JP2005348421A - Print control apparatus, print control method and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a print control apparatus and print control method in which a color conversion table optimal for the environment of a user can be generated. <P>SOLUTION: When an installer operation is executed in a computer 21 constituting an image processing device 20, a color conversion table 21b2b is formed from a pre-conversion color conversion table 21b2c at step S130 and according to a processing of increasing lattice points in this case, the lattice points are increased by nonlinear interpolation calculation using Lagrange interpolation equation at step S430 or the lattice points are increased by linear interpolation. Furthermore, the number of lattice points may be fixed or may be the number of lattice points in accordance with environment or input image by which the color conversion table 21b2b having a pertinent size can be formed from the pre-conversion color conversion table 21b2c having a small size. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides a color in which gradation color data in a conversion destination color space is associated with a grid point in the conversion color space in order to convert gradation color data between different color spaces. The present invention relates to a print control device, a print control method, and a color conversion device that generate a conversion table.

  Conventionally, a color printing system that performs color printing of a color image on a computer is known as this type of color conversion table.

  Inside a computer, a color image is displayed with gradations in three primary colors (R, G, B) of red, green, and blue for each pixel arranged vertically and horizontally. In a general color printing apparatus, cyan, magenta, and yellow are displayed. Printing is performed with three colors (C, M, Y) or four colors (C, M, Y, K) with black added thereto and no gradation display. Therefore, for color printing, color conversion work from the display of the three primary colors (R, G, B) of red, green and blue to the display of three colors (C, M, Y) of cyan, magenta, and yellow, and gradation display Therefore, it is necessary to perform gradation conversion from gradation to display without gradation. Although the color space itself is a single space, the display must be different depending on how the coordinates are taken. Therefore, for the sake of convenience, the color space is hereinafter referred to as a color space corresponding to the way of taking the coordinates.

  The color conversion from the (R, G, B) display to the (C, M, Y) display is not uniquely determined by the conversion formula, and the color space having the coordinates of each gradation has a corresponding relationship with each other. Usually, it is usually converted sequentially from this correspondence. Here, if at least the conversion source (R, G, B) display has 256 gradations for each color, it is necessary to have a color conversion table of about 16.7 million (256 × 256 × 256) elements.

  As a result of considering efficient use of storage resources, instead of preparing correspondences for all coordinate values, prepare correspondences for appropriate discrete grid points and use interpolation operations together. I have to. That is, when obtaining the correspondence of the (C, M, Y) color space for the color of a certain coordinate in the (R, G, B) color space, the correspondence of the grid points surrounding the coordinates is used. The correspondence of the same coordinates is obtained through operations such as linear interpolation.

  Such a color conversion table is generally provided in a printer driver, and only one printer driver including the color conversion table is provided corresponding to each color printing apparatus. Therefore, the color conversion table is also specified as the number of grid points appropriately determined from comparison with the storage resource.

  In the above-described conventional color conversion table, the printer driver providing side creates a color conversion table based on comparison with general storage resources, so it is not always optimal depending on the user's environment. There was a problem. That is, depending on the user's environment, it may be still large, or it may be better to have a larger size.

  Furthermore, since the print quality varies depending on the size of the color conversion table, there is a problem that a color conversion table having a certain size is not sufficient.

  SUMMARY An advantage of some aspects of the invention is that it provides a print control apparatus and a print control method capable of generating a color conversion table optimal for a user's environment and the like.

  In order to achieve the above object, the invention according to claim 1 sets a plurality of grid points in a conversion source color space in order to convert gradation color data between different color spaces, and the grid points. A print control apparatus for generating image data for printing with reference to a color conversion table in which gradation color data in a conversion destination color space is associated with a driver program for print control and a small number of When executing printing by the auxiliary storage device that stores the original color conversion table indicating the conversion correspondence at the grid points and the driver program, the grid points of the original color conversion table are increased by non-linear interpolation calculation. Interpolating means for generating the color conversion table in the main storage area and means for generating the printing image data by performing linear interpolation based on the generated color conversion table That it is constituted.

  In the invention according to claim 1 configured as described above, what originally exists is an original color conversion table with a small number of grid points, and requires only a small amount of storage resources. Then, the interpolating unit generates a color conversion table by increasing the grid points of the original color conversion table by interpolation calculation, and uses the generated color conversion table for color conversion.

  The number of grid points in the original color conversion table should be relatively small compared to the generated color conversion table, and does not necessarily need to be a very small number. In particular, in the case of a three-dimensional lattice point, the number of lattice points changes by the third power. That is, the size of the color conversion table becomes 1/8 just by halving the grid points, and even a slight difference will have a great effect on the storage resource.

  Various operations can be applied to the interpolation calculation means. As an example, the invention according to claim 2 is the print control apparatus according to claim 1, wherein the interpolation means includes a plurality of grid points. From the correspondence, the configuration includes nonlinear interpolation calculation means for performing interpolation by nonlinear interpolation calculation.

