the above configuration, the correction amount of the main color calculated by the correction to reduce the amount of the color material is a color close to the main color, such as the complementary color of the main color, among the colors of the color materials other than the main color material. Since the calculated correction amount of the main color is reduced, the above correction does not reduce the value of the grid point data that is the color separation amount of the main color. The amount of color material applied to the print medium can be suppressed to a predetermined value or less. At this time, the decrease in the main color is regarded as the increase in the complementary color, so that the reproduction of the color gamut using many main colors is not particularly impaired.

  As a result, it is possible to prevent the amount of correction of the coloring material for the main color from being increased more than necessary, and the reproduction of a sufficient color gamut is not impaired.

Embodiments of the present invention will be described below in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of an image processing apparatus according to an embodiment of the present invention. The image processing apparatus according to the present embodiment is configured as software or hardware processing in a printer, as will be described later with reference to FIG. Of course, the application of the present invention is not limited to such a form, and may be, for example, processing by software such as a printer driver operating in a personal computer.

  FIG. 1 shows that R, G, and B 8-bit image data is converted into color material ink C, M, Y, K, and G 8-bit color separation data used in the printer of this embodiment. The process of making quantized C, M, Y, K, and G data of 2 bits each is shown. In the figure, a color matching processing unit 101 performs color conversion for matching the color reproduction range of input image data RGB with the color reproduction range of the printer. Then, the color separation processing unit 102 obtains lattice point data by referring to the color separation table based on the R′G′B ′ data from the color matching processing unit 101, and performs an interpolation operation using the lattice point data. As a result, the R′G′B ′ data is converted into data C, M, Y, K, and G for each color ink used in the printer. Further, the halftone processing unit 103 converts the 8-bit data of each color ink obtained by the ink separation processing unit 102 into binary data C ′, M ′, Y ′, K ′, and G ′ for use by the printer. The ink color separation table unit 105 provides a color separation table (lookup table form) used in the color conversion processing by the ink color separation processing unit 102, and the color separation table creation unit 104 will be described later with reference to FIG. As described above, the ink color separation table is created.

  FIG. 2 is a block diagram showing a configuration of a printing system according to an embodiment of the present invention, and shows a system including a printer constituting the image processing apparatus shown in FIG.

  In FIG. 2, a computer 201 and a monitor 202 constitute a host device for a printer 203. That is, the computer 201 holds image data for printing so that an image displayed on the monitor 202 is printed by the printer 203 and supplies the image data to the printer 203 for printing. The printer 203 has the image processing configuration shown in FIG. 1 and functions as an image processing apparatus. Specifically, each processing unit shown in FIG. 1 is configured by a CPU, a RAM, and a ROM that constitute a control unit of the printer 203, and processes described later with reference to FIGS. The printer 203 includes an inkjet printing mechanism in the present embodiment. That is, the recording heads of Y (yellow), M (magenta), C (cyan), K (black) basic color ink and special color G (green) ink are scanned on the printing medium, and the printing medium is scanned during this scanning. In addition, each of the inks is discharged, and printing is performed by conveying the print medium by a predetermined amount. In the following description, a case where only G (green) ink is used as the special color ink will be described as an example. However, the application of the present invention is not limited to green as described above, but red (R) and blue (B) are further used, and these may be used alone or two of them. Of course. Of course, the printing method is not limited to the above-described inkjet method. For example, an electrophotographic system using toner as a color material can also be used.

  In the above printing system, the image data held in the computer 201 is sent to the printer 203 via a cable with the printer 203. Note that image data may be supplied to the printer 203 from another host device connected to a network (not shown). When the image data is sent, the printer 203 first performs color matching processing for matching the color gamut of the monitor 202 with the color gamut of the printer 203 by the color matching processing unit 101 shown in FIG. Specifically, color conversion is performed by using an interpolation operation together with the lookup table. The color matching processed R′G′B ′ data is color-separated by the color separation processing unit 102 by interpolation using the table data of the color separation table unit 105 using a lookup table created in advance. More specifically, the color separation data C, M, Y, K, and G are read by referring to the color separation table unit 105 using the data R ′, G ′, and B ′, and the data R is read from the read values. Interpolation is performed based on the values of ', G', and B ', and finally color separation data C, M, Y, K, and G obtained by color separation are obtained. These 8-bit data are converted into binary data C ′, M ′, Y ′, and K ′ used in the printer by the halftone processing unit 103 and used for printing. It should be noted that the quantization performed by the halftone processing unit 103 is not limited to binarization, and it is of course possible to use values such as 4-value and 5-value according to the dot pattern to be used and the form of the printing mechanism.

