JP2007096430A - Apparatus, method, and program for generating color reproduction range - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of generating a color reproduction range for acquiring the color reproduction range at the design of a printer and accurately particularizing the color reproduction range. <P>SOLUTION: In the method of generating the color reproduction range, a print condition is acquired in generating information indicating the color reproduction range, color values are obtained when printing using a plurality of color material amounts is executed under the print condition on the basis of a predetermined model, and information indicating the color reproduction range is acquired by tying color values acquired in a device independent color space by line segments below a predetermined threshold value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for determining a color reproduction range.

In a printing apparatus, even if the same machine is used, the color reproduction range changes when the printing conditions change, such as the type of color material, the type of print medium, and the amount of color material used. Since the color reproduction range is an important factor that determines the capability and image quality of the printing apparatus, it is necessary to examine it accurately and carefully when designing the printing apparatus (for example, when creating a color conversion profile). Conventionally, a technique for acquiring a color reproduction range has been proposed (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2005-18171

In the conventional technology described above, the color reproduction range cannot be acquired when designing the printing apparatus, and the color reproduction range cannot be specified accurately.
That is, in the above conventional technique, an image signal is acquired by reading a plurality of samples using a reading device such as a scanner. Therefore, in order to obtain the color reproduction range, it is necessary that the printing results obtained by printing with at least a plurality of samples are obtained. However, at the time of designing a printing apparatus, it is not determined how to combine and print color materials in order to express a certain color. Further, even if a combination of color materials for outputting a certain color is tentatively determined by a color separation process or the like, it is unclear whether the combination sufficiently brings out the capability of the printing apparatus. Therefore, even if the color reproduction range of the printing apparatus capable of measuring the printing result and obtaining the printing result is determined, this color reproduction range cannot be used for the examination at the time of designing the printing apparatus.

Furthermore, in the color values determined based on a plurality of samples, it is impossible to determine whether or not these color values form the outline of the color reproduction range, and only the outline of the color reproduction range can be determined. . For example, the color reproduction range is not necessarily convex outward in all regions, and a concave portion may be formed in part. In the above-described conventional technology, only the outermost color value is selected for each divided area, and with this configuration, the color reproduction range having a complicated shape cannot be accurately specified. .
The present invention has been made in view of the above problems, and is a color reproduction range generation technique that cannot acquire a color reproduction range when designing a printing apparatus and that can accurately specify a color reproduction range. For the purpose of provision.

  In order to achieve the above object, the present invention acquires color values when printing is performed with a plurality of color material amounts based on a predetermined model, and information indicating a color reproduction range based on the acquired color values To get. Therefore, according to this model, it is possible to obtain color values corresponding to the amount of color material without actually printing many patches, and to obtain a color reproduction range without actually printing many patches. Can do. Further, since the color value acquisition means can convert the color material amount into a color value according to the printing conditions, the color reproduction range for each printing condition can be simulated. Accordingly, it is possible to acquire a plurality of color reproduction ranges at the time of designing a printing apparatus, and to determine preferable printing conditions based on each color reproduction range.

  Note that the color value acquisition means can acquire the color value without performing printing (without measuring the print result) by converting the color material amount into the color value based on the model. Is extremely important. In other words, if you use a model that calculates the color value from the color material amount, you can obtain the color value by calculation, so it is very easy to acquire color values for a very large number of color material amounts. It is also possible to acquire color values for all possible color material amounts depending on the case.

As described above, when a large number of color values are used, a large number of color values forming the outline of the color reproduction range can be obtained, and the color reproduction range can be accurately defined. On the other hand, assuming that the print result is colorimetric, it is extremely complicated to obtain a large number of colorimetric values, and the number of color values that can be obtained by performing colorimetric work is a realistic number (for example, Limited to about 10 ³ ). For this reason, even if the outline of the color reproduction range is defined based on these color values, the shape is not accurately described.

  In particular, when the number of color materials used in the printing apparatus is large, such as six colors, the number of combinations of the color materials becomes extremely large. In the present invention, even if the number of colors of the color material increases, the processing load does not change much. Therefore, the effect of the present invention becomes more prominent as the number of colors of the color material increases. In addition, assuming that it is possible to compare a plurality of color reproduction ranges under different printing conditions and derive preferable printing conditions, it is necessary to repeat color measurement with slight changes in printing conditions in a configuration that measures the color of printed matter. It is not feasible. In this sense, the effect of generating the color reproduction range based on the model is extremely large.

  The printing conditions may be any conditions that can affect the color reproduction range. That is, if the color reproduction range changes due to changing the conditions, even if the color value is different even if the color material amount is the same or the amount of usable color material is changed, all such conditions are met. It is. The printing condition acquisition unit may be configured to receive information indicating at least two or more different printing conditions.

  The color value acquisition unit only needs to be able to calculate color values corresponding to a plurality of color material amounts under at least two or more printing conditions. Accordingly, different models may be applicable depending on the printing conditions, and the amount of color material that can be selected with the same model may be varied depending on the printing conditions, and various configurations can be employed. In any case, it is only necessary that the color value corresponding to the color material amount can be acquired in accordance with the printing conditions.

  The color reproduction range acquisition unit only needs to be able to acquire information indicating the color reproduction range based on the acquired color value. Here, the information indicating the color reproduction range only needs to indicate the color reproduction range, that is, the range of possible color values, and the accuracy may vary depending on the amount of color material calculated based on the model, but at least The color reproduction range (that is, information indicating the color range that can be expressed by the printing apparatus in the color space) may be acquired based on the color value.