  In the invention according to claim 2 configured as described above, the non-linear interpolation calculating means of the interpolating means interpolates the grid points by the non-linear interpolation calculation from the correspondence relationship of the plurality of grid points.

  By performing the non-linear interpolation calculation, the correspondence at the increased grid point is accurately reproduced. Therefore, even if the number of grid points in the original color conversion table is reduced, it is possible to obtain a very reproducible result.

  On the other hand, the interval between grid points in the original color conversion table is also related to this interpolation calculation. As an example, the invention according to claim 3 is the original color conversion table in the print control apparatus according to claim 2. Is a configuration in which lattice points are evenly spaced.

  In the non-linear interpolation calculation, the grid point spacing does not necessarily have to be uniform, but if the grid spacing is not uniform, the coefficients of the calculation formula become complicated. And, when trying to increase the lattice points by interpolation calculation at least in a three-dimensional cube, it is necessary to obtain an intermediate lattice point from a plurality of lattice points for each axial direction. In such a case, if the coefficients of the calculation formula become complicated, the interpolation calculation becomes complicated, and the work is troublesome. On the other hand, when the lattice point spacing is uniform, some of the coefficients and the like are constant, and a loop processing is easily applied.

  Of course, in some interpolation operations other than the non-linear interpolation calculation, equality may be preferable, and in some cases, non-uniformity may be preferable, and can be appropriately changed according to the interpolation calculation.

  Further, as an example of using an operation other than the non-linear interpolation calculation, the invention according to claim 4 is the print control apparatus according to claim 1, wherein the interpolation means performs linear interpolation calculation from a correspondence relationship between a plurality of grid points. The linear interpolation calculation means for performing the interpolation is provided.

  In the case of linear interpolation, there is a merit that the arithmetic expression itself is not complicated, and there is a property that the lattice points necessary for the arithmetic are two points in the axial direction. Therefore, by making the lattice points finer in the part where the correspondence changes greatly, it becomes possible to easily obtain an accurate correspondence, and conversely, in the part where the correspondence does not change much, the lattice points are coarsened. It becomes easy.

  The number of grid points to be increased by the interpolation calculation means is not necessarily constant, and as an example, the interpolation means has a configuration in which the number of grid points to be increased by interpolation can be selected.

  The size of the color conversion table changes depending on the increased number of grid points, and depending on the interpolation calculation, the grid points may affect the conversion accuracy in color conversion. Therefore, by selecting the number of grid points to be increased by interpolation, it is possible to set the number of grid points optimal for the user's environment.

  In this case, according to a fifth aspect of the present invention, in the print control device according to any one of the first to fourth aspects, the interpolation means sets the number of grid points to be increased according to the environment. is there.

  The size of the color conversion table changes depending on the number of grid points, and the hit rate at the time of color conversion also changes. Further, depending on the position of the grid point to be increased, the interpolation calculation may be facilitated. Therefore, optimal color conversion can be provided by increasing the number of grid points comprehensively according to the environment. The policy for selecting grid points that increase according to the environment is to use a large color conversion table if there are many storage resources, and to increase the color conversion accuracy when the color conversion accuracy is higher as there are more grid points. If it is desired to increase the number of grid points, it is sufficient to increase the number of grid points, and if interpolation / division by a power of 2 is easy at the time of interpolation calculation, the interval between grid points may be set to a power of 2. .

  Further, in selecting a grid point to be increased in the same manner, the invention according to claim 6 is the printing control apparatus according to any one of claims 1 to 4, wherein the interpolation means increases the number of grid points to be increased. Is set according to the type of the converted image.

  As described above, the more the number of grid points, the higher the color conversion accuracy may be. In such a case, some images may require a high color conversion accuracy and others may not require so much. For this reason, if the information of the converted image requires high color conversion accuracy, the number of lattice points is increased as much as possible. If the information of the converted image does not require so much color conversion accuracy, the number of lattice points is not increased. As a policy in this case, for example, when the type of converted image can be known from the operating system or the like, if the file extension is a bitmap, it is determined that the importance of color information such as a photograph is high. While increasing the number of grid points as much as possible, if the file extension indicates draw data or a business graph, it is effective to judge that the importance of color information is low and not increase the grid points so much. is there.

  As another example of the embodiment of the idea of the present invention, the invention according to claim 8 is that the plurality of grid points are provided in the conversion source color space in order to convert the gradation color data between different color spaces. A print control method for generating image data for printing with reference to a color conversion table that is set and associated with this grid point and gradation color data in the conversion destination color space, for print control The original color conversion table showing the correspondence of conversion at a small number of grid points with the driver program is stored in the auxiliary storage device, and when executing the printing by the driver program, the grid points of the original color conversion table are nonlinearly stored. The color conversion table is generated in the main storage area of the computer by increasing by interpolation calculation, and the image data for printing is generated by performing linear interpolation based on the generated color conversion table. It is characterized by a door.

  That is, it is not necessarily limited to a substantial apparatus, and there is no difference that the method is also effective.