  The table data stored in the ink color separation table unit 105 is created in advance by the color separation table creation unit 104. The generation processing according to the embodiment of the present invention will be described with reference to FIGS. To do.

  FIG. 3 is a diagram showing a cube in a three-dimensional color space defined by R, G, and B signals. As shown in the figure, the position in the cube, that is, which color is determined according to the value of each 8-bit data of R, G, B. The eight vertices of the cube indicate R, G, B, Y, M, C, K, and W.

  FIG. 4 is a diagram schematically illustrating a color separation table of the color separation table unit 105. That is, the color separation table unit 105 represents a predetermined position (color) in the cube defined by the input data R ′, G ′, and B ′ as a lattice point, and color separation data corresponding to the lattice point. (Grid data) Y, M, C, K, and spot color G values are stored as table data. Then, the color separation unit 102 identifies a predetermined grid point based on the input R′G′B ′ data, reads out the grid point data of the grid point and a predetermined grid point around it, and outputs the grid point data. Interpolation processing is performed using. As the interpolation method, any known interpolation method such as tetrahedral interpolation or cube interpolation can be used.

FIG. 5 is a diagram illustrating a method for creating a color separation table.
In the present embodiment, first, as shown in FIG. 5, six lines W-C, M, Y, R, G, B connecting the eight vertices of the cube, C, M, Y, R, G, For each of the six lines B-K, M-R, R-Y, Y-G, GC, MB, B-C, and W-K, the lattice points of the lattice points on that line Data is obtained, and then, lattice point data of lattice points other than these lattice points is obtained by interpolation. Here, when the number of bits of input data of the ink color separation processing unit 102 is 8, W, C, M, Y, R, G, B, K, and the coordinates of each vertex are:
W = (255, 255, 255), indicating white, ie the color of the print paper,
C = (0,255,255), indicating the cyan primary color,
M = (255, 0, 255), indicating the magenta primary color,
Y = (255, 255, 0), indicating a yellow primary color,
R = (255, 0, 0), indicating the red primary color,
G = (0,255,0), indicating the green primary color,
B = (0, 0, 255), indicating the blue primary color,
K = (0, 0, 0), indicating black, that is, the darkest point by the printer.

  FIG. 6 is a flowchart showing the color separation table creation process described above by the color separation table creation unit 104.

  As shown in the figure, in the table creation processing of the present embodiment, first, in step S6-1, a driving amount correction rate k (n) used for driving amount correction processing described later in step S6-4 is set to k (n). 0) = 1.0, and a correction coefficient α is set. Note that the initial value k (0) is not obtained for each lattice point, and one same k (0) is set in the entire driving amount correction process. That is, in this embodiment, as will be described later, the driving amount correction process is performed integrally on the entire table.

  Next, in step S6-2, the lines WK, MR, RY, YG, GC, CB, BM, and WC, M, Y, R , G, and B-K, the grid point data of the grid points are obtained, and a color separation table for these grid points is created. In this embodiment, for a combination of values obtained by equally dividing the values of 0 to 255 represented by 8 bits for C, M, Y, K, and spot color G into 16 equal parts, a patch is printed out in advance by a printer, Measures colors and holds each colorimetric value. On the other hand, the lattice point data (color separation data) of the lattice point corresponding to the vertex is, for example, (C, M, Y, K, G) = (0, 0, 255, 0, 0) at the vertex Y in advance. Determine. Then, lattice point data (color separation data) of lattice points on the line connecting the vertices is obtained as follows. For example, in the case of a line connecting the vertices Y and R, (C, M, Y, K, G) = (0, 0, 255, 0, 0), ( (0, 255, 255, 0, 0), the colorimetric values of the printed patches are obtained based on the set of values, and are distributed evenly on the line connecting the two colorimetric values in the uniform color space. The grid points are defined in. Then, data (Y, M, C, K, G) output from patches of the colorimetric values closest to the colorimetric values of the equally distributed grid points are obtained as the grid point data of the respective grid points. In the above basic table creation, by selecting a patch to set the optimum UCR amount and BG amount for each hue, the color reproduction range of the printer is maximized, and the influence of the granularity due to black is as much as possible. A suppressed table can be set. Of course, some of the lines set in this step may be set to pass through grid points corresponding to the spot color according to the spot color to be used.