  As described above, various conditions can be adopted as printing conditions. As a preferable example, any one of a coloring material used for printing, a printing medium, a usage limit of the coloring material, and a coloring material recording method or A configuration including a combination can be employed. In this sense, if the color material used for printing (for example, the type and composition of ink and toner) changes, the color value can vary even with the same color material amount (weight and coverage of the print medium). The color material can be a printing condition. Further, according to this configuration, it is possible to compare the difference in the color reproduction range due to the color material. Printing conditions may be set by setting the number of color materials to be used among the color materials having the number of colors prepared in advance. According to this configuration, it is possible to acquire a change in the color reproduction range according to the number of color materials used. The same applies to the print medium. If the print medium such as plain paper, glossy paper, matte paper, etc. changes, the color value can vary even with the same amount of color material, and in this sense, the print medium can be a printing condition. Further, according to this configuration, it is possible to compare the difference in the color reproduction range depending on the print medium.

  Furthermore, if the color material usage limit varies, even if other conditions are the same, the color values that can be expressed are different, so the color material usage limit can be a printing condition. According to this configuration, it is possible to compare the differences in the color reproduction range due to the color material usage amount limitation, and it is possible to specify a preferable usage amount limitation in view of the color reproduction range. The color material usage limit may be any condition that regulates the amount of the color material. For example, the color material use amount depends on the condition that regulates the upper limit of the color material amount that can be used, the brightness, and the gradation of the color material. Various conditions such as a condition for defining an impossible color can be adopted. The former is used for preventing the bending of the print medium by defining the amount of the color material that can be used when one or more color materials are used. The latter is used for preventing the graininess from being noticeable by suppressing the use of a color material that is noticeable compared to the surroundings.

  The color material recording method is a recording method that can be selected by a printing apparatus, and includes all methods in which the color reproduction range can vary due to a difference in the recording method. For example, it includes various recording methods such as halftone algorithm, print sheet feed amount control in an inkjet printer, print resolution, selection of unidirectional printing or bidirectional printing, presence / absence of automatic color correction processing, print quality, and the like. Of course, when these recording methods and other conditions are related to each other, for example, when the usage limit varies by changing the recording method, the other conditions may change when one of the conditions is selected. In addition, the printing conditions may be set in advance, and the printing conditions acquisition unit may acquire these conditions.

  As described above, various conditions can be adopted as printing conditions. As an example, the above model is created corresponding to the color material and print medium used for the printing, and the amount of color material used It is possible to adopt a configuration in which the color value is acquired by changing the limit. According to this configuration, it is possible to acquire a color reproduction range for each color material usage amount limitation, and to compare differences in color reproduction ranges due to color material usage amount limitation. Of course, in this configuration, if different models are constructed by changing the color material used for printing and the print medium, the color reproduction range is compared depending on the color material used for printing and the print medium. It becomes possible.

  As a specific example of the model in the color value acquisition unit, a model that calculates the color value based on the spectral reflectance can be adopted. That is, a model for specifying the coverage by the color material on the print medium is constructed in association with the amount of the color material recorded on the print medium, and the color material and the print medium recorded on the print medium are further predetermined. If a model that defines each spectral reflectance when the light is irradiated is constructed, it is possible to acquire the spectral reflectance of the printing result in an arbitrary color material amount based on such information. If the spectral reflectance is calculated, it is possible to convert the spectral reflectance into a color value by a known formula.

As a result, it is possible to convert an arbitrary color material amount into a color value based on the model. As long as this model is obtained, a large number of color material amounts can be converted into color values without performing printing at all. It becomes possible. Here, it is sufficient that the color value can be acquired without performing printing and color measurement by calculating the color value based on the model. Therefore, the model is not limited to the above, and even if printing or colorimetry is performed at the time of creating the model, the color value can be set without performing printing and colorimetry after the model is created once. It only has to be acquired. As another model, for example, a density gradation value indicating a color material amount is converted into an RGB luminance component on the basis of Lambert Beer's Law (New Color Science Handbook 2nd Edition, Tokyo University Press, page 222), and the RGB A model or the like that converts a luminance component into a color value (L ^* a ^* b ^* value or the like) can be employed.

  The color reproduction range acquisition unit only needs to be able to acquire information indicating the color reproduction range based on the color value. Since the color reproduction range indicates the range of colors that can be expressed in the printing apparatus, it is sufficient that the color values existing in the outline of the color reproduction range can be acquired. A configuration in which color values are connected by lines can be employed. According to this configuration, the shape of the color reproduction range can be visualized in the device-independent color space. Note that the device-independent color space may be a space in which color values expressed by device-independent colors can be plotted, and is preferably three-dimensional, but may be two-dimensional.

  As a method for connecting a plurality of color values with lines, various methods can be employed, for example, a delaunay method or the like. According to the delaunay method, it is possible to generate a triangle (tetrahedron in the case of 3D) having the color value as a vertex by connecting a plurality of color values with lines, and easily visualize the shape of the color reproduction range be able to. However, in the present invention, in order to express a color reproduction range that should form a concave portion, a line segment longer than a predetermined threshold is not a line connecting color values. For example, a tetrahedron having a line segment longer than the threshold is deleted.

  In other words, when the outer surface of the color reproduction range is a recess, the line disappears when a line segment that spans the recess is formed when the color values are connected to form a solid, but the outline of the color reproduction range is generally The curved line that gradually changes, and the line segment straddling the concave portion is a long line segment as compared with other line segments. Therefore, if a threshold value is set in advance and a color value is not formed in a line segment longer than the threshold value, the color reproduction range can be visualized without erasing the concave portion formed on the outer surface of the color reproduction range. be able to. Accordingly, it is possible to acquire a color reproduction range as accurate as possible within the range that can be formed from the acquired color values. Note that the algorithm for connecting the color values is not limited to the above algorithm. For example, even if a process for forming a convex hull is adopted, the color values are connected by a line that is equal to or less than a predetermined threshold value. Disappearance can be prevented.