  By the way, the color conversion apparatus provided with such a color conversion table may exist alone or may be used in a state of being incorporated in a certain device. The embodiment is included. Therefore, it can be changed as appropriate, such as software or hardware.

  As an example, when converting gradation color data of a different color space to a color space corresponding to printing ink, an original color conversion table that stores conversion correspondences at a small number of grid points is used. It is also possible to generate a color conversion table by increasing the number of grid points by interpolation calculation, and perform color conversion using the generated color conversion table.

  That is, the printer driver refers to the color conversion table in order to convert gradation color data in a different color space with respect to the color space corresponding to the printing ink. In this case, a small number of grid points are used. The number of grid points is increased by interpolation from the original color conversion table, and color conversion is performed using the color conversion table with the increased number of grid points.

  When the software of the color conversion apparatus is embodied as an embodiment of the idea of the invention, it naturally exists on a recording medium on which such software is recorded as in claim 9 and must be used. . Of course, the recording medium may be a magnetic recording medium, a magneto-optical recording medium, or any recording medium that will be developed in the future. In addition, the duplication stages such as the primary duplication product and the secondary duplication product are equivalent without any question. In addition, in the case of software, it is possible to perform the process of increasing the grid points as described above in the installation work, and that the present invention is used even when the communication method is used as a supply method. However, the providing side functions as a software providing device, and the present invention is similarly used.

  Further, even when a part is software and a part is realized by hardware, there is nothing completely different in the idea of the invention, and a part is stored on a recording medium, and it is appropriately changed as necessary. It may be in the form of being read. Furthermore, it goes without saying that the present invention can also be applied to a color facsimile machine or color copier that uses such a color conversion table.

  As described above, the present invention generates a color conversion table in which grid points are increased from a small-size original color conversion table, and therefore requires a minimum storage resource in a state where color conversion is not performed. A color conversion table having a required size when performing color conversion can be provided, and a more flexible printing control apparatus can be provided. Of course, it can be expanded only when necessary and not expanded when unnecessary, or can be left in an expanded state if there is enough storage resources.

  Furthermore, since the number of grid points to be increased can be selected, a color conversion table suitable for the user environment can be generated more flexibly, such as determining the size of the color conversion table according to the user's storage resources. . In addition, since it is possible to generate a color conversion table of a plurality of sizes, it is possible to select and use them as necessary.

  According to the second aspect of the present invention, since the lattice points are increased by the non-linear interpolation calculation, the accuracy of the increased lattice points is increased, and a good color conversion result can be obtained. In other words, an advantageous effect can be obtained even if the number of lattice points is reduced.

  Furthermore, according to the third aspect of the invention, by making the lattice points of the original color conversion table equal intervals, the nonlinear interpolation calculation can be prevented from becoming complicated, and the calculation time can be reduced.

  Furthermore, according to the fourth aspect of the invention, it is possible to easily perform an interpolation calculation using linear interpolation with a small calculation amount. Further, if the simplicity of linear interpolation is used, there is a merit that it is possible to improve accuracy while being simple by making the lattice points dense at large change portions.

  Furthermore, according to the fifth aspect of the present invention, since the number of grid points corresponding to the environment is selected, the user does not have to perform troublesome setting work.

  Further, according to the invention of claim 6, since the increase of the grid points is selected according to the converted image, the color conversion table is unnecessarily enlarged too much or the color conversion table is enlarged only insufficiently. It is possible to eliminate problems such as not doing so.

  Furthermore, according to the eighth aspect of the present invention, as described above, it is possible to provide a print control method capable of generating a more flexible color conversion table.

  Furthermore, according to the ninth aspect of the present invention, as described above, a record in which a color conversion table manufacturing program capable of generating a more flexible color conversion table is recorded in a computer-readable manner. It can be provided as a medium.

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

  FIG. 1 is a block diagram illustrating an image processing system according to an embodiment of the present invention, and FIG. 2 is a block diagram illustrating a specific hardware configuration example.

  In the figure, an image input device 10 captures a color image and outputs gradation color specification data to the image processing device 20, and the image processing device 20 performs predetermined image processing and outputs it to the image output device 30. The image output device 30 displays the original color image.

  Here, a specific example of the image input device 10 corresponds to the scanner 11 or the digital still camera 12, and a specific example of the image processing device 20 corresponds to a computer system including the computer 21 and the hard disk 22. Specific examples correspond to the printer 31, the display 32, and the like. A recording medium capable of recording a program that causes a computer or the like to execute the present invention corresponds to a recording medium such as a CD-ROM 24 that is read into the computer by the drive device 23.

  The scanner 11 as the image input apparatus 10 outputs gradation data of RGB (green, blue, red), for example, as gradation color data, and the printer 31 as the image output apparatus 30 has gradation color data. Assuming that binary data of CMY (cyan, magenta, yellow) is required as input, the specific role of this computer 21 as the image processing device 20 is to convert RGB gradation data into binary data of CMY. Is to convert. Even if the display 32 inputs RGB gradation data, the scanner 11 and the display 32 usually have different color characteristics, and the computer 21 converts the RGB gradation data into RGB gradation data. Processing will be performed. The same can be said for the digital still camera 12.

