JP4349444B2 - Color gamut information creation device and color gamut information creation program - Google Patents

Description

The present invention relates to a color gamut information generating equipment Contact and color gamut information creating program, in particular, the color that can reflect the scooped color gamut, creating a gamut information can be reproduced more faithfully gamut the present invention relates to frequency information creating equipment you and gamut information creation program.

  Conventionally, there is a system in which an image is input from an input device and the image is output by an output device. In such a system, color matching processing (color gamut compression) is performed in order to correct a difference in appearance due to a difference in color gamut (color gamut) between the input device and the output device.

  The color matching process will be described with reference to FIG. FIG. 12 is a diagram schematically illustrating an example of the configuration of a conventional color matching processing system. The color matching processing system shown in FIG. 12 includes an input-side printer 200 as an input device, an output-side printer 202 as an output device, and a color matching device 204. When the RGB data 206 is input from an external device such as a personal computer, the input side printer 200 and the output side printer 202 form an image on the recording paper 208 according to the RGB data 206.

  Here, because the input-side printer 200 is a higher model than the output-side printer 202, the color range (that is, the color gamut) that can be output by the output-side printer 202 is the color gamut of the input-side printer 202. If there is a color that can be output by the input-side printer 202 but cannot be output by the output-side printer 202, even if the same RGB data 206 is input, the recording paper 208 is output as an output result. The appearance of the entire image formed above will be different.

  Therefore, the color matching device 204 acquires the color gamut of the input-side printer 200 and the color gamut of the output-side printer 202, compares them, and can output the data on the input-side printer 200. Then, correction is performed for colors that cannot be output, and processing for making the appearance of the entire image closer is performed.

  With reference to FIG. 13, a process until the color matching apparatus 204 acquires the color gamut of the printer will be described. FIG. 13A shows a conventional input side printer 200, RGB data 206 for test print input to the input side printer 200, and input side printer 200 as a result of input of the RGB data for test print. FIG. 2 is a diagram schematically illustrating a recording sheet 208 on which color patches are formed by 200. The color of the color patch formed on the recording paper 208 can be measured by a colorimeter.

  FIG. 13B is an image diagram of the color space of the L * a * b * color system in which the colorimetric values obtained by measuring the color patches are plotted. The points plotted in the color space based on the colorimetric values are referred to as colorimetric points. The color gamut of the input side printer 200 can be specified by the distribution range of the colorimetric points in the color space. As one of methods for expressing such a color gamut, a method using a convex hull is known.

FIG. 14 is a diagram illustrating an example of a technique for expressing a color gamut using a conventional convex hull. As described with reference to FIG. 13B, each colorimetric point positioned in the color space is distributed three-dimensionally. First, as shown in FIG. The distributed colorimetric points are projected onto the plane 211 for each hue and dropped in two dimensions. Next, as shown in FIG. 14B, a convex hull 210 that is a convex figure including all colorimetric points projected in two dimensions is considered. The vertex for forming such a convex hull 210 can be obtained by using a known algorithm such as the Gift Wrapping method. When the vertex is determined, the range of the convex hull 210 corresponding to the color gamut can be expressed numerically using the coordinates of the vertex. Note that the output side printer 202 can also express the color gamut numerically by the same method.
JP 2002-2448066 A

  However, when the conventional concept of the convex hull is used as it is for expressing the color gamut, there is a problem that the color gamut cannot be expressed.

  With reference to FIG. 14C, the color gamut blur will be described. FIG. 14C is a diagram showing the convex hull 210 by a solid line and the color gamut 212 when the color gamut is taken into consideration by a wavy line. As shown in FIG. 14C, when the distance between the point A and the point B is quite long and the point C exists around the middle of the straight line AB, the straight line AB is the color gamut in the actual color gamut. In other words, the color gamut is blurred at the point C, and the straight line AC and the straight line CB form the color gamut. Such a point C cannot be selected by the conventional color gamut determination method using the convex hull 210.

  With reference to FIG. 15, problems that occur when the color gamut is not accurately expressed will be further described. FIG. 15A is a diagram in which a colorimetric point, a color gamut 212 of the input-side printer 200 formed as a convex hull including the colorimetric point, and a color gamut 214 of the output-side printer 202 are overlapped. FIG. 6B is an enlarged view of the main part of FIG. As shown in FIG. 15, the color gamut 212 of the input side printer 200 is wider than the color gamut 214 of the output side printer 202.

  According to the conventional color matching device 204, the color within the color gamut 212 of the input side printer 202, but the color such as point B outside the color gamut 214 of the output side printer 202 is the color of the output side printer 202. The mapping is performed in the area 214.

  However, as shown in FIG. 15B, the point B included in the color gamut 212 of the input-side printer 200 is a point at the boundary of the color gamut 212, but there are no colorimetric points around it. Perhaps the color gamut in the vicinity is actually faded and is expected to be a color that does not actually occur in the input side printer 200.

  Nevertheless, the color matching device 204 does not actually occur even in the input side printer 200. For the color such as point B, for example, any color in the color gamut 214 of the output side printer 202 is used. For example, the color of point C is assigned. The color generated by the point C in the input-side printer 200 is assigned with a point that is slightly less saturated than the point C in order to smooth the color gamut boundary.

  As a result, in the combination of the input side printer 200 and the output side printer 202, the color of the point C of the output side printer 202 is not used, and the color gamut that the output side printer 202 originally has cannot be fully utilized. It becomes.

The present invention has been made in order to solve the above-described problems, and gamut information that can create gamut information that reflects the gamut of the gamut and can reproduce the gamut more faithfully. is an object of the present invention to provide a preparation equipment you and gamut information creation program.

In order to achieve this object, the color gamut information creating apparatus according to claim 1 is based on each colorimetric value when the colorimetric value indicating the characteristics of the device is positioned on a plane having a constant hue angle in the color space. The color gamut information corresponding to the color gamut indicated as the distribution range of the feature points to be positioned is created, and the vertexes of the color gamut generated with at least three or more feature points as vertices among the feature points And gamut information creating means for creating gamut information based on the vertices extracted by the extracting means, and the vertices extracted by the extracting means are all in the gamut. The distance between vertices adjacent to each other is a predetermined value or less, and a vector from one vertex to one adjacent vertex adjacent to the one vertex, and other features other than the adjacent vertex from the one vertex Point to point A cross product of the torque, the outer product of when the distance from the apex of the 1 to the other feature points is less than the predetermined value, is always positive or always satisfies the relationship of a negative, the extraction When the orthogonal coordinate system is set on the plane, the means is one of the feature points located on the plane, the feature point having the maximum x coordinate, the minimum x coordinate, the maximum y coordinate, and the minimum y coordinate. When the point is the first vertex at the start, the distance from the first vertex is not more than the predetermined value, and when the first vertex is the maximum value or the minimum value of the x coordinate, start point extraction means for extracting a second vertex having a minimum angle with the x-axis when the y-coordinate is the maximum value or the minimum value, and a straight line connecting the feature point and the second vertex among the feature points; , The angle formed by the straight line connecting the first vertex and the second vertex is the minimum A feature point that extracts a feature point that satisfies a condition that a distance from the first vertex is within a predetermined range, and a feature point that satisfies the condition is extracted by the next point extraction unit. Then, the next point extraction repetition that repeats feature point extraction by the next point extraction unit using the second vertex as the first vertex and the feature point extracted by the next point extraction unit as the second vertex And the color gamut information creating means creates color gamut information corresponding to the color gamut including the points extracted by the start point extracting means, the next point extracting means, and the next point extracting and repeating means as vertices. It is characterized by being.

  The terms x-axis, y-axis, x-coordinate, and y-coordinate described in the claims are used as a general term for axes or coordinates that are orthogonal to each other in an orthogonal coordinate system. Is not intended to be limited to this.

The color gamut information creation device according to claim 2, when positioning the colorimetric values indicating the characteristics of the device on a plane having a constant hue angle in the color space , as a distribution range of feature points positioned based on each colorimetric value Color gamut information corresponding to the indicated color gamut, and extracting means for extracting vertices of the color gamut generated using at least three or more feature points as vertices among the feature points; and Color gamut information creating means for creating color gamut information based on the vertices extracted by the extracting means, and any of the vertices extracted by the extracting means has a distance between vertices adjacent to each other in the gamut. A cross product of a vector from one vertex to one adjacent vertex adjacent to the one vertex and a vector from the one vertex to another feature point other than the adjacent vertex that is equal to or less than a predetermined value Before Cross product when the distance from one vertex to the other feature points is less than the predetermined value, always satisfies a positive or always relationship is negative, the extracting means, orthogonal coordinate system to the plane Of the feature points positioned on the plane, the feature point having the maximum x coordinate, the minimum x coordinate, the maximum y coordinate, and the minimum y coordinate is set as the first vertex at the start. A first vertex extracting means for extracting; and a second vertex extracting means for extracting a second vertex adjacent to the first vertex in the color gamut, wherein the second vertex extracting means is a distance from the first vertex. Out of the feature points having a value less than or equal to the predetermined value, an outer product of a vector from the first vertex to the feature point and a vector from the first vertex to another feature point other than the feature point is the first product. The distance from the vertex to the other feature point is the predetermined distance In the following case, a feature point that satisfies the relationship of always positive or always negative is extracted as the second vertex, and when the second vertex is extracted by the second vertex extraction means, A second vertex extraction repeating unit that repeats the extraction of the second vertex by the second vertex extraction unit, with the two vertices being the first vertex, and the color gamut information creation unit includes the first vertex extraction unit or the second vertex Color gamut information corresponding to a color gamut including a point extracted by the vertex extraction means as a vertex is created.