  Next, in step S6-3, internal interpolation processing is performed based on the lattice point data of the lattice points on each line obtained in step S6-2, and lattice point data is obtained for lattice points other than the lines.

  A known process can be used for the internal interpolation process. The outline is as follows. First, cyan, magenta, yellow, black, and green ink colors are sequentially selected to determine the ink amount corresponding to each grid point. Next, a tetrahedron to be interpolated is selected and further divided into a plurality of triangles. For example, in the case of a tetrahedron composed of vertices R, Y, K, and W, it can be divided into a surface triangle and an inner triangle. First, the triangle is divided into vertices R-Y-K, R-Y-W, K-W-R, and K-W-Y. Next, the inside of the tetrahedron RYKW is divided into a number of inner triangles corresponding to the number of lattice points on a plane parallel to the triangle RYW. Next, a two-dimensional interpolation process is performed on each target triangle divided as described above. Then, the distance between the ink contour line of the interpolation processing result and each grid point is calculated, and the ink amount of the target grid point is determined. That is, the smallest calculated distance is determined as the ink amount of the target grid point among the calculation results of the ink contour lines of the interpolation processing result and the respective grid distances. Interpolation processing can be performed by performing the above-described processing for each of the transition and sequential ink colors.

After the internal interpolation process in step S6-3, a driving amount correction process is performed in step S6-4. In this process, correction is performed using the correction rate k, but the correction rate k is changed according to the result of the overshoot amount check in step S6-7 shown below. That is, for a color separation table, when there is a grid point having grid point data that is determined to exceed the placement amount, the grid point data is corrected by multiplying the values of all grid point data in the table by the correction factor k. Do. Here, the driving amount correction rate k (n) varies depending on the number of times n of the loop constituted by each step from step S6-4 to step S6-7. Further, the driving amount correction rate k is set to k (n) = αk (n−1). That is, when the process returns to the process of step S6-4 by the determination of step S6-7, the correction factor k is multiplied by α each time. If the initial value k (0) is used, it can be expressed as k (n) = α ⁿ k (0).

Next, the grid point data of the entire color separation table is corrected by applying the driving amount correction rate k (n). Thus, by performing the driving amount correction integrally on the entire table, it is possible to reduce the influence on the smoothing process. In addition, even if it is not an overall correction in this way, the driving amount correction may be locally performed such as 3 × 3 × 3 in accordance with the smoothing process described later in step S6-6. It is possible to reduce the influence of the driving amount correction on the smoothing.
Thereby, in the color separation table, the lattice points where the driving amount exceeds are corrected little by little, and finally, the color separation table becomes such that the driving amount does not exceed.

  Next, in step S6-5, color correction processing is performed, thereby suppressing reduction in color gamut and the like due to driving amount correction processing. In other words, while maintaining the color gamut reproduction accurately, the shot amount correction suppresses the correction of the spot color and other colors for which the shot amount correction is desired to be relatively large, and the overall shot amount is appropriate. It is limited to.

FIG. 7 is a flowchart showing details of the color correction processing.
As shown in FIG. 7, first, in step S7-1, a line on the color separation table for which color correction is desired is specified. For example, a grid point representing a green hue is selected from the grid points whose grid point data is obtained in step S6-3, and a set of these grid points is set as the line. In the following, the present embodiment will be described by taking as an example the case where a green hue line is specified. That is, in this case, the line of the green hue is specified so that the green color gamut can be used to the maximum. In addition to this line representing the green hue, in addition to this, a line representing the hue in the vicinity thereof can also be specified as a line representing the green hue. In this case, it goes without saying that the following processing is performed for each line.
Next, in step S7-2, the lattice point that maximizes the total ink ejection amount in the line specified as described above is determined. In step S7-3, the color separation data (grid point data) of the grid point is checked, and the color component having the maximum color separation value (printing amount) is obtained and used as the main color. In the present embodiment, G (green) is the main color.