  As the threshold value, various values can be set as long as the concave portion of the color reproduction range can be formed. As a preferable configuration, a cell set in advance in the device-independent color space can be used. That is, it is considered that the device-independent color space is divided into a plurality of cells having the same size in advance and the color values included in the cells are connected. At this time, if color values are acquired based on a large number of color material amounts, cells that include color values and that are outermost in the device-independent color space can be easily defined. Here, the cell is preferably a square or a cube.

  If the outermost cell in the device-independent color space can be defined, the color reproduction range can be visualized by connecting the color value included in each cell with a line, but at this time, the color value included in each cell The distance when is farthest is twice the length of vertices located diagonally in the cell. Therefore, if this distance is used as a threshold value, when connecting a color value in one cell and a color value in another cell, it is not necessary to skip one or more cells and connect the color value. It is possible to connect the color values with a line without any problem.

  Also, if you define a cell and define a threshold based on the cell, you can define the length of the line segment that connects the color values, so you can extract the cells that contain at least one color value and extract the color value. By performing the tying process, it is possible to define the resolution when expressing the color reproduction range. That is, it is possible to define how finely the outline of the color reproduction range is expressed. Therefore, the size of the cell may be defined based on the required resolution of the color reproduction range.

  In addition, if a cell is defined, it is easy to select a preferable color material amount and color value. That is, when a plurality of color values are present in a cell when color values are acquired based on a large number of color material amounts, if a color material preferable for use in a printing apparatus is selected from among them, the color material amount and The color reproduction range can be evaluated after defining the color value. In order to select whether or not it is preferable for use in a printing apparatus, various indexes can be adopted, for example, CII (Color Inconstancy Index), MI (Metameric Index), etc. can be adopted. For CII, Billmeyer and Saltzman's Principles of Color Technology, 3rd edition, John Wiley & Sons, Inc, 2000, p.129, for MI, Billmeyer and Saltzman's Principles of Color Technology, 3rd edition, John Wiley & Sons, Inc, See 2000, p.127.

  Furthermore, in a configuration in which cells are defined in advance in the device-independent color space, information indicating a color reproduction range may be acquired by connecting two color values included in the same cell and adjacent cells. Even in this configuration, when connecting the color value in one cell and the color value in another cell, it is not necessary to skip one or more cells and connect the color value. Can be connected with a line. The adjacent cell includes both a cell sharing a side and a cell sharing a vertex.

  Of course, the above invention can be realized not only by the apparatus but also by a method, and can also be realized by a program for executing processing performed by the apparatus. In addition, the idea of the invention is that the apparatus, method, and program according to the present invention may be implemented independently, or may be implemented together with other apparatuses, methods, and programs while being incorporated in a certain device. Is not limited to this, and includes various aspects, and can be changed as appropriate.

  Further, it can be provided as a recording medium on which the program of the present invention is recorded. The recording medium for this program 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. Further, even when a part is software and a part is realized by hardware, the idea of the invention is not completely different, and a part is stored on a recording medium and is appropriately changed as necessary. It may be in the form of being read. Further, not all functions are necessarily realized by a single program, but may be realized by a plurality of programs. In this case, what is necessary is just to make each function implement | achieve in a some computer.

Here, embodiments of the present invention will be described in the following order.
(1) Configuration of the color reproduction range generation device:
(1-1) Color reproduction range generation processing:
(2) Printing model:
(3) Other embodiments:

(1) Configuration of the color reproduction range generation device:
FIG. 1 is a block diagram illustrating a hardware configuration and a software configuration of a color reproduction range generation apparatus that generates a color reproduction range according to printing conditions. The computer 10 includes a CPU 11 that is the center of arithmetic processing, and the CPU 11 controls the entire computer 10 via a system bus. The system bus is connected to a ROM 12, a RAM 13, a hard disk 14, a USB I / F, a CRTI / F, an input device I / F, etc. (not shown).

  The hard disk 14 stores an operating system (OS) as software, a color reproduction range generation program 20 for simulating the color reproduction range for each printing condition, and the like. Forwarded to The CPU 11 executes various programs under the control of the OS while appropriately accessing the RAM 13 as a temporary work area.

  The hard disk 14 stores model data 14a indicating a printing model defined in advance as data used by the color reproduction range generation program 20, and after generating the color reproduction range, data indicating the color reproduction range. Are recorded as the color reproduction range data 14b. In the present embodiment, the printing model calculation module, which will be described later, is configured to simulate color values when printing is performed on a specific ink set and a specific print medium.

  Therefore, in the present embodiment, simulation is performed based on the model indicated by the model data 14a, and the spectral reflectance in a state where ink is recorded, the spectral reflectance of the print medium, and the level of the ink amount. Data indicating the coverage of the print medium corresponding to the tone value is model data 14a. The spectral reflectance is a reflectance for each wavelength of light obtained on the assumption that light from a predetermined light source is applied to the ink or the print medium. The color reproduction range data 14b is data for connecting the color values constituting the outline of the color reproduction range with lines, and indicates the color values connected with the lines. Therefore, the shape of the color reproduction range can be visualized by plotting the color values in the space with reference to the color reproduction range data 14b and connecting the color values with lines.

  A keyboard 17 and a mouse 16 (not shown) are connected to the input device I / F as operation input devices. A display 18 for display is connected to the CRTI / F. Therefore, the computer 10 can accept the operation contents by the keyboard 17 and the mouse 16 and can display various information on the display 18.