The color gamut information creating apparatus according to claim 3, when positioning the colorimetric values indicating the characteristics of the device on a plane having a constant hue angle in the color space , as a distribution range of feature points positioned based on each colorimetric value Color gamut information corresponding to the indicated color gamut, and extracting means for extracting vertices of the color gamut generated using at least three or more feature points as vertices among the feature points; and Color gamut information creating means for creating color gamut information based on the vertices extracted by the extracting means, and any of the vertices extracted by the extracting means has a distance between vertices adjacent to each other in the gamut. A cross product of a vector from one vertex to one adjacent vertex adjacent to the one vertex and a vector from the one vertex to another feature point other than the adjacent vertex that is equal to or less than a predetermined value Before If the distance from one vertex to the other feature points cross product is equal to or less than the predetermined value, always satisfies a positive or always relationship is negative, for setting a Cartesian coordinate system in the plane, Prior to the extraction means, at least two of the feature points positioned on the plane are selected from among the feature points having the maximum x coordinate, the minimum x coordinate, the maximum y coordinate, and the minimum y coordinate. Selection means, distance acquisition means for acquiring a distance between feature points selected by the selection means, and when one distance is acquired by the distance acquisition means, a value smaller than the distance is set as the predetermined value. And a predetermined value determining means for determining, as the predetermined value, a value smaller than a maximum value among the acquired distances when a plurality of distances are acquired by the distance acquiring means.

The color gamut information creating apparatus according to claim 4 , wherein when colorimetric values indicating device characteristics are positioned in the color space, colors corresponding to color gamuts indicated as distribution ranges of feature points positioned based on the respective colorimetric values A gamut information is created, and a closed space generated with at least four or more feature points as vertices among the feature points as the color gamut, an extraction means for extracting the vertices, and an extraction means Color gamut information creating means for creating color gamut information based on the extracted vertices, and all the vertices extracted by the extracting means have a distance between vertices adjacent to each other in the gamut being a predetermined value or less. And a normal vector for a surface generated by two vertices whose distance from one vertex is equal to or less than the predetermined value and the one vertex, and the two vertices from the one vertex Other special features A inner product of the vector to the point, the inner product of the case where the distance from the apex of the 1 to the other feature points is within the predetermined value, is always positive or always satisfies the relationship of a negative When an orthogonal coordinate system is set in the color space, among the feature points positioned in the color space, the x coordinate is maximum, the x coordinate is minimum, the y coordinate is maximum, the y coordinate is minimum, the z coordinate is maximum, z The distance of at least one side of a solid composed of feature points with the smallest coordinates is acquired, and when the distance of one side is acquired, a value smaller than that distance is determined as the predetermined value, and the distance between a plurality of sides is determined. When it is acquired, a predetermined value determining means for determining a value smaller than the maximum value among the acquired distances as the predetermined value is provided.

Note that the terms x-coordinate, y-coordinate, and z-coordinate described in the claims are used as a general term for coordinates expressed in an orthogonal coordinate system, and the names of the coordinates are not intended to be limited thereto.

The color gamut information creation program according to claim 5, when positioning a colorimetric value indicating device characteristics on a plane having a constant hue angle in a color space, as a distribution range of feature points positioned based on each colorimetric value An extraction step for causing a computer to generate color gamut information corresponding to the indicated color gamut, and extracting the gamut vertices generated using at least three or more feature points as vertices among the feature points; The gamut information creating step for creating gamut information based on the vertices extracted in the extracting step, and the vertices extracted in the extracting step are all the gamut A distance between vertices adjacent to each other at a predetermined value or less and a vector from one vertex to one adjacent vertex adjacent to the one vertex; An outer product of a vector from the one vertex to another feature point other than the adjacent vertex, and the outer product when the distance from the one vertex to the other feature point is equal to or less than the predetermined value is always Satisfying the relationship of positive or always negative, and when the orthogonal coordinate system is set in the plane, the extraction step has a maximum x coordinate, a minimum x coordinate among the feature points positioned in the plane, One of the feature points having the maximum y coordinate and the minimum y coordinate is set as the first vertex at the start, and the distance from the first vertex is not more than the predetermined value, and the first vertex is the maximum of the x coordinate. A starting point extracting step of extracting a second vertex having an angle with the y-axis when the value is a minimum value or a minimum value with respect to the x-axis when the first vertex is a maximum value or a minimum value of the y coordinate; , Connecting the feature point and the second vertex A feature point that minimizes an angle formed by a line and a straight line connecting the first vertex and the second vertex and that satisfies the condition that the distance from the first vertex is within a predetermined range is extracted. When the feature point satisfying the condition is extracted by the next point extraction step and the next point extraction step, the second vertex at that time is set as the first vertex, and the feature point extracted by the next point extraction step is The second vertex is a next point extraction repeating step that repeats the extraction of feature points in the next point extraction step, and the color gamut information creation step includes the start point extraction step, the next point extraction step, the next point extraction repetition, and the like. Color gamut information corresponding to the color gamut including the point extracted by the return step as a vertex is created.

According to the color gamut information creation device according to any one of claims 1 to 3, any of the vertices extracted by the extraction unit has a distance between vertices adjacent to each other in the color gamut being a predetermined value or less. An outer product of a vector from one vertex to one adjacent vertex adjacent to the one vertex and a vector from the one vertex to another feature point other than the adjacent vertex, Since the outer product when the distance to other feature points is less than or equal to a predetermined value satisfies the relationship that it is always positive or always negative, if there is a color gamut, It is possible to extract the vertices to be expressed, and to create color gamut information that can reproduce the color gamut more faithfully based on the extracted vertices.

  Here, “vertices adjacent to each other in the color gamut” means that when the color gamut is generated by connecting the extracted vertices, one vertex is interposed between the vertices. . That is, two vertices constituting both ends of one side correspond to “vertices adjacent to each other in the color gamut”.

  “Create gamut information based on the vertices extracted by the extracting means” means that the gamut is a range formed by connecting only the vertices extracted by the extracting means, and the gamut information about the gamut. The color gamut information about the color gamut is defined as a color gamut that is generated by connecting a plurality of vertices including three or more vertices extracted by the extraction means. It is intended to include creating.

According to the color gamut information generating apparatus according to claim 1, wherein, among the Japanese Choten, straight line and, angle line and forms a minimum connecting the first apex and the second apex connecting the its feature points and the second vertex When the feature point satisfying the condition that the distance from the first vertex is within the predetermined range is extracted by the next point extraction means, the second vertex at that time is set as the first vertex, and The feature point extraction by the next point extraction means is repeated with the extracted feature point as the second vertex. Therefore, there is an effect that vertices representing color gamut blur can be extracted. Also, when one vertex is extracted, the next extracted is the vertex adjacent to that one vertex, so how to connect each vertex to generate a color gamut There is an effect that it can be easily determined.

  The next point extraction means is a feature point having a minimum angle formed by a straight line connecting the feature point and the second vertex and a straight line connecting the first vertex and the second vertex. Any means can be used as long as it can extract a feature point that satisfies the condition that the distance from the first vertex is within a predetermined range, and the specific calculation method is not limited.

According to the color gamut information creation device according to claim 2 , among the feature points whose distance from the first vertex is equal to or less than a predetermined value, a vector from the first vertex to the feature point, and the feature point from the first vertex. The feature point satisfying the relationship that the outer product of the vector to the other feature point other than the first feature point is always positive or always negative when the distance from the first vertex to the other feature point is equal to or smaller than a predetermined value. When two vertices are extracted by the second vertex extracting means, extraction of the second vertex by the second vertex extracting means is repeated with the second vertex at that time as the first vertex. Therefore, there is an effect that vertices representing color gamut blur can be extracted. In addition, when one vertex is extracted, the next extracted is the vertex adjacent to that one vertex, so how to connect each vertex to form a color gamut There is an effect that it can be easily determined.