  When the main color is determined, it is next determined in step S7-4 whether or not a color component which is a complementary color of the color determined as the main color exists in the color separation of the present embodiment. When the main color is green (G), the complementary colors are cyan (C) and yellow (Y), which are used as the color materials in this embodiment. In this determination, it is determined that a complementary color exists, and step S7- 5, the correction of the correction amount of the complementary color determined above and the correction amount of the main color are corrected.

On the other hand, if it is determined that the complementary color does not exist, it is determined in step S7-6 whether the light color component of the main color exists in the color separation. If it exists, in step S7-7, the correction of the shot amount correction and the correction amount of the main color are corrected for this light color.
Further, if it is determined in step S7-6 that there is no light color material of the main color, in step S7-8, the correction of the driving amount correction and the correction of the main color for the color components other than the main color in the main color separation are performed. Correct the correction amount.

Next, the correction processing in steps S7-5, S7-7, and S7-8 will be described.
FIG. 8 is a flowchart showing in detail the correction processing in steps S7-5, S7-7, and S7-8. In the following, the process will be described by taking as an example the case where green is the primary color (spot color) and its complementary color exists.

  In FIG. 8, first, in step S8-1, the driving amount of each color before the driving amount correction is performed in the immediately preceding step S6-4 is calculated. In step S8-2, the driving amount for each color after the driving amount correction in the immediately preceding step S6-4 is calculated. Then, in step S8-3, for the special color (G (green) in the present embodiment) that is the main color, the difference (before and after the driving amount before and after the driving amount correction) obtained as described above. In the same manner, in step S8-4, for each of the colors other than the special colors (C (cyan), M (magenta), Y (yellow), K (black) in this embodiment)) Calculate the difference before and after correction (difference between before and after placement). The final applied amount correction amount is calculated for the complementary color component. In other words, this is a process in which the correction (correction) of the spot color is assigned to the complementary color component, and the added amount is used as the correction amount of the complementary color.

  FIG. 9 is a flowchart showing details of this processing. In the figure, first, in step S9-1, complementary color components A and B are determined for a special color X which is a main color. In this embodiment, since the special color is green, the complementary color component A is determined to be yellow, and the complementary color component B is determined to be cyan. If there are multiple spot colors, a complementary color is determined for each spot color.

  FIG. 10 is a diagram illustrating an example of the hue angle. 10-1 indicates a hue vector of Y (yellow) ink, 10-2 indicates a hue vector of G (green), and 10-3 indicates a hue vector of C (cyan). P1 represents the difference between the hue angle of the cyan hue vector and that of the green hue vector, and P2 represents the difference between the hue vector of green and the hue vector of yellow.

Next, in step S9-2, the correction amounts of the complementary color components A and B are calculated. The calculation is performed according to the following colors based on the difference between before and after implantation amounts determined above and the hue angle based on the dye vector.
Correction amount of complementary color component A = difference before and after the shot amount of spot color × (P1 / (P1 + P2))
Correction amount of complementary color component B = difference before and after the shot amount of spot color × (P2 / (P1 + P2))

  In this way, the process of assigning the difference before and after the spot color placement amount corresponding to the spot color correction amount to the complementary color components is performed, and if there are multiple complementary color components, distribution according to the respective complementary color component placement amount I do.

In step S9-3, the correction amount of each of the color-collecting components obtained above is added to the original correction amount of the complementary color components A and B, thereby obtaining the final driving amount correction amount of each component. The calculation formula is as follows.
Complement color component A final applied amount correction amount = difference between complementary color component A applied amount before and after + complementary color component A corrected amount Complementary color component B final applied amount corrected amount = complementary color component B applied amount before and after difference + Correction amount of complementary color component B

  After the final correction amount of the complementary color component is calculated by the processing in step S8-5 described in detail above, the spot color shot amount is returned to before the shot amount correction in the next step S8-6. In other words, in the present embodiment, the spot color, which is the main color, is set to the shot amount before correction so that the spot color ink shot amount is not reduced by the shot amount correction. Of course, the application of the present invention is not limited to such a form. For example, by adding the amount allocated to the complementary color components (in the above example, the sum of the correction amounts of the catching color components A and B) to the driving amount after correcting the spot color, the driving amount of the spot color is reduced. You may make it suppress.