(1-1) Color reproduction range generation processing:
In the present embodiment, a color reproduction range generation program 20 is provided in the computer 10, and the user simulates the color reproduction range by executing the color reproduction range generation program 20. The color reproduction range generation program 20 includes a printing condition acquisition unit 21, a color value acquisition unit 22, and a color reproduction range acquisition unit 23. The color value acquisition unit 22 further includes a sample generation module 22a and a printing model calculation module 22b. The color reproduction range acquisition unit 23 includes an outline extraction module 23a and a line segment generation processing module 23b.

  FIG. 2 is a flowchart of the color reproduction range generation process. When the color reproduction range generation program 20 is executed, the print condition acquisition unit 21 displays a UI (not shown) on the display 18 and print conditions using the keyboard 17 or the like. Is accepted (step S100). In the present embodiment, the print medium and the ink set are defined in advance, and are configured to simulate a color reproduction range when the ink usage limit and the number of ink colors are varied. That is, in this embodiment, the printing conditions are the ink usage limit and the number of ink colors.

  More specifically, the usage amount of ink is specified by gradation data for each color, and when the ink usage amount limit is changed, the limitation of the gradation data can be changed. For example, it is possible to specify the upper limit of the usage amount when using ink of 1 to 6 colors for all of 1 to 6 colors, and it is possible to set printing conditions by specifying a desired upper limit. Of course, the usage limit is not limited to the upper limit, and various other limitations can be set, such as a restriction that a specific ink cannot be used until the gradation value of the other ink reaches a certain level. . The number of ink colors is the number of ink colors used in an ink set prepared in advance. For example, it is possible to set the printing conditions by specifying to use all the colors of six ink sets or to use four of them.

  In any case, in step S100, the user-desired printing condition is instructed from the pre-selectable printing conditions, and the printing condition acquisition unit 21 acquires the instructed printing conditions. . In the present embodiment, the processing in step S100 corresponds to the processing in the printing condition acquisition unit. When the printing condition acquisition unit 21 acquires the printing conditions, the sample generation module 22a of the color value acquisition unit 22 generates a plurality of combinations (samples) by combining the gradation data for each color that specifies the amount of ink used ( Step S105).

In this embodiment, since the information indicating the color reproduction range is obtained by visualizing the outline of the color reproduction range, the sample may be a sample that forms the outline and satisfies the printing condition. At the stage of generating the sample, it is unclear what combination of gradation data forms the outline and satisfies the printing condition. Therefore, in the present embodiment, a large number of samples are first generated regardless of whether or not an outline is formed, and gradation values that equally divide a gradation value range (for example, 10 equal parts) are extracted and combined. number by (e.g., 11 ⁶⁾ to produce a sample.

  After generating a large number of samples, the printing model calculation module 22b refers to the printing conditions acquired in step S100 and acquires samples that match the specified printing conditions (step S110). That is, samples that do not satisfy the ink usage limit specified in the printing conditions are excluded, and samples that do not match the number of ink colors specified in the printing conditions are excluded.

When samples that match the printing conditions are acquired, the printing model calculation module 22b refers to the model data 14a and converts the gradation data of these samples into color values (step S115). The printing model calculation module 22b obtains a spectral reflectance when the printed matter is printed with the predetermined light source when printing is performed with arbitrary gradation data, and further, based on the spectral reflectance, a color value (for example, , L ^* a ^* b ^* value). Therefore, according to the printing model calculation module 22b, the color value when printing is performed with the ink amount specified by the gradation data is calculated based on the model. The processing of the printing model calculation module 22b will be described in detail later. In the present embodiment, steps S105 to S115 described above correspond to the processing in the color value acquisition unit.

The left side of FIG. 3 shows an explanatory diagram for explaining the state after the gradation data of the sample is converted into color values. The left side of FIG. 3 schematically shows a state in which the color values corresponding to the gradation data of the sample are plotted in the L ^* a ^* b ^* space which is a device-independent color space. As shown in the figure, a large number of plot points are distributed in the L ^* a ^* b ^* space. When these plot points are connected, the outermost contour is visualized and the color reproduction range is visualized.

On the other hand, in step S105, since the sample is generated regardless of whether or not it exists in the outline, the plot points shown on the left side of FIG. 3 have many points that exist inside the solid representing the color reproduction range. include. Therefore, the outline extraction module 23a of the color reproduction range acquisition unit 23 extracts points existing in the vicinity of the outline and performs processing for thinning out other points. For this purpose, the outline extraction module 23a divides the L ^* a ^* b ^* space into a plurality of cells (step S120).

For example, each gradation value range of L ^* value, a ^* value, and b ^* value is divided equally, and a cell composed of a cube having the same size is created with a combination of values obtained by the division as vertices. On the left side of FIG. 3, an example in which the L ^* a ^* b ^* space is divided into 16 equal parts is shown on each axis of L ^* a ^* b ^* . After creating a cell, the cell further outline extraction module 23a analyzes the L ^* a ^* b ^* values in each cell, present in the outermost among the cells comprising at least one of L ^* a ^* b ^* values within ( A cell existing in the outline is extracted (step S125). By this processing, it is possible to exclude most of the points existing inside the solid indicating the color reproduction range.

If cells existing in the outline are extracted, a solid representing the color reproduction range can be visualized by connecting the L ^* a ^* b ^* values included in these cells with lines, and therefore the line segment generation processing module 23b. Performs processing to generate a line segment connecting L ^* a ^* b ^* values. For this purpose, the line segment generation processing module 23b first sets a threshold value based on the cell size (step S130). In the present embodiment, the threshold is set to twice the length connecting the diagonal vertices at the farthest positions among the cubes in the cell.