  Note that the second vertex extraction means includes a vector from the first vertex to the feature point among the feature points whose distance from the first vertex is a predetermined value or less, and other than the feature point from the first vertex. A means for extracting a feature point that satisfies the relationship that the outer product of a vector to a feature point is always positive or always negative when the distance from the first vertex to another feature point is a predetermined value or less. There is no limitation to the specific calculation method.

According to the color gamut information generating apparatus according to claim 3, x-coordinate is the maximum, x coordinate is minimum, y-coordinate maximum, at least one of the two points of the y-coordinate is the minimum of the feature points is selected, the The distance between the selected feature points is acquired by the distance acquisition means. And when one distance is acquired by the distance acquisition means, a value smaller than that distance is determined as a predetermined value, and when a plurality of distances are acquired by the distance acquisition means, the maximum value among the acquired distances is determined. Since the smaller value is determined as the predetermined value, an appropriate predetermined value corresponding to the distribution range of the feature points can be determined by a simple calculation process.

According to the color gamut information creating device according to claim 4, the vertices extracted by the extraction unit are all such that the distance between adjacent vertices in the color gamut is equal to or less than a predetermined value, and from one vertex. A normal vector for a surface generated by two vertices whose distance is equal to or less than a predetermined value and the one vertex, and a vector from the one vertex to another feature point other than the two vertices Since the inner product satisfies the relationship that the inner product when the distance from the one vertex to the other feature point is within the predetermined value, the relationship is always positive or always negative. If this exists, it is possible to extract the vertices representing the drowning, and to create color gamut information that can reproduce the color gamut more faithfully based on the extracted vertices. effective.

5. The color gamut information creation device according to claim 4 , further comprising a feature point having a maximum x coordinate, a minimum x coordinate, a maximum y coordinate, a minimum y coordinate, a maximum z coordinate, and a minimum z coordinate. When the distance of at least one side of the solid to be obtained is acquired and the distance of one side is acquired, a value smaller than that distance is determined as the predetermined value, and when the distance of a plurality of sides is acquired, the acquired distance Since a value smaller than the maximum value is determined as the predetermined value, an appropriate predetermined value corresponding to the distribution range of the feature points can be determined by simple arithmetic processing.

According to the color gamut information creation program according to any one of claims 5 to 7, all the vertices extracted by the extraction step have a distance between vertices adjacent to each other in the color gamut being a predetermined value or less. An outer product of a vector from one vertex to one adjacent vertex adjacent to the one vertex and a vector from the one vertex to another feature point other than the adjacent vertex, Since the outer product when the distance to other feature points is less than or equal to a predetermined value satisfies the relationship that it is always positive or always negative, if there is a color gamut, It is possible to extract the vertices to be expressed, and to create color gamut information that can reproduce the color gamut more faithfully based on the extracted vertices.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing the overall configuration of a color data processing system including a color data processing apparatus 10 which is an embodiment of a color gamut information creation apparatus of the present invention. A color data processing system as shown in FIG. 1 includes a color data processing device 10, and an input side printer 30 and an output side printer 50 connected to the color data processing device 10. The color data processing device 10 is a device for converting color data in order to bring the appearance of the entire image formed by the input side printer 30 close to the appearance of the entire image formed by the output side printer 50. .

  As shown in FIG. 1, the color data processing apparatus 10 includes a CPU 11, a ROM 12, a RAM 13, an HDD 14, an input device 15, a display device 16, and a network interface 18 (I / F 18). .

  The CPU 11 is a central processing process that comprehensively controls the color data processing apparatus 10, and executes various programs such as a program that executes the processes shown in the flowcharts of FIGS.

  The ROM 12 is a non-rewritable memory that stores various control programs executed by the CPU 11 and data necessary for executing the control programs by the CPU 11. A program for executing the processing shown in the flowcharts of FIGS. 4, 5, and 7 is stored in the ROM 12. In particular, a color gamut forming program 120 (an example of a color gamut information creating program) for executing the processing shown in the flowcharts of FIGS. 5 and 7 is stored.

  Further, the ROM 12 stores a hue angle list 121. The hue angle list 121 describes a plurality of hue angles.

  The hue angle will be described with reference to FIG. FIG. 2A is a conceptual diagram showing the color space 60 of the L * a * b * color system in a three-dimensional manner. As shown in FIG. 2 (a), the hue angle φ is an angle shifted from the counterclockwise hue from 0 to the positive axis of a *, and is a value indicating the hue.

  In the hue angle list 121, for example, hue angles from 0 ° to 180 ° are described in increments of 9 °. According to the color data processing apparatus 10 of the present embodiment, the color gamut information is created for the hue section 61 (see FIG. 2A) of this hue angle, which will be described in detail later.

  Returning to FIG. The RAM 13 is a memory for temporarily storing data and programs necessary for various processes executed by the CPU 11, and includes an outer shell point memory 131, an input side gamut information memory 132, and an output side gamut information memory. 133 is provided.

  Outer shell point memory 131 stores a colorimetric point (hereinafter referred to as outer shell point) located in the outermost shell among the colorimetric points projected onto hue section 61 (see FIG. 2A). It is. In this embodiment, when a colorimetric value (L * a * b * value) obtained in advance by measuring the color output from the device is positioned in the color space 60, the colorimetric point value is plotted based on each colorimetric point value. This point is referred to as a colorimetric point (an example of a feature point described in the claims). The distribution range of the colorimetric points corresponds to the device color gamut.

  The hue cross section 61 and the outer shell point 64 will be described with reference to FIG. First, as shown in FIG. 2A, the hue section 61 is defined as a plane having a certain hue angle in the color space 60 and including all points on the achromatic color axis (L * axis) 63. Surface. In FIG. 2, only a part of the outer shell points 64 are denoted by reference numerals for easy understanding of the drawing.

  In the color data processing apparatus 10 of the present embodiment, a solid color gamut is cut at a plurality of hue sections 61, the outer shell points 64 are extracted for each hue section 61, and the outer shell points 64 are generated as vertices. The method of calculating the range as the color gamut 62 is employed.

  Specifically, first, assuming one hue section 61, all colorimetric points within a predetermined range from the hue section 61 are projected onto the hue section 61. Next, out of the colorimetric points projected on the hue section 61, the outer shell point 64 is obtained.

  FIG. 2B is a diagram showing the outer shell point 64 in the hue section 61. As shown in FIG. 2B, the outer shell point 64 (corresponding to the vertex described in the claims) is the vertex of the polygon when a polygon including all projected colorimetric points is formed. It is a point that constitutes. Such outer shell points 64 can be extracted by executing outer shell point extraction processing (S54) described later with reference to FIG. In the color data processing apparatus 10 of the present embodiment, a range generated by connecting points stored in the outer shell point memory 131 is defined as a color gamut 62 corresponding to the hue angle φ.

  Returning to FIG. The input-side color gamut information memory 132 is a memory that stores color gamut information representing the color gamut 62 of the input-side printer 30, and the output-side color gamut information memory 133 is a color gamut representing the color gamut 62 of the output-side printer 50. A memory for storing information. In the color data processing apparatus 10 of the present embodiment, the surface of the color gamut 62 determined by using the outer shell point 64 is expressed using a polar coordinate system.

  FIG. 2C illustrates a polar coordinate system that represents the surface of the color gamut 62. As shown in FIG. 2C, a certain point (for example, 50) on the achromatic color axis 63 is set as the origin O, a radius r representing the distance from the origin, and an OX axis 66 perpendicular to the achromatic color axis 63. The surface of the color gamut 62 can be expressed by the deviation angle θ with respect to. Polar coordinate data represented by the moving radius r and the deflection angle θ is stored in the input-side gamut information memory 132 or the output-side printer 50 as hue information representing the gamut 62.

  Returning to FIG. The HDD 14 is a hard disk drive and is provided with an RGBtoRGB ′ table 141.

  The RGBtoRGB ′ table 141 will be described with reference to FIG. FIG. 3A is a diagram schematically showing the configuration of the RGBtoRGB ′ table 141. As shown in FIG. 3, the RGBtoRGB ′ table 141 indicates how RGB data (RGB values) to be output to the output-side printer 50 in order to perform color matching between the input-side printer 30 and the output-side printer 50. It is a table which shows whether it should correct to RGB data (RGB 'value).

  In the color data processing apparatus 10 of this embodiment, RGB data input to the input side printer 30 via the network 20 is read, converted using the RGBtoRGB ′ table 141, and the converted RGB data is output to the output side printer 50. Output to. As a result, the appearance of the entire image formed by the input side printer 30 can be brought closer to the appearance of the entire image formed by the output side printer 50. The RGBtoRGB ′ table 141 is created using the color gamut information of the input-side printer 30 and the color gamut information of the output-side printer 50, but is a well-known process and will not be described in detail.