Next, in step S8-7, the final driving amount of the complementary color component is calculated. That is, the final driving amount of the complementary color component of the spot color is a value obtained by subtracting the collection driving amount correction amount from the driving amount before the driving amount correction.
Further, in step S8-8, the ink amount is calculated from the driving amount for each color.

  As described above, in order to avoid a major correction of the color separation amount of the main color, the main color usage by the driving amount correction is performed by allocating the correction amount of the main color by the driving amount correction to the complementary color components. The amount of ink can be prevented from decreasing, and thus the color gamut can be sufficiently expanded by using the main color while maintaining the color reproducibility while keeping the ink ejection amount below a certain value. In other words, by making the decrease in the correction amount of the main color the increase in the correction amount of the complementary color, it is possible to perform color correction without causing much color difference, and maintain good color reproducibility. Can do.

  After the color correction process in step S6-5, a smoothing process is performed in step S6-6. For example, a 3 × 3 × 3 low-pass filter having predetermined parameters is sequentially filtered while changing lattice points. Specifically, filtering is performed on lattice point data of lattice points in the range of 3 × 3 × 3 around the processing target lattice points using the parameters of each filter element.

  Next, in step S6-7, with respect to the table after the smoothing process, the lattice point data of the entire table is compared with the maximum placement amount of the print medium, and the lattice points having lattice point data exceeding the placement amount. Check if there is. If there is no place where the driving amount is exceeded, the present process is terminated. If there is a place where the driving amount is exceeded, the process returns to step S6-4 through the process of step S6-8. In step S6-8, using the result checked in step S6-7, a grid point exceeding the driving amount is recorded in the color separation table.

  As described above, if there is a line such as another hue for which correction of the color component is to be controlled in the processing described with reference to FIGS. 7 to 9, the line is specified in step S7-1, and the same processing is repeated thereafter.

  As described above, with respect to the grid point data of the color separation table, the overshooting amount is corrected little by little, and the impact on the smoothing process in step S6-6 is minimized. By performing the amount-of-imprint correction process, it is possible to prevent the ink amount from being exceeded in the printed image and to control the generation of a pseudo contour.

  FIG. 11 is a diagram showing a result of color separation according to the present embodiment, and FIG. 12 is a diagram showing a result of color separation by color separation processing according to the conventional method described above. In the cube shown in FIG. 4, color separation is performed for each lattice point representing the color from the maximum saturation point of the green in the gamut to the black in the color representing the outermost point (color) in the gamut of the green hue. It is a figure which shows data (Lattice point data: Actually, the grid points are discontinuous, and the color separation data is also discontinuous, but it is continuously represented as a line connecting them).

  In these drawings, the line indicated by the solid line is the value of the color separation data before the driving amount correction, and the line indicated by the broken line is the value of the color separation data after the driving amount correction. Further, 1100 and 1200 indicate the maximum value of the driving amount limitation, and 1106 and 1206 indicate the total driving amount before the driving amount correction. Further, 1101 to 1105 and 1201 to 1205 indicate color separation data values before C, M, Y, K, and G driving amount correction, respectively. On the other hand, 1112 and 1212 indicate the total driving amount after the driving amount correction. Reference numerals 1107 to 1111 and 1207 to 1211 denote color separation data values after the driving amount correction for C, M, Y, K, and G, respectively.

  According to the color separation of the present embodiment shown in FIG. 11, as is clear from FIG. 11, the color separation data value 1111 of the main color green does not change from the color separation data value 1105 before the correction by the shot amount correction. The amount of driving has not decreased. Further, by this color separation, the total shot amount 1112 after correction is set to a shot amount limit 1100 or less. On the other hand, according to the color separation shown in FIG. 12, the amount of green is reduced, for example, the color separation data value 1211 is decreased in a portion where the color separation data value 1205 is smaller than the color separation data value 1205 before correction. As described above, according to the present embodiment, when correction is performed at a uniform magnification, when the color separation value is large, the correction amount is prevented from increasing correspondingly and the spot color implantation amount is prevented from decreasing. Can do.

(Second Embodiment)
The second embodiment of the present invention relates to a printing system using six color materials of light cyan and similar light magenta having a low density such as cyan, magenta, yellow, black, and dye as ink. This embodiment also uses the same configuration as that described with reference to FIGS.