  The processing performed inside the computer 21 is shown in FIG. As shown in the figure, an operating system 21a is operating in the computer 21, and a printer driver 21b and a video driver 21c corresponding to the printer 31 and the display 32 are incorporated therein. On the other hand, the application 21d is controlled by the operating system 21a to execute processing, and executes predetermined processing in cooperation with the printer driver 21b and the video driver 21c as necessary.

  The print data generated by the application 21d is input to the printer driver 21b via the operating system 21a, and the printer driver 21b converts the image data into a format requested by the printer 31. This conversion corresponds to the above-described processing for converting RGB gradation data into CMY binary data. Here, the printer driver 21b refers to the rasterizer 21b1 that cuts out the scanning range of the print head in the printer 31 from the image data generated by the application 21d in predetermined screen units, and refers to the color conversion table for each pixel in the scanning range. The color conversion unit 21b2 converts RGB gradation data into CMY gradation data, and the gradation conversion unit 21b3 converts gradations of CMY gradation data into binary data. Note that the display image data generated by the application 21d is written into a predetermined screen memory by the video driver 21c and displayed on the display 32 via a hardware circuit.

  The color conversion unit 21b2 is also called a color correction module, and includes color conversion software 21b2a for executing color conversion calculation processing and a color conversion table 21b2b. The color conversion table 21b2b associates the gradation color data in the conversion destination color space with the grid points in the conversion source color space in order to convert gradation color data between different color spaces. More specifically, it is a three-dimensional lookup table for reading out CMY gradation data using the three-dimensional RGB gradation data as coordinate values as shown in FIG. Then, the color conversion software 21b2a performs a process of reading out CMY gradation data using the RGB gradation data of each pixel as a coordinate value.

  The printer driver 21b including the color converter 21b2 is developed on the hard disk 22 by the installation program shown in FIG. This installer performs step S110 for device check, step S120 for developing the driver software including the color conversion software 21b2a on the hard disk 22, and a predetermined interpolation operation from a small size original color conversion table 21b2c. Step S130 for generating the size color conversion table 21b2b.

  That is, the step S130 for generating the color conversion table 21b2b of a predetermined size from the small-size original color conversion table 21b2c by the interpolation operation constitutes the print control apparatus according to the present invention, and the procedure constitutes the color conversion table manufacturing method. doing. Although this specific method will be described later, in this embodiment, although it is embodied as an installer of the printer driver 21b, as a function thereof, a color conversion table 21b2b of a predetermined size is converted from a small size original color conversion table 21b2c. Anything can be generated. Accordingly, software that generates the color conversion table independently may be used, or it may be configured by hardware including wire logic. Further, as described later, the color conversion software 21b2a can be configured to generate the color conversion table 21b2b as necessary.

  Next, the interpolation calculation process will be described in detail.

  First, a case where nonlinear interpolation calculation is employed as an example of interpolation calculation processing will be described.

  If n points (Xi, Yi) (i = 0, 1,..., n−1) are given, n−1 satisfying Yi = P (Xi) (i = 0, 1,..., n−1). Polynomial

Is uniquely determined. However, no two Xi are equal. A closed expression representing this polynomial

Is the Lagrange interpolation formula. Note that “Π” on the right side is equal to ((X−Xj) / (Xi−Xj)) multiplied by all j except j = i. FIG. 6 shows a coding list showing a specific execution method of this interpolation operation in C language.

  Now, by using such an interpolation calculation, a new size between the grid coordinates is newly obtained using the small-size original color conversion table 21b2c having only five grid coordinates in each axis direction as shown in FIG. It is possible to divide between the grid coordinates by increasing the three grid coordinates. In this case, the lattice coordinate interval corresponds to “64” gradation, and lattice numbers “0” to “4” are attached to the respective lattice coordinates of the original color conversion table 21b2c. Further, by newly dividing the interval between the lattice coordinates, the lattice numbers “0” to “16” are obtained in the color conversion table 21b2b, and the lattice coordinate interval becomes “16” gradation. Note that it is impossible to provide grid points that are uniformly distributed in this way as “256” gray scales. In terms of calculation, the grid points are “0” to “256” (the actual number of gray scales + 1). Assuming the number, the calculation is simplified by shifting the last grid number (for example, 256) to the last grid number (corresponding to 255) in the actual gradation range at the end of the calculation.

  To briefly describe the storage format in the installation program of the original color conversion table 21b2c, as shown in the upper part of FIG. 8, the RGB components are coordinated to correspond to the three colors of CMY respectively. The number of elements is an array of (5, 5, 5, 3), and is written in solid from the beginning of the file. Accordingly, in order to refer to the corresponding data in the original color conversion table 21b2c, the grid number pointers Pr, Pg, Pb corresponding to the R axis, the G axis, and the B axis are set, respectively, and (Pr × 5 Cyan (C) reads the “1” byte, magenta (M) reads the “2” byte, and yellow (Y) reads the “3” byte, with × 5 × 3 + Pg × 5 × 3 + Pb × 3) as the offset address. become.