  Returning to FIG. The input device 15 is used to input data or commands to the color data processing device 10 and includes a keyboard and a mouse. The display device 16 displays characters, images, and the like for visually confirming the processing contents executed by the color data processing device 10 and the input data, for example, a CRT display, a liquid crystal display, or the like. It is comprised by.

  The I / F 18 connects the color data processing apparatus 10 to the network 20 and controls data input / output with the input side printer 30 or the output side printer 50 via the network 20.

  As shown in FIG. 1, the CPU 11, ROM 12, RAM 13, HDD 14, input device 15, display device 16, and I / F 18 described above are connected to each other via a bus line 19.

  On the other hand, the input-side printer 30 connected to the above-described color data processing apparatus 10 via the network 20 includes a CPU 31, a ROM 32, a RAM 33, an image forming unit 34, and an interface 37 (I / F 37). ing. The output-side printer 50 connected to the color data processing apparatus 10 via the network 20 includes a CPU 51, a ROM 52, a RAM 53, an image forming unit 54, and an interface 57 (I / F 57). . Since both the input-side printer 30 and the output-side printer 50 can be configured by known printers, only the configuration of the input-side printer 30 will be described below.

  The CPU 31 controls the operation of the input side printer 30 and executes various programs. The ROM 32 is a memory in which a program for controlling the operation of the input side printer 30 is stored, and an RGBtoLab table 321 is stored therein.

  FIG. 3B is a diagram schematically illustrating the configuration of the RGBtoLab table 321. As shown in FIG. 3B, the RGB to Lab table 321 includes values obtained by changing each color value of RGB values in, for example, 9 steps, and (0, 32, 64, 96, 128, 160, 192, 224). 255) is a table in which L * a * b * values obtained by measuring the colors of patches formed on the recording paper by the printer when the respective values are input are obtained by colorimetry. The range (that is, the color gamut 62) that can be expressed by the input side printer 30 can be covered by the L * a * b * values stored in the RGBtoLab table 321. Note that the creation of the RGBtoLab table 321 and storage in the ROM 12 are performed at the factory when the input-side printer 30 is manufactured, for example.

  Returning to FIG. The image forming unit 34 includes, for example, a recording head that ejects ink, a carriage that reciprocates the recording head in the main scanning direction, and a conveyance unit that intermittently conveys recording paper below the recording head that ejects ink. In accordance with the RGB data input via the network 20, a color image is formed on the recording paper.

  The I / F 37 connects the input-side printer 30 to the network 20 and controls data input / output with the color data processing apparatus 10 via the network 20.

  As shown in FIG. 1, the above-described CPU 31, ROM 32, RAM 33, image forming unit 34, and I / F 37 are connected to each other via a bus line 39.

  Next, the color conversion table creation process executed in the color data processing apparatus 10 configured as described above will be described with reference to the flowcharts of FIGS. In this color conversion table creation processing, color gamut information is created for each of the input-side printer 30 and the output-side printer 50, and an RGBtoRGB ′ table 141 (see FIG. 3A) is created based on the color gamut information. It is processing. FIG. 4 is a flowchart showing the color conversion table creation process.

  As shown in FIG. 4, in the color conversion table creation process, first, the RGBtoLab table 321 (see FIG. 3B) of the input side printer 30 is read (S2). Next, based on the colorimetric values (L * a * b * values) stored in the RGBtoLab table 321, color gamut information of the input side printer 30 is created, and the color gamut information is stored in the input side color gamut information memory. The color gamut forming process stored in 132 is executed (S4).

  Next, the RGBtoLab table 521 of the output side printer 50 is read (S6). Then, based on the colorimetric values stored in the RGBtoLab table 521, color gamut information for the output side printer 50 is created, and the color gamut forming process for storing the color gamut information in the output side color gamut information memory 133 is performed. (S8). The color gamut information creation processing (S4, S8) will be described later with reference to FIG.

  Although the color data processing apparatus 10 according to the present embodiment is described as reading the RGBtoLab tables 321 and 521 stored in the input side printer 30 or the output side printer 50 itself, the acquisition of the RGBtoLab tables 321 and 521 is described. The means is not limited to this. For example, the RGBtoLab table provided by a printer vendor or the like may be acquired via the Internet (not shown).

  Next, color gamut compression of the input side printer 30 is performed (S10). This is a process of compressing the color gamut of the input-side printer 30 in accordance with the color gamut of the output-side printer 50, and specifically, is stored in the RGBtoLab table 321 of the input-side printer 30 read in step S2. In this process, the L * a * b * values in the RGBtoLab table 321 are converted so that all the L * a * b * values are included in the color gamut 62 of the output-side printer 50.

  Next, the LabtoRGB relationship of the output side printer 50 is obtained (S12). As described above, since the RGB to Lab table 521 is stored in the ROM 52 of the output-side printer 50, the Lab to RGB relationship indicating the relationship of the RGB values to the L * a * b * values can be obtained using this. Although a specific algorithm is known, detailed description is omitted.

  Next, using the RGBtoLab table 321 of the input side printer 30 subjected to color gamut compression and the LabtoRGB relationship of the output side printer 50 obtained in step S12, the RGBtoRGB ′ table 141 (see FIG. 3A). ) Is created (S14), and the process is terminated. As described above, the RGBtoLab table 321 of the input side printer 30 in which all the L * a * b * values are stored in the color gamut 62 of the output side printer 50 by the color gamut compression is created. By combining the L * a * b * values in the table 321 and the L * a * b * values related to the LabtoRGB of the output side printer 50 obtained in step S12, the RGBtoRGB ′ table 141 can be created. It is.

  The RGBtoRGB ′ table 141 created by this color conversion table creation processing is stored in the HDD 14 of the color data processing apparatus 10. As a result, color matching between the image formed by the input-side printer 30 and the image formed by the output-side printer 50 becomes possible.

  With reference to FIG. 5, the color gamut forming process (S4, S8) executed in the color data processing apparatus 10 will be described. FIG. 5 is a flowchart showing the color gamut forming process (S4, S8). In the color gamut forming process (S4) executed after reading the RGBtoLab table 321 of the input side printer 30, the color gamut forming process creates color gamut information of the input side printer 30. On the other hand, the color gamut forming process (S8) executed after reading the RGBtoLab table 521 of the output side printer 50 creates the color gamut information of the output side printer 30.

  First, the colorimetric values (L * a * b * values) included in the RGBtoLab table read immediately before are converted into L * C * h * (S42). Here, C * is a value representing the hue, and h * is a value representing the hue angle.

  Next, one hue angle φ is read from the plurality of hue angles described in the hue angle list 121 (S44). The value of h * representing the hue angle is included in a range of ± 4.5 ° including the read hue angle φ or in a range of ± 4.5 ° including the hue angle (φ + 180). The h * value is extracted, and the extracted L * C * h * value is converted again into the L * a * b * value (S46). Since the hue section 61 having the hue angle φ and the hue section 61 having the hue angle (φ + 180) can be processed as one plane, the color data processing apparatus 10 according to the present embodiment processes the hue angle φ and the hue angle. The process of (φ + 180) is performed simultaneously. The hue section 61 having the hue angle φ and the hue section 61 having the hue angle (φ + 180) processed simultaneously are simply referred to as a hue section 61 having the hue angle φ.

  Next, the extracted L * a * b * values are converted into two-dimensional coordinate data expressed in the xy orthogonal coordinate system (S47). This coordinate data is obtained by projecting a colorimetric point positioned in the color space 60 corresponding to the extracted L * a * b * value onto a hue section 61 having a hue angle φ. This is data indicating the position of a point.

Next, among the coordinate data obtained by the conversion, the color measurement point 65 _xmax that takes the maximum x coordinate x_max, the color measurement point 65 ymax that takes the maximum y coordinate y_max, and the color _measurement point 65 that takes the minimum x coordinate x_min. _The color measurement point 65 _ymin taking _xmin and the minimum y coordinate y_min is extracted based on the coordinate data of each color measurement point (S50).

FIG. 6 is a diagram showing a hue section 61 and an xy coordinate system set for the hue section 61. As shown in FIG. 6, the colorimetric points 65 _xmax , 65 _ymax , 65 _xmin , and 65 _ymin extracted in step S <b> 50 among the colorimetric points projected onto the hue section 61 are all in the color gamut 62. This also corresponds to a point corresponding to the outer shell point 64 that forms.

Returning to FIG. Next, xmax Hakairoten ₆₅ extracted in step _{S50, 65 ymax, 65 xmin,} 65 determine the distance between _ymin (S51). Specifically, the distance between the _color measurement point 65 _xmax and the color _measurement point 65 _ymax , the distance between the color _measurement point 65 _ymax and the color _measurement point 65 _xmin , the color measurement point 65 _xmin and the color measurement point 65 _ymin. And the distance between the colorimetric point 65 _ymin and the colorimetric point 65 _xmax .