  By using the six color materials, the color components of color separation are C, M, Y, K, Lc (light cyan), and Lm (light magenta). In this color separation table creation, for example, when it is desired to suppress the amount of correction for cyan hue and sufficiently expand the color gamut by cyan, the same color correction processing as the processing shown in FIGS. Thus, the cyan correction amount can be suppressed (the correction amount is set to 0 in the examples shown in these drawings). Specifically, in step S7-6 of FIG. 7, since the light color component Lc exists in C, which is the main color, the correction amount correction process is performed in step S7-7.

(Third embodiment)
The third embodiment of the present invention relates to a printing system that uses four color materials of cyan, magenta, yellow, and black as ink. This embodiment also uses the same configuration as that described with reference to FIGS.

  By using the above four color materials, the color components for color separation are C, M, Y, and K. In this color separation table creation, for example, when it is desired to suppress the amount of correction for cyan hue and sufficiently expand the color gamut by cyan, the same color correction processing as the processing shown in FIGS. Thus, the cyan correction amount can be suppressed (the correction amount is set to 0 in the examples shown in these drawings). Specifically, in step S7-6 in FIG. 7, it is determined that the light color component Lc does not exist in C, which is the main color, and correction processing for correction amounts of all colors other than the main color is performed in step S7-8. Do.

  That is, for the primary color cyan, the correction amount is set to 0 to prevent a decrease in the use amount of the primary color and to increase the correction amounts of the other colors magenta, yellow, and black that substitute for the complementary color component of cyan.

(Other embodiments)
As is apparent from the above description, particularly the processing of steps S7-4 and S7-6 shown in FIG. 7, for example, a system having a complementary color or a light color as a color component related to color separation. In color separation, depending on the line to be selected, (1) if the complementary color component of the main color component exists, it is treated as the complementary color component, and (2) if the complementary color component of the main color component does not exist, the main color component If there is a light color component, the light color component is treated as a substitute for the complementary color component. (3) If there is no complementary color component of the main color component and there is no light color component, it is in addition to the main color component. Sequential processing is also possible in which all colors are treated as complementary color components.

(Still another embodiment)
As described above, the present invention can be applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.) but also to an apparatus composed of a single device (for example, a copying machine, a facsimile machine). May be.

  Further, the functions of the embodiments shown in FIGS. 6 to 9 are realized in an apparatus or a computer in the system connected to the various devices so as to operate the various devices so as to realize the functions of the above-described embodiments. The present invention includes a program implemented by operating the various devices according to a program stored in a computer (CPU or MPU) of the system or apparatus.

  In this case, the software program code itself realizes the functions of the above-described embodiments, and the program code itself and means for supplying the program code to the computer, for example, the program code are stored. The storage medium constitutes the present invention.

  As a storage medium for storing the program code, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  Further, by executing the program code supplied by the computer, not only the functions of the above-described embodiments are realized, but also the OS (operating system) in which the program code is running on the computer, or other application software, etc. It goes without saying that the program code is also included in the embodiment of the present invention even when the functions of the above-described embodiment are realized in cooperation with the embodiment.

  Further, after the supplied program code is stored in a memory provided in a function expansion board of a computer or a function expansion unit connected to the computer, a CPU provided in the function expansion board or function storage unit based on an instruction of the program code However, it is needless to say that the present invention also includes a case where the function of the above-described embodiment is realized by performing part or all of the actual processing.

1 is a block diagram illustrating a configuration of an image processing apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating a configuration of a printing system according to an embodiment of the present invention. It is a figure which shows the cube of the three-dimensional color space prescribed | regulated by R, G, B signal. 3 is a diagram schematically showing a color separation table of a color separation table unit 105. FIG. It is a figure explaining the preparation method of a color separation table. It is a flowchart which shows the creation process of the color separation table concerning one Embodiment of this invention. 7 is a flowchart showing details of color correction processing shown in FIG. 6. It is a flowchart which shows the detail of the correction process of step S6-5 shown in FIG. FIG. 9 is a flowchart showing details of processing for obtaining a correction amount of a complementary color component shown in FIG. 8. It is a figure which shows the example of a hue angle. It is a figure which shows the result of the color separation by the color separation process shown in FIG. It is a figure which shows the result of the color separation by the color separation process of a prior art. It is a flowchart which shows the table preparation process of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Color matching process part 102 Color separation process part 103 Halftone process part 104 Color separation table preparation part 105 Color separation table part 201 Computer 202 Monitor 203 Printer