  Of course, such a storage format is merely an example, and for example, an arrangement may be made such that cyan is arranged for all coordinates and magenta and yellow are arranged for all coordinates sequentially. Alternatively, the file may be stored in a compressed state. However, when the array is written in solid, the read address can be calculated with the pointer value as will be described later, and the regularity at the time of reading can be freely set.

  On the other hand, the storage format of the color conversion table 21b2b is shown in the lower part of FIG. 8, and as described above, the grid points between the grid points of the original color conversion table 21b2c are divided into four to form three new grid coordinates. Therefore, the number of elements is an array of (17, 17, 17, 3), and the data is written in solid from the beginning of the file. Therefore, if the same grid number pointers Pr, Pg, Pb as before are set in order to refer to the corresponding data in the color conversion table 21b2b, (Pr × 17 × 17 × 3 + Pg × 17 × 3 + Pb × 3) from the beginning of the file. ) As an offset address, cyan (C) reads the “1” byte, magenta (M) reads the “2” byte, and yellow (Y) reads the “3” byte.

  The process of increasing the grid points of the color conversion table 21b2b is shown in the flowchart of FIG. In this process, as shown in FIG. 8, since there are matching grid points in the original color conversion table 21b2c and the color conversion table 21b2b, the grid point data is transferred while performing the work of transferring the grid point data in step S210. The blank data is inserted into the file and expanded as a file on the hard disk 22. Thereafter, in step S220, a nested loop process is executed for the grid number of each axis in order to fill the corresponding data for all grid points of the color conversion table 21b2b. Since the grid numbers are “0” to “16”, the processing is repeated with “0” to “16” set as pointers for the R, G, and B axes. In the innermost loop, it is determined whether or not the grid points indicated by the R-axis, G-axis, and B-axis pointers match the grid points transferred from the original color conversion table 21b2c. A process of calculating point correspondence data is executed. However, if there is a match, the corresponding data already exists, so the interpolation calculation process is skipped.

  An example of the interpolation calculation process is shown in FIGS. First, before explaining the flow, the concept of the nonlinear calculation shown in FIG. 11 will be explained.

  When the Lagrangian interpolation formula shown in Equation 2 is applied based on the corresponding data of four points, even if the interpolation calculation of the P point (Rp, Gp, Bp) shown in FIG. It is unclear whether the point will be passed. Therefore, assuming a cube composed of four lattice points in each axial direction before and after the P point is located, and performing interpolation calculation in order for each axial direction in this cube, the four points necessary for the calculation of the P point are obtained. We will calculate the correspondence data for one point. Here, the grid coordinates for each axis are set as {R1, R2, R3, R4} {G1, G2, G3, G4} {B1, B2, B3, B4}.

  First, assuming a straight line parallel to the G-axis direction passing through point P (point of Δ in the figure), the straight line passes through four RB planes that pass through the lattice coordinates of the G axis. Each intersection is indicated by a circle in the figure, and its coordinates are (Rp, G4, Bp), (Rp, G3, Bp), (Rp, G2, Bp), (Rp, G1, Bp). is there. Since the correspondence data of this intersection point itself is unknown, a straight line parallel to the B axis is assumed on the RB plane intersecting each intersection point. This straight line passes through the four RG planes that pass through the lattice coordinates of the B axis. Of the four straight lines, attention is paid to the point where the coordinate of the G axis is “G1”, and each intersection is indicated by a dot in the figure. The coordinates are (Rp, G1, B1), (Rp, G1, B2), (Rp, G1, B3), (Rp, G1, B4), and the corresponding data is still unknown. However, assuming a straight line parallel to the R axis passing through these intersections, all of them now pass through the grid points. That is, the straight line passing through the intersection (Rp, G1, B1) passes through (R1, G1, B1), (R2, G1, B1), (R3, G1, B1), (R4, G1, B1).

  If this is traced back, the correspondence of one dot from the four (R1, G1, B1), (R2, G1, B1), (R3, G1, B1), (R4, G1, B1) Data can be obtained, and in the same way, when the correspondence data of the four dots are obtained, the correspondence data of one circle can be obtained. By repeating this, it is possible to obtain the correspondence data of the four points, and if so, the correspondence data of the points Δ can be calculated.

  A more specific calculation of this process is shown in FIG. 12, and in the innermost nest, correspondence data D (Ri, Gj, Bk) of four lattice points with i = 1 to 4 is used, and the R axis Corresponding data f (j) (corresponding data of points ●) with the component value Rp in the direction is calculated. If four f (j) are obtained with j = 1 to 4, the corresponding data g (k) (corresponding to the ○ points) in the component value Bp in the B-axis direction is used in the upper nest. Data). If four g (k) are obtained with k = 1 to 4, h (corresponding data of Δ points) can be calculated using this in the uppermost nest.