  After determining the threshold value, the line segment generation processing module 23b generates a line segment so as to form a tetrahedron with the color value as a vertex by the delaunay method (step S135), and the side longer than the threshold value among the sides of this tetrahedron Is deleted (step S140). As a result, a line segment indicating the outline of the color reproduction range is formed while representing the concave portion as much as possible, and information for accurately visualizing the color reproduction range can be acquired.

  The right side of FIG. 3 shows a diagram for explaining the threshold value. That is, on the right side of FIG. 3, eight cells are extracted and shown. As shown in this figure, the diagonal line connecting the farthest vertices in each cell indicates the distance of the farthest point included in each cell. Show. Therefore, if a threshold is set to twice the length connecting the diagonal vertices at the farthest of the cubes in a cell, and a line segment longer than this threshold is cut, two adjacent cells (vertices) Two color values at the farthest distance are connected, but two color values at a farther distance are not connected. As a result, it is possible to connect color values without forming long line segments that cause the recesses to disappear.

  FIG. 4 is an explanatory diagram for explaining how to prevent the disappearance of the recesses. In the figure, for ease of explanation, the color reproduction range and the cell are shown in two dimensions, and an example is shown in which a triangle is formed when connecting color values and a side longer than the threshold is cut. As described above, the technical idea is the same regardless of whether the processing is in three dimensions or the processing in two dimensions shown in FIG.

The left side of FIG. 4 shows the color reproduction range G when the L ^* a ^* b ^* space is cut at a certain L ^* value, and the right side of FIG. A two-dimensional cell (that is, a square) formed in the region is shown. In the two-dimensional cell, the color value is indicated by a black circle. In this cell, the left side of the figure is the inside of the color reproduction range, but since the cell existing at the outer corner is extracted in step S125, the color values of the objects connecting the line segments are concentrated on the surface of the color reproduction range. ing.

  Each black circle is connected as a solid line by the delaunay method to form a triangle with each black circle as a vertex. However, since the broken line shown on the right side of FIG. 4 is longer than the threshold value, this broken line is not connected. As shown on the right side of FIG. 4, the broken line is a line segment that disappears the concave portion. However, in the present invention, since the broken line is not connected, the concave portion remains formed on the inner side (left side in FIG. 4). . Accordingly, the color reproduction range can be visualized while accurately expressing the concave portion.

When the line segments connecting the color values are determined as described above, the line segment generation processing module 23b generates the color reproduction range data 14b that is information indicating these line segments, records the data on the hard disk 14, and displays the display 18. (Step S145). Various forms can be adopted for display on the display 18. For example, a perspective image of the L ^* a ^* b ^* space is expressed, and the color values are plotted in this space, and each color value is connected by a line segment, or the outermost triangle formed by each line segment is colored. Various configurations such as shown can be adopted. Of course, the L ^* a ^* b ^* space may be cut so that the color reproduction range in a certain plane can be visually recognized. In the present embodiment, the processing in steps S130 to S145 corresponds to the processing in the color reproduction range acquisition unit.

  By the above processing, it is possible to generate information indicating the color reproduction range under the printing conditions specified in step S100 and to visually recognize the color reproduction range. By repeating the above processing while changing the printing conditions. The color reproduction range for each printing condition can be simulated. Therefore, it is possible to simulate the color reproduction range at the time of designing a printing apparatus capable of printing under each printing condition, and the color reproduction range is determined so as to optimize the combination of cost and image quality. It becomes possible to design a printing apparatus on the above.

  FIG. 5 is an explanatory diagram for explaining how the color reproduction range is simulated. In the same figure, as in the example described above, the model data 14a is irradiated with light from a predetermined light source on the print medium A and the specific six-color ink (CMYKlclm (C: cyan, M: magenta). , Y: Yellow, K: Black, lc: Light Cyan, lm: Light Magenta)) are recorded on the printing medium A and the light is emitted from a predetermined light source, and the gradation value of the ink amount is obtained. The example of the state in which the data which show the coverage of the printing medium A by the corresponding ink is defined is shown.

  At this time, if the color reproduction range is simulated by setting the ink usage limit (duty A) determined based on a specific rule as the printing condition, the color reproduction range under this condition is visualized (FIG. 5). (A)). Further, if the color reproduction range is simulated by setting different usage amount limits (duty B) of ink, the color reproduction range when printing is performed with duty B on the print medium A and the six color inks is visualized. (FIG. 5B). Further, if the number of inks used is set to 4 colors (for example, CMYK) and duty A as the printing conditions, the color reproduction range when printing on the printing medium A can be visualized under these conditions ( FIG. 5 (c)).

  As described above, if the color reproduction range under various printing conditions can be visualized, a preferable duty can be set by comparing the respective color reproduction ranges. In addition, the number of ink colors can be determined in consideration of cost and image quality. Furthermore, it is possible to consider whether or not to change to another ink set, or to change to another print medium. Since the above simulation can be performed without actually printing after the above model is determined, it is extremely easy compared to a configuration in which a color reproduction range is generated after printing and colorimetry. In addition, a study based on the color reproduction range can be performed.

(2) Printing model:
Next, an example of the printing model will be described in detail. The printing model described below is a model called Cellular Yule-Nielsen Spectral Neugebauer Model. This model is based on the well-known spectroscopic Neugebauer model and the Yule-Nielsen model. In the following description, a model using three types of CMY inks will be described, but it is easy to extend this to a model using a plurality of arbitrary inks.