  Then, among the obtained distances, the maximum distance is set as the maximum distance D, and a value of 1/3 of the maximum distance D is stored in the RAM 13 as the reference distance d (S52). Since this reference distance d is a value used in shell point extraction processing (S54) described later, detailed description thereof will be described later.

  Next, an outer shell point extraction process (S54) is executed. This shell point extraction process (S54) is a process of extracting shell points that define the color gamut 62, and details will be described later with reference to FIG.

  Next, using the extracted coordinate data of the outer shell points, color gamut information that is polar coordinate data representing the surface of the color gamut 62 is created and stored in the input side color gamut information memory 132 or the output side color gamut information memory 133. (S56). Then, it is determined whether or not all the hue angles φ described in the hue angle list 121 have been processed (S58). If there is an unprocessed hue angle φ (S58: No), the process returns to S44 to perform the process. repeat.

  If it is determined that the processing for all the hue angles φ described in the hue angle list 121 is completed while the processing is repeated in this way (S58: Yes), the color gamut forming processing is ended.

  According to this color gamut forming process, the color gamut information of the input side printer 30 or the color gamut information of the output side printer 50 can be created based on the RGBtoLab tables 321 and 521 read immediately before.

  With reference to FIG. 7, the outer shell point extraction process (S54) executed in the color data processing apparatus 10 will be described. FIG. 7 is a flowchart showing the shell point extraction process (S54).

In this outer shell point extraction process (S54), first, the colorimetric point 65 _xmin taking the minimum x coordinate x_min extracted earlier is extracted and stored as the point A in the outer shell point memory 131 (see FIG. 1). (S542). Next, the angle variable α is initialized to 0 (S544).

  Next, it is determined whether all colorimetric points other than point A have been processed (S546). Since this determination is denied at first (S546: No), one colorimetric point other than the point A is selected and its coordinate data is read (S548). Then, the angle β indicating the positional relationship between the selected colorimetric point and the point A is calculated based on the point A and the coordinate data read in S548 (S550).

  FIG. 8A is an explanatory diagram for explaining the angle β. As shown in FIG. 8A, in the outer shell point extraction process (S54) of the present embodiment, the angle β is determined by the line connecting the selected colorimetric point (point P) and the point A and the y-axis. The angle formed by the negative direction is defined as a counterclockwise angle with the negative direction of the y-axis being 0 °. Therefore, when the angle β shows the maximum value (see FIG. 8B), it can be determined that the selected colorimetric point is an outer shell point adjacent to the point A.

  Returning to FIG. Next, it is determined whether or not the calculated β is larger than α (S552). Initially, since the angle variable α is initialized to 0, it is first determined that β is larger than α (S52: Yes). Next, a distance d2 from the point A to the selected colorimetric point is calculated (S553). Next, it is determined whether or not the calculated distance d2 is greater than the reference distance d (S554). When the calculated distance d2 is larger than the reference distance d (S554: Yes), that is, when one extracted point is far away from the point A, it is determined that the outer shell point 64 is not adjacent to the point A. , The process returns to S546.

  On the other hand, when the calculated distance d2 is less than the reference distance d (S554: No), that is, when one extracted point is in the vicinity of the point A and can be the adjacent shell point 64 of the point A, α = β , The colorimetric point extracted in the process of S548 is stored in the RAM 13 as a point B (S555), and the process returns to S546. Then, the next colorimetric point is selected and the coordinate data is read (S548), and the process is repeated. By repeating this process, the colorimetric point having the maximum angle β can be determined as the point B.

  FIG. 8B is a diagram illustrating a positional relationship between the points A and B. As shown in FIG. 8B, the point B which is the outer shell point adjacent to the point A constituting the color gamut 62 can be extracted by setting the colorimetric point having the maximum angle β as the point B. it can. Note that the point B to be extracted in steps S546 to S555 is a colorimetric point that satisfies the condition that all points other than the points A and B are located on one side of the straight line connecting the points A and B. The specific calculation method for extracting the point B is not limited to the calculation method described above. For example, when the point B is extracted based on the clockwise angle β ′ with the positive direction of the y-axis being 0 °, various calculation methods such as extracting the point where β ′ is the minimum as the point B, etc. There is.

  Returning to FIG. When the point B is determined in this way and the processing is completed for all the colorimetric points other than the point A (S546: Yes), the angle variable α is initialized to 360 (S556). Next, it is determined whether all colorimetric points other than point A have been processed (S558). Since this determination is denied at first (S558: No), one colorimetric point other than the point A is selected and its coordinate data is read (S560). Then, an angle γ formed by the straight line connecting the selected colorimetric point and the point B and the straight line connecting the point A and the point B is calculated (S562).

  FIG. 8C is a diagram showing the positional relationship between the points A and B and the newly selected colorimetric point. As shown in FIG. 8C, the angle γ is an angle from a straight line connecting the point A and the point B to a straight line connecting the newly selected colorimetric point P and the point B, This is a counterclockwise angle.

  Returning to FIG. Next, it is determined whether or not the calculated γ is smaller than α (S564). First, since the angle variable α is initialized to 360, first, it is determined that γ is smaller than α (S564: Yes).

  Next, a distance d2 from the point B to the colorimetric point selected in step S560 is calculated (S566). Next, it is determined whether or not the calculated distance d2 is larger than the reference distance d (S568). When the calculated distance d2 is larger than d (S568: Yes), that is, when one extracted point is far away from the point B, it is determined that it is not an outer shell point adjacent to the point B, and S558. Return to the process.

On the other hand, when the calculated distance d2 is within d (S568: No), that is, when one extracted point is in the vicinity of the point B and can be an adjacent shell point of the point B, α = γ is set and S560 The colorimetric point extracted in the step is stored in the RAM 13 as a point C (S570). Then, it is determined whether or not the point C is the colorimetric point 65 _xmin where x is the minimum (S572). If all the outer shell points 64 have not been extracted yet, this determination is denied (S572: No), and the process returns to S558 and is repeated. By repeating the process in this manner, the colorimetric point at which the distance from the point B is within the reference distance d and the angle γ is minimum is set as the point C.

  Note that the points C to be extracted in steps S556 to S574 are colorimetric points other than the points B and C, and all the colorimetric points whose distance from the point B is within the reference distance d are point B. Any colorimetric point that satisfies the condition of being located on one side of a straight line connecting point C may be used, and a specific calculation method for extracting point C is not limited to the above-described calculation method. For example, when calculating the outer product of the vector from the point B to the point C and the vector from the point B to the other colorimetric points, a point whose distance from the point B is within the reference distance d is determined as the other measurement. In the case of color points, a point C whose outer product is always positive or always negative may be extracted.

  When the processing of all colorimetric points is completed in this way (S558), point B is set as point A, point C is set as point B, and the coordinate data is stored in the outer shell point memory 131 (see FIG. 1) (S574). ). In the processing of S574, storing the coordinate data in the outer shell point memory 131 corresponds to “extracting the vertex of the color gamut” described in the claims. Each shell point extracted as point A, point B, and point C is stored in the shell point memory 131 (see FIG. 1) in association with the order of extraction.

  Next, it returns to the process of S556 and repeats a process. That is, the process of extracting the next point C with the point C extracted previously as the point B is performed.

When it is determined that the point C has reached the minimum colorimetric point 65 _xmin while repeating the process in this way (S572: Yes), the outer shell point extraction process (S54) is terminated.

  According to the outer shell point extraction process (S54) of the present embodiment, the distance between vertices adjacent to each other in the color gamut is equal to or less than the reference distance d, and one outer shell point 64 to one outer shell point. 64 is an outer product of a vector to one adjacent shell point 64 adjacent to 64 and a vector from the one shell point 64 to a colorimetric point other than the adjacent shell point 64, and one shell It is possible to extract the shell point 64 that satisfies the relationship that the outer product when the distance from the point to the other colorimetric point is equal to or less than the reference distance d is always positive or always negative. In other words, all the colorimetric points other than the outer shell point 64 within the reference distance d from one outer shell point 64 are all adjacent outer points adjacent to the outer shell point 64 and the outer shell point 64. The outer shell point 64 is extracted so as to exist on one side of a straight line connecting the shell point 64.

  FIG. 9A is a diagram showing a color gamut 62 formed by connecting the outer shell points 64 extracted by the outer shell point extraction processing (S54) of the present embodiment. As shown in FIG. 9A, according to the outer shell point extraction process (S54) of the present embodiment, the condition that the distance between the outer shell points 64 is within the reference distance d is provided. If there is a blur, an outer shell point 64 representing the blur is extracted, and color gamut information that can reproduce the color gamut more faithfully based on the extracted outer shell point 64 is obtained. Can be created.