  Returning to the flowchart shown in FIG. 10, in step S310, the assigned lattice group is specified. As shown in FIG. 11 and FIG. 12, it is easy to execute the calculation with four grid points fixed in each axis direction. Therefore, the calculation routine is made into a subroutine that can be executed using the coordinate values of the cube. Therefore, before executing the operation for interpolating the lattice points, a cube composed of four lattice points in each axial direction including the lattice points is specified. In step S320, the correspondence data at the lattice points of the cube is moved to the work area.

  Since the relationship shown in FIG. 11 is specified in the work area, in the subsequent step S330, the non-linear operation is executed by the nest processing shown in FIG. When moving to the work area, an offset in each axis direction occurs. Therefore, the offset amount is stored when moving, and the coordinate value (Rp) considering the offset amount is also added to the coordinate value of the increasing grid point. , Gp, Bp). In FIG. 12, the nesting process is performed in three stages corresponding to the three-dimensional interpolation. However, it is possible to perform the nesting process corresponding to the higher-dimensional interpolation.

  In this way, by performing non-linear calculation at grid points other than the grid points of the original color conversion table 21b2c, a complete color conversion table 21b2b can be obtained when the loop processing for each axis is completed.

  In the above-described embodiment, Lagrange's interpolation formula is used as a specific process of the non-linear operation. However, other operations can be used, for example, spline interpolation. Spline interpolation can be used with continuity up to the derivative, and in this sense, it is a stiff interpolation in case the continuity of the derivative becomes a problem. However, the calculation has to be complicated, and FIG. 13 shows a coding list showing the specific execution method of the spline interpolation calculation in C language.

  In addition, as other nonlinear interpolation calculations, Neville interpolation, Newton interpolation, or the like can be used. In these cases, the calculation is easy numerically.

  On the other hand, the lattice spacing is constant for the lattice points described above. As a result, the corresponding data is moved using the specific cube as a work area, and the calculation can be executed in an easy-to-understand manner. However, the lattice spacing does not necessarily have to be constant, and it is also possible to execute using a coefficient that takes into account the lattice spacing.

  Furthermore, in the above-described embodiment, the non-linear interpolation shown in FIGS. 10 to 12 is used in the interpolation calculation processing in step S220, but linear interpolation can also be used as shown in FIGS. is there.

  In FIG. 14, the positions of the lattice points before increasing the lattice points are indicated by white circles, and the positions of the lattice points after the increase of the lattice points are indicated by black circles. A new grid point is provided. Therefore, the initial lattice number shown in the figure is exactly twice the lattice number as shown in parentheses. It is assumed that the initial number of grid points is “i”. FIG. 15 is a flowchart showing the procedure of the CPU that executes the linear interpolation process, FIG. 16 shows the state of the first corresponding data movement, and FIG. 17 shows the lattice points to be interpolated. FIG. 18 shows the state of the interpolation calculation.

  Assuming that lattice points with half the distance between lattice points are formed on each axis, the lattice coordinates of the lattice points before interpolation are automatically (0, 2, 4, 6, 8) as shown in parentheses in FIG. ...) and interpolate between them. Returning to the flowchart shown in FIG. 15, first, in step S <b> 410, the CPU performs a process of moving grid point data already in the table to a predetermined position in the new table. For example, as shown in FIG. 16, the correspondence data of the lattice coordinates (0, 0, 0) is the correspondence data of the lattice coordinates (0, 0, 0) of the new table. The correspondence data is the correspondence data of the grid coordinates (0, 0, 2) of the new table, and the correspondence data of the grid coordinates (0, 0, 2) is the correspondence data of the grid coordinates (0, 0, 4) of the new table. And so on.

  When interpolating lattice points by linear interpolation, the calculation differs depending on the position in the lattice body consisting of eight surrounding lattice points. That is, in the case of a grid point existing on the side, it is interpolated from two grid points on both sides, and in the case of a grid point existing on the surface, it is interpolated from the surrounding four grid points and exists at the center. If it does, it is interpolated from eight grid points.

  As an order of increasing the grid points, first, in step S420, processing for generating grid points on the grid sides is executed. In the arithmetic processing of the CPU, parameters are given for each axis and processing is performed in a nested loop. Therefore, blocks are also nested in the figure.

  The parameters are given as “0”, “2”, “4”, “6”, “8”, etc. for each axis, and the corresponding data of the grid coordinate (1, 0, 0) in the R-axis direction is set to the grid coordinate ( 0,0,0) and (2,0,0). That is, as shown in FIG. 18, the correspondence data X1 of the lattice coordinates (0, 0, 0) and the correspondence data X2 of the lattice coordinates (2, 0, 0) are added, and the result X3 is divided by “2”. It becomes thing X4. Here, the division of “2” corresponds to a 1-bit right shift in binary data, and can be executed very easily. Of course, it may be added after first performing a 1-bit right shift. In this case, overflow in the calculation process can be prevented. Hereinafter, lattice points on the lattice side are generated from all combinations of the parameters.