FIG. 6 is a diagram showing a spectral Neugebauer model (a model for calculating the spectral reflectance from the ink recording state as shown on the left side of FIG. 6A). In the spectral Neugebauer model, the spectral reflectance R (λ) of an arbitrary printed material is given by the following equation (1).

Here, a _i is the area ratio of the i-th region, and Ri (λ) is the spectral reflectance of the i-th region. The subscript i includes an area without ink (w), an area where only cyan ink is recorded (c), an area where only magenta ink is recorded (m), and an area where only yellow ink is recorded (y ), An area (r) where magenta ink and yellow ink are recorded, an area (g) where yellow ink and cyan ink are recorded, an area (b) where cyan ink and magenta ink are recorded, and a CMY It means the area (k) where three inks are recorded. Further, f _c , f _m , and _fy are the ratio of the area covered with only one type of CMY ink when it is ejected (referred to as “ink coverage”, corresponding to the coverage in the above embodiment). It is. The spectral reflectance Ri (λ) is obtained by measuring the color patch with a spectral reflectance meter.

The ink coverages f _c , f _m , and _fy are given by the Murray-Davis model shown in FIG. In the Murray-Davis model, for example, the area ratio f _c of cyan ink is a nonlinear function of the cyan ink ejection amount d _c and is given in the form of a one-dimensional lookup table. The reason why the ink coverage is a nonlinear function of the ink discharge amount is that the ink spreads sufficiently when a small amount of ink is discharged per unit area, but the ink overlaps when a large amount of ink is discharged. This is because the area covered with ink does not increase so much.

ここで、ｎは１以上の所定の係数であり、例えばｎ＝１０に設定することができる。式（２ａ）および式（２ｂ）は、ユール・ニールセン分光ノイゲバウアモデル(Yule-Nielsen Spectral Neugebauer Model)を表す式である。 When the Yule-Nielsen model for spectral reflectance is applied, the above equation (1) can be rewritten as the following equation (2a) or (2b).

Here, n is a predetermined coefficient of 1 or more, and can be set to n = 10, for example. Expressions (2a) and (2b) are expressions representing the Yule-Nielsen Spectral Neugebauer Model.

  The Cellular Yule-Nielsen Spectral Neugebauer Model is the above-mentioned Yule-Nielsen Spectral Neugebauer Model that divides the space formed by the ink coverage into multiple cells. .

FIG. 7A shows an example of cell division in the cell division Yule-Nielsen spectroscopic Neugebauer model. Here, for simplicity, we depict cell division of a two-dimensional space including two axes of the ink coverage f _m of the ink area coverage f _c and the magenta and cyan. These axes f _c and f _m can also be considered as axes indicating the ink discharge amounts d _c and d _m . White circles are cell division grid points (called “nodes”), and the two-dimensional space is divided into nine cells C1 to C9. Spectral reflectances R ₀₀ , R ₁₀ , R ₂₀ , R ₃₀ , R ₀₁ , R ₁₁ ... R ₃₃ are determined in advance for the printed matter (color patch) at 16 nodes.

FIG. 7B shows the shape of the ink coverage _fc (d) corresponding to this cell division. Here, table via one ink amount in the range 0 to D _max of the ink is divided into three sections, the ink coverage f _c (d) is a curve that monotonously increases from 0 to 1 for each section Has been.

FIG. 7C shows a calculation method of the spectral reflectance Rsmp (λ) of the sample in the center cell C5 of FIG. The spectral reflectance Rsmp (λ) is given by the following equation (3).

Here, the ink coverages f _c and f _m are values given in the graph of FIG. 7B, and are values defined in the cell C5. Further, the values of the spectral reflectances R ₁₁ (λ), R ₁₂ (λ), R ₂₁ (λ), and R ₂₂ (λ) at the four vertices of the cell C5 are determined according to the above equation (3). It is adjusted to give (λ) correctly. Thus, if the space formed with the ink coverage is divided into a plurality of cells, the spectral reflectance Rsmp (λ) of the sample can be calculated with higher accuracy than when the space is not divided. Note that the cell division node value is preferably set independently for each ink color.

By the way, in the model shown in FIG. 7A, it is normal that the spectral reflectance at all nodes cannot be obtained by measuring the color patch. This is because bleeding occurs when a large amount of ink is ejected, and a color patch of uniform color cannot be printed. FIG. 8 shows a method for obtaining a spectral reflectance that cannot be measured. This is an example in the case of using only two types of ink, cyan and magenta. The spectral reflectance R (λ) of an arbitrary color patch printed with two types of inks of cyan and magenta is given by the following equation (4).

上述したように右辺の各項はすべて既知である。従って、式（５）を解くことによって、未知の分光反射率Ｒb(λ)を算出することができる。 Of the plurality of parameters included in the above equation (4), only the spectral reflectance Rb (λ) when both the cyan ink and the magenta ink are 100% ejection amounts is unknown, and the values of the other parameters are Assume that it is known. At this time, if the formula (4) is modified, the following formula (5) is obtained.

As described above, all the terms on the right side are known. Therefore, the unknown spectral reflectance Rb (λ) can be calculated by solving the equation (5).

  Spectral reflectances of secondary colors other than the cyan and magenta secondary colors can be obtained in the same manner. If the spectral reflectances of a plurality of secondary colors are obtained, the spectral reflectances of a plurality of tertiary colors can be obtained in the same manner. In this way, by sequentially obtaining higher-order spectral reflectances, it is possible to obtain all the spectral reflectances at each node in the space formed by the cell coverage ink coverage.