  In the present embodiment, as an example, the distance of 1/3 of the maximum distance D is set as the reference distance d. However, a value of about 1/3 to 1/2 of the maximum distance D is set as the reference distance d. The present inventor has found that the outer shell points 64 necessary and sufficient for expressing drowning can be extracted.

  Further, according to the shell point extraction process (S54), when one shell point 64 is extracted as a point C, the next point C is extracted as a point C adjacent to the shell point 64. Since it is the outer shell point 64, the extracted order of the outer shell points 64 is stored in the outer shell point memory 131 (see FIG. 1). It can also be easily determined whether or not the color gamut 62 that is a closed figure is formed.

  FIG. 9B is formed by connecting the color gamut 62 of the input-side printer 30 formed according to the color gamut information created by the color gamut information creation process of the present embodiment and the vertex of the conventional convex hull. 3 is a diagram showing a comparison between a color gamut 67 of an input-side printer 30 and a color gamut 68 of an output-side printer 50. FIG. As described above, according to the color gamut information created by the color gamut information creation process of the present embodiment, the color gamut is more faithful than the color gamut 67 formed simply by connecting the vertices of the convex hull. Can be reproduced. Therefore, useless use of the color gamut 68 of the output side printer 50 for compression of colors that do not actually exist is suppressed, and the entire color gamut 68 of the output side printer 50 can be used effectively. is there.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications and changes can be easily made without departing from the spirit of the present invention. Can be inferred.

  For example, according to the color data processing apparatus 10 of the above-described embodiment, the colorimetric point is projected onto the hue section 61 and the outer shell point 64 is determined for each hue section 61. It is also possible to obtain the outer shell point 64 as it is in three dimensions without projecting it on the cross section 61.

FIGS. 10A to 10C are diagrams for explaining a modification example of the outer shell point extraction process when the closed space including the colorimetric points is used as the color gamut. First, as shown in FIG. 10A, among the colorimetric points positioned in the color space, the colorimetric point 65 _aMAX having the largest a * coordinate and the colorimetric point 65 _aMIN having the smallest a * coordinate, and b * coordinate. Is a tetrahedron _composed of a colorimetric point 65 _bMAX having the largest b * coordinate, a colorimetric point 65 _bMIN having the smallest b * coordinate, a colorimetric point 65 _LMAX having the largest L * coordinate, and a colorimetric point 65 _LMIN having the smallest L * coordinate. The distance of at least one side of the octahedral solid is acquired from the above, and when the distance of one side is acquired, a value smaller than that distance is determined as the reference distance d, and acquired when the distance of a plurality of sides is acquired Of these distances, a value smaller than the maximum value D is determined as the reference distance d (predetermined value determining means). Then, the process is started with the colorimetric point 65 _LMAX as the point A which is the start point.

  Next, as shown in FIG. 10B, two arbitrary colorimetric points other than the point A are extracted and set as a point B and a point C. The points B and C are within a reference distance d from the point A in the color space. Then, a normal vector 69 of the surface ABC is obtained. Then, a relationship between an arbitrary point P whose distance from the point A is within the reference distance d and the surface ABC is obtained, and it is determined whether or not all the points are on one side of the surface ABC. Specifically, the inner product of the vector 70 from the point A to the point P and the normal vector 69 is calculated, and it is determined whether or not the inner products for all the points are all negative or all positive.

  Then, the same determination process is repeated for each colorimetric point, and points B and C satisfying such conditions are extracted (an example of the extracting means described in the claims), thereby being the outer shell point 64. Point B and point C can be extracted.

  Next, by repeating the process of searching for the surface ABC that satisfies the above conditions again with the point B as the point A and the point C as the point B, all the outer shell points of the solid color gamut can be extracted.

  FIG. 10C is a diagram showing an example of a solid color gamut formed by connecting the outer shell points 64 extracted by the above method. By providing the restriction of the reference distance d, as shown in FIG. 10 (c), the outer shell point 64 of the three-dimensional portion can be extracted, which is compared with the color gamut formed by the convex hull. More accurate color gamut information can be created.

  With reference to FIG.10 (d), another modification of this embodiment is demonstrated. In steps S556 to S574 of the shell point extraction process (S54) of the above-described embodiment, in order to extract the point C, all the colorimetric points are searched, and the colorimetric point satisfying the condition is extracted as the point C. It was. Instead, if the method described below is used, the number of colorimetric points to be searched can be reduced.

FIG. 10D is a diagram showing the colorimetric points projected on the hue section 61. As shown in FIG. 10D, first, the colorimetric points projected on the hue section 61 are classified into four groups. That is, the colorimetric point 65 _xmin having the smallest x and the colorimetric point 65 _ymaX having the largest y are group 1 included in the rectangular area having the diagonal vertices and the colorimetric point 65 _ymax and x having the largest y. Group 2 included in a rectangular area having the maximum colorimetric point colorimetric point 65 _xmax as a vertex on the diagonal line, x is the maximum colorimetric point 65 _xmax and y is the minimum colorimetric point 65 _ymin on the diagonal line Group 3 included in the rectangular area having the vertex of, and group 4 included in the rectangular area having the color measuring point 65 _ymin having the smallest y and the color measuring point 65 _xmin having the smallest x in the diagonal line Classify.

When the outer shell point 64 is extracted between the _colorimetric point 65 _xmin having the smallest x and the colorimetric point 65 _ymaX having the largest y, only the colorimetric point of group 1 is searched, and y is the largest. when x from Hakairoten _{65 ymax} of extracting the hull point 64 during the period until the maximum Hakairoten _{65 xmax} is only the search target Hakairoten group 2, x is the largest Hakairoten 65 when y is extracted hull point 64 during the period until the smallest Hakairoten _{65 ymin} from _xmax, only the search target Hakairoten group 3, y is the x from the smallest Hakairoten _{65 ymin} minimum When the outer shell point 64 is extracted up to the colorimetric point 65 _xmin, only the colorimetric points of group 4 are searched. In this way, the number of colorimetric points to be searched for when extracting the point C can be reduced, so that the processing load can be reduced.

  FIG. 11 is a flowchart illustrating an example of a shell point extraction process (S54) according to a modification. As shown in FIG. 11, various modifications can be considered for the shell point extraction process (S54).

As shown in FIG. 11, first, a colorimetric point 65 _xmin that takes the minimum x-coordinate x_min extracted earlier is extracted and stored as point A in the shell point memory 131 (see FIG. 1) (S152). .

  Next, one colorimetric point is selected as point B (S154). Then, it is determined whether or not the point B has become the point A (S156). If the determination is affirmative (S156: Yes), the process returns to S154.

  On the other hand, if the determination in S156 is negative (S156: No), the distance between point A and point B is calculated, and it is determined whether the calculated distance is less than the reference distance d (S158). . If the determination in S158 is negative (S158: No), the process returns to S154.

  On the other hand, if the determination in S158 is affirmative (S158: Yes), it is then determined whether all colorimetric points other than point A and point B have been processed (S160). Initially, the determination in S160 is negative (S160: No), one colorimetric point is selected as point C (S162), and it is determined whether or not point C has become point A. (S164). When the point C has become the point A (S164: Yes), the process returns to S160.

  On the other hand, when the point C has never become the point A (S164: No), the distance between the point A and the point C is calculated, and it is determined whether or not the distance is less than the reference distance d ( S166). If the determination in S166 is negative (S166: No), the process returns to S160.

  On the other hand, if the determination in S166 is affirmative (S166: Yes), the cross product of vector AB (vector from point A to point B) and vector AB (vector from point A to point C) is calculated, and RAM 13 (See FIG. 1) (S168). Then, the process returns to S160.

  When the process is repeated for all the colorimetric points other than point A and point B while repeating the process in this way (S160: Yes), it is next determined whether or not all the outer products calculated in step S168 are positive. Judgment is made (S170). If the determination in S170 is negative (S170: No), point B is not the outer shell point 64, and the process returns to S154.

  On the other hand, if the determination in S170 is affirmative (S170: Yes), it is determined whether or not the point B is a point where x is the minimum (S172). Since this determination is denied at first (S172: No), the point B is set as the point A, and the coordinate data is stored in the outer shell point memory 131 (see FIG. 1) (S174).

  As described above, when the determination in S172 is affirmed while the process is repeated (S172: Yes), the shell point extraction process (S54) is terminated.

  According to the shell point extraction process (S54) of the modified example, first, when the point A that should become the shell point 64 is extracted, from the point A to the point B with the point A as a reference from the next. When the outer product of the vector AB to the point A and the vector AC from the point A to the point C other than the point B is equal to or less than the reference distance d, it is always positive or always negative. A point B that satisfies a certain relationship is extracted, and the extraction of the point B is repeated. Therefore, the same effect as that of the above-described embodiment can be obtained.