  In step S430, processing for generating lattice points on the lattice surface is executed. In this case as well, since processing is performed in a nested loop, “0”, “2”, “4”, “6”, “8” are given as parameters for each axis, and the grid coordinates for the plane parallel to the RG plane Corresponding data of (1, 1, 0) is generated from data of lattice coordinates (0, 0, 0), (0, 2, 0), (2, 0, 0), (2, 2, 0). In this case, the average value of the four grid points is taken, and the four data may be added and then divided by “4”. The division of “4” corresponds to a 2-bit right shift in binary data and can be executed very easily. Hereinafter, lattice points on the lattice plane are generated from all combinations of these parameters.

  Finally, in step S440, a process of generating a center point lattice point is executed. In this case, “1”, “3”, “5”, “7”... Are given as parameters for each axis, and the corresponding data of the lattice coordinates (1, 1, 1) is eight lattice coordinates (0, 0,0), (0,0,2), (0,2,0), (0,2,2), (2,0,0), (2,0,2), (2,2, 0), (2, 2, 2). In this case, the average value of the eight grid points is taken, and it is sufficient to add them after performing a 3-bit right shift so as not to overflow. Thereafter, lattice points of all center points are generated from all combinations of the parameters.

  By performing the above processing, the interpolation of grid points is completed. In the present embodiment, the grid points are increased so that the grid interval is halved. However, the present invention is not limited to this example, and the grid points can be increased or decreased as necessary, and the grid points are increased within the allowable range of storage resources. Just do it.

  In addition, although the lattice interval of the lattice points is constant in the linear interpolation calculation described above, even if the lattice interval is appropriately changed in the linear interpolation, the basis of the calculation is only correspondence data of two points on both sides. Even if the lattice spacing is changed, the calculation is easy. Therefore, the interpolation accuracy can be improved while facilitating calculation by reducing the lattice spacing in the portion where the change curve of the corresponding data is large.

  On the other hand, in both the non-linear interpolation and the linear interpolation, the grid points to be increased are not necessarily fixed, and can be changed as necessary.

  As an example of the process of increasing the grid points, the flowchart of FIG. 19 shows a system-corresponding grid point increasing process for generating a table in accordance with the system configuration of the system.

  In this example, the CPU type representing the computing capacity is input in step S510, the clock representing the computing speed is similarly input in step S520, and the memory capacity that affects the computing capacity and the computing speed in step S530. In step S540, the remaining capacity of the generation destination hard disk is input.

  In step S550, the system correspondence table set in advance corresponding to these combinations is referred to, and the most appropriate number of grid points is read out. When the number of grid points is obtained, a grid point increasing process is performed in step S560. As a general tendency, the number of grid points stored in this system correspondence table increases as the calculation capacity and calculation speed increase, and increases as the remaining capacity of the hard disk increases. You should set it like this. Of course, the input elements of the device configuration are not limited to these, and the weight is not constant. For example, when the remaining capacity of the hard disk is large, it is not impossible to create a full-size table although there is a balance with the cache.

  In this case, it may be inquired between step S540 and step S550 as to whether or not there are a lot of bitmap data such as photographs or a lot of draw data data as a user's usage environment. And if there is a lot of bitmap data, the number of grid points can be increased assuming an environment that emphasizes color reproducibility such as photographs, and if there is a lot of draw data data Assuming an environment where color reproducibility such as a business graph is not so important, the number of grid points may be reduced.

  Until now, the grid conversion process 21b2b is generated by increasing the grid points at the time of installation. However, the color conversion table 21b2b having a size necessary for printing is stored in a high-speed accessible storage unit such as a RAM of the computer 21. You may make it produce | generate. In normal times, a small original color conversion table 21b2c is stored in the hard disk, and the merit of creating the color conversion table 21b2b of a size necessary for printing on the RAM that can be accessed at high speed is very great. Of course, as in the case of hard disks, the size to be developed can be determined by setting the grid spacing in consideration of the remaining capacity available in the RAM, the amount of image data to be output, the desired output quality, etc. That's fine.

  As shown in FIG. 3, when the application 21d performs printing, the printer driver 21b is activated via the operating system 21a. At this time, the file type is passed to the printer driver 21b. The printer driver 21b determines whether it is a bitmap system or a draw data system from the file type (for example, bmp) at this time, sets the number of grid points corresponding to the bitmap system, and generates the color conversion table 21b2b. . What is necessary is just to set about the magnitude | size of the number of this grid point with the tendency similar to the case by the installer mentioned above. Of course, the method of determining the type of input data is not limited to such a file type, and it may be determined based on whether the actual input data has a large or small number of colors, or the operating system determines the type of object. It may be determined and notified to the printer driver.