  The model data 14a indicates the spectral reflectance value at each node in the space formed by the ink coverage obtained by dividing the cells as shown in FIG. 7A and the ink coverage shown in FIG. 7B. And a one-dimensional lookup table. The printing model calculation module 22b shown in FIG. 1 is configured to calculate a spectral reflectance Rsmp (λ) for arbitrary ink amount data using these. Furthermore, it has data indicating the spectral distribution and color matching function of an arbitrary light source, and the tristimulus value is calculated by adding the product of the spectral reflectance Rsmp (λ) for each wavelength. Is converted by a known formula to obtain a color value.

(3) Other embodiments:
The above embodiment is an example, and various configurations are employed as long as the color reproduction range can be generated for each printing condition without performing printing by simulating the color reproduction range based on the model. Can do. For example, the threshold value is not limited to twice the diagonal line of the cell, and two color values included in the same cell and adjacent cells are connected to each other, and other color values are not connected to each other by a line segment. May be. Even in this configuration, the color reproduction range can be visualized without erasing the concave portion.

  In addition, as long as the upper limit length can be defined in advance so that the concave portion does not disappear, various other configurations are possible, and the threshold value is not necessarily set based on the cell. However, if the threshold is determined based on the cell, the degree of unevenness formed on the surface of the color reproduction range can be adjusted based on the size of the cell, so the resolution of the unevenness can be adjusted according to the size of the cell. Is possible.

  Furthermore, the printing conditions are not limited to the ink usage limit and the number of ink colors as described above, and various other printing conditions can be employed. For example, by creating model data 14a for a plurality of print media and ink sets in advance and making them selectable, the combination of print media and ink sets can be made variable as printing conditions. Further, the ink recording method may be included in the printing conditions. For example, a halftone algorithm can be selected. In this case, a model for determining the amount and coverage of ink recorded by each halftone algorithm may be constructed in advance, and this configuration makes it possible to simulate different color reproduction ranges by the halftone algorithm.

  In addition, the printing condition may include the printing paper feed amount control method and the presence / absence of bidirectional printing in the inkjet printer. That is, in an inkjet printer, ink is recorded with a plurality of nozzles on adjacent rasters by controlling the feeding and printing direction of printing paper, and the nozzles that record ink on each of the adjacent rasters are two specific nozzles. In some cases, control is performed to prevent printing of lines parallel to the main scanning direction. At this time, the amount of ink used may be different depending on these control methods. Therefore, the printing conditions may be determined by designating a control method (recording method) instead of limiting the amount of ink used.

  Also, if the amount of ink per discharge varies depending on the print quality, or if the spectral reflectance fluctuates depending on the presence or absence of automatic color correction processing, these factors are included in the printing conditions, depending on the printing conditions. The color reproduction range may be simulated with a different model. With the above configuration, the color reproduction ranges can be compared according to the recording method at the time of printing. Of course, other elements may be included in the printing conditions. For example, if printing is performed with a color value such that the MI or CII is equal to or less than a predetermined threshold, it is possible to visualize the color reproduction range in a state where the MI or CII is equal to or less than the predetermined threshold. It is.

  Furthermore, in the above-described embodiment, it is possible to remove the cells other than the cells existing in the outline and thin out the color values to be subjected to line segment generation processing, and to perform the processing at high speed. However, the thinning processing is essential. Not that. For example, if the computer has resources capable of performing processing at high speed, the line segment generation processing may be performed without performing thinning processing. Furthermore, the application target of the present invention is not limited to an ink jet printer, and can be used for simulating a color reproduction range in various printers (for example, printers using toner ink).

  Furthermore, the above model may be another model. For example, a model constructed as follows based on Lambert-Beer's law can be employed. First, for each ink color, a plurality of gradation values (for example, about 16 to 32 in 256 gradations) are extracted, and an ink amount is specified based on the extracted gradation values (for example, gradation values and The ink amount is specified as linear), and a patch is printed with each color and a single color for each ink amount. As a result, a plurality of patches are printed for each single color. Accordingly, the colorimeter measures the color of the patch and the paper white without ink, and obtains CMY density values for each color.

尚、式（６）は濃度を輝度に変換する一般的な式であるが、本実施形態ではＣＭＹ濃度を色成分毎の独立変数とし、中間ＲＧＢ輝度を求めるものとした。ここで、Ｔｒ，Ｔｇ，Ｔｂを中間ＲＧＢ輝度と呼んでおり、各インク単色の各パッチにおけるＲ輝度成分，Ｇ輝度成分，Ｂ輝度成分を示している。また、Ｄｃ，Ｄｍ，ＤｙはＣ濃度成分，Ｍ濃度成分，Ｙ濃度成分を示しており、ｉはインク色を区別するための符号である。 Further, by substituting this CMY density value into the following equation (6), RGB luminance (referred to as intermediate RGB luminance) is calculated for each patch of each ink color.

Equation (6) is a general equation for converting density to luminance, but in this embodiment, CMY density is an independent variable for each color component, and intermediate RGB luminance is obtained. Here, Tr, Tg, and Tb are called intermediate RGB luminances, and indicate R luminance component, G luminance component, and B luminance component in each patch of each ink single color. Dc, Dm, and Dy indicate a C density component, an M density component, and a Y density component, and i is a code for distinguishing ink colors.

  According to the above calculation, since the intermediate RGB brightness when printing with each ink single color is obtained for the gradation value, the correspondence between the intermediate RGB brightness and the gradation value of each ink single color is obtained. , It is possible to calculate intermediate RGB brightness corresponding to an arbitrary gradation value of a single ink color by interpolation calculation.