  In the above-described embodiment, all the shell points in the hue section 61 are extracted by the shell point extraction process (S54). However, some shell points 64 (for example, FIG. 10D) are extracted. Only the outer shell points 64 included in the group 3 and the group 4 described with reference are extracted by steps S556 to S574 of the outer shell point extraction process (S54), and other outer shell points (for example, FIG. The shell points 64) included in group 1 and group 2 shown in d) may be extracted by a known process. This is because the hue blur tends to be a problem particularly in colors with low brightness.

  In the above-described embodiment, the outer shell point extraction process (S54) has been described as being executed for the hue sections 61 of all hue angles. However, for example, the outer shell point extraction process (S54) is performed only when processing is performed on the hue section 61 of a color such as blue where the color gamut tends to be a problem, and the hue sections 61 of other colors are executed. The outer shell point may be extracted by a known process.

  In the above-described embodiment, the target of color matching performed by the color data processing apparatus 10 is a printer. However, the present invention is not limited to the printer. For example, color matching is performed for other devices such as a monitor, a scanner, and a camera. It may be a thing to do.

  In the above-described embodiment, the color data processing apparatus 10 has been described as executing the color conversion table creation process (see FIG. 4), but the device side, for example, the input side printer 30 or the output side printer 50, A process corresponding to the color conversion table creation process may be executed.

1 is a block diagram showing an overall configuration of a color data processing system including a color data processing apparatus according to an embodiment of the present invention. (A) is an image figure which shows the color space of L * a * b * color system in three dimensions, (b) is a figure which shows the outer shell point in a hue cross section, (c) is a color gamut. It is a figure explaining the polar coordinate system showing the surface of this. (A) is a figure which shows typically the structure of a RGBtoRGB 'table, (b) is a figure which shows the structure of a RGBtoLab table typically. It is a flowchart which shows a color conversion table creation process. It is a flowchart which shows a color gamut formation process. It is a figure which shows a hue cross section and xy coordinate system set to the hue cross section. It is a flowchart which shows an outer shell point extraction process. (A) is explanatory drawing explaining angle (beta), (b) is a figure which shows the positional relationship of the point A and the point B, (c) is newly selected with the point A and the point B It is a figure which shows the positional relationship with another colorimetric point. (A) is a figure which shows the color gamut formed by connecting the outer-shell point extracted by the outer-shell point extraction process of this embodiment, (b) is the color gamut information creation process of this embodiment. Compare the color gamut of the input printer formed according to the created color gamut information, the color gamut of the input printer formed by connecting the vertices of the conventional convex hull, and the color gamut of the output printer. FIG. (A) to (c) are diagrams showing modified examples of the shell point extraction process when a closed space including a colorimetric point is used as a color gamut, and (d) is a diagram showing a measurement measured on a hue section. It is a figure which shows a color point. It is a flowchart which shows an example of the shell point extraction process (S54) of a modification. It is a figure which shows typically an example of a structure of the conventional color matching processing system. (A) shows a conventional input side printer, RGB data for test print input to the input side printer, and color patches formed by the input side printer as a result of input of the RGB data for test print. FIG. 5B is a diagram schematically showing the recording sheet, and (b) shows a color space of the L * a * b * color system in which the colorimetric values obtained by measuring the color patches are plotted. It is an image figure. It is a figure explaining an example of the method of expressing a color gamut using the conventional convex hull. (A) is a diagram showing a colorimetric point, a color gamut of an input side printer formed as a convex hull including the colorimetric point, and a color gamut of an output side printer, and (b) It is a figure which expands and shows the principal part of (a).

10 Color data processing device (color gamut information creation device)
11 CPU (computer)
30 Input side printer (device, input side device)
50 Output printer (device, output device)
60 color space 61 hue section (plane)
62 Color Gamut 120 Color Gamut Formation Program (Color Gamut Information Creation Program)
d Reference distance (predetermined value)
φ Hue angle S4, S8 Color gamut formation processing (color gamut information creation means, color gamut information creation process, color gamut information creation step)
S50 selection means S51 distance acquisition means S52 predetermined value determination means S54 shell point extraction processing (extraction means, extraction process, extraction step)
S152 First vertex extraction means S174 Second vertex extraction means S542, S555 Start point extraction means S574 Start point extraction means, next point extraction means

Claims (8)