  As described above, when the installer is executed by the computer 21 constituting the image processing apparatus 20, the color conversion table 21b2b is generated from the original color conversion table 21b2c in step S130. In S430, the number of grid points may be increased by nonlinear interpolation calculation using Lagrange's interpolation formula, the number of grid points may be increased by linear interpolation, etc. The number of grid points may correspond to the input image, and the color conversion table 21b2b having an appropriate size can be generated from the original color conversion table 21b2c having a small size.

1 is a block diagram of an image processing system to which a color conversion table manufacturing apparatus according to an embodiment of the present invention is applied. It is a block diagram of a specific hardware configuration example of the image processing system. It is a block diagram which shows the software configuration of a computer. It is a figure which shows the concept of a three-dimensional lookup table. It is a flowchart of an installation program. It is the figure which coded Lagrange's interpolation calculation in C language. It is a figure which shows the lattice coordinate of an original color conversion table. It is a figure which shows the file structure of an original color conversion table and a color conversion table. It is a flowchart of a lattice point increase processing program. It is a flowchart of a non-linear interpolation program. It is a conceptual diagram which shows the procedure in the case of nonlinear interpolation by the Lagrange interpolation formula. It is a flowchart corresponding to Lagrange interpolation calculation. It is the figure which coded the spline interpolation calculation in C language. It is explanatory drawing which shows the lattice coordinate before and behind increasing a lattice point. It is a flowchart of a lattice point increase processing program for linear interpolation. It is a figure which shows the file structure of an original color conversion table and a color conversion table. It is a schematic explanatory drawing which shows the position of the lattice point to be interpolated. It is explanatory drawing which shows the state of the calculation which used bit shift together. It is a flowchart of a system corresponding | compatible grid point increase processing program.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Image processing apparatus 21 ... Computer 21a ... Operating system 21b ... Printer driver 21b1 ... Rasterizer 21b2 ... Color conversion unit 21b2a ... Color conversion software 21b2b ... Color conversion table 21b2c ... Original color conversion table 21b3 ... Tone conversion unit 21c ... Video Driver 21d ... Application 22 ... Hard disk 23 ... Drive device 24 ... CD-ROM

Claims (9)

In order to convert gradation color specification data between different color specification spaces, a plurality of grid points are set in the conversion source color specification space, and the gradation color specification data in the conversion destination color specification space is set to these lattice points. A print control apparatus that generates image data for printing with reference to a corresponding color conversion table,
An auxiliary storage device for storing a driver program for print control and a primary color conversion table indicating a correspondence relationship of conversion at a small number of grid points;
When executing printing with the above driver program,
Interpolation means for increasing the lattice points of the original color conversion table by nonlinear interpolation to generate the color conversion table in the main memory area of the computer;
A printing control apparatus that realizes a means for generating image data for printing by performing linear interpolation based on a generated color conversion table.   2. The printing control apparatus according to claim 1, wherein the interpolation means includes nonlinear interpolation calculation means for performing interpolation by nonlinear interpolation calculation from a correspondence relationship between a plurality of grid points.   3. The print control apparatus according to claim 2, wherein the original color conversion table includes lattice points with equal intervals.   2. The print control apparatus according to claim 1, wherein the interpolation means includes linear interpolation calculation means for performing interpolation by linear interpolation calculation from a correspondence relationship between a plurality of grid points.   5. The print control apparatus according to claim 1, wherein the interpolation means sets the number of grid points to be increased according to the environment.   5. The print control apparatus according to claim 1, wherein the interpolation unit sets the number of grid points to be increased according to the type of the converted image.   2. The print control apparatus according to claim 1, wherein the color conversion table is referred to by a computer, and at the normal time, the original color conversion table is stored in an auxiliary storage device of the computer and the color conversion table is referenced. A print control apparatus that is sometimes expanded in a main storage area of the computer. In order to convert gradation color specification data between different color specification spaces, a plurality of grid points are set in the conversion source color specification space, and the gradation color specification data in the conversion destination color specification space is set to these lattice points. A print control method for generating image data for printing with reference to a corresponding color conversion table,
A driver program for print control and a primary color conversion table showing the correspondence of conversion at a small number of grid points are stored in the auxiliary storage device,
When executing printing with the above driver program,
Increase the grid points of the original color conversion table by nonlinear interpolation to generate the color conversion table in the main memory area of the computer,
A printing control method, wherein linear printing is performed based on the generated color conversion table to generate the image data for printing. In order to convert gradation color specification data between different color specification spaces, a plurality of grid points are set in the conversion source color specification space, and the gradation color specification data in the conversion destination color specification space is set to these lattice points. A recording medium recording a print control program for generating image data for printing with reference to a corresponding color conversion table,
A driver program for print control and a primary color conversion table showing the correspondence of conversion at a small number of grid points are stored in the auxiliary storage device,
When executing printing with the above driver program,
An interpolation function for generating the color conversion table in the main memory area of the computer by increasing the lattice points of the original color conversion table by nonlinear interpolation;
A recording medium on which a printing control program is recorded, characterized in that a computer realizes a function of performing linear interpolation based on a generated color conversion table to generate image data for printing.

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