以上のようにして、ＲＧＢ輝度が算出されると、算出されたＲＧＢ輝度を３×３のマトリクスによってＸＹＺ表色系での値に変換し、このＸＹＺ表色系の値をさらにＬ^*ａ^*ｂ^*表色系での値に変換する。ここで、ｉはインク色を区別するための符号である。 Therefore, in order to further convert the intermediate RGB luminance into a color value, the RGB luminance corresponding to the color in a state where the ink colors are combined is calculated by the following equation (7).

When the RGB luminance is calculated as described above, the calculated RGB luminance is converted into a value in the XYZ color system using a 3 × 3 matrix, and the value of the XYZ color system is further converted to L ^* a ^*. b ^* Converted to a value in the color system. Here, i is a code for distinguishing ink colors.

By the above calculation, the RGB luminance is calculated by substituting the intermediate RGB luminance obtained by interpolation from the single-tone gradation value in an arbitrary color into the equation (7), and the L ^* a ^* b ^* value is calculated from this RGB luminance. Will be calculated. Therefore, a color value corresponding to an arbitrary gradation value can be acquired. As a result, any tone value can be converted to a color value, so a model that converts any ink amount to a color value by creating an expression or lookup table indicating this conversion has been built. become. Therefore, by executing step S115 using this model, it is possible to simulate the color reproduction range for each printing condition, as in the process shown in FIG.

  In the model according to the present invention, even if it is necessary to measure a certain number of patches for the construction of this model, it is not necessary to perform color measurement in order to obtain a color value corresponding to an arbitrary ink amount. Therefore, it is possible to simulate the color reproduction range for many samples generated in step S105 without printing, and once the model is built, it is possible to examine the printing conditions when designing the printing apparatus. become. Furthermore, in any of the above models, the color reproduction range can be set without determining rules (separation rules: rules such as undercolor removal) for specifying a large number of ink combinations necessary for outputting a certain color. Can be simulated. Therefore, the color reproduction range can be examined without being restricted by this rule.

It is a block diagram which shows a color reproduction range production | generation apparatus. It is a flowchart of a color reproduction range generation process. It is explanatory drawing of the color value in a device independent color space, a cell, and a threshold value. It is explanatory drawing for demonstrating a mode that the loss | disappearance of a recessed part is prevented. It is explanatory drawing explaining a mode that a color reproduction range is simulated. It is a figure which shows a spectral Neugebauer model. It is a figure which shows a cell division | segmentation Yule-Nielsen spectroscopic Neugebauer model. It is a figure which shows the method of calculating | requiring the spectral reflectance which cannot be measured in a cell division | segmentation Yule-Nielsen spectroscopic Neugebauer model.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Computer, 11 ... CPU, 12 ... ROM, 13 ... RAM, 14 ... Hard disk, 14a ... Model data, 14b ... Color reproduction range data, 16 ... Mouse, 17 ... Keyboard, 18 ... Display, 20 ... Color reproduction range generation Program, 21 ... Print condition acquisition unit, 22 ... Color value acquisition unit, 22a ... Sample generation module, 22b ... Printing model calculation module, 23 ... Color reproduction range acquisition unit, 23a ... Outline extraction module, 23b ... Line segment generation processing module

Claims (9)

Printing condition acquisition means for acquiring printing conditions;
Color value acquisition means for acquiring a color value based on a predetermined model when printing is performed with a plurality of color material amounts under the above printing conditions;
A color reproduction range generation device comprising color reproduction range acquisition means for acquiring information indicating a color reproduction range based on an acquired color value.   2. The color reproduction range generation according to claim 1, wherein the printing condition includes any one or a combination of a color material used for printing, a print medium, a color material usage limit, and a color material recording method. apparatus.   The model is created in advance corresponding to the color material and print medium used for the printing, and the color value acquisition means acquires a plurality of color material amounts for each use amount limit of the color material and obtains the color. 3. The color reproduction range generation apparatus according to claim 2, wherein a value is acquired.   The model is based on the spectral reflectance when the color material recorded on the print medium and the print medium are irradiated with predetermined light and the coverage by the color material on the print medium. The color reproduction range generating apparatus according to claim 1, wherein a color value is obtained by calculating a spectral reflectance when printing is performed.   The said color reproduction range acquisition means acquires the information which shows a color reproduction range by connecting the said acquired color value with the line below a predetermined threshold value within apparatus independent color space, The said claim | item characterized by the above-mentioned. The color reproduction range production | generation apparatus in any one of Claims 1-4.   6. The color reproduction range acquisition unit according to claim 5, wherein the threshold value is twice the length of vertices located diagonally in a predetermined cell in the device-independent color space. Color reproduction range generator.   The color reproduction range acquisition means defines a cell in advance in a device-independent color space, and acquires information indicating the color reproduction range by connecting two color values included in the same cell and adjacent cells. The color reproduction range generation device according to claim 1, wherein the color reproduction range generation device is a color reproduction range generation device. A color reproduction range generation method for generating information indicating a color reproduction range,
A printing condition acquisition step for acquiring printing conditions;
A color value acquisition step of acquiring a color value based on a predetermined model when printing is performed with a plurality of color material amounts under the printing conditions;
A color reproduction range generation method comprising: a color reproduction range acquisition step of acquiring information indicating a color reproduction range based on an acquired color value. A color reproduction range generation program for generating information indicating a color reproduction range,
A print condition acquisition function for acquiring print conditions;
A color value acquisition function for acquiring a color value based on a predetermined model when printing is performed with a plurality of color material amounts under the printing conditions;
A color reproduction range generation program that causes a computer to realize a color reproduction range acquisition function that acquires information indicating a color reproduction range based on an acquired color value.

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