When colorimetric values indicating device characteristics are positioned on a plane with a constant hue angle in the color space, color gamut information corresponding to the color gamut indicated as the distribution range of feature points located based on each colorimetric value is created. A color gamut information creation device,
Extracting means for extracting vertices of the color gamut generated using at least three or more feature points as vertices among the feature points;
Gamut information creating means for creating gamut information based on the vertices extracted by the extracting means,
Each of the vertices extracted by the extraction means is such that the distance between vertices adjacent to each other in the color gamut is equal to or less than a predetermined value, and from one vertex to one adjacent vertex adjacent to the one vertex. And a vector from the one vertex to another feature point other than the adjacent vertex, and the distance from the one vertex to the other feature point is equal to or less than the predetermined value Satisfy the relationship that the outer product is always positive or always negative,
The extraction means includes
When an orthogonal coordinate system is set for the plane, among the feature points positioned on the plane, one of the feature points having the maximum x coordinate, the minimum x coordinate, the maximum y coordinate, and the minimum y coordinate is started. The first vertex of the hour,
When the distance from the first vertex is equal to or less than the predetermined value, and the first vertex is the maximum value or the minimum value of the x coordinate, the angle formed with the y axis, and when the first vertex is the maximum value or the minimum value of the y coordinate start point extracting means for extracting a second vertex having a minimum angle with the x-axis;
Among the feature points, the feature point has a minimum angle formed by a straight line connecting the feature point and the second vertex and a straight line connecting the first vertex and the second vertex, and the first vertex A next point extracting means for extracting a feature point that satisfies a condition that the distance from is within a predetermined range;
When the feature point satisfying the condition is extracted by the next point extraction unit, the second vertex at that time is set as the first vertex, and the feature point extracted by the next point extraction unit is set as the second vertex. A next point extraction repeating unit that repeats extraction of feature points by the point extracting unit;
The color gamut information creating means includes
The starting point extracting means, runner-up extraction means, creating color gamut information it characterized in that to create a color gamut information corresponding to the color gamut that includes the vertex points extracted by the runner-up extraction repeating unit apparatus. When colorimetric values indicating device characteristics are positioned on a plane with a constant hue angle in the color space, color gamut information corresponding to the color gamut indicated as the distribution range of feature points located based on each colorimetric value is created. A color gamut information creation device,
Extracting means for extracting vertices of the color gamut generated using at least three or more feature points as vertices among the feature points;
Gamut information creating means for creating gamut information based on the vertices extracted by the extracting means,
Each of the vertices extracted by the extraction means is such that the distance between vertices adjacent to each other in the color gamut is equal to or less than a predetermined value, and from one vertex to one adjacent vertex adjacent to the one vertex. And a vector from the one vertex to another feature point other than the adjacent vertex, and the distance from the one vertex to the other feature point is equal to or less than the predetermined value Satisfy the relationship that the outer product is always positive or always negative,
The extraction means includes
When an orthogonal coordinate system is set for the plane, among the feature points positioned on the plane, one of the feature points having the maximum x coordinate, the minimum x coordinate, the maximum y coordinate, and the minimum y coordinate is started. First vertex extraction means for extracting as the first vertex of the time;
A second vertex extracting means for extracting a second vertex adjacent to the first vertex in the color gamut,
The second vertex extraction means includes a vector from the first vertex to the feature point among the feature points whose distance from the first vertex is equal to or less than the predetermined value, and a feature other than the feature point from the first vertex. A second feature point satisfying a relationship that an outer product with a vector to another feature point is always positive or always negative when a distance from the first vertex to the other feature point is equal to or smaller than the predetermined value Which is extracted as a vertex,
When the second vertex extraction means extracts the second vertex, the second vertex extraction repeater repeats the second vertex extraction by the second vertex extraction means, with the second vertex at that time as the first vertex With
The color gamut information creating means includes
The color gamut information generating device characterized in that to create a color gamut information corresponding to the color gamut that includes the vertex points extracted by the first vertex extraction means or said second vertex extraction means. When colorimetric values indicating device characteristics are positioned on a plane with a constant hue angle in the color space, color gamut information corresponding to the color gamut indicated as the distribution range of feature points located based on each colorimetric value is created. A color gamut information creation device,
Extracting means for extracting vertices of the color gamut generated using at least three or more feature points as vertices among the feature points;
Gamut information creating means for creating gamut information based on the vertices extracted by the extracting means,
Each of the vertices extracted by the extraction means is such that the distance between vertices adjacent to each other in the color gamut is equal to or less than a predetermined value, and from one vertex to one adjacent vertex adjacent to the one vertex. And a vector from the one vertex to another feature point other than the adjacent vertex, and the distance from the one vertex to the other feature point is equal to or less than the predetermined value Satisfy the relationship that the outer product is always positive or always negative,
When an orthogonal coordinate system is set on the plane, the feature point is positioned on the plane, and at least one of the feature points having the maximum x coordinate, the minimum x coordinate, the maximum y coordinate, and the minimum y coordinate Selection means for selecting two points prior to the extraction means;
Distance acquisition means for acquiring a distance between feature points selected by the selection means;
When one distance is acquired by the distance acquisition means, a value smaller than that distance is determined as the predetermined value, and when a plurality of distances are acquired by the distance acquisition means, the maximum value among the acquired distances color gamut information generating device you anda predetermined value determining means for determining a value smaller than a predetermined value. A color gamut information creation device that creates color gamut information corresponding to a color gamut indicated as a distribution range of feature points positioned based on each color measurement value when positioning a colorimetric value indicating device characteristics in a color space. And
Extracting means for extracting the vertexes using the closed space generated by using at least four or more feature points as vertices among the feature points as the color gamut;
Gamut information creating means for creating gamut information based on the vertices extracted by the extracting means,
The vertices extracted by the extracting means are both two vertices in which the distance between adjacent vertices in the color gamut is less than or equal to a predetermined value and the distance from one vertex is less than or equal to the predetermined value And an inner product of one normal vector for the surface generated by the one vertex and a vector from the one vertex to another feature point other than the two vertices, The inner product when the distance to the other feature point is within the predetermined value satisfies the relationship that is always positive or always negative;
When an orthogonal coordinate system is set in the color space, among the feature points positioned in the color space, the x coordinate is maximum, the x coordinate is minimum, the y coordinate is maximum, the y coordinate is minimum, the z coordinate is maximum, and the z coordinate The distance of at least one side of a solid composed of the smallest feature points is acquired, and when the distance of one side is acquired, a value smaller than that distance is determined as the predetermined value, and the distance of a plurality of sides is acquired. maximum value gamut information generating apparatus you characterized in that it comprises a predetermined value determining means for determining a smaller value as the predetermined value than of the distance obtained when being. When positioning colorimetric values indicating device characteristics on a plane with a constant hue angle in the color space, the computer displays color gamut information corresponding to the color gamut indicated as the distribution range of feature points located based on each colorimetric value. A color gamut information creation program to be created by
An extraction step of extracting vertices of the color gamut generated using at least three or more feature points as vertices among the feature points;
Causing the computer to execute a color gamut information creation step of creating color gamut information based on the vertices extracted by the extraction step;
All the vertices extracted by the extraction step are such that the distance between vertices adjacent to each other in the color gamut is equal to or less than a predetermined value and that one vertex is adjacent to one vertex. And a vector from the one vertex to another feature point other than the adjacent vertex, and the distance from the one vertex to the other feature point is equal to or less than the predetermined value Satisfy the relationship that the outer product is always positive or always negative,
The extraction step includes
When an orthogonal coordinate system is set for the plane, among the feature points positioned on the plane, one of the feature points having the maximum x coordinate, the minimum x coordinate, the maximum y coordinate, and the minimum y coordinate is started. The first vertex of the hour,
When the distance from the first vertex is equal to or less than the predetermined value, and the first vertex is the maximum value or the minimum value of the x coordinate, the angle formed with the y axis, and when the first vertex is the maximum value or the minimum value of the y coordinate a starting point extracting step of extracting a second vertex having a minimum angle with the x-axis;
Among the feature points, the feature point has a minimum angle formed by a straight line connecting the feature point and the second vertex and a straight line connecting the first vertex and the second vertex, and the first vertex A next point extracting step for extracting a feature point that satisfies a condition that a distance from the predetermined range is within a predetermined range;
When the feature point satisfying the condition is extracted by the next point extraction step, the second vertex at that time is set as the first vertex, and the feature point extracted by the next point extraction step is set as the second vertex. A next point extraction repetition step that repeats feature point extraction by the point extraction step,
The color gamut information creating step includes
A color gamut information creation program for creating color gamut information corresponding to a color gamut including a point extracted by the start point extraction step, the next point extraction step, and the next point extraction repetition step as a vertex. . When positioning colorimetric values indicating device characteristics on a plane with a constant hue angle in the color space, the computer displays color gamut information corresponding to the color gamut indicated as the distribution range of feature points located based on each colorimetric value. A color gamut information creation program to be created by
An extraction step of extracting vertices of the color gamut generated using at least three or more feature points as vertices among the feature points;
Causing the computer to execute a color gamut information creation step of creating color gamut information based on the vertices extracted by the extraction step;
All the vertices extracted by the extraction step are such that the distance between vertices adjacent to each other in the color gamut is equal to or less than a predetermined value and that one vertex is adjacent to one vertex. And a vector from the one vertex to another feature point other than the adjacent vertex, and the distance from the one vertex to the other feature point is equal to or less than the predetermined value Satisfy the relationship that the outer product is always positive or always negative,
The extraction step includes
When an orthogonal coordinate system is set for the plane, among the feature points positioned on the plane, one of the feature points having the maximum x coordinate, the minimum x coordinate, the maximum y coordinate, and the minimum y coordinate is started. A first vertex extraction step for extracting as the first vertex of the time;
A second vertex extracting step of extracting a second vertex adjacent to the first vertex in the color gamut,
In the second vertex extraction step, among the feature points whose distance from the first vertex is equal to or less than the predetermined value, a vector from the first vertex to the feature point, and a feature other than the feature point from the first vertex. A second feature point satisfying a relationship that an outer product with a vector to another feature point is always positive or always negative when a distance from the first vertex to the other feature point is equal to or smaller than the predetermined value Which is extracted as a vertex,
When the second vertex is extracted by the second vertex extraction step, the second vertex extraction repeat step that repeats the extraction of the second vertex by the second vertex extraction step with the second vertex at that time as the first vertex With
The color gamut information creating step includes
A color gamut information creation program for creating color gamut information corresponding to a color gamut including a point extracted by the first vertex extraction step or the second vertex extraction step as a vertex. When positioning colorimetric values indicating device characteristics on a plane with a constant hue angle in the color space, the computer displays color gamut information corresponding to the color gamut indicated as the distribution range of feature points located based on each colorimetric value. A color gamut information creation program to be created by
An extraction step of extracting vertices of the color gamut generated using at least three or more feature points as vertices among the feature points;
Causing the computer to execute a color gamut information creation step of creating color gamut information based on the vertices extracted by the extraction step;
All the vertices extracted by the extraction step are such that the distance between vertices adjacent to each other in the color gamut is equal to or less than a predetermined value and that one vertex is adjacent to one vertex. And a vector from the one vertex to another feature point other than the adjacent vertex, and the distance from the one vertex to the other feature point is equal to or less than the predetermined value Satisfy the relationship that the outer product is always positive or always negative,
When an orthogonal coordinate system is set on the plane, the feature point is positioned on the plane, and at least one of the feature points having the maximum x coordinate, the minimum x coordinate, the maximum y coordinate, and the minimum y coordinate A selection step of selecting two points prior to the extraction step;
A distance acquisition step of acquiring a distance between the feature points selected by the selection step;
When one distance is acquired by the distance acquisition step, a value smaller than the distance is determined as the predetermined value, and when a plurality of distances are acquired by the distance acquisition step, the maximum value among the acquired distances A gamut information creating program for causing the computer to execute a predetermined value determining step for determining a smaller value as the predetermined value. A color gamut information creation program for causing a computer to create color gamut information corresponding to a color gamut indicated as a distribution range of feature points positioned based on each colorimetric value when positioning colorimetric values indicating device characteristics in the color space Because
An extraction step of extracting the vertices with the closed space generated using at least four or more feature points as vertices among the feature points as the color gamut;
Causing the computer to execute a color gamut information creating step for creating color gamut information based on the vertices extracted by the extraction step;
The vertices extracted by the extraction step are two vertices in which the distance between adjacent vertices in the color gamut is not more than a predetermined value and the distance from one vertex is not more than the predetermined value. And an inner product of one normal vector for the surface generated by the one vertex and a vector from the one vertex to another feature point other than the two vertices, The inner product when the distance to the other feature point is within the predetermined value satisfies the relationship that is always positive or always negative;
When an orthogonal coordinate system is set in the color space, among the feature points positioned in the color space, the x coordinate is maximum, the x coordinate is minimum, the y coordinate is maximum, the y coordinate is minimum, the z coordinate is maximum, and the z coordinate The distance of at least one side of a solid composed of the smallest feature points is acquired, and when the distance of one side is acquired, a value smaller than that distance is determined as the predetermined value, and the distance of a plurality of sides is acquired. If so, a color gamut information creation program causing the computer to execute a predetermined value determining step of determining a value smaller than a maximum value among the obtained distances as the predetermined value.

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