Claims (9)

A color separation table used in processing for converting an image signal into a color material signal used in a printing apparatus, and a color in which grid point data is stored as the color material signal in association with a grid point defined by the image signal In an image processing apparatus that creates a disassembly table,
Table data creation means for obtaining grid point data for grid points constituting the color separation table;
Among the grid point data obtained by the table data creation means, the grid point data whose value exceeds a predetermined value determined that the color material applied to the print medium in the printing apparatus is excessive with respect to the print medium Means for correcting the value to be smaller,
The correction amount calculated by the correction means for the color material of the main color selected from the color material is set to a color correction amount that can generate a color close to the main color among the color materials other than the main color. , According to the ratio of the difference in hue angle between the main color and the color material color other than the main color, the colors close to the main colors are assigned to colors that can be generated, and the calculated main color Color correction means for reducing the correction amount of
An image processing apparatus comprising:   The correction means selects a grid point having the maximum amount of applied color material from the plurality of grid points on a line constituted by the selected grid points, and selects the maximum grid of the selected grid points. The image processing apparatus according to claim 1, wherein a color having a point data value is a main color.   The color correction means is a color capable of generating a color that can generate a color close to the primary color, and when there is a complementary color of the primary color in the color of the color material used in the printing apparatus, the complementary color 2. When there is no color, the light color of the colorant having a high density of the main color is used, and when there is neither the complementary color nor the light color, all colors other than the main color are used. The image processing apparatus according to claim 2.   4. The image processing apparatus according to claim 1, further comprising a smoothing unit that performs a smoothing process on the lattice point data created by the table data creating unit. A color separation table used in processing for converting an image signal into a color material signal used in a printing apparatus, and a color in which grid point data is stored as the color material signal in association with a grid point defined by the image signal In an image processing method for creating a decomposition table,
A table data creation step for obtaining grid point data for grid points constituting the color separation table;
Among the grid point data obtained by the table data creation means, the grid point data whose value exceeds a predetermined value determined that the color material applied to the print medium in the printing apparatus is excessive with respect to the print medium Correcting the value to reduce the value,
The correction amount calculated by the correction means for the color material of the main color selected from the color material is set to a color correction amount that can generate a color close to the main color among the color materials other than the main color. , According to the ratio of the difference in hue angle between the main color and the color material color other than the main color, the colors close to the main colors are assigned to colors that can be generated, and the calculated main color A color correction process for reducing the correction amount of
An image processing method comprising:   The correction step selects a grid point having the maximum amount of applied color material from the plurality of grid points on a line constituted by the selected grid points, and selects the maximum grid of the selected grid points. 6. The image processing method according to claim 5, wherein a color having a point data value is set as a main color.   In the color correction step, as a color capable of generating a color that can generate a color close to the main color, if there is a complementary color of the main color in the color of the color material used in the printing apparatus, the complementary color is used. 6. When there is no color, the light color of the colorant having a high density of the main color is used, and when there is neither the complementary color nor the light color, all colors other than the main color are used. The image processing method according to claim 6.   8. The image processing apparatus according to claim 5, further comprising a smoothing step of performing a smoothing process on the lattice point data created by the table data creation step. A color separation table used in a process of converting an image signal into a color material signal used in a printing apparatus on a computer, and grid point data as the color material signal corresponding to a grid point defined by the image signal A program for executing image processing for creating a stored color separation table, wherein the image processing includes:
A table data creation step for obtaining grid point data for grid points constituting the color separation table;
Among the grid point data obtained by the table data creation means, the grid point data whose value exceeds a predetermined value determined that the color material applied to the print medium in the printing apparatus is excessive with respect to the print medium Correcting the value to reduce the value,
The correction amount calculated by the correction means for the color material of the main color selected from the color material is set to a color correction amount that can generate a color close to the main color among the color materials other than the main color. , According to the ratio of the difference in hue angle between the main color and the color material color other than the main color, the colors close to the main colors are assigned to colors that can be generated, and the calculated main color A color correction process for reducing the correction amount of
The program characterized by having